1.
Bar (unit)
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The bar is a metric unit of pressure, but is not approved as part of the International System of Units. It is defined as equal to 100000 Pa, which is slightly less than the current average atmospheric pressure on Earth at sea level. The bar and the millibar were introduced by the Norwegian meteorologist Vilhelm Bjerknes, use of the bar is deprecated by some professional bodies in some fields. The International Astronomical Union also lists it under Non-SI units and symbols whose continued use is deprecated, as of 2004, the bar is legally recognized in countries of the European Union. Units derived from the bar include the megabar, kilobar, decibar, centibar, the notation bar, though deprecated by various bodies, represents gauge pressure, i. e. pressure in bars above ambient or atmospheric pressure. The bar is defined using the SI derived unit, pascal,1 bar ≡100000 Pa. Thus,1 bar is equal to,100 kPa 1×105 N/m21000000 Ba, notes,1 millibar =1 one-thousandth bar, or 1×10−3 bar 1 millibar =1 hectopascal. The word bar has its origin in the Greek word βάρος, the units official symbol is bar, the earlier symbol b is now deprecated and conflicts with the use of b denoting the unit barn, but it is still encountered, especially as mb to denote the millibar. Between 1793 and 1795, the bar was used for a unit of weight in an early version of the metric system. Atmospheric air pressure is given in millibars where standard sea level pressure is defined as 1013 mbar,101.3,1.013 bar. Despite the millibar not being an SI unit, meteorologists and weather reporters worldwide have long measured air pressure in millibars as the values are convenient, for example, the weather office of Environment Canada uses kilopascals and hectopascals on their weather maps. In contrast, Americans are familiar with the use of the millibar in US reports of hurricanes, in fresh water, there is an approximate numerical equivalence between the change in pressure in decibars and the change in depth from the water surface in metres. Specifically, an increase of 1 decibar occurs for every 1.019716 m increase in depth, in sea water with respect to the gravity variation, the latitude and the geopotential anomaly the pressure can be converted into meters depth according to an empirical formula. As a result, decibars are commonly used in oceanography, many engineers worldwide use the bar as a unit of pressure because, in much of their work, using pascals would involve using very large numbers. In the automotive field, turbocharger boost is often described in bars outside the USA), unicode has characters for mb and bar, but they exist only for compatibility with legacy Asian encodings and are not intended to be used in new documents. The kilobar, equivalent to 100 MPa, is used in geological systems. Bar and bara are sometimes used to indicate absolute pressures and bar and this usage is deprecated and fuller descriptions such as gauge pressure of 2 bar or 2 bar gauge are recommended.0 Unported License but not under the GFDL. Non-SI units accepted for use with the SI
2.
Pascal (unit)
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The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Youngs modulus and ultimate tensile strength. It is defined as one newton per square meter and it is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal which is equal to one millibar, the unit of measurement called standard atmosphere is defined as 101,325 Pa and approximates to the average pressure at sea-level at the latitude 45° N. Meteorological reports typically state atmospheric pressure in hectopascals, the unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre by the 14th General Conference on Weights, one pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre. The unit of measurement called atmosphere or standard atmosphere is 101325 Pa and this value is often used as a reference pressure and specified as such in some national and international standards, such as ISO2787, ISO2533 and ISO5024. In contrast, IUPAC recommends the use of 100 kPa as a standard pressure when reporting the properties of substances, geophysicists use the gigapascal in measuring or calculating tectonic stresses and pressures within the Earth. Medical elastography measures tissue stiffness non-invasively with ultrasound or magnetic resonance imaging, in materials science and engineering, the pascal measures the stiffness, tensile strength and compressive strength of materials. In engineering use, because the pascal represents a small quantity. The pascal is also equivalent to the SI unit of energy density and this applies not only to the thermodynamics of pressurised gases, but also to the energy density of electric, magnetic, and gravitational fields. In measurements of sound pressure, or loudness of sound, one pascal is equal to 94 decibels SPL, the quietest sound a human can hear, known as the threshold of hearing, is 0 dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa, the units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals unit, exceptions include Canada and Portugal, which use kilopascals. In many other fields of science, the SI is preferred, many countries also use the millibar or hectopascal to give aviation altimeter settings. In practically all fields, the kilopascal is used instead. Centimetre of water Metric prefix Orders of magnitude Pascals law
3.
Atlantic hurricane
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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
4.
1920 Atlantic hurricane season
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The 1920 Atlantic hurricane season featured tropical storms and hurricanes only in the month of September. Although no hurricane season was defined at the time, the delineation of such is June 1 to November 30. The first system, a hurricane, developed on September 7 while the last, of note, four of the six cyclones co-existed with another tropical cyclone during the season. Of the seasons six tropical cyclones, five tropical storms. Furthermore, none of these strengthened into a major hurricane—Category 3 or higher on the modern-day Saffir–Simpson hurricane wind scale—marking the seventh such occurrence since 1900, the strongest hurricane of the season peaked as only as a strong Category 2 with winds of 110 mph. The second hurricane caused one death and $1.45 million in damage in Louisiana, the left one fatality in North Carolina. The seasons activity was reflected with an accumulated cyclone energy rating of 30 and it is only calculated for full advisories on tropical systems at or exceeding 39 mph, which is tropical storm strength. The first known storm of the season was identified on September 7 as a 40 mph tropical storm over Atlantic Ocean. Traveling towards the northwest, the storm intensified, attaining hurricane-status late on September 9. The following day, a ship in the vicinity of the recorded a pressure of 985 mbar. Around 1200 UTC, the hurricane turned towards the north and intensified into a modern-day Category 2 hurricane on the Saffir-Simpson Hurricane Scale early on September 11, the storm continued to intensify through September 12 when it reached its peak intensity with winds of 110 mph. After maintaining this intensity for 18 hours, the hurricane began to weaken as it turned towards the northwest, by 0000 UTC on September 14, the storm weakened to a Category 1 hurricane. The system began to undergo a transition, completing the process early the next day. The system tracked nearly due east before dissipating on September 16 to the north of the Azores islands, an area of disturbed weather developed into a tropical depression northwest of Colombia on September 16. Afterwards, it weakened over land, before dissipating on September 23 over eastern Kansas. As it approached the United States Gulf Coast, the forced a estimated 4,500 people to evacuate off of Galveston Island. At landfall, the hurricane generated strong winds along a swath of the coast, uprooting trees and causing damage to homes. Heavy rainfall associated with the peaked at 11.9 in in Robertsdale
5.
1921 Atlantic hurricane season
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The 1921 Atlantic hurricane season ran through the summer and the first half of fall in 1921. The season was average, with six tropical cyclones forming during the season. A tropical storm formed in the western Caribbean before moving across the Yucatan peninsula into the southern Gulf of Mexico, the storm recurved towards the north, strengthening into a category 1 hurricane before it struck Sargent, Texas. During the night of June 21, winds increased to 68 miles per hour at Corpus Christi, a barge with 18,000 gallons of oil sank in Port Aransas, Texas. A storm surge of 7.1 feet was measured at Pass Cavallo, as the cyclone moved inland, it passed directly over Palacios, Texas, Wharton, Texas, and Wallis, Texas. Winds gusted to 60 miles per hour at both Galveston, Texas and Houston, Texas, heavy rains accompanied the system, with 10.10 inches recorded at Matagorda, Texas. A category 1 struck Tampico, Mexico in early September after moving northwest from the Gulf of Mexico, after it dissipated on September 8, an extremely heavy rainfall event ensued across central Texas, which continued into September 11. In Williamson County, Texas, a new 18-hour rainfall record was set for the United States as 36.40 inches was recorded at Thrall, the deluge led to one of the most destructive floods in the history of San Antonio, Texas. Water rose to 7 feet deep in the city, forcing people to evacuate vertically within taller buildings, the most significant river floods occurred on the Little and San Gabriel rivers, where 159 people perished. Combined with the toll from elsewhere across the region,215 people died due to this storm. A Cape Verde-type hurricane, Three formed about 500 miles east of the island of Trinidad and it moved westward and struck the Windward Islands as a Category 1 hurricane. It tracked northward as a Category 2 hurricane and after a short lull was upgraded back to a Category 3 hurricane and it became an extratropical cyclone well off the coast of Newfoundland and accelerated before dissipating about 100 miles off the southern tip of Greenland. A category 1 formed in the Atlantic and never approached land, another notable system was a tropical storm that made a transatlantic journey from off the coast of South Carolina to just southwest of the Azores. It was later determined that it was extratropical for most of the journey, the most notable storm of the season was the Tampa Bay hurricane of 1921. It developed in the southwestern Caribbean Sea on October 20 and it tracked north-northwestward, steadily strengthening into a hurricane on October 22. The storm turned more north-northeastward, and upon reaching the Gulf of Mexico on October 24 it rapidly intensified to a 140 mph Category 4 and it weakened as it continued to the northeast, making landfall north of Clearwater on October 25 as a Category 3 hurricane. It crossed Florida, turned eastward across the Atlantic, and became extratropical on October 28 southwest of Bermuda and its small and quick nature, as well as well-executed warnings, only caused $3 million in damage, with 6 casualties. Tropical Storm Seven formed on November 19 and it made landfall in Cuba before dissipating on November 25
6.
1923 Atlantic hurricane season
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The 1923 Atlantic hurricane season ran its course from Summer through Fall of 1923. The season was slightly below average with 9 tropical storms, of which 4 became hurricanes, on June 19 a weak tropical depression formed from the tail end of a dying cold front, north of Western Bahamas and east of Florida. The tropical depression moved north after its formation. Failing to intensify further it was absorbed by a cold front sweeping down the East Coast on June 22. The peak winds from this system were 25 knts from ship observations on June 19, the lowest pressure was 1012 millibars. Due to the nature of this system and lack of gale winds it was evaluated as a tropical depression and was not included in HURDAT. In 2009 this tropical depression was first detected from Historical Weather Maps when Landsea, early on June 22, a broad area of low pressure was observed in the Bay of Campeche where it intensified into a tropical depression later that day. It remained at that intensity for the three days while drifting slowly northeastward, while its pressure continued to gradually fall. By late June 25, it had begun to become better organized, the storm clipped the southeastern Louisiana and made landfall as a minimal tropical storm over extreme southern Mississippi and Alabama on June 26. Excessive rains fell in the vicinity of the cyclone and further up the East Coast of the United States, the system weakened into a tropical depression while over southeastern Alabama late on June 26. The cyclone turned in a easterly direction under the influence of an extratropical low. On June 27, it regained tropical storm intensity as it reached the Atlantic Ocean off the Georgia–South Carolina coast, on June 28, the cyclone reached a peak intensity of 60 mph and a peripheral pressure of 999 mbar. At this time, the low to the northwest began to affect this tropical storm more heavily. This storm was first introduced to HURDAT in a 2009 reanalysis of the basin, the season began late with a tropical storm observed northeast of Turks and Caicos on August 30. The cyclone turned north and then northeast, very close to Bermuda, after passing Bermuda and reaching hurricane strength, the storm turned north and slowed down. For two days, the storm drifted northward across the Atlantic, reaching a peak intensity of 105 mph. On September 8, the weakened to a Category 1 hurricane. The storm became extratropical shortly before striking Newfoundland, on the evening of September 9 and this tropical storm formed near the coast of Africa on September 7, however it was short lived and never approached land
7.
1924 Atlantic hurricane season
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The 1924 Atlantic hurricane season featured the earliest known Category 5 hurricane – a tropical cyclone with maximum sustained winds exceeding 155 mph. The first system, Tropical Storm One, was first detected in the northwestern Caribbean Sea on June 18, the final system, an unnumbered tropical depression, dissipated on November 24. These dates fall within the period with the most tropical activity in the Atlantic. Of the 13 tropical cyclones of the season, six existed simultaneously, the season was average with 11 tropical storms, three of which strengthened into hurricanes. Further, two of those three intensified into hurricanes, which are Category 3 or higher on the Saffir–Simpson hurricane wind scale. The most significant storm of the season was Hurricane Ten, nicknamed the 1924 Cuba hurricane and it struck western Cuba as a Category 5 hurricane, before weakening and making landfall in Florida as a Category 1 hurricane. Severe damage and 90 fatalities were reported at both locations. Another system, Hurricane Four, brought winds and flooding to the Leeward Islands. The storm left 59 deaths,30 of which were on Montserrat alone, several other tropical cyclones had minor impacts on land, including Tropical Storms One, Eight, and Ten, as well as Hurricanes Three and Five. Overall, the storms of the 1924 Atlantic hurricane season caused at least 150 fatalities. The seasons activity was reflected with a low accumulated cyclone energy rating of 100, ACE is only calculated for full advisories on tropical systems at or exceeding 34 knots or tropical storm strength. A tropical storm was detected 75 miles southeast of Chetumal, Quintana Roo on June 18 and it made landfall on northern Belize with estimated winds near 45 mph. Pressures were progressively decreasing over the days in the northwestern Caribbean Sea. The tropical system crossed the Yucatán Peninsula, emerging over the Bay of Campeche on June 19 with 40 mph winds and it re-strengthened over water and re-attained winds of 45 mph. Early on June 21, the storm made landfall 115 miles south of Tampico, the cyclone was classified as a weak disturbance, and strong winds were not recorded throughout the life span of the storm. Squalls affected the Texas coast, prompting advisories for small watercraft, heavy rainfall was reported in Mexico. Toward the end of July, a cold front off the east coast of Florida resulted in the formation of a tropical storm. The storm tracked northeast, steadily intensifying to reach winds of 65 mph as it passed near the Outer Banks of North Carolina
8.
Tropical cyclone
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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
