1.
Nature
–
Nature, in the broadest sense, is the natural, physical, or material world or universe. Nature can refer to the phenomena of the world. The study of nature is a part of science. Although humans are part of nature, human activity is understood as a separate category from other natural phenomena. The word nature is derived from the Latin word natura, or essential qualities, innate disposition, and in ancient times, literally meant birth. Natura is a Latin translation of the Greek word physis, which related to the intrinsic characteristics that plants, animals. This usage continued during the advent of scientific method in the last several centuries. Within the various uses of the word today, nature often refers to geology, for example, manufactured objects and human interaction generally are not considered part of nature, unless qualified as, for example, human nature or the whole of nature. Depending on the context, the term natural might also be distinguished from the unnatural or the supernatural. Earth is the planet known to support life, and its natural features are the subject of many fields of scientific research. Within the solar system, it is third closest to the sun, it is the largest terrestrial planet and its most prominent climatic features are its two large polar regions, two relatively narrow temperate zones, and a wide equatorial tropical to subtropical region. Precipitation varies widely with location, from several metres of water per year to less than a millimetre,71 percent of the Earths surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the land in the Northern Hemisphere. Earth has evolved through geological and biological processes that have left traces of the original conditions, the outer surface is divided into several gradually migrating tectonic plates. The interior remains active, with a layer of plastic mantle. This iron core is composed of a solid phase. Convective motion in the core generates electric currents through dynamo action, the atmospheric conditions have been significantly altered from the original conditions by the presence of life-forms, which create an ecological balance that stabilizes the surface conditions. Geology is the science and study of the solid and liquid matter that constitutes the Earth, the geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations
Nature
–
Hopetoun Falls,
Australia
Nature
–
Bachalpsee in the
Swiss Alps
Nature
–
Lightning strikes during the eruption of the
Galunggung volcano,
West Java, in 1982.
Nature
–
View of the
Earth, taken in 1972 by the
Apollo 17 astronaut crew. This image is the only photograph of its kind to date, showing a fully sunlit hemisphere of the Earth.
2.
Weather
–
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the lowest level of the atmosphere, Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, weather is understood to mean the weather of Earth. Weather is driven by air pressure, temperature and moisture differences between one place and another and these differences can occur due to the suns angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the largest scale atmospheric circulations, the Hadley Cell, the Ferrel Cell, the Polar Cell, Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earths axis is tilted relative to its orbital plane, on Earths surface, temperatures usually range ±40 °C annually. Over thousands of years, changes in Earths orbit can affect the amount and distribution of energy received by the Earth, thus influencing long-term climate. Surface temperature differences in turn cause pressure differences, higher altitudes are cooler than lower altitudes as most atmospheric heating is due to contact with the Earths surface while radiative losses to space are mostly constant. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The Earths weather system is a system, as a result. Human attempts to control the weather have occurred throughout history, and there is evidence that human activities such as agriculture, studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the Solar System, Jupiters Great Red Spot, is a storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies, a stars corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind, on Earth, the common weather phenomena include wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes, typhoons, almost all familiar weather phenomena occur in the troposphere. Weather does occur in the stratosphere and can affect weather lower down in the troposphere, Weather occurs primarily due to air pressure, temperature and moisture differences between one place to another. These differences can occur due to the sun angle at any particular spot, in other words, the farther from the tropics one lies, the lower the sun angle is, which causes those locations to be cooler due the spread of the sunlight over a greater surface. The strong temperature contrast between polar and tropical air gives rise to the large scale atmospheric circulation cells and the jet stream, Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow
Weather
–
Thunderstorm near Garajau,
Madeira
Weather
–
Cumulus mediocris cloud surrounded by
stratocumulus
Weather
–
New Orleans, Louisiana, after being struck by Hurricane Katrina. Katrina was a
Category 3 hurricane when it struck although it had been a category 5 hurricane in the
Gulf of Mexico.
Weather
–
Early morning sunshine over
Bratislava, Slovakia
3.
Season
–
A season is a division of the year marked by changes in weather, ecology and hours of daylight. Seasons result from the orbit of the Earth around the Sun. During May, June, and July, the northern hemisphere is exposed to direct sunlight because the hemisphere faces the sun. The same is true of the hemisphere in November, December. It is the tilt of the Earth that causes the Sun to be higher in the sky during the months which increases the solar flux. However, due to lag, June, July, and August are the hottest months in the northern hemisphere and December, January. In temperate and subpolar regions, four calendar-based seasons are recognized, spring, summer, autumn or fall. Ecologists often use a model for temperate climate regions, prevernal, vernal, estival, serotinal, autumnal. Many tropical regions have two seasons, the rainy, wet, or monsoon season and the dry season, some have a third cool, mild, or harmattan season. Seasons often held special significance for agrarian societies, whose lives revolved around planting and harvest times, in some parts of the world, some other seasons capture the timing of important ecological events such as hurricane season, tornado season, and wildfire season. The most historically important of these are the three seasons—flood, growth, and low water—which were previously defined by the annual flooding of the Nile in Egypt. The seasons result from the Earths axis of rotation being tilted with respect to its orbital plane by an angle of approximately 23.5 degrees, regardless of the time of year, the northern and southern hemispheres always experience opposite seasons. This is because during summer or winter, one part of the planet is directly exposed to the rays of the Sun than the other. For approximately half of the year, the northern hemisphere tips toward the Sun, for the other half of the year, the same happens, but in the southern hemisphere instead of the northern, with the maximum around December 21. The two instants when the Sun is directly overhead at the Equator are the equinoxes. Also at that moment, both the North Pole and the South Pole of the Earth are just on the terminator, and hence day and night are equally divided between the northern and southern hemispheres. Around the March equinox, the northern hemisphere will be experiencing spring as the hours of daylight increase, the effect of axial tilt is observable as the change in day length and altitude of the Sun at noon during a year. Between this effect and the daylight hours, the axial tilt of the Earth accounts for most of the seasonal variation in climate in both hemispheres
Season
–
Red and green trees in spring
Season
–
A tree in winter
Season
–
The six ecological seasons
Season
–
The four calendar seasons, depicted in an ancient Roman mosaic from
Tunisia.
4.
Winter
–
Winter is the coldest season of the year in polar and temperate climates, between autumn and spring. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun, different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, in many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the elevation with respect to the North or South Pole is at its most negative value, meaning this day will have the shortest day. The English word winter comes from the Proto-Indo-European root wend, relating to water, the tilt of the Earths axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23. 44° to the plane of its orbit, when it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun, from the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun. During winter in either hemisphere, the altitude of the Sun causes the sunlight to hit that hemisphere at an oblique angle. In regions experiencing winter, the amount of solar radiation is spread out over a larger area. This effect is compounded by the distance that the light must travel through the atmosphere. Compared with these effects, the changes in the distance of the earth from the sun are negligible, the manifestation of the meteorological winter in the northerly snow–prone parallels is highly variable depending on elevation, position versus marine winds and the amount of precipitation. A case in point is Canada, a country associated with tough winters. Winnipeg on the Great Plains at a distance from large bodies of water has a January high of −11.3 °C. In comparison, Vancouver on the coast with an influence from moderating Pacific winds has a January low of 1.4 °C with days well above freezing at 6.9 °C. Both areas are on the 49th parallel north and in the western half of the continent. Winter is often defined by meteorologists to be the three months with the lowest average temperatures. This corresponds to the months of December, January and February in the Northern Hemisphere, the coldest average temperatures of the season are typically experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Blizzards often develop and cause many transportation delays, diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °F due to air with slightly higher moisture from aloft mixing with colder, surface based air
Winter
–
A
snow -covered park in front of the
Cathedral of Learning in
Pittsburgh,
Pennsylvania during winter
Winter
–
Conifer forest in the
Pillapalu,
Estonia, in January 2014
Winter
–
The Old Town of
Tallinn,
Estonia, full of snow on 1 January 2010
Winter
–
Tierra del Fuego,
Argentina
5.
Spring (season)
–
Spring is one of the four conventional temperate seasons, following winter and preceding summer. There are various definitions of spring, but local usage of the term varies according to local climate, cultures. When it is spring in the Northern Hemisphere, it will be autumn in the Southern Hemisphere, at the spring equinox, days are approximately 12 hours long with day length increasing as the season progresses. Spring and springtime refer to the season, and also to ideas of rebirth, rejuvenation, renewal, resurrection, subtropical and tropical areas have climates better described in terms of other seasons, e. g. dry or wet, monsoonal or cyclonic. Often, cultures have locally defined names for seasons which have little equivalence to the terms originating in Europe, Spring is the time when many plants begin to grow and flower. Meteorologists generally define four seasons in many areas, spring, summer, autumn. These are demarcated by the values of their average temperatures on a monthly basis, the three warmest months are by definition summer, the three coldest months are winter and the intervening gaps are spring and autumn. Spring, when defined in this manner, can start on different dates in different regions, in most Northern Hemisphere, temperate locations, spring months are March, April and May, although differences exist from country to country. Most Southern Hemisphere, temperate locations have opposing seasons with spring in September, October and November, in Australia and New Zealand, spring conventionally begins on 1 September and ends 30 November. In some cultures in the Northern Hemisphere, the astronomical Vernal equinox is taken to mark the first day of spring, in Persian culture the first day of spring is the first day of the first month which begins on 20 or 21 March. In other traditions, the equinox is taken as mid-spring, similarly, according to the Celtic tradition, which is based solely on daylight and the strength of the noon sun, spring begins in early February and continues until early May. In Ireland, spring traditionally starts on February 1, St Brigids Day, the beginning of spring is not always determined by fixed calendar dates. These indicators, along with the beginning of spring, vary according to the local climate, most ecologists divide the year into six seasons that have no fixed dates. In addition to spring, ecological reckoning identifies an earlier separate prevernal season between the hibernal and vernal seasons and this is a time when only the hardiest flowers like the crocus are in bloom, sometimes while there is still some snowcover on the ground. During early spring, the axis of the Earth is increasing its tilt relative to the Sun, the hemisphere begins to warm significantly, causing new plant growth to spring forth, giving the season its name. Any snow begins to melt, swelling streams with runoff and any frosts become less severe, in climates that have no snow, and rare frosts, air and ground temperatures increase more rapidly. Many flowering plants bloom at this time of year, in a succession, sometimes beginning when snow is still on the ground. In normally snowless areas, spring may begin as early as February, heralded by the blooming of deciduous magnolias, cherries, and quince, or August in the same way
Spring (season)
–
Colorful spring
garden flowers
Spring (season)
–
A
sour cherry blooming in spring
Spring (season)
–
A blooming field of
garland chrysanthemum, a typical spring flower in
Israel
Spring (season)
–
Celebration stage of 1st day of Falgun, beginning of spring season in Bangladesh, 2014
6.
Summer
–
Summer is the hottest of the four temperate seasons, falling between spring and autumn. At the summer solstice, the days are longest and the nights are shortest, the date of the beginning of summer varies according to climate, tradition and culture. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, a variable seasonal lag means that the meteorological center of the season, which is based on average temperature patterns, occurs several weeks after the time of maximal insolation. Under meteorological definitions, all seasons are set to start at the beginning of a calendar month. This meteorological definition of summer also aligns with the commonly viewed notion of summer as the season with the longest days of the year, the meteorological reckoning of seasons is used in Australia, Austria, Denmark, the former Soviet Union and Japan. It is also used by many in the United Kingdom, in Ireland, the summer months according to the national meteorological service, Met Éireann, are June, July and August. However, according to the Irish Calendar, summer begins on 1 May, school textbooks in Ireland follow the cultural norm of summer commencing on 1 May rather than the meteorological definition of 1 June. Reckoning by hours of daylight alone, summer solstice marks the midpoint, not the beginning, midsummer takes place over the shortest night of the year, which is the summer solstice, or on a nearby date that varies with tradition. Where a seasonal lag of half a season or more is common, by this method, in North America, summer is the period from the summer solstice to the autumn equinox. The similar Canadian tradition starts summer on Victoria Day one week prior and ends, as in the United States, on Labour Day. In Chinese astronomy, summer starts on or around 5 May, with the known as lìxià, i. e. establishment of summer. In Australia and New Zealand, summer begins on 1 December. Summer is traditionally associated with hot or warm weather, in the Mediterranean regions, it is also associated with dry weather, while in other places it is associated with rainy weather. The wet season is the period of vegetation growth within the savanna climate regime. Where the wet season is associated with a shift in the prevailing winds. In the northern Atlantic Ocean, a tropical cyclone season occurs from 1 June to 30 November. The statistical peak of the Atlantic hurricane season is 10 September, the Northeast Pacific Ocean has a broader period of activity, but in a similar time frame to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and March, in the North Indian basin, storms are most common from April to December, with peaks in May and November
Summer
–
A field during summer in
Belgium
Summer
–
Wet season
thunderstorm at night in
Darwin, Australia.
Summer
–
Image of
Hurricane Lester from late August 1992.
Summer
7.
Tropics
–
The tropics are a region of the Earth surrounding the equator. The tropics are also referred to as the zone and the torrid zone. The tropics include all the areas on the Earth where the Sun is at a point directly overhead at least once during the solar year. The tropics are distinguished from the climatic and biomatic regions of Earth, which are the middle latitudes. Tropical is sometimes used in a sense for a tropical climate to mean warm to hot and moist year-round. Many tropical areas have a dry and wet season, the wet season, rainy season or green season, is the time of year, ranging from one or more months, when most of the average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics, under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is distributed through the year. When the wet season occurs during the season, or summer, precipitation falls mainly during the late afternoon. The wet season is a time when air quality improves, freshwater quality improves and vegetation grows significantly, floods cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients diminish and erosion increases, the incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for the wetter regime, unfortunately, the previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Regions within the tropics may well not have a tropical climate, there are alpine tundra and snow-capped peaks, including Mauna Kea, Mount Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina. Under the Köppen climate classification, much of the area within the tropics is classed not as tropical but as dry including the Sahara Desert. Tropical plants and animals are those native to the tropics. Tropical ecosystems may consist of rainforests, dry forests, spiny forests, desert. There are often significant areas of biodiversity, and species present, particularly in rainforests. In biogeography, the tropics are divided into Paleotropics and Neotropics, together, they are sometimes referred to as the Pantropic
Tropics
–
Tropical sunset over the sea in
Kota Kinabalu,
Malaysia
Tropics
–
World map with the intertropical zone highlighted in red
Tropics
–
Coconut palms in the warm, tropical climate of Northern
Brazil
Tropics
–
Tropical forest near
Fonds-Saint-Denis,
Martinique
8.
Wet season
–
The rainy season, or monsoon season, is the time of year when most of a regions average annual rainfall occurs. It usually lasts one or more months, the term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics, under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. In contrast to areas with savanna climates and monsoon regimes, Mediterranean climates have wet winters, some areas with pronounced rainy seasons will see a break in rainfall mid-season, when the intertropical convergence zone or monsoon trough moves to higher latitudes in the middle of the warm season. When the wet season occurs during a season, or summer, precipitation falls mainly during the late afternoon. In the wet season, air quality improves, fresh water quality improves, rivers overflow their banks, and some animals retreat to higher ground. Soil nutrients diminish and erosion increases, the incidence of malaria increases in areas where the rainy season coincides with high temperatures, particularly in tropical areas. Some animals have adaptation and survival strategies for the wet season, often, the previous dry season leads to food shortages in the wet season, as the crops have yet to mature. In areas where the rainfall is associated with a wind shift. Further, much of the total each day occurs in the first minutes of the downpour. However, since rain forests have rainfall spread evenly through the year and it is different for places with a Mediterranean climate. This shift in the jet stream brings much of the precipitation to the region. The peninsula of Italy has weather very similar to the western United States in this regard, areas with a savanna climate in Sub-Saharan Africa, such as Ghana, Burkina Faso, Darfur, Eritrea, Ethiopia, and Botswana have a distinct rainy season. Also within the climate regime, Florida and South Texas have a rainy season. Northern Guyana has two wet seasons, one in spring and the other in early winter. In western Africa, there are two rainy seasons across southern sections, but only one across the north. Within the Mediterranean climate regime, the west coast of the United States and the Mediterranean coastline of Italy, Greece, similarly, the wet season in the Negev desert of Israel extends from October through May. At the boundary between the Mediterranean and monsoon climates lies the Sonoran desert, which receives the two rainy seasons associated with each climate regime, the wet season is known by many different local names throughout the world
Wet season
–
Wet season storm at night in
Darwin, Australia.
Wet season
–
Rainfall distribution by month in
Cairns,
Australia.
Wet season
–
Monsoon in the
Vindhya mountain range, central
India.
Wet season
–
Equatorial
savanna in the
East Province of
Cameroon.
9.
Storm
–
A storm is any disturbed state of an environment or astronomical bodys atmosphere especially affecting its surface, and strongly implying severe weather. Heavy snowfall can allow special recreational activities to take place which would not be possible otherwise, the English word comes from Proto-Germanic *sturmaz meaning noise, tumult. Storms are created when a center of low pressure develops with a system of high pressure surrounding it and this combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. Small localized areas of low pressure can form from hot air rising off hot ground, resulting in smaller disturbances such as dust devils, There are many varieties and names for storms, Ice storm — Ice storms are one of the most dangerous forms of winter storms. When surface temperatures are below freezing, but a layer of above-freezing air remains aloft, rain can fall into the freezing layer. In general,8 millimetres of accumulation is all that is required, especially in combination with breezy conditions, Ice storms also make unheated road surfaces too slick to drive upon. Ice storms can vary in range from hours to days and can cripple small towns. Blizzard — There are varying definitions for blizzards, both time and by location. In general, a blizzard is accompanied by winds, heavy snow. Snow storms, especially ones with a liquid equivalent and breezy conditions, can down tree limbs, cut off power. Ocean Storm — Storm conditions out at sea are defined as having sustained winds of 48 knots or greater, usually just referred to as a storm, these systems can sink vessels of all types and sizes. Firestorm — Firestorms are conflagrations which attain such intensity that they create and it is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires. The Peshtigo Fire is one example of a firestorm, Firestorms can also be deliberate effects of targeted explosives such as occurred as a result of the aerial bombings of Dresden. Nuclear detonations generate firestorms if high winds are not present, dust devil — a small, localized updraft of rising air. Wind storm— A storm marked by high wind with little or no precipitation, windstorm damage often opens the door for massive amounts of water and debris to cause further damage to a structure. European windstorms and derechos are two type of windstorms, high wind is also the cause of sandstorms in dry climates. Squall — sudden onset of wind increase of at least 16 knots or greater sustained for at least one minute, gale — An extratropical storm with sustained winds between 34-48 knots. Thunderstorm — A thunderstorm is a type of storm that generates lightning and it is normally accompanied by heavy precipitation
Storm
–
A
shelf cloud associated with a heavy or severe
thunderstorm over
Enschede,
Netherlands.
Storm
–
Desert storms are often accompanied by violent winds, and pass rapidly.
Storm
–
Satellite image of the intense
nor'easter responsible for the
North American blizzard of 2006. Note the
hurricane -like eye at the center.
Storm
–
Classic storm of summer, in
Sierras de Córdoba,
Argentina.
10.
Cloud
–
The experiment began operation in November 2009. The primary goal is to understand the influence of cosmic rays on aerosols and clouds. Although its design is optimised to address the cosmic ray question, CLOUD allows as well to measure aerosol nucleation, atmospheric aerosols and their effect on clouds are recognised by the IPCC as main source of uncertainty in present radiative forcing and climate models. The core of the experiment is a steel chamber of 26m³ volume filled with synthetic air made from liquid nitrogen. The chamber atmosphere and pressure is being measured and regulated by various instrumentations, the aerosol chamber can be exposed to an adjustable particle beam simulating GCRs at various altitude or latitude. The chamber contains a field cage to control the drift of small ions. The ionisation produced by cosmic rays can be removed with an electric field. Besides, humidity and temperature inside the chamber can be regulated, CERN posted a 2009 progress report on the CLOUD project. J. Kirkby reviews developments in the CERN CLOUD project and planned tests and he describes cloud nucleation mechanisms which appear energetically favourable and depend on GCRs. On 24 August 2011, preliminary research published in the journal Nature showed there was a connection between Cosmic Rays and aerosol nucleation, the first CLOUD experiments showed that sulphuric acid as such has a much smaller effect than had been assumed. In 2014, CLOUD researchers presented newer experimental results showing an interaction between oxidised biogenic vapours and sulphuric acid and this new process may account for seasonal variations in atmospheric aerosol particles, which are being related to higher global tree emissions in the northern hemisphere summer. Besides biogenic vapours produced by plants, another class of trace vapours and these are found close to their primary sources, e. g. animal husbandry, while alpha-pinene is generally found over landmasses. The experiments show that sulfuric acid and oxidized organic vapors at low concentrations reproduce suitable particle nucleation rates, CLOUD insofar allows to explain a large fraction of cloud seeds in the lower atmosphere involving sulphuric acid and biogenic aerosols. This result does not support the hypothesis that cosmic rays significantly affect climate, dunne et al. have presented the main outcomes of 10 years of results obtained at the CLOUD experiment performed at CERN. They have studied in detail the physico-chemical mechanisms and the kinetics of aerosols formation
Cloud
11.
Cumulonimbus cloud
–
If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines and these clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may develop as part of a supercell. Cumulonimbus is abbreviated Cb and are designated in the D2 family, towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. The cumulonimbus base may extend several miles across and occupy low to middle altitudes- formed at altitude from approximately 200 to 4,000 m, peaks typically reach to as much as 40,000 ft, with extreme instances as high as 70,000 ft or more. Well-developed cumulonimbus clouds are characterized by a flat, anvil-like top, the shelf of the anvil may precede the main clouds vertical component for many miles, and be accompanied by lightning. Occasionally, rising air parcels surpass the level and form an overshooting top culminating at the maximum parcel level. When vertically developed, this largest of all clouds usually extends through all three cloud regions, even the smallest cumulonimbus cloud dwarfs its neighbors in comparison. Cumulonimbus calvus, cloud with puffy top, similar to cumulus congestus which it develops from, cumulonimbus capillatus, cloud with cirrus-like, fibrous-edged top. Cumulonimbus incus, cloud with anvil top Arcus, low, horizontal cloud formation associated with the edge of thunderstorm outflow. Pannus, accompanied by a layer of fractus species cloud forming in precipitation. Pileus, small cap-like cloud over parent cumulonimbus, velum, a thin horizontal sheet that forms around the middle of a cumulonimbus. Incus, cumulonimbus with flat anvil-like cirriform top caused by wind shear where the air currents hit the inversion layer at the tropopause. Mamma or mammatus, consisting of bubble-like protrusions on the underside, tuba, column hanging from the cloud base which can develop into a funnel cloud or tornado. They are known to very low, sometimes just 20 feet above ground level. Flanking line is a line of small cumulonimbus or cumulus generally associated with severe thunderstorms, rain, precipitation that reaches the ground as liquid, often in a precipitation shaft. Virga, precipitation that evaporates before reaching the ground, cumulonimbus storm cells can produce torrential rain of a convective nature and flash flooding, as well as straight-line winds. Most storm cells die after about 20 minutes, when the precipitation causes more downdraft than updraft, causing the energy to dissipate
Cumulonimbus cloud
–
Cumulonimbus
Cumulonimbus cloud
–
Cumulonimbus calvus
Cumulonimbus cloud
–
A clearly developed cumulonimbus capillatus displaying the classic anvil shape
Cumulonimbus cloud
–
Arcus cloud (shelf cloud) leading a thunderstorm
12.
Arcus cloud
–
An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two types of arcus. Roll clouds also may arise in the absence of thunderstorms, forming along the cold air currents of some sea breeze boundaries. A shelf cloud is a low, horizontal, wedge-shaped arcus cloud, a shelf cloud is attached to the base of the parent cloud, which is usually a thunderstorm, but could form on any type of convective clouds. Rising cloud motion often can be seen in the part of the shelf cloud, while the underside often appears turbulent. Cool, sinking air from a storm clouds downdraft spreads out across the land surface and this outflow cuts under warm air being drawn into the storms updraft. As the lower cooler air lifts the warm moist air, its water condenses, creating a cloud which often rolls with the different winds above, people seeing a shelf cloud may believe they have seen a wall cloud. This is likely a mistake, since an approaching shelf cloud appears to form a wall made of cloud, a shelf cloud usually appears on the leading edge of a storm, and a wall cloud will usually be at the rear of the storm. A sharp, strong gust front will cause the lowest part of the edge of a shelf cloud to be ragged and lined with rising fractus clouds. In a severe case there will be vortices along the edge, a very low shelf cloud accompanied by these signs is the best indicator that a potentially violent wind squall is approaching. An extreme example of this phenomenon looks almost like a tornado and is known as a gustnado, a roll cloud is a low, horizontal, tube-shaped, and relatively rare type of arcus cloud. They differ from shelf clouds by being completely detached from other cloud features, roll clouds usually appear to be rolling about a horizontal axis. They are a wave called a soliton, which is a wave that has a single crest. One of the most famous frequent occurrences is the Morning Glory cloud in Queensland, Australia, one of the main causes of the Morning Glory cloud is the mesoscale circulation associated with sea breezes that develop over the Cape York Peninsula and the Gulf of Carpentaria. However, similar features can be created by downdrafts from thunderstorms and are not exclusively associated with coastal regions. Coastal roll clouds have been seen in places, including California, the English Channel, Shetland Islands, the North Sea coast, coastal regions of Australia. Archived from the original on July 15,2013
Arcus cloud
–
Panorama of a strong shelf cloud, a type of arcus cloud
Arcus cloud
–
A time-lapse photography of shelf cloud just before a
thunderstorm at
Pondicherry
Arcus cloud
–
Underside of a weak shelf cloud
Arcus cloud
–
A shelf cloud over
Enschede,
Netherlands
13.
Downburst
–
A downburst is a strong ground-level wind system that emanates from a point source above and blows radially, that is, in a straight line in all directions, from the point of contact at ground level. Downbursts are created by an area of significantly rain-cooled air that, after reaching ground level, dry downbursts are associated with thunderstorms with very little rain, while wet downbursts are created by thunderstorms with high amounts of rainfall. Microbursts and macrobursts are downbursts at very small and larger scales respectively, another variety, the heat burst, is created by vertical currents on the backside of old outflow boundaries and squall lines where rainfall is lacking. Heat bursts generate significantly higher temperatures due to the lack of rain-cooled air in their formation, Downbursts create vertical wind shear or microbursts, which is dangerous to aviation. This is because the properties of a downburst are completely different from those of a tornado. To differentiate between tornado damage and damage from a downburst, the term straight-line winds is applied to damage from microbursts, Downbursts are particularly strong downdrafts from thunderstorms. Downbursts in air that is free or contains virga are known as dry downbursts. Most downbursts are less than 4 km in extent, these are called microbursts, Downbursts larger than 4 km in extent are sometimes called macrobursts. Downbursts can occur over large areas, straight-line winds are very strong winds that can produce damage, demonstrating a lack of a rotational damage pattern. Such rotational damage patterns are associated with cyclonic storms including tornadoes, straight-line winds are common with the gust front of a thunderstorm or originate with a downburst from a thunderstorm. These events can cause damage, even in the absence of a tornado. The winds can reach 130 km/h and can last for periods of twenty minutes, such straight-line wind events are most common during the spring when instability is highest and weather fronts routinely cross the country. Straight-line wind events in the form of derechos can take place in areas outside of the traditional tornado alley, straight-line winds may be damaging to marine interests. Small ships, cutters and sailboats are at risk from this meteorological phenomenon, the formation of a downburst starts with hail or large raindrops falling through drier air. Hailstones melt and raindrops evaporate, pulling latent heat from surrounding air, cooler air has a higher density than the warmer air around it, so it sinks to the ground. As the cold air hits the ground it out and a mesoscale front can be observed as a gust front. Areas under and immediately adjacent to the downburst are the areas which receive the highest winds and rainfall, also, because the rain-cooled air is descending from the middle troposphere, a significant drop in temperatures is noticed. Due to interaction with the ground, the downburst quickly loses strength as it fans out, Downbursts usually last only a few minutes and then dissipate, except in the case of squall lines and derecho events
Downburst
–
The curl phase soon after an intense microburst had an impact on the surface
Downburst
–
Downburst damages in a straight line. (Source
NOAA)
14.
Microburst
–
A microburst is a small downdraft that moves in a way opposite to a tornado. Microbursts are found in strong thunderstorms, there are two types of microbursts within a thunderstorm, wet microbursts and dry microbursts. They go through three stages in their cycle, the downburst, outburst, and cushion stages, a microburst can be particularly dangerous to aircraft, especially during landing, due to the wind shear caused by its gust front. A microburst often has high winds that can knock over fully grown trees and they usually last from a couple of seconds to several minutes. Fujita also coined the term macroburst for downbursts larger than 4 km, a distinction can be made between a wet microburst which consists of precipitation and a dry microburst which typically consists of virga. Microbursts are recognized as capable of generating wind speeds higher than 75 m/s, Microbursts have also been called air bombs. When rain falls below the base or is mixed with dry air, it begins to evaporate. The cool air descends and accelerates as it approaches the ground, when the cool air approaches the ground, it spreads out in all directions and this divergence of the wind is the signature of the microburst. High winds spread out in type of pattern showing little or no curvature are known as straight-line winds. Wet microbursts are downbursts accompanied by significant precipitation at the surface which are warmer than their environment and these downbursts rely more on the drag of precipitation for downward acceleration of parcels than negative buoyancy which tend to drive dry microbursts. As a result, higher mixing ratios are necessary for these downbursts to form, melting of ice, particularly hail, appears to play an important role in downburst formation, especially in the lowest 1 km above ground level. These factors, among others, make forecasting wet microbursts a difficult task, the evolution of downbursts is broken down into three stages, the contact stage, the outburst stage, and the cushion stage. The virtual temperature correction usually is small and to a good approximation. In some storms this term has an effect on updrafts but there is not much reason to believe it has much of an impact on downdrafts. The second term is the effect of buoyancy on vertical motion, clearly, in the case of microbursts, one expects to find that B is negative meaning the parcel is cooler than its environment. This cooling typically takes place as a result of phase changes, precipitation particles that are small, but are in great quantity, promote a maximum contribution to cooling and, hence, to creation of negative buoyancy. The major contribution to this process is from evaporation, the last term is the effect of water loading. Whereas evaporation is promoted by large numbers of small droplets, it requires a few large drops to contribute substantially to the downward acceleration of air parcels
Microburst
–
Illustration of a microburst The air moves in a downward motion until it hits ground level. It then spreads outward in all directions. The wind regime in a microburst is opposite to that of a tornado.
Microburst
–
Tree damage from a downburst
Microburst
–
Dry microburst schematic
Microburst
–
Wet microburst schematic
15.
Heat burst
–
In meteorology, a heat burst is a rare atmospheric phenomenon characterized by gusty winds and a rapid increase in temperature and decrease in dew point. Heat bursts typically occur during night-time and are associated with decaying thunderstorms, the parcel descends rapidly, warming due to compression, overshoots its equilibrium level and reaches the surface, similar to a downburst. Recorded temperatures during heat bursts have reached well above 38 °C, more extreme events have also been documented, where temperatures have been reported to exceed 120 °F. However, such extreme events have never been officially verified. Heat bursts are characterized by extremely dry air and are sometimes associated with very strong, even damaging. In general, heat bursts occur during the spring and summer seasons. During the late spring and summer seasons, thunderstorms tend to generate day heating, due to a potential temperature increase, heat bursts normally occur at night. In rare cases, heat bursts have been recorded to occur during the daytime as well, Heat bursts have lasted for times spanning from a couple of minutes to several hours. The rare phenomenon is usually accompanied by gusty winds, extreme temperature changes. They occur near the end of a thunderstorm cluster. Dry air and a low-level inversion are also present during the storm, as the thunderstorm starts to dissipate, the layer of clouds start to rise. After the layer of clouds rise, a rain-cooled layer remains, the cluster shoots a burst of unsaturated air down towards the ground. In doing so, the system all of its up-draft related fuel. The raindrops begin to evaporate into dry air, which emphasizes the effects of the heat bursts, as the unsaturated air descends, the air pressure increases. The descending air parcel warms at the dry adiabatic rate of approximately 10° Celsius per 1000 meters of descent. The warm air from the cluster replaces the cool air on the ground, the effect is similar to someone blowing down on a puddle of water. On 4 March 1990, the National Weather Service in Goodland, Kansas detected a system that had weakening, light rain showers and it was followed by gusty winds and a temperature increase. A heat burst was being observed, the detection proved that heat bursts can occur in both summer months and winter months. The occurrence also proved that a thunderstorm was not needed in the development of heat bursts
Heat burst
–
Heat bursts are a variety of downburst.
16.
Dust storm
–
A dust storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand, fine particles are transported by saltation and suspension, a process that moves soil from one place and deposits it in another. Drylands around North Africa and the Arabian peninsula are the main sources of airborne dust. Also with some contributions from Iran, Pakistan and India into the Arabian Sea, the term dust storm is more likely to be used when finer particles are blown long distances, especially when the dust storm affects urban areas. As the force of wind passing over loosely held particles increases, particles of sand first start to vibrate, as they repeatedly strike the ground, they loosen and break off smaller particles of dust which then begin to travel in suspension. At wind speeds above that which causes the smallest to suspend, there will be a population of dust grains moving by a range of mechanisms, suspension, saltation, a study from 2008 finds that the initial saltation of sand particles induces a static electric field by friction. Saltating sand acquires a negative charge relative to the ground which in turn loosens more sand particles which then begin saltating and this process has been found to double the number of particles predicted by previous theories. Particles become loosely held mainly due to drought or arid conditions, gust fronts may be produced by the outflow of rain-cooled air from an intense thunderstorm. S. Following the passage of a dry cold front, convective instability resulting from cooler air riding over heated ground can maintain the dust storm initiated at the front. In desert areas, dust and sand storms are most commonly caused by either thunderstorm outflows, the vertical extent of the dust or sand that is raised is largely determined by the stability of the atmosphere above the ground as well as by the weight of the particulates. In some cases, dust and sand may be confined to a shallow layer by a low-lying temperature inversion. In other instances, dust may be lifted as high as 20,000 feet high, drought and wind contribute to the emergence of dust storms, as do poor farming and grazing practices by exposing the dust and sand to the wind. One poor farming practice which contributes to dust storms is dryland farming, particularly poor dryland farming techniques are intensive tillage or not having established crops or cover crops when storms strike at particularly vulnerable times prior to revegetation. In a semi-arid climate, these practices increase susceptibility to dust storms, however, soil conservation practices may be implemented to control wind erosion. A sandstorm can transport and carry large volumes of sand unexpectedly, Dust storms can carry large amounts of dust, with the leading edge being composed of a wall of thick dust as much as 1.6 km high. Dust and sand storms which come off the Sahara Desert are locally known as a simoom or simoon, the haboob is a sandstorm prevalent in the region of Sudan around Khartoum, with occurrences being most common in the summer. The Sahara desert is a key source of dust storms, particularly the Bodélé Depression and an area covering the confluence of Mauritania, Mali, and Algeria. Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s, causing loss in Niger, Chad, northern Nigeria
Dust storm
–
A sandstorm approaching
Al Asad,
Iraq, just before nightfall on April 27, 2005.
Dust storm
–
A convoy endures a dust storm in Iraq during the
invasion of 2003.
Dust storm
–
A
dust storm in
Sydney which covered most of eastern
Australia in September 2009.
17.
Haboob
–
A haboob is a type of intense dust storm carried on an atmospheric gravity current, also known as a weather front. Haboobs occur regularly in arid regions throughout the world, during thunderstorm formation, winds move in a direction opposite to the storms travel, and they move from all directions into the thunderstorm. When the storm collapses, and begins to release precipitation, wind directions reverse, gusting outward from the storm, Haboobs can also form when a strong thunderstorm weakens rapidly, and releases a microburst. When this downdraft of cold air, or downburst, reaches the ground, it blows dry, loose silt and clay up from the desert and this wall of dust can be up to 100 km wide and several kilometers in elevation. At their strongest, haboob winds often travel at 35–100 km/h, often rain does not appear at ground level as it evaporates in the hot, dry air. The evaporation cools the air even further and accelerates it. Occasionally, when the rain does persist, it can contain a quantity of dust. Severe cases are called mud storms, eye and respiratory system protection are advisable for anyone who must be outside during a haboob. Moving to shelter is highly advised during a strong event, Haboobs have been observed in the Sahara desert, as well as across the Arabian Peninsula, throughout Kuwait, and in the most arid regions of Iraq. Haboob winds in the Arabian Peninsula, Iraq, Kuwait are frequently created by the collapse of a thunderstorm, african haboobs result from the northward summer shift of the inter-tropical front into North Africa, bringing moisture from the Gulf of Guinea. Haboobs in Australia may be associated with cold fronts. As with haboobs in the Arabian Peninsula, Iraq and Kuwait, the arid and semiarid regions of North America—in fact, any dry region—may experience haboobs. In North America, the most common terms for these events are either dust storm or sandstorm. In the U. S. they frequently occur in the deserts of Arizona, including around the cities of Yuma and Phoenix, in New Mexico, including Albuquerque, in eastern California, and in Texas. They also sometimes accur in the Columbia Basin, of Eastern Washington, if the storms are strong enough, they can reach as far east as the Rathdrum Prairie and the Palouse, in the Idaho Panhandle Global dust storms on Mars have been compared to haboobs on Earth. Haboob Photos @ HikeArizona. COM Haboobs, Arizona Department of Transportation, the Bibliography of Aeolian Research Haboob on Winds of the World Short Video of the 5 July 2011 Arizona Haboob on YouTube Time-lapse video of the 5 July 2011 Arizona Haboob
Haboob
–
A haboob moves across the
Llano Estacado toward
Yellow House Canyon, near the residential community of
Ransom Canyon, Texas (18 June 2009)
Haboob
–
A haboob heads into
Albuquerque, summer 2013.
Haboob
–
A haboob closes in on
Nyala Airport
Haboob
–
Dust Bowl era haboob approaching
Spearman, Texas, on 14 April 1935.
18.
Monsoon
–
Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is sometimes used for locally heavy but short-term rains. The major monsoon systems of the world consist of the West African and Asia-Australian monsoons, the inclusion of the North and South American monsoons with incomplete wind reversal has been debated. The south-west monsoon winds are called Nairutya Maarut in India, the English monsoon came from Portuguese monção, ultimately from Arabic mawsim and/or Hindi mausam, perhaps partly via early modern Dutch monsun. Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of the Indian sub-continent and Asia around 50 million years ago. Because of studies of records from the Arabian Sea and that of the wind-blown dust in the Loess Plateau of China, testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program. The monsoon has varied significantly in strength since this time, largely linked to climate change. A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago, then, during ice periods, the sea level fell and the Indonesian Seaway closed. When this happened, cold waters in the Pacific were impeded from flowing into the Indian Ocean and it is believed that the resulting increase in sea surface temperatures in the Indian Ocean increased the intensity of monsoons. Five episodes during the Quaternary at 2.22 Ma,1.83 Ma,0.68 Ma,0.45 Ma and 0.04 Ma were identified which showed a weakening of Leeuwin Current. The weakening of the LC would have an effect on the sea surface temperature field in the Indian Ocean, thus these five intervals could probably be those of considerable lowering of SST in the Indian Ocean and would have influenced Indian monsoon intensity. The impact of monsoon on the weather is different from place to place. In some places there is just a likelihood of having a more or less rain. In other places, quasi semi-deserts are turned into green grasslands where all sorts of plants. The Indian Monsoon turns large parts of India from a kind of semi-desert into green lands, see photos only taken 3 months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, Monsoons are large-scale sea breezes which occur when the temperature on land is significantly warmer or cooler than the temperature of the ocean. These temperature imbalances happen because oceans and land absorb heat in different ways, in contrast, dirt, sand, and rocks have lower heat capacities, and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at an even temperature
Monsoon
–
Advancing monsoon clouds and showers in Aralvaimozhy, near
Nagercoil,
India
Monsoon
–
Monsoon clouds over
Lucknow,
Uttar Pradesh.
Monsoon
–
Western Ghats on May 28 in dry season, 2010
Monsoon
–
Western Ghats on August 28 in rainy season, 2010
19.
Gale
–
A gale is a very strong wind. There are conflicting definitions of how strong a wind must be to be considered a gale, the U. S. National Weather Service defines a gale as 34–47 knots of sustained surface winds. Forecasters typically issue gale warnings when winds of strength are expected. Other sources use minima as low as 28 knots and maxima as high as 90 knots, through 1986, the National Hurricane Center used the term gale to refer to winds of tropical force for coastal areas, between 33 knots and 63 knots. The 90 knots definition is very non-standard, a common alternative definition of the maximum is 55 knots. The most common way of measuring winds is with the Beaufort scale and it is an empirical measure for describing wind speed based mainly on observed sea conditions. Its full name is the Beaufort Wind Force Scale, on the Beaufort Wind Scale, a gale is classified as,7, Moderate Gale,8, Fresh Gale,9, Strong Gale and 10, Storm/Whole Gale. There is a unique Beaufort Scale number and a unique Arrow Indication for each type of Wind Description mentioned above, the word gale is derived from the older gail, but its origin is uncertain
Gale
–
After a Gale – Wreckers by James Hamilton
20.
Sirocco
–
It arises from a warm, dry, tropical airmass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, the Siroccos duration may be as short as half a day or may last several days. Many people attribute health problems to the Sirocco, either because of the heat and dust along the African coastal regions, the dust within the Sirocco winds can cause abrasion in mechanical devices and penetrate buildings. Sirocco winds with speeds of up to 100 kilometres per hour are most common during autumn and they reach a peak in March and in November when it is very hot, with a maximum speed of about 100 km/h. When combined with a tide, the Sirocco can cause the Acqua Alta phenomenon in the Venetian Lagoon. Winds of the world Names of Winds Local Mediterranean winds Sirocco
Sirocco
–
A sirocco from Libya blowing dust over the Mediterranean, Malta, Italy, Croatia, Montenegro, Albania and Greece
Sirocco
–
Tramontane
21.
Firestorm
–
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires and wildfires, although the word has been used to describe certain large fires, the phenomenons determining characteristic is a fire with its own storm-force winds from every point of the compass. The Black Saturday bushfires and the Great Peshtigo Fire are possible examples of forest fires with some portion of combustion due to a firestorm. A firestorm is created as a result of the effect as the heat of the original fire draws in more and more of the surrounding air. This draft can be increased if a low-level jet stream exists over or near the fire. As the updraft mushrooms, strong inwardly-directed gusty winds develop around the fire and this would seem to prevent the firestorm from spreading on the wind, but the tremendous turbulence created may also cause the strong surface inflow winds to change direction erratically. A firestorm may also develop into a mesocyclone and induce true tornadoes/fire whirls and this occurred with the 2002 Durango fire, and probably with the much greater Peshtigo Fire. The greater draft of a firestorm draws in greater quantities of oxygen, the intense heat of a firestorm manifests largely as radiated heat, which may ignite flammable material at a distance ahead of the fire itself. This also serves to expand the area and the intensity of the firestorm, the very high temperatures ignite anything that might possibly burn, until the firestorm runs low on fuel. Thus the fire front is essentially stationary and the spread of fire is prevented by the in-rushing wind. At Hiroshima, this inrushing to feed the fire is said to have prevented the firestorm perimeter from expanding, large wildfire conflagrations are distinct from firestorms if they have moving fire fronts which are driven by the ambient wind and do not develop their own wind system like true firestorms. In Australia, the prevalence of eucalyptus trees that have oil in their leaves results in forest fires that are noted for their extremely tall, hence the bush fires appear more as a firestorm than a simple forest fire. Sometimes, emission of gases from swamps has a similar effect. For instance, methane explosions enforced the Peshtigo Fire, for example, the black rain that began to fall at ~20 minutes after the atomic bombing of Hiroshima produced in total 5–10 cm of black soot-filled rain in a 1–3 hour period. Moreover, if the conditions are right, a large pyrocumulus can grow into a pyrocumulonimbus and produce lightning, apart from city and forest fires, pyrocumulus clouds can also be produced by volcanic eruptions due to the comparable amounts of hot buoyant material formed. The same underlying combustion physics can also apply to structures such as cities during war or natural disaster. Firestorms are thought to have part of the mechanism of large urban fires, such as accompanied the 1906 San Francisco earthquake. Firestorms were also created by the raids of World War II in cities like Hamburg
Firestorm
–
View of one of the
Tillamook Burn fires in August 1933.
Firestorm
–
Picture of a pyro-cumulonimbus taken from a commercial airliner cruising at about 10 km. In 2002 various sensing instruments detected 17 distinct pyrocumulonimbus cloud events in North America alone.
Firestorm
–
Braunschweig burning after aerial firebombing attack in 1944. Notice that a firestorm event has yet to develop in this picture, as single isolated fires are seen burning, and not the single large mass fire that is the identifying characteristic of a firestorm.
Firestorm
–
Hiroshima after the bombing and firestorm. No known aerial photography of the firestorm exists.
22.
Lightning
–
Lightning is a sudden electrostatic discharge that occurs during a thunder storm. This discharge occurs between electrically charged regions of a cloud, between two clouds, or between a cloud and the ground. The charged regions in the atmosphere temporarily equalize themselves through this discharge referred to as an if it hits an object on the ground. Lightning causes light in the form of plasma, and sound in the form of thunder, Lightning may be seen and not heard when it occurs at a distance too great for the sound to carry as far as the light from the strike or flash. This article incorporates public domain material from the National Oceanic and Atmospheric Administration document Understanding Lightning, the details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. The main charging area in a thunderstorm occurs in the part of the storm where air is moving upward rapidly and temperatures range from -15 to -25 Celsius. At that place, the combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets, small ice crystals, the updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is larger and denser. The differences in the movement of the precipitation cause collisions to occur, when the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud, the larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward the lower part of the storm. The result is that the part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. This part of the cloud is called the anvil. While this is the charging process for the thunderstorm cloud. In addition, there is a small but important positive charge buildup near the bottom of the cloud due to the precipitation. Many factors affect the frequency, distribution, strength and physical properties of a lightning flash in a particular region of the world. These factors include ground elevation, latitude, prevailing wind currents, relative humidity, proximity to warm and cold bodies of water, to a certain degree, the ratio between IC, CC and CG lightning may also vary by season in middle latitudes. Lightnings relative unpredictability limits a complete explanation of how or why it occurs, the actual discharge is the final stage of a very complex process. At its peak, a thunderstorm produces three or more strikes to the Earth per minute
Lightning
–
A lightning flash during a
thunderstorm
Lightning
–
Lightning in
Belfort,
France
Lightning
–
View of lightning from an airplane flying above a system.
Lightning
–
A lightning strike from cloud to ground in the California,
Mojave Desert
23.
Supercell
–
A supercell is a thunderstorm that is characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. For this reason, these storms are referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe, supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres away. Supercells are often put into three types, Classic, Low-precipitation, and High-precipitation. LP supercells are found in climates that are more arid, such as the high plains of the United States. Supercells are usually isolated from other thunderstorms, although they can sometimes be embedded in a squall line. Typically, supercells are found in the sector of a low pressure system propagating generally in a north easterly direction in line with the cold front of the low pressure system. Because they can last for hours, they are known as quasi-steady-state storms, supercells have the capability to deviate from the mean wind. If they track to the right or left of the wind, they are said to be right-movers or left-movers. Supercells can sometimes develop two separate updrafts with opposing rotations, which splits the storm into two supercells, one left-mover and one right-mover, supercells can be any size – large or small, low or high topped. They usually produce copious amounts of hail, torrential rainfall, strong winds, supercells are one of the few types of clouds that typically spawn tornadoes within the mesocyclone, although only 30% or fewer do so. Supercells can occur anywhere in the world under the weather conditions. The first storm to be identified as the type was the Wokingham storm over England. Browning did the work that was followed up by Lemon. Supercells occur occasionally in many other regions, including eastern China. The areas with highest frequencies of supercells are similar to those with the most occurrences of tornadoes, see tornado climatology and Tornado Alley. The current conceptual model of a supercell was described in Severe Thunderstorm Evolution and Mesocyclone Structure as Related to Tornadogenesis by Leslie R. Lemon, supercells derive their rotation through tilting of horizontal vorticity caused by wind shear. Strong updrafts lift the air turning about an axis and cause this air to turn about a vertical axis
Supercell
–
A
low precipitation supercell shelf cloud.
Shelf cloud forms when a cooler air mass under-flows the warmer moisture laden air.
Supercell
–
A supercell. While many ordinary thunderstorms (squall line, single-cell, multi-cell) are similar in appearance, supercells are distinguishable by their large-scale rotation.
Supercell
–
Idealized view of an LP supercell
Supercell
–
High precipitation supercell
24.
Thunderstorm
–
Thunderstorms occur in association with a type of cloud known as a cumulonimbus. They are usually accompanied by winds, heavy rain, and sometimes snow, sleet, hail, or, in contrast. Thunderstorms may line up in a series or become a rainband, strong or severe thunderstorms, known as supercells, rotate as do cyclones. Thunderstorms result from the upward movement of warm, moist air. As the warm, moist air moves upward, it cools, condenses, as the rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earths surface, as the droplets fall, they collide with other droplets and become larger. Thunderstorms can form and develop in any location but most frequently within the mid-latitude. Thunderstorms are responsible for the development and formation of many weather phenomena. Thunderstorms, and the phenomena that occur along them, pose great hazards. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, stronger thunderstorm cells are capable of producing tornadoes and waterspouts. There are four types of thunderstorms, single-cell, multi-cell cluster, multi-cell lines, supercell thunderstorms are the strongest and the most associated with severe weather phenomena. Mesoscale convective systems formed by vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the lightning that accompanies them. Several means are used to study thunderstorms, weather radar, weather stations, past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Beyond the Earths atmosphere, thunderstorms have also observed on the planets of Jupiter, Saturn, Neptune. Warm air has a lower density than air, so warmer air rises upwards. Clouds form as relatively warmer air, carrying moisture, rises within cooler air, the moist air rises, and, as it does so, it cools and some of the water vapor in that rising air condenses. If enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form and produce lightning, Meteorological indices such as convective available potential energy and the lifted index can be used to assist in determining potential upward vertical development of clouds
Thunderstorm
–
A thunderstorm over
Corfu.
Thunderstorm
–
A typical thunderstorm over a field
Thunderstorm
–
Warm, moist updraft from a thunderstorm associated with a southward-moving frontal boundary. Taken from Texarkana, Texas looking north.
Thunderstorm
–
Stages of a thunderstorm's life.
25.
Severe thunderstorm
–
Thunderstorms occur in association with a type of cloud known as a cumulonimbus. They are usually accompanied by winds, heavy rain, and sometimes snow, sleet, hail, or, in contrast. Thunderstorms may line up in a series or become a rainband, strong or severe thunderstorms, known as supercells, rotate as do cyclones. Thunderstorms result from the upward movement of warm, moist air. As the warm, moist air moves upward, it cools, condenses, as the rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earths surface, as the droplets fall, they collide with other droplets and become larger. Thunderstorms can form and develop in any location but most frequently within the mid-latitude. Thunderstorms are responsible for the development and formation of many weather phenomena. Thunderstorms, and the phenomena that occur along them, pose great hazards. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, stronger thunderstorm cells are capable of producing tornadoes and waterspouts. There are four types of thunderstorms, single-cell, multi-cell cluster, multi-cell lines, supercell thunderstorms are the strongest and the most associated with severe weather phenomena. Mesoscale convective systems formed by vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the lightning that accompanies them. Several means are used to study thunderstorms, weather radar, weather stations, past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Beyond the Earths atmosphere, thunderstorms have also observed on the planets of Jupiter, Saturn, Neptune. Warm air has a lower density than air, so warmer air rises upwards. Clouds form as relatively warmer air, carrying moisture, rises within cooler air, the moist air rises, and, as it does so, it cools and some of the water vapor in that rising air condenses. If enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form and produce lightning, Meteorological indices such as convective available potential energy and the lifted index can be used to assist in determining potential upward vertical development of clouds
Severe thunderstorm
–
A thunderstorm over
Corfu.
Severe thunderstorm
–
A typical thunderstorm over a field
Severe thunderstorm
–
Warm, moist updraft from a thunderstorm associated with a southward-moving frontal boundary. Taken from Texarkana, Texas looking north.
Severe thunderstorm
–
Stages of a thunderstorm's life.
26.
Storm surge
–
Most casualties during tropical cyclones occur as the result of storm surges. The deadliest storm surge on record was the 1970 Bhola cyclone, the low-lying coast of the Bay of Bengal is particularly vulnerable to surges caused by tropical cyclones. The deadliest storm surge in the twenty-first century was caused by the Cyclone Nargis, the next deadliest in this century was caused by the Typhoon Haiyan, which killed more than 6,000 people in the central Philippines in 2013 and resulted in economic losses estimated at $14 billion. Louis, Diamondhead and Pass Christian in Mississippi, a high storm surge occurred in New York City from Hurricane Sandy in October 2012, with a high tide of 14 ft. The pressure effects of a tropical cyclone will cause the level in the open ocean to rise in regions of low atmospheric pressure. The rising water level will counteract the low pressure such that the total pressure at some plane beneath the water surface remains constant. This effect is estimated at a 10 mm increase in sea level for every millibar drop in atmospheric pressure, strong surface winds cause surface currents at a 45° angle to the wind direction, by an effect known as the Ekman Spiral. Wind stresses cause a phenomenon referred to as wind set-up, which is the tendency for water levels to increase at the downwind shore, intuitively, this is caused by the storm simply blowing the water towards one side of the basin in the direction of its winds. Because the Ekman Spiral effects spread vertically through the water, the effect is proportional to depth. The pressure effect and the wind set-up on an open coast will be driven into bays in the way as the astronomical tide. The Earths rotation causes the Coriolis effect, which bends currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. When this bend brings the currents into more contact with the shore it can amplify the surge. The effect of waves, while powered by the wind, is distinct from a storms wind-powered currents. Powerful wind whips up large, strong waves in the direction of its movement, although these surface waves are responsible for very little water transport in open water, they may be responsible for significant transport near the shore. When waves are breaking on a more or less parallel to the beach. The rainfall effect is experienced predominantly in estuaries, Hurricanes may dump as much as 12 in of rainfall in 24 hours over large areas, and higher rainfall densities in localized areas. As a result, watersheds can quickly surge water into the rivers that drain them and this can increase the water level near the head of tidal estuaries as storm-driven waters surging in from the ocean meet rainfall flowing from the estuary. This situation well exemplified by the southeast coast of Florida
Storm surge
–
Total destruction of the
Bolivar Peninsula (Texas) by
Hurricane Ike 's meteotsunamic storm surge in 2008
Storm surge
–
Extratropical storm surge model (ETSSM) showing negative water levels, developed bt the
National Weather Service. Similar to the SLOSH model, the ETSSM runs off the GFS computer model, and can provide guidance on above or below average water levels in a certain geographical domain as the result of a storm system's influence.
Storm surge
–
Hurricane Ike meteotsunamic storm surge damage in
Gilchrist, Texas in 2008.
27.
Tornado
–
A tornado is a rapidly rotating column of air that spins while in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Most tornadoes have wind speeds less than 110 miles per hour, are about 250 feet across, the most extreme tornadoes can attain wind speeds of more than 300 miles per hour, are more than two miles in diameter, and stay on the ground for dozens of miles. Various types of tornadoes include the multiple vortex tornado, landspout and waterspout, waterspouts are characterized by a spiraling funnel-shaped wind current, connecting to a large cumulus or cumulonimbus cloud. They are generally classified as non-supercellular tornadoes that develop over bodies of water and these spiraling columns of air frequently develop in tropical areas close to the equator, and are less common at high latitudes. Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirls, downbursts are frequently confused with tornadoes, though their action is dissimilar. Tornadoes have been observed and documented on every continent except Antarctica, however, the vast majority of tornadoes occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America. There are several scales for rating the strength of tornadoes, the Fujita scale rates tornadoes by damage caused and has been replaced in some countries by the updated Enhanced Fujita Scale. An F0 or EF0 tornado, the weakest category, damages trees, an F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes, Doppler radar data, photogrammetry, and ground swirl patterns may also be analyzed to determine intensity and assign a rating. The word tornado is a form of the Spanish word tronada. This in turn was taken from the Latin tonare, meaning to thunder and it most likely reached its present form through a combination of the Spanish tronada and tornar, however, this may be a folk etymology. A tornado is also referred to as a twister, and is also sometimes referred to by the old-fashioned colloquial term cyclone. The term cyclone is used as a synonym for tornado in the often-aired 1939 film The Wizard of Oz, the term twister is also used in that film, along with being the title of the 1996 tornado-related film Twister. A tornado is a rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud. For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. Scientists have not yet created a definition of the word, for example. Tornado refers to the vortex of wind, not the condensation cloud and this results in the formation of a visible funnel cloud or condensation funnel. There is some disagreement over the definition of cloud and condensation funnel
Tornado
–
A tornado near
Anadarko, Oklahoma. The funnel is the thin tube reaching from the cloud to the ground. The lower part of this tornado is surrounded by a
translucent dust cloud, kicked up by the tornado's strong winds at the surface. The wind of the tornado has a much wider radius than the funnel itself.
Tornado
–
A tornado near
Seymour, Texas 1987
Tornado
–
This tornado has no funnel cloud; however, the rotating dust cloud indicates that strong winds are occurring at the surface, and thus it is a true tornado.
Tornado
–
A wedge tornado, nearly a mile wide, which hit
Binger, Oklahoma in 1981
28.
Cyclone
–
In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. A cyclone differs from a hurricane or typhoon only on the basis of location, a hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a cyclone occurs in the south Pacific or Indian Ocean. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure, the largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes and dust devils lie within the smaller mesoscale, Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the Tropical Upper Tropospheric Trough during the summer months in the Northern Hemisphere. Cyclones have also seen on extraterrestrial planets, such as Mars. Cyclogenesis describes the process of formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones and these zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their cycle, extratropical cyclones occlude as cold air masses undercut the warmer air. A cyclones track is guided over the course of its 2 to 6 day life cycle by the flow of the subtropical jet stream. Weather fronts mark the boundary between two masses of air of different temperature, humidity, and densities, and are associated with the most prominent meteorological phenomena. Strong cold fronts typically feature narrow bands of thunderstorms and severe weather, such fronts form west of the circulation center and generally move from west to east, warm fronts form east of the cyclone center and are usually preceded by stratiform precipitation and fog. Warm fronts move poleward ahead of the cyclone path, occluded fronts form late in the cyclone life cycle near the center of the cyclone and often wrap around the storm center. Tropical cyclogenesis describes the process of development of tropical cyclones, Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core. Cyclones can transition between extratropical, subtropical, and tropical phases, mesocyclones form as warm core cyclones over land, and can lead to tornado formation. Waterspouts can also form from mesocyclones, but more often develop from environments of high instability, henry Piddington published almost 40 papers dealing with tropical storms from Calcutta between 1835 and 1855 in The Journal of the Asiatic Society. He also coined the term cyclone, meaning the coil of a snake, in 1842, he published his landmark thesis, Laws of the Storms. There are a number of characteristics common to all cyclones
Cyclone
–
An extratropical cyclone near Iceland on September 4, 2003
Cyclone
–
Polar low over the
Barents Sea on February 27, 1987
Cyclone
–
Subtropical Storm Andrea in
2007
Cyclone
–
Cyclone Catarina, a rare
South Atlantic tropical cyclone viewed from the
International Space Station on March 26, 2004
29.
Mesocyclone
–
A mesocyclone is a vortex of air within a convective storm. It is air that rises and rotates around a vertical axis and they are most often cyclonic, that is, associated with a localized low-pressure region within a severe thunderstorm. Such thunderstorms can feature strong surface winds and severe hail, mesocyclones often occur together with updrafts in supercells, within which tornadoes may form at the interchange with certain downdrafts. Mesocyclones are localized, approximately 2 km to 10 km in diameter within strong thunderstorms, thunderstorms containing persistent mesocyclones are supercell thunderstorms. Mesocyclones occur on the mesoscale, a general term used in meteorology to denote organization on scales from a few up to hundreds of kilometers. Doppler radar is used to identify mesocyclones, a mesovortex is a similar but typically smaller and weaker rotational feature associated with squall lines. Mesocyclones form when strong changes of wind speed and/or direction with height sets parts of the part of the atmosphere spinning in invisible tube-like rolls. The convective updraft of a thunderstorm then draw up this spinning air, tilting the rolls orientation upward, the wall cloud tends to form closer to the center of the mesocyclone. As it descends, a funnel cloud may form near its center and this is the first visible stage of tornadogenesis. The best way to detect and verify the presence of a mesocyclone is by Doppler weather radar, nearby high values of opposite sign within velocity data are how they are detected. Thus the word mesocyclone is associated with weather radar terminology, mesocyclones are most often identified in the right-rear flank of supercell thunderstorms and squall lines, and may be distinguished by a hook echo rotation signature on a weather radar map. Visual cues such as a wall cloud or tornado may also hint at the presence of a mesocyclone. This is why the term has entered into wider usage in connection with rotating features in severe storms, tornado formation generally occurs in one of two ways. In the first method, two conditions must be first satisfied, one, an invisible horizontal spinning effect must be first formed upon the Earths surface. This is usually formed by sudden changes in direction or speed. Second, a thundercloud, or occasionally a cumulus cloud, must be present, during a thunderstorm, the updrafts presented are occasionally powerful enough to lift the horizontal spinning row of air upwards, turning it into a vertical air column. This vertical air column then becomes the structure for the tornado. Tornadoes that form in this way are classified as weak tornadoes
Mesocyclone
–
Mesocyclones are sometimes visually identifiable by a rotating wall cloud like the one in this thunderstorm over Texas.
Mesocyclone
–
Storm relative motion of a tornado-producing mesocyclone over Greensburg, Kansas on May 4 2007. The storm was producing an F5 tornado at the time of the image.
Mesocyclone
–
A tornado near
Anadarko, Oklahoma
30.
Anticyclone
–
Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure, sir Francis Galton first discovered anticyclones in the 1860s. Preferred areas within a flow pattern in higher levels of the hydrosphere are beneath the western side of troughs. High-pressure systems are referred to as anticyclones. Their circulation is sometimes referred to as cum sole, subtropical high pressure zones form along the descending portion of the Hadley cell circulation. Upper-level high-pressure areas lie over tropical cyclones due to their warm core nature, surface anticyclones form due to downward motion through the troposphere, the atmospheric layer where weather occurs. Preferred areas within a flow pattern in higher levels of the troposphere are beneath the western side of troughs. Because they weaken with height, these systems are cold. Heating of the earth near the equator forces upward motion and convection along the trough or intertropical convergence zone. The divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft, as air moves towards the mid-latitudes, it cools and sinks leading to subsidence near the 30° parallel of both hemispheres. This circulation known as the Hadley cell forms the subtropical ridge, many of the worlds deserts are caused by these climatological high-pressure areas. Because these anticyclones strengthen with height, they are known as warm core ridges, in the absence of rotation, the wind tends to blow from areas of high pressure to areas of low pressure. The stronger the pressure difference between a system and a low-pressure system, the stronger the wind. The coriolis force caused by Earths rotation gives winds within high-pressure systems their clockwise circulation in the northern hemisphere, friction with land slows down the wind flowing out of high-pressure systems and causes wind to flow more outward from the center. High-pressure systems are associated with light winds at the surface and subsidence of air from higher portions of the troposphere. Subsidence will generally warm an air mass by adiabatic heating, thus, high pressure typically brings clear skies. Because no clouds are present to reflect sunlight during the day, there is more incoming solar radiation, at night, the absence of clouds means that outgoing longwave radiation is not blocked, giving cooler diurnal low temperatures in all seasons. If the surface level relative humidity rises towards 100 percent overnight, the movement of continental arctic air masses to lower latitudes produces strong but vertically shallow high-pressure systems
Anticyclone
–
True color satellite image of an unusual anticyclone off southern
Australia in the Southern Hemisphere, on September 8, 2012, showing a counter-clockwise rotation around an oval area of clear skies.
Anticyclone
–
Hadley cell circulation tends to create anticyclonic patterns in the
Horse latitudes, depositing drier air and contributing to the world's great deserts.
Anticyclone
–
The subtropical ridge shows up as a large area of black (dryness) on this water vapor satellite image from September 2000.
Anticyclone
–
Golden Gate Bridge in fog
31.
Tropical cyclone
–
Depending on its location and strength, a tropical cyclone is referred to by names such as hurricane, typhoon /taɪˈfuːn/, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface and this energy source differs from that of mid-latitude cyclonic storms, such as noreasters and European windstorms, which are fueled primarily by horizontal temperature contrasts. The strong rotating winds of a tropical cyclone are a result of the conservation of momentum imparted by the Earths rotation as air flows inwards toward the axis of rotation. As a result, they form within 5° of the equator. Tropical cyclones are typically between 100 and 2,000 km in diameter, Tropical refers to the geographical origin of these systems, which form almost exclusively over tropical seas. Cyclone refers to their nature, with wind blowing counterclockwise in the Northern Hemisphere. The opposite direction of circulation is due to the Coriolis effect, in addition to strong winds and rain, tropical cyclones are capable of generating high waves, damaging storm surge, and tornadoes. They typically weaken rapidly over land where they are cut off from their energy source. For this reason, coastal regions are vulnerable to damage from a tropical cyclone as compared to inland regions. Heavy rains, however, can cause significant flooding inland, though their effects on human populations are often devastating, tropical cyclones can relieve drought conditions. They also carry heat away from the tropics and transport it toward temperate latitudes. Tropical cyclones are areas of low pressure in the troposphere. On Earth, the pressures recorded at the centers of tropical cyclones are among the lowest ever observed at sea level, the environment near the center of tropical cyclones is warmer than the surroundings at all altitudes, thus they are characterized as warm core systems. The near-surface wind field of a cyclone is characterized by air rotating rapidly around a center of circulation while also flowing radially inwards. At the outer edge of the storm, air may be nearly calm, however, due to the Earths rotation, as air flows radially inward, it begins to rotate cyclonically in order to conserve angular momentum. At an inner radius, air begins to ascend to the top of the troposphere and this radius is typically coincident with the inner radius of the eyewall, and has the strongest near-surface winds of the storm, consequently, it is known as the radius of maximum winds. Once aloft, air flows away from the center, producing a shield of cirrus clouds
Tropical cyclone
–
Hurricane Isabel (2003) as seen from orbit during
Expedition 7 of the
International Space Station. The
eye, eyewall, and surrounding
rainbands, characteristics of tropical
cyclones, are clearly visible in this view from space.
Tropical cyclone
–
Typhoon Nabi as seen from the
International Space Station, on September 3, 2005.
Tropical cyclone
–
Map of the cumulative tracks of all tropical cyclones during the 1985–2005 time period. The
Pacific Ocean west of the
International Date Line sees more tropical cyclones than any other basin, while there is almost no activity in the
Atlantic Ocean south of the
Equator.
Tropical cyclone
–
Tropical Storm Franklin, an example of a strongly
sheared tropical cyclone in the
North Atlantic hurricane basin during
2005
32.
Extratropical cyclone
–
Extratropical cyclones are capable of producing anything from cloudiness and mild showers to heavy gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale low pressure systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, the term cyclone applies to numerous types of low pressure areas, one of which is the extratropical cyclone. The descriptor extratropical signifies that this type of cyclone generally occurs outside the tropics and they are termed mid-latitude cyclones if they form within those latitudes, or post-tropical cyclones if a tropical cyclone has intruded into the mid latitudes. Weather forecasters and the public often describe them simply as depressions or lows. Terms like frontal cyclone, frontal depression, frontal low, extratropical low, non-tropical low, Extratropical cyclones are classified mainly as baroclinic, because they form along zones of temperature and dewpoint gradient known as frontal zones. They can become barotropic late in their cycle, when the distribution of heat around the cyclone becomes fairly uniform with its radius. Extratropical cyclones form anywhere within the regions of the Earth. A study of extratropical cyclones in the Southern Hemisphere shows that between the 30th and 70th parallels, there are an average of 37 cyclones in existence during any 6-hour period, a separate study in the Northern Hemisphere suggests that approximately 234 significant extratropical cyclones form each winter. Extratropical cyclones form along linear bands of temperature/dewpoint gradient with significant vertical wind shear, initially, cyclogenesis, or low pressure formation, occurs along frontal zones near a favorable quadrant of a maximum in the upper level jetstream known as a jet streak. The favorable quadrants are usually at the rear and left front quadrants. The divergence causes air to rush out from the top of the air column and this in turn forces convergence in the low-level wind field and increased upward motion within the column. The increased upward motion causes atmospheric pressure at ground level to lower and this is because the upward air motion counteracts gravity, lessening the weight of the atmosphere in that location. The lowered pressure strengthens the cyclone, as the cyclone strengthens, the cold front sweeps towards the equator and moves around the back of the cyclone. Meanwhile, its associated warm front progresses more slowly, as the air ahead of the system is denser. Later, the cyclones occlude as the portion of the cold front overtakes a section of the warm front, forcing a tongue, or trowal. Eventually, the cyclone will become cold and begin to weaken. Atmospheric pressure can fall very rapidly when there are upper level forces on the system
Extratropical cyclone
–
Approximate areas of extratropical cyclone formation worldwide
Extratropical cyclone
Extratropical cyclone
–
Hurricane Florence in the north Atlantic after completing its transition to an extratropical cyclone from a hurricane
Extratropical cyclone
–
QuikSCAT image of typical extratropical cyclones over the ocean. Note the maximum winds are on the outside of the occlusion.
33.
European windstorm
–
European windstorm is a name given to the strongest extratropical cyclones which occur across the continent of Europe. They form as cyclonic windstorms associated with areas of low atmospheric pressure and they are most common in the autumn and winter months. On average, the month when most windstorms form is January, the seasonal average is 4.6 windstorms. However, when they track further south they can affect almost any country in Europe and these phenomena vary in terms of physical mechanisms, atmospheric structure, spatial extent, duration, severity level, predictability, and location relative to cyclone and fronts. On average these storms cause economic damage €1.9 billion per year and they rank as the second highest cause of global natural catastrophe insurance loss. Up to the half of the 19th century, European windstorms were named after the person who spotted them. Usually, they would be named either by the year, the date, however, a storm may still be named differently in different countries. 2011 storm Dagmar in Norway and Sweden is known as Patrick in Germany, an alternative Scottish naming system arose in 2011 via social media/Twitter which resulted in the humorous naming of Hurricane Bawbag and Hurricane Fannybaws. Such usage of the term Hurricane is not without precedent, as the 1968 Scotland storm was referred to as Hurricane Low Q, the UK Met Office and Irish forecasting service Met Éireann held discussions about developing a common naming system for Atlantic storms. An independent forecaster, the European Windstorm Centre, also has its own naming list, the university subsequently started to name every area of high or low pressure within its weather forecasts, from a list of 260 male and 260 female names submitted by its students. The female names were assigned to areas of low pressure while male names were assigned to areas of high pressure, the DWD subsequently banned the usage of the names by their offices during July 1991, after complaints had poured in about the naming system. However, the order was leaked to the German press agency, Deutsche Presse-Agentur, Germanys ZDF television channel subsequently ran a phone in poll on 17 July 1991 and claimed that 72% of the 40,000 responses favored keeping the names. This made the DWD pause and think about the naming system, during 1998 a debate started about if it was discrimination to name areas of high pressure with male names and the areas of low pressure with female names. The issue was resolved by alternating male and female names each year. The naming comes with the chance that the system will be notable. The money raised by this is used by the department to maintain weather observations at the Free University. Several European languages use cognates of the word huracán to indicate particularly strong winds occurring in Europe. The term hurricane as applied to these storms is not in reference to the structurally different tropical cyclone of the same name, in English, use of term hurricane to refer to European windstorms is mostly discouraged, as these storms do not display the structure of tropical storms
European windstorm
–
Conceptual model for a European Windstorm and the associated strong wind 'footprints'. Note that storm track, footprint locations and footprint sizes vary by case, and that all footprints are not always present.
European windstorm
–
2015 list of storm names from UK
Met Office and
Met Eireann
European windstorm
–
Satellite picture of
Cyclone Oratia on 30 October 2000
European windstorm
–
Damaged pylon in Germany after
Windstorm Kyrill 2007
34.
Atlantic Hurricane
–
An Atlantic hurricane or tropical storm is a tropical cyclone that forms in the Atlantic Ocean, usually in the summer or fall. A hurricane differs from a cyclone or typhoon only on the basis of location, a hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a cyclone occurs in the south Pacific or Indian Ocean. Tropical cyclones can be categorized by intensity, Tropical storms have one-minute maximum sustained winds of at least 39 mph, while hurricanes have one-minute maximum sustained winds exceeding 74 mph. Most North Atlantic tropical storms and hurricanes form between June 1 and November 30, in recent times, tropical disturbances that reach tropical storm intensity are named from a predetermined list. On average, in the North Atlantic basin 11.3 named storms occur each season, the climatological peak of activity is around September 11 each season. In March 2004, Catarina was the first hurricane-intensity tropical cyclone recorded in the Southern Atlantic Ocean. Tropical cyclones are steered by the flow throughout the depth of the troposphere. Specifically, air flow around high pressure systems and toward low pressure areas influence hurricane tracks, south of the subtropical ridge, surface easterly winds prevail. If the subtropical ridge is weakened by a trough, a tropical cyclone may turn poleward and then recurve. Poleward of the ridge, westerly winds prevail and generally steer tropical cyclones that reach northern latitudes toward the east. The westerlies also steer extratropical cyclones with their cold and warm fronts from west to east, generally speaking, the intensity of a tropical cyclone is determined by either the storms maximum sustained winds or lowest barometric pressure. The following table lists the most intense Atlantic hurricanes in terms of their lowest barometric pressure, in terms of wind speed, Hurricane Allen was the strongest Atlantic tropical cyclone on record, with maximum sustained winds of 190 mph. However, these measurements are suspect since instrumentation used to document wind speeds at the time would likely succumb to winds of such intensity, nonetheless, their central pressures are low enough to rank them among the strongest recorded Atlantic hurricanes. Owing to their intensity, the strongest Atlantic hurricanes have all attained Category 5 classification, Hurricane Opal, the strongest Category 4 hurricane recorded, intensified to reach a minimum pressure of 916 mbar, a pressure typical of Category 5 hurricanes. Nonetheless, the pressure remains too high to list Opal as one of the ten strongest Atlantic tropical cyclones, however, this was later superseded by Hurricane Patricia in 2015 in the east Pacific, which had a pressure reading of 872 mbar. Preceding Wilma is Hurricane Gilbert, which had held the record for most intense Atlantic hurricane for 17 years. The 1935 Labor Day hurricane, with a pressure of 892 mbar, is the third strongest Atlantic hurricane, since the measurements taken during Wilma and Gilbert were documented using dropsonde, this pressure remains the lowest measured over land. However, with a pressure of 895 mbar, Rita is the strongest tropical cyclone ever recorded in the Gulf of Mexico
Atlantic Hurricane
–
Tracks of North Atlantic tropical cyclones (1851—2012)
Atlantic Hurricane
–
The subtropical ridge (in the Pacific) shows up as a large area of black (dryness) on this water vapor satellite image from September 2000
Atlantic Hurricane
–
Hurricane Katrina was the costliest and one of the five deadliest hurricanes in the history of the United States
35.
Typhoon
–
A typhoon is a mature tropical cyclone that develops in the western part of the North Pacific Ocean between 180° and 100°E. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, for organizational purposes, the northern Pacific Ocean is divided into three regions, the eastern, central, and western. While the RSMC names each system, the name list itself is coordinated among 18 countries that have territories threatened by typhoons each year. Only the Philippines use their own naming list for systems approaching the country, a typhoon differs from a cyclone or hurricane only on the basis of location. A hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, within the northwestern Pacific there are no official typhoon seasons as tropical cyclones form throughout the year. While the majority of storms form between June and November, a few storms do occur between December and May, on average, the northwestern Pacific features the most numerous and intense tropical cyclones globally. Like other basins, they are steered by the ridge towards the west or northwest, with some systems recurving near. The Philippines receive the brunt of the landfalls, with China, some of the deadliest typhoons in history have struck China. Southern China has the longest record of typhoon impacts for the region, Taiwan has received the wettest known typhoon on record for the northwest Pacific tropical cyclone basins. The term typhoon is the name in the northwest Pacific for a severe tropical cyclone, whereas hurricane is the regional term in the northeast Pacific. Elsewhere this is called a cyclone, severe tropical cyclone. The Oxford English Dictionary cites Urdu ṭūfān and Chinese tai fung giving rise to early forms in English. The earliest forms -- touffon, later tufan, tuffon, and others -- derive from Urdu ṭūfān, from 1699 appears tuffoon, later tiffoon, derived from Chinese with spelling influenced by the older Urdu-derived forms. The modern spelling dates to 1820, preceded by tay-fun in 1771 and ty-foong. The Urdu source word توفان ṭūfān comes via Persian from Arabic طوفان, the Chinese source is the word tai fung, cited as a common dialect form of Mandarin dà big and fēng wind. In Mandarin the word for the windstorm is 大风 and in Cantonese 大風, the modern Japanese word is also derived from Chinese, 台風. The first character in Japanese has a modern meaning of pedestal or stand. So the Japanese characters originally had a meaning of typhoon wind, the Ancient Greek Τυφῶν is not unrelated and has secondarily contaminated the word
Typhoon
–
Three different tropical cyclones spinning over the western Pacific Ocean on August 7, 2006. The cyclone on the lower right has intensified into a typhoon.
Typhoon
–
Tracks of all tropical cyclones in the northernwestern
Pacific Ocean between 1980 and 2005. The vertical line to the right is the
International Date Line.
36.
Derecho
–
A derecho is a widespread, long-lived, straight-line wind storm that is associated with a land-based, fast-moving group of severe thunderstorms. Derechos can cause hurricane-force winds, tornadoes, heavy rains, and they may occur at any time of the year and occur as frequently at night as during the daylight hours. Derecho comes from the Spanish word in adjective form for straight, organized areas of thunderstorm activity reinforce pre-existing frontal zones, and can outrun cold fronts. The resultant mesoscale convective system forms at the point of the best upper level divergence in the pattern in the area of best low level inflow. The convection then moves east and toward the equator into the warm sector, when the convection is strong linear or curved, the MCS is called a squall line, with the feature placed at the leading edge of the significant wind shift and pressure rise. Derechos are squall lines that are bow- or spearhead-shaped on weather radar and, thus, squall lines typically bow out due to the formation of a mesoscale high pressure system which forms within the stratiform rain area behind the initial line. This high pressure area is formed due to strong descending motion behind the squall line, the size of the bow may vary, and the storms associated with the bow may die and redevelop. Warm season derechos in the Northern Hemisphere form in west to flow at mid levels of the troposphere with moderate to high levels of instability. Derechos form within environments of low-level warm air advection and significant low-level moisture and its common definition is a thunderstorm complex that produces a damaging wind swath of at least 250 miles, featuring a concentrated area of convectively-induced wind gusts exceeding 50 knots. Some studies add a requirement that no more two or three hours separate any two successive wind reports. Derechos typically possess a high or rapidly increasing forward speed and they have a distinctive appearance on radar with several unique features, such as the rear inflow notch and bookend vortices, and usually they manifest two or more downbursts. There are four types of derechos, Serial derecho – This type of derecho is usually associated with a deep low. Single-bow – A very large bow echo around or upwards of 250 miles long and this type of serial derecho is less common than the multi-bow kind. An example of a serial derecho is the derecho that occurred in association with the October 2010 North American storm complex. Multi-bow – Multiple bow derechos are embedded in a squall line typically around 250 miles long. One example of a serial derecho is a derecho that occurred during the 1993 Storm of the Century in Florida. Because of embedded supercells, tornadoes can spin out of these types of derechos and this is a much more common type of serial derecho than the single-bow kind. Multi-bow serial derechos can be associated with line echo wave patterns on weather radar, progressive derecho – A line of thunderstorms take the bow-shape and may travel for hundreds of miles along stationary fronts
Derecho
–
A shelf cloud along the leading edge of a derecho photographed in
Minnesota
Derecho
–
Composite radar image of the
June 2012 North American derecho (a progressive derecho) as it moved from Indiana to Virginia
Derecho
–
A typical multi-bow serial derecho
Derecho
–
A typical progressive derecho
37.
Landspout
–
A landspout is a term coined by meteorologist Howard B. Bluestein in 1985 for a kind of tornado not associated with the mesocyclone of a thunderstorm, the parent cloud does not contain a preexisting midlevel mesocyclone. The landspout was so named because it looks like a weak Florida Keys waterspout over land, landspouts form during the growth stage of a cumulus congestus cloud by stretching boundary layer vorticity upward and into the cumulus congestuss updraft. They generally are smaller and weaker than supercellular tornadoes and do not contain a mesocyclone or pre-existing rotation in the cloud, because of this, landspouts are rarely detected by Doppler weather radar. Landspouts share a strong resemblance and development process to that of waterspouts, usually taking the form of a translucent, landspouts are considered tornadoes since a rotating column of air is in contact with both the surface and a cumuliform cloud. Not all landspouts are visible, and many are first sighted as debris swirling at the surface before eventually filling in with condensation, landspouts are most common in semi-arid climates characterized by high cloud bases and considerable low-level instability. These conditions tend to favor the High Plains of the United States from Spring through Summer, the potential for damage is further minimized over sparsely populated regions such as the High Plains. Dust devil Gustnado Waterspout Whirlwind Advanced Spotters Field Guide Online Tornado FAQ
Landspout
–
A landspout near
North Platte, Nebraska on May 22, 2004. Note the characteristic smooth, tubular shape, similar to that of a
waterspout.
38.
Dust devil
–
A dust devil is a strong, well-formed, and relatively long-lived whirlwind, ranging from small to large. The primary vertical motion is upward, Dust devils are usually harmless, but can on rare occasions grow large enough to pose a threat to both people and property. They are comparable to tornadoes in both are a weather phenomenon of a vertically oriented rotating column of wind. Most tornadoes are associated with a larger parent circulation, the mesocyclone on the back of a supercell thunderstorm, Dust devils form as a swirling updraft under sunny conditions during fair weather, rarely coming close to the intensity of a tornado. In the southwestern United States, a dust devil is called a dancing devil. In Death Valley, California, it may be called an auger or a dust whirl. The Navajo refer to them as chiindii, ghosts or spirits of dead Navajos, if a chindi spins clockwise, it is said to be a good spirit, if it spins counterclockwise, it is said to be a bad spirit. The Australian English term willy-willy or whirly-whirly is thought to derive from Yindjibarndi or a neighbouring language, in Aboriginal myths, willy-willies represent spirit forms. They are often quite scary spirits, and parents may warn their children if they misbehave. There is a story of the origin of the brolga in which a bad spirit descends from the sky and captures the young being, in Saudi Arabia, Kuwait, Kazakhstan, and Jordan, they often reach hundreds of meters in height and are referred to as djin. Egypt has its fasset el afreet, or ghosts wind, in Iran, this kind of wind is usually called Gerd Baad, or round wind. Among the Kikuyu of Kenya, the dust devil is known as ngoma cia aka, in Brazil, a dust devil is called redemoinho after moinho de vento. In some traditions, it contains a dancing Saci, also, sometimes it is associated to local religion and beliefs. In Portugal it is known locally as remoinho, Dust devils form when hot air near the surface rises quickly through a small pocket of cooler, low-pressure air above it. If conditions are just right, the air may begin to rotate, the secondary flow in the dust devil causes other hot air to speed horizontally inward to the bottom of the newly forming vortex. As more hot air rushes in toward the developing vortex to replace the air that is rising, a dust devil, fully formed, is a funnel-like chimney through which hot air moves, both upwards and in a circle. As the hot air rises, it cools, loses its buoyancy, as it rises, it displaces air which descends outside the core of the vortex. This cool air returning acts as a balance against the spinning hot-air outer wall, the spinning effect, along with surface friction, usually will produce a forward momentum
Dust devil
–
A dust devil in
Arizona.
Dust devil
–
A dust devil in
Kraków,
Poland.
Dust devil
–
A dust devil in
Ramadi,
Iraq.
Dust devil
–
Dust devil on
Mars (
MGS).
39.
Fire whirl
–
A fire whirl – also commonly known as a fire devil, fire tornado, firenado, or fire twister – is a whirlwind induced by a fire and often made up of flame or ash. They usually start with a whirl of wind or smoke, Fire whirls may occur when intense rising heat and turbulent wind conditions combine to form whirling eddies of air. These eddies can contract into a structure that sucks in burning debris. The literal fire tornado is a phenomenon, much more powerful and destructive than the ordinary fire whirl. When this tornado forms in or enters the zone, it fans flames enormously, draws flame and burning debris into itself. A fire tornado is generated by the fires own effect on local airflow, as with any fire whirl, the fire also has to be enormous in order to create a pyrocumulonimbus cloud powerful enough for it to be classified as a supercell thunderstorm. Then the conditions have to be just right in order for a tornado to form. A fire whirl consists of a core of ash, the part that is actually on fire & ash, a fire whirl can reach up to 2,000 °F, hot enough to potentially reignite ashes sucked up from the ground. Often, fire whirls are created when a wildfire or firestorm creates its own wind, the carbon-rich gases released by burning vegetation on the ground are fuel for mvels up the core until it reaches a region where there is enough fresh, heated oxygen to set it ablaze. This causes the tall and skinny appearance of a fire whirls core, real-world fire whirls usually move fairly slowly. Fire whirls can set objects in their paths ablaze and can hurl burning debris out into their surroundings, the winds generated by a fire whirl can also be dangerous. Large fire whirls can create wind speeds of more than 100 mph – strong enough to knock down trees –, Fire whirls can last for an hour or more, and they cannot be extinguished directly. Many whirlwinds were produced by the four-day-long firestorm coincident with conditions that produced severe thunderstorms, a fire tornado, uncommon in New Zealand wildfires, formed on day three of the 2017 Port Hills fires in Christchurch. Pilots estimated the column to be 100 metres high. There are currently three known types of fire whirls, Type 1, Stable and centered over burning area, Type 2, Stable or transient, downwind of burning area. Type 3, Steady or transient, centered over an area adjacent to an asymmetric burning area with wind. There is evidence suggesting that the whirl in the Hifukusho-ato area. Church, Christopher R. John T. Snow, Jean Dessens, intense Atmospheric Vortices Associated with a 1000 MW Fire
Fire whirl
–
A fire whirl with flames in the vortex
Fire whirl
–
Another fire whirl
40.
Waterspout
–
A waterspout is an intense columnar vortex that occurs over a body of water. Some are connected to a cumulus cloud, some to a cumuliform cloud. In the common form, it is a tornado over water. While it is weaker than most of its land counterparts. Most waterspouts dont suck up water, they are small and weak rotating columns of air over water, although rare, waterspouts have been observed in connection with lake-effect snow precipitation bands. Waterspouts exist on a microscale, where their environment is less than two kilometers in width, the cloud from which they develop can be as innocuous as a moderate cumulus, or as great as a supercell. While some waterspouts are strong and tornadic in nature, most are much weaker, weak tornadoes, known as landspouts, have been shown to develop in a similar manner. More than one waterspout can occur in the vicinity at the same time. As many as nine simultaneous waterspouts have been reported on Lake Michigan, waterspouts not associated with a rotating updraft of a supercell thunderstorm are known as non-tornadic or fair-weather waterspouts, and are by far the most common type. Fair-weather waterspouts occur in waters and are associated with dark, flat-bottomed. Waterspouts of this type rapidly develop and dissipate, having life cycles shorter than 20 minutes and they usually rate no higher than EF0 on the Enhanced Fujita scale, generally exhibiting winds of less than 30 m/s. They are most frequently seen in tropical and subtropical climates, with upwards of 400 per year observed in the Florida Keys, fair-weather waterspouts are very similar in both appearance and mechanics to landspouts, and largely behave as such if they move ashore. A tornado which travels from land to a body of water would also be considered a tornadic waterspout, however, in some areas, such as the Adriatic, Aegean and Ionian seas, tornadic waterspouts can make up half of the total number. A winter waterspout, also known as a devil, an icespout, an ice devil. The term winter waterspout is used to differentiate between the warm season waterspout and this rare winter season event. Very little is known about this phenomenon and only six known pictures of this event exist to date, four of which were taken in Ontario, there are a couple of critical criteria for the formation of a winter waterspout. Very cold temperatures need to be present over a body of water enough to produce fog resembling steam above the waters surface. Like the more efficient lake-effect snow events, winds focusing down the axis of long lakes enhance wind convergence and they are not restricted to saltwater, many have been reported on lakes and rivers including the Great Lakes and the St. Lawrence River
Waterspout
–
A waterspout near Florida. The two flares with smoke trails are for indicating wind direction and general speed near the bottom of the photograph.
Waterspout
–
Non-tornadic waterspouts seen from the beach at Kijkduin near
The Hague, the
Netherlands on 27 August 2006.
Waterspout
–
Tornadic waterspout on 15 July 2005 off the coast of
Punta Gorda, Florida, caused by a severe thunderstorm.
Waterspout
–
A large winter waterspout over
Lake Ontario, just off the shore of
Whitby, Ontario on 26 January 1994.
41.
Winter storm
–
In temperate continental climates, these storms are not necessarily restricted to the winter season, but may occur in the late autumn and early spring as well. Very rarely, they may form in summer, though it would have to be a cold summer. Snowstorms are storms where large amounts of snow fall, two inches of snow is enough to create serious disruptions to traffic and school transport. This is particularly true in places where snowfall is not typical, snowfalls in excess of 6 inches are usually universally disruptive. A massive snowstorm with winds and other conditions meeting certain criteria is known as a blizzard. A large number of heavy snowstorms, some of which were blizzards, occurred in the United States during 1888 and 1947 as well as the early and mid-1990s. The snowfall of 1947 exceeded 2 feet with drifts and snow piles from plowing that reached 12 feet and for months, the 1993 Superstorm manifested as a blizzard in most of the affected areas. Large snowstorms could be dangerous, a 6 in snowstorm will make some unplowed roads impassable. Snowstorms exceeding 12 in especially in southern or generally warm climates will cave the roofs of some homes, standing dead trees can also be brought down by the weight of the snow, especially if it is wet or very dense. Even a few inches of dry snow can form drifts many feet high under windy conditions, snowstorms are usually considered less dangerous than ice storms. However, the snow can bring secondary dangers, mountain snowstorms can produce cornices and avalanches. An additional danger, following a winter, is spring flooding if the snow melts suddenly because of a dramatic rise in air temperature. Deaths can occur from hypothermia, infections brought on by frostbite or car accidents due to slippery roads, fires and carbon monoxide poisoning can occur after a storm causes a power outage. There are also cases of heart attacks caused by overexertion while shoveling heavy wet snow. It is difficult to predict what form this precipitation will take, therefore, weather forecasters just predict a wintry mix. Usually, this type of precipitation occurs at temperatures between −2 and 2 °C, snowstorms generally occur when different types of air masses in the mid-latitudes interact. These storms feed on differences in temperature and moisture, initially, a wave is typically formed in the mid levels of the atmosphere as a result of a variety of things, be it a mountain range, injection of vorticity, or several other reasons. The boundaries between the air masses constitute the warm and cold fronts of the new cyclone/storm, snowstorms that produce a lot of snow require an outside source of moisture, such as the Gulf of Mexico or the Atlantic Ocean in the United States
Winter storm
–
Chicago 's Fullerton Harbor looking south during the
January 31–February 2, 2011 North American winter storm (left) and on a clear day for comparison
Winter storm
Winter storm
–
Approaching winter storm in
Salt Lake City.
Winter storm
42.
Ice storm
–
An ice storm is a type of winter storm characterized by freezing rain, also known as a glaze event or, in some parts of the United States, as a silver thaw. The U. S. National Weather Service defines an ice storm as a storm results in the accumulation of at least 0. 25-inch of ice on exposed surfaces. From 1982 to 1994, ice storms were more common than blizzards and they are generally not violent storms but instead are commonly perceived as gentle rains occurring at temperatures just below freezing. The formation of ice begins with a layer of above-freezing air above a layer of sub-freezing temperatures closer to the surface, frozen precipitation melts to rain while falling into the warm air layer, and then begins to refreeze in the cold layer below. If the precipitate refreezes while still in the air, it will land on the ground as sleet, alternatively, the liquid droplets can continue to fall without freezing, passing through the cold air just above the surface. This thin layer of air then cools the rain to a temperature below freezing, however, the drops themselves do not freeze, a phenomenon called supercooling. When the supercooled drops strike ground or anything else below 0 °C, while meteorologists can predict when and where an ice storm will occur, some storms still occur with little or no warning. In the United States, most ice storms are in the part of the country. An ice storm in February 1994 resulted in ice accumulation as far south as Mississippi. More timber was damaged than that caused by Hurricane Camille, an ice storm in eastern Washington in November 1996 directly followed heavy snowfall. The combined weight of the snow and 25 to 37 millimeters of ice caused damage and was considered the most severe ice storm in the Spokane area since 1940. The freezing rain from an ice storm covers everything with heavy, in addition to hazardous driving or walking conditions, branches or even whole trees may break from the weight of ice. Falling branches can block roads, tear down power and telephone lines, even without falling trees and tree branches, the weight of the ice itself can easily snap power lines and also break and bring down power/utility poles, even electricity pylons with steel frames. This can leave people without power for anywhere from days to a month. According to most meteorologists, just one quarter of an inch of ice accumulation can add about 500 pounds of weight per line span, damage from ice storms is easily capable of shutting down entire metropolitan areas. Additionally, the loss of power during ice storms has indirectly caused numerous illnesses, at lower levels, CO poisoning causes symptoms such as nausea, dizziness, fatigue, and headache, but high levels can cause unconsciousness, heart failure, and death. The relatively high incidence of CO poisoning during ice storms occurs due to the use of methods of heating and cooking during prolonged power outages. Gas generators, charcoal and propane barbecues, and kerosene heaters contribute to CO poisoning when they operate in confined locations, CO is produced when appliances burn fuel without enough oxygen present, such as basements and other indoor locations
Ice storm
–
Wires sagging after an ice storm. Besides disrupting transportation, ice storms can disrupt utilities by snapping lines and poles.
Ice storm
–
A graph showing the formation of different kinds of precipitation.
Ice storm
–
Devastation caused by an ice storm
Ice storm
–
A tree covered in ice from the
December 2008 New England ice storm.
43.
Blizzard
–
A blizzard is a severe snowstorm characterized by strong sustained winds of at least 35 mph and lasting for a prolonged period of time—typically three hours or more. A ground blizzard is a condition where snow is not falling but loose snow on the ground is lifted. In the United States, the National Weather Service defines a blizzard as a severe Snow storm characterized by strong winds causing blowing snow that results in low visibilities, the difference between a blizzard and a snowstorm is the strength of the wind, not the amount of snow. While severe cold and large amounts of drifting snow may accompany blizzards, Blizzards can bring whiteout conditions, and can paralyze regions for days at a time, particularly where snowfall is unusual or rare. A severe blizzard has winds over 72 km/h, near zero visibility, in Antarctica, blizzards are associated with winds spilling over the edge of the ice plateau at an average velocity of 160 km/h. Ground blizzard refers to a condition where loose snow or ice on the ground is lifted. The Australia Bureau of Meteorology describes a blizzard as, Violent and very cold wind which is laden with snow, some part, at least, Blizzard conditions of cold temperatures and strong winds can cause wind chill values that can result in hypothermia or frostbite. The wind chill factor is the amount of cooling the body feels due to the combination of wind. They are most common in the Great Plains, the Great Lakes states, and the states along the coast. Another storm system occurs when a cold core low over the Hudson Bay area in Canada is displaced southward over southeastern Canada, the Great Lakes, and New England. When the rapidly moving cold front collides with warmer air coming north from the Gulf of Mexico, strong winds, significant cold air advection. With few trees or other obstructions to wind and blowing. In a true whiteout there is no visible horizon, people can become lost in their own front yards, when the door is only 3 m away, and they would have to feel their way back. Motorists have to stop their cars where they are, as the road is impossible to see, a noreaster is a macro-scale storm along the upper East Coast of the United States and Atlantic Canada. It gets its name from the direction the wind is coming from, the term is most often used in the coastal areas of New England and Atlantic Canada. This type of storm has characteristics similar to a hurricane, more specifically it describes a low-pressure area whose center of rotation is just off the East Coast and whose leading winds in the left-forward quadrant rotate onto land from the northeast. High storm waves may sink ships at sea and cause coastal flooding, notable noreasters include The Great Blizzard of 1888, one of the worst blizzards in U. S. history. It dropped 100–130 cm of snow and had sustained winds of more than 45 miles per hour that produced snowdrifts in excess of 50 feet, railroads were shut down and people were confined to their houses for up to a week
Blizzard
–
Visibility reduced by blowing snow during a blizzard
Blizzard
–
Blizzard into
Tochal Skiing resort,
Tehran and involved skiers.
Blizzard
–
Impact of blizzard in
Serra da Estrela,
Portugal
Blizzard
–
Drifted snow near
Burrow-with-Burrow, Lancashire, England, January 1963
44.
Ground blizzard
–
Ground blizzard refers to a weather condition where loose snow or ice on the ground is lifted and blown by strong winds. While the term ground blizzard is often associated with blowing and drifting snow conditions. Often such criteria will be determined by a countrys governing weather agency or other similar body, in vertical advection conditions, the winds exhibit large-scale upward motion lifting the snow into the atmosphere creating drifting waves of snow up to 500 meters in height. The extreme conditions can quickly bury a two home and make breathing very difficult if not impossible if caught outdoors. Ground blizzards occur throughout the world, however unlike other winter storms, the most important topographic element in a blizzard is the requirement for a vast amount of large open and relatively flat land. Any type of flora, especially coniferous forms, will catch any drifting snow significantly reducing the blizzards effects, the environment must also support temperatures cold enough to prevent any snow on the ground from melting and bonding the ice crystals together. Ground blizzards are most common in the Arctic and Antarctic during seasonal periods, such as the spring. Ground blizzards are common in the Canadian Prairies and U. S Midwest as well as Siberia
Ground blizzard
–
A ground blizzard in Ontario, March 21st, 2004
45.
Snowsquall
–
A snowsquall is a sudden moderately heavy snow fall with blowing snow and strong, gusty surface winds. It is often referred to as a whiteout and is similar to a blizzard but is localized in time or in location, there are two primary types of snowsqualls, lake effect and frontal. When arctic air moves over large expanses of open waters in winter. Whiteout conditions will affect narrow corridors from shores to inland areas aligned along the wind direction. This will be enhanced when the air mass is uplifted by higher elevations. The name originates from the Great Lakes area of North America, regions in lee of oceans, such as the Canadian Maritimes could experience such snowsqualls. The areas affected by lake-effect snow are called snowbelts and deposition rate of many inches of snow per hour are common in these situations, extremely cold air over still warm water in early winter can even produce thundersnow, snow showers accompanied by lightning and thunder. A frontal snowsquall is an intense frontal convective line, when temperature is near freezing at the surface, the strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path and this is similar to a line of thunderstorms in the summer but the tops of the clouds are only 5,000 to 10,000 feet, often difficult to see on radar. Forecasting these types of events is equivalent to summer severe weather forecast for squall lines, presence of a frontal trough with wind shift. However, the dome behind the trough is at 850 mbar instead of a higher level. In cases where there is an amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning. Both types of snowsqualls are very dangerous for motorists and airplanes or generally any traveler unfortunate enough to get stuck in one, the change in conditions is very sudden, and slippery conditions and abrupt loss of visibility due to whiteouts often cause multiple-vehicle collisions. In the case of lake effect snow, heavy amounts of snow can accumulate in short periods of time, possibly causing road closures, for instance, on January 9,2015, a localized, heavy snow squall caused a 193-vehicle pile-up on I-94 highway near Galesburg, Michigan
Snowsquall
–
A hybrid Frontal-Lake Effect Snowsquall hitting Toronto, Canada during rush hour.
Snowsquall
–
Radar trace of lake effect snowsqualls off the Great Lakes from US radars
Snowsquall
–
Radar image of a strong snowsquall off Lake Huron in December 2010. This particular storm dumped well over 200cm of snow north of
London, Ontario. [
citation needed]
Snowsquall
–
A linear single banded snow squall over Southern Ontario
46.
Precipitation
–
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, rain, sleet, snow, graupel, Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and precipitates. Thus, fog and mist are not precipitation but suspensions, because the vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated, Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers, moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is active when freezing rain is occurring. A stationary front is often present near the area of freezing rain, provided necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely stratus and cumulonimbus. Eventually, the droplets will grow large enough to form raindrops. Lake-effect snowfall can be locally heavy, thundersnow is possible within a cyclones comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation, on the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. The movement of the trough, or intertropical convergence zone. Precipitation is a component of the water cycle, and is responsible for depositing the fresh water on the planet. Approximately 505,000 cubic kilometres of water falls as precipitation each year,398,000 cubic kilometres of it over the oceans and 107,000 cubic kilometres over land. Given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres, Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Precipitation may occur on celestial bodies, e. g. when it gets cold, Mars has precipitation which most likely takes the form of frost. Precipitation is a component of the water cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 km3 of water falls as precipitation each year,398,000 km3 of it over the oceans, given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres. Mechanisms of producing precipitation include convective, stratiform, and orographic rainfall, Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice
Precipitation
–
A thunderstorm with heavy precipitation
Precipitation
–
Long-term mean precipitation by month
Precipitation
–
Late-summer
rainstorm in
Denmark
Precipitation
–
Lenticular cloud forming due to mountains over Wyoming
47.
Graupel
–
Graupel, also called soft hail or snow pellets, is precipitation that forms when supercooled droplets of water are collected and freeze on falling snowflakes, forming 2–5 mm balls of rime. The term graupel comes from the German language, the METAR code for graupel is GS. Under some atmospheric conditions, snow crystals may encounter supercooled water droplets and these droplets, which have a diameter of about 10 µm, can exist in the liquid state at temperatures as low as −40 °C, far below the normal freezing point. Contact between a crystal and the supercooled droplets results in freezing of the liquid droplets onto the surface of the crystal. This process of growth is known as accretion. Crystals that exhibit frozen droplets on their surfaces are referred to as rimed. When this process continues so that the shape of the snow crystal is no longer identifiable. Graupel was formerly referred to by meteorologists as soft hail, however, graupel is easily distinguishable from hail in both the shape and strength of the pellet and the circumstances in which it falls. Ice from hail is formed in hard, relatively uniform layers, graupel forms fragile, oblong shapes and falls in place of typical snowflakes in wintry mix situations, often in concert with ice pellets. Graupel is also fragile enough that it will fall apart when touched. However, observations of snow crystals with a scanning electron microscope clearly show cloud droplets measuring up to 50 µm on the surface of the crystals. The rime has been observed on all four forms of snow crystals, including plates, dendrites, columns. As the riming process continues, the mass of frozen, accumulated cloud droplets obscures the form of the snow crystal. Graupel commonly forms in high-altitude climates and is denser and more granular than ordinary snow, due to its rimed exterior. Macroscopically, graupel resembles small beads of polystyrene, the combination of density and low viscosity makes fresh layers of graupel unstable on slopes, and layers of 20–30 cm present a high risk of dangerous slab avalanches. In addition, thinner layers of graupel falling at low temperatures can act as ball bearings below subsequent falls of more stable snow. Graupel tends to compact and stabilise approximately one or two days after falling, depending on the temperature and the properties of the graupel, merriam-Webster Online Dictionary, accessed September 12,2006. The Weather Channel, accessed September 12,2006, national Snow and Ice Data Center, accessed September 12,2006
Graupel
–
Handful of graupel pellets.
Graupel
–
Falling graupel
Graupel
–
Graupel encasing an unseen snow crystal.
Graupel
–
Rime on both ends of a columnar snow crystal.
48.
Hail
–
Hail is a form of solid precipitation. It is distinct from ice pellets, though the two are often confused and it consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets falls generally in cold weather while hail growth is inhibited during cold surface temperatures. Unlike graupel, which is made of rime, and ice pellets, the METAR reporting code for hail 5 mm or greater is GR, while smaller hailstones and graupel are coded GS. Hail is possible within most thunderstorms as it is produced by cumulonimbus, Hail formation requires environments of strong, upward motion of air with the parent thunderstorm and lowered heights of the freezing level. In the mid-latitudes, hail forms near the interiors of continents, while in the tropics, there are methods available to detect hail-producing thunderstorms using weather satellites and weather radar imagery. Severe weather warnings are issued for hail when the stones reach a size, as it can cause serious damage to human-made structures and, most commonly. Any thunderstorm which produces hail that reaches the ground is known as a hailstorm, Hail has a diameter of 5 millimetres or more. Hailstones can grow to 15 centimetres and weigh more than 0.5 kilograms, unlike ice pellets, hailstones are layered and can be irregular and clumped together. Although the diameter of hail is varied, in the United States, stones larger than 2 cm are usually considered large enough to cause damage. The Meteorological Service of Canada issues severe thunderstorm warnings when hail that size or above is expected, the US National Weather Service has a 2.5 cm or greater in diameter threshold, effective January 2010, an increase over the previous threshold of ¾-inch hail. Other countries have different thresholds according local sensitivity to hail, for grape growing areas could be adversely impacted by smaller hailstones. Hailstones can be large or very small, depending on how strong the updraft is. These types of strong updrafts can also indicate the presence of a tornado, the growth rate is maximized where air is near a temperature of −13 °C. Like other precipitation in clouds, hail begins as water droplets. As the droplets rise and the temperature goes below freezing, they become supercooled water, a cross-section through a large hailstone shows an onion-like structure. This means the hailstone is made of thick and translucent layers, alternating layers that are thin, white. Former theory suggested that hailstones were subjected to multiple descents and ascents, falling into a zone of humidity and this up and down motion was thought to be responsible for the successive layers of the hailstone
Hail
–
A hailstorm in
San Jose,
CA,
Hail
–
A large hailstone, about 6 cm (2.4 in) in diameter
Hail
–
Hail shaft
Hail
–
Severe thunderstorms containing hail can exhibit a characteristic green coloration
49.
Ice pellets
–
Ice pellets are a form of precipitation consisting of small, translucent balls of ice. Pellets generally do not freeze into a solid mass unless mixed with freezing rain, the METAR code for ice pellets is PL. Ice pellets are known to Americans as sleet, the term used by the U. S. National Weather Service. However, the term refers to a mixture of rain and snow in most Commonwealth countries. Because of this, Environment Canada never uses the term sleet, Ice pellets form when a layer of above-freezing air is located between 1,500 and 3,000 meters above the ground, with sub-freezing air both above and below it. This causes the partial or complete melting of any snowflakes falling through the warm layer, as they fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets. However, if the layer beneath the warm layer is too small. In most parts of the world, ice pellets only occur for brief periods, in these areas, ice pellet accumulations of 2–5 cm are not unheard of. The effects of a significant accumulation of ice pellets are not unlike an accumulation of snow, one significant difference is that for the same volume of snow, an equal volume of ice pellets is significantly heavier and thus more difficult to clear away. Additionally, a volume of ice pellets takes significantly longer to melt compared to a volume of fresh snowfall. Freezing rain Graupel Hail Sleet Media related to Ice pellets at Wikimedia Commons
Ice pellets
–
An accumulation of ice pellets
Ice pellets
–
Ice pellets next to a
U.S. penny for scale
50.
Diamond dust
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Diamond dust is a ground-level cloud composed of tiny ice crystals. This meteorological phenomenon is referred to simply as ice crystals and is reported in the METAR code as IC. Diamond dust generally forms under otherwise clear or nearly clear skies and it is most commonly observed in Antarctica and the Arctic, but it can occur anywhere with a temperature well below freezing. In polar regions diamond dust may continue for days without interruption. Diamond dust is similar to fog in that it is a cloud based at the surface, however, generally fog refers to a cloud composed of liquid water. Also, fog is a dense enough cloud to significantly reduce visibility, while diamond dust is very thin. However, diamond dust can often reduce the visibility, in cases to under 600 m. The depth of the diamond dust layer can vary substantially from as little as 20 to 30 m to 300 metres. Because diamond dust does not always reduce visibility it is often first noticed by the brief flashes caused when the crystals, tumbling through the air. This glittering effect gives the phenomenon its name since it looks like many tiny diamonds are flashing in the air. Serial photos of Diamond Dust These ice crystals form when a temperature inversion is present at the surface. If the relative humidity increase near the surface is large enough then ice crystals may form, to form diamond dust the temperature must be below the freezing point of water,0 °C, or the ice cannot form or would melt. However, diamond dust is not often observed at temperatures near 0 °C, at temperatures between 0 °C and about −39 °C increasing the relative humidity can cause either fog or diamond dust. This is because small droplets of water can remain liquid well below the freezing point. In the interior of Antarctica diamond dust is common at temperatures below about −25 °C. Diamond dust is often associated with halos, such as sun dogs, light pillars, like the ice crystals in cirrus or cirrostratus clouds, diamond dust crystals form directly as simple hexagonal ice crystals — as opposed to freezing drops — and generally form slowly. This combination results in crystals with well defined shapes - usually either hexagonal plates or columns - which, like a prism, can reflect and/or refract light in specific directions. While diamond dust can be seen in any area of the world that has cold winters, it is most frequent in the interior of Antarctica, once melted, the total precipitation for the year was only 25 mm
Diamond dust
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Halo display at the South Pole (1980), featuring a
parhelion,
22° halo,
parhelic circle,
upper tangent arc and
Parry arc. Diamond dust is visible as point-like reflections of individual crystals close to the camera.
Diamond dust
Diamond dust
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Subhorizon halos in
Ischgl:
subsun, subparhelion and partial 22° halo, with the glint of ice crystals around the subsun.
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This article incorporates text from a publication now in the public domain: Chambers, Ephraim, ed. (1728). "article name needed". Cyclopædia, or an Universal Dictionary of Arts and Sciences (first ed.). James and John Knapton, et al.
This article incorporates text from a publication now in the 
