The eye is a region of mostly calm weather at the center of strong tropical cyclones. The eye of a storm is a circular area, typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weather occurs, the cyclones lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm. In strong tropical cyclones, the eye is characterized by light winds and clear skies, surrounded on all sides by a towering, symmetric eyewall. In weaker tropical cyclones, the eye is well defined and can be covered by the central dense overcast. Weaker or disorganized storms may feature an eyewall that does not completely encircle the eye or have an eye that features heavy rain. In all storms, the eye is the location of the minimum barometric pressure - where the atmospheric pressure at sea level is the lowest. A typical tropical cyclone will have an eye of approximately 30–65 km across, the eye may be clear or have spotty low clouds, it may be filled with low- and mid-level clouds, or it may be obscured by the central dense overcast.
There is, very little wind and rain, especially near the center and this is in stark contrast to conditions in the eyewall, which contains the storms strongest winds. Due to the mechanics of a cyclone, the eye. While normally quite symmetric, eyes can be oblong and irregular, a large ragged eye is a non-circular eye which appears fragmented, and is an indicator of a weak or weakening tropical cyclone. An open eye is an eye which can be circular, but the eyewall does not completely encircle the eye, indicating a weakening, both of these observations are used to estimate the intensity of tropical cyclones via Dvorak analysis. Eyewalls are typically circular, distinctly polygonal shapes ranging from triangles to hexagons occasionally occur. While typical mature storms have eyes that are a few miles across, rapidly intensifying storms can develop an extremely small, clear. Storms with pinhole eyes are prone to fluctuations in intensity. Small/minuscule eyes—those less than 10 nmi across—often trigger eyewall replacement cycles and this can take place anywhere from fifteen to hundreds of kilometers outside the inner eye.
The storm develops two concentric eyewalls, or an eye within an eye, in most cases, the outer eyewall begins to contract soon after its formation, which chokes off the inner eye and leaves a much larger but more stable eye. While the replacement cycle tends to weaken storms as it occurs and this may trigger another re-strengthen cycle of eyewall replacement
National Hurricane Center
The Technology and Science Branch provides technical support for the center, which includes new infusions of technology from abroad. Research to improve operational forecasts is done through the Hurricane Forecast Improvement Project, during the Atlantic and northeast Pacific hurricane seasons, the Hurricane Specialists Unit issues routine tropical weather outlooks for the northeast Pacific and northern Atlantic oceans. When tropical storm or hurricane conditions are expected within 48 hours, the first hurricane warning service was set up in the 1870s from Cuba with the work of Father Benito Viñes. C. in 1902. The central office in Washington, which evolved into the National Meteorological Center and Weather Prediction Center, Hurricane advisories issued every six hours by the regional hurricane offices began at this time. The Jacksonville hurricane warning office moved to Miami, Florida in 1943, Tropical cyclone naming began for Atlantic tropical cyclones using the Joint Army/Navy Phonetic Alphabet by 1947.
In 1950, the Miami Hurricane Warning Office began to prepare the annual hurricane season summary articles, in the 1953 Atlantic season, the United States Weather Bureau began naming storms which reach tropical storm intensity with human names. The National Hurricane Research Project, begun in the 1950s, used aircraft to study tropical cyclones, on July 1,1956, a National Hurricane Information Center was established in Miami, Florida which became a warehouse for all hurricane-related information from one United States Weather Bureau office. The Miami Hurricane Warning Office moved from Lindsey Hopkins Hotel to the Aviation Building 4 miles to the northwest on July 1,1958, the Miami HWO moved to the campus of the University of Miami in 1964, and was referred to as the NHC in 1965. The Miami HWO tropical cyclone reports were regularly and took on their modern format in 1964. Beginning in 1973, the National Meteorological Center duties gained advisory responsibility for tracking and publicizing inland tropical depressions, the World Meteorological Organization assumed control of the Atlantic hurricane naming list in 1977.
In 1978, the NHCs offices moved off the campus of the University of Miami across U. S. Highway 1 to the IRE Financial Building, male names were added into the hurricane list beginning in the 1979 season. The hurricane warning offices remained active past 1983, in 1984, the NHC was separated from the Miami Weather Service Forecast Office, which meant the meteorologist in charge at Miami was no longer in a position above the hurricane center director. By 1988, the NHC gained responsibility for eastern Pacific tropical cyclones as the former Eastern Pacific Hurricane Center in San Francisco was decommissioned, in 1992, Hurricane Andrew blew the WSR-57 weather radar and the anemometer off the roof of NHCs/the Miami State Weather Forecast offices. The radar was replaced with a WSR-88D NEXRAD system in April 1993 installed near Metro Zoo, in 1995, the NHC moved into a new hurricane-resistant facility on the campus of Florida International University, capable of withstanding 130 mph winds. Its name was changed to the Tropical Prediction Center in 1995, after the name change to TPC, the Hurricane Specialists were grouped as a separate NHC unit under the Tropical Prediction Center, separating themselves from the Tropical Analysis and Forecast Branch.
On October 1,2010, the Tropical Prediction Center was renamed the NHC, the World Meteorological Organization continues to create and maintain the annual hurricane naming lists. Naming lists use a rotation, with the deadliest or most notable storm names retired from the rotation. The director of the National Hurricane Center is Richard Knabb, for the fiscal year of 2008, the budget for the NHC was $6.8 million
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 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, 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
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, can cause significant flooding inland, though their effects on human populations are often devastating, tropical cyclones can relieve drought conditions. They 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 flowing radially inwards. At the outer edge of the storm, air may be nearly calm, 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
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 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, 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 and ground swirl patterns may 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, this may be a folk etymology. A tornado is referred to as a twister, and is 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 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
In earth science, erosion is the action of surface processes that remove soil, rock, or dissolved material from one location on the Earths crust, transport it away to another location. Eroded sediment or solutes may be transported just a few millimetres, the rates at which such processes act control how fast a surface is eroded. Feedbacks are possible between rates of erosion and the amount of eroded material that is carried by, for example. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, while erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the rate of erosion in the region. Excessive erosion causes both on-site and off-site problems, on-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers.
In some cases, the end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of bodies, as well as sediment-related damage to roads. Intensive agriculture, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, and the surface runoff which may result from rainfall, produces four types of soil erosion, splash erosion, sheet erosion, rill erosion. Splash erosion is generally seen as the first and least severe stage in the erosion process. In splash erosion, the impact of a falling raindrop creates a crater in the soil. The distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rate is greater than the rate at which water can infiltrate into the soil.
If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope, sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimetres or less and this means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow
Puerto Rico, officially the Commonwealth of Puerto Rico and briefly called Porto Rico, is an unincorporated territory of the United States located in the northeast Caribbean Sea. It is an archipelago that includes the island of Puerto Rico and a number of smaller ones such as Mona, Culebra. The capital and most populous city is San Juan and its official languages are Spanish and English, though Spanish predominates. The islands population is approximately 3.4 million, Puerto Ricos rich history, tropical climate, diverse natural scenery, renowned traditional cuisine, and attractive tax incentives make it a popular destination for travelers from around the world. Four centuries of Spanish colonial government transformed the ethnic and physical landscapes primarily with waves of African captives, and Canarian. In the Spanish imperial imagination, Puerto Rico played a secondary, in 1898, following the Spanish–American War, the United States appropriated Puerto Rico together with most former Spanish colonies under the terms of the Treaty of Paris.
Puerto Ricans are natural-born citizens of the United States, Puerto Rico does not have a vote in the United States Congress, which governs the territory with full jurisdiction under the Puerto Rico Federal Relations Act of 1950. As a U. S. territory, American citizens residing on the island are disenfranchised at the level and may not vote for president. However, Congress approved a constitution, allowing U. S. citizens on the territory to elect a governor. A fifth referendum will be held in June 2017, with only Statehood, in early 2017, the Puerto Rican government-debt crisis posed serious problems for the government. The outstanding bond debt that had climbed to $70 billion or $12,000 per capita at a time with 12. 4% unemployment, the debt had been increasing during a decade long recession. Puerto Ricans often call the island Borinquen – a derivation of Borikén, its indigenous Taíno name, the terms boricua and borincano derive from Borikén and Borinquen respectively, and are commonly used to identify someone of Puerto Rican heritage.
The island is known in Spanish as la isla del encanto. Columbus named the island San Juan Bautista, in honor of Saint John the Baptist, eventually traders and other maritime visitors came to refer to the entire island as Puerto Rico, while San Juan became the name used for the main trading/shipping port and the capital city. The islands name was changed to Porto Rico by the United States after the Treaty of Paris of 1898, the anglicized name was used by the US government and private enterprises. The name was changed back to Puerto Rico by a joint resolution in Congress introduced by Félix Córdova Dávila in 1931, the ancient history of the archipelago known today as Puerto Rico is not well known. The scarce archaeological findings and early Spanish scholarly accounts from the colonial era constitute the basis of knowledge about them. The first comprehensive book on the history of Puerto Rico was written by Fray Íñigo Abbad y Lasierra in 1786, the first settlers were the Ortoiroid people, an Archaic Period culture of Amerindian hunters and fishermen who migrated from the South American mainland
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 do not suck up water, they are small, 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 that are 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 sub-tropical 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 be considered a tornadic waterspout, however, in some areas, such as the Adriatic and Ionian seas, tornadic waterspouts can make up half of the total number. A winter waterspout, 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
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature, when noted on weather radar imagery, this precipitation elongation is referred to as banded structure. Rainbands within tropical cyclones are curved in orientation, tropical cyclone rainbands contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm. The extent of rainbands around a tropical cyclone can help determine the cyclones intensity, rainbands spawned near and ahead of cold fronts can be squall lines which are able to produce tornadoes. Rainbands associated with cold fronts can be warped by mountain barriers perpendicular to the fronts orientation due to the formation of a low-level barrier jet, bands of thunderstorms can form with sea breeze and land breeze boundaries, if enough moisture is present. If sea breeze rainbands become active enough just ahead of a cold front, banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts of rain or snow.
Behind extratropical cyclones, rainbands can form downwind of relative warm bodies of such as the Great Lakes. If the atmosphere is cold enough, these rainbands can yield heavy snow, rainbands in advance of warm occluded fronts and warm fronts are associated with weak upward motion, and tend to be wide and stratiform in nature. Wider rain bands can occur behind cold fronts, which tend to have more stratiform and these bands in the comma head are associated with areas of frontogensis, or zones of strengthening temperature contrast. Southwest of extratropical cyclones, curved flow bringing cold air across the relatively warm Great Lakes can lead to narrow lake effect snow bands which bring significant localized snowfall, rainbands exist in the periphery of tropical cyclones, which point towards the cyclones center of low pressure. Rainbands within tropical cyclones require ample moisture and a low level pool of cooler air, bands located 80 kilometres to 150 kilometres from a cyclones center migrate outward.
They are capable of producing heavy rains and squalls of wind, as well as tornadoes, some rainbands move closer to the center, forming a secondary, or outer, eyewall within intense hurricanes. Within this method, the extent of banding and difference in temperature between the eye and eyewall is used to assign a maximum sustained wind and a central pressure. Central pressure values for their centers of low pressure derived from this technique are approximate, different programs have been studying these rainbands, including RAINEX. Convective rainbands can form parallel to terrain on its windward side and their spacing is normally 5 kilometres to 10 kilometres apart. If enough moisture is present, sea breeze and land breeze fronts can form convective rainbands, sea breeze front thunderstorm lines can become strong enough to mask the location of an approaching cold front by evening. The edge of ocean currents can lead to the development of bands due to heat differential at this interface. Downwind of islands, bands of showers and thunderstorms can develop due to low level wind convergence downwind of the island edges, offshore California, this has been noted in the wake of cold fronts