Tropical Cyclone

See also: Cyclone, Hurricane, Typhoon

In Meteorology, a tropical cyclone is a type of Cyclone (depression) which takes form in the oceans of the intertropical zone . Structurally, a tropical cyclone is a broad zone of Nuage S stormy in rotation around its center and accompanied by forts Vent S. One can classify them in the category of the systems convectifs of méso-scale since they have a diameter lower than a traditional depression, said synoptic , and that their principal energy source is the release of Latent heat caused by the steam condensation in altitude in their storms. One can thus regard the tropical cyclone as a heat engine, within the meaning of the Thermodynamique.

Importance of condensation as primary source of energy differentiates the tropical cyclones from the other weather phenomena, like the depressions of the average latitudes, which rather draw their energy in the preexistent Gradient S of Température in the atmosphere. To preserve the energy source of its thermodynamic machine, a tropical cyclone must remain above the warm water, which brings the humidity of the atmosphere necessary to him. The strong winds and the reduced atmospheric pressure within the cyclone stimulate the evaporation, which maintains the phenomenon.

The heat emission latent in the higher levels of the storm raises the temperature inside the cyclone from 15 to 20 °C above the room temperature in the Troposphère outside the cyclone. For this reason, one says tropical cyclones which they are storms with “hot core”. Let us note however that this hot core is present only in altitude - the affected area by the cyclone on the surface is usually colder of a few degrees compared to the normal, because of the clouds and the Précipitation.

Classification and terminology

Types

See also: Nomenclature of the tropical cyclones

The tropical cyclones are divided into three principal groups: tropical depressions, tropical storms, and a third group whose name varies according to the areas.

  • a Tropical depression is an organized system of clouds, water and storms with an atmospheric circulation defined on the surface and constant winds maximum of less than 17 Mètre S by second (33 node S or 38 mi/h or 62 km/h)

  • a Tropical storm is an organized system of clouds, water and storms with a circulation defined on the surface and constant winds maximum between 17 and 33 meters a second (34-63 node or 39-73 mi/h or 62-119 km/h)

  • a tropical cyclone whose maximum constant wind exceeds 33 meters a second (approximately 119 km/h). The term used varies according to the areas, as follows:

    • Hurricane (disputed origin: of Hurican , the Caribbean one for “Gods of the evil” or Arawak huracana meaning “wind of summer”) in the Atlantic Northern, the Peaceful ocean in the east of the date-line, and the Southern Pacific in the east of 160°E
    • Typhoon in the Northern Pacific in the west of the date-line
    • tropical Cyclone in the South-western Pacific in the west of 160°E, and in the Indian Ocean.

This terminology is defined by the World Meteorological Organization (OMM).

In other places in the world, the tropical cyclones received the names of Baguio to the Filipino , of Chubasco to the Mexico and Taino in Haiti. The term Willy-willy often found in the literature as a local term in Australia is erroneous because it indicates in fact a Swirl of dust,

Categories

See also: Scale of Saffir-Simpson

One uses a scale from 1 to 5 to categorize the hurricanes according to the force of their wind, according to the scale of Saffir-Simpson. An hurricane force 1 has the weakest winds, whereas an hurricane force 5 is most intense. This classification is relative, bus of the cyclones of category lower can all the same cause damage higher than those of the higher categories, according to the struck place and the dangers which they cause. In fact, the tropical storms can they also cause serious damage and losses of life, especially because of the floods.

The National Hurricane Center (the center of forecast of the tropical cyclones to the the United States) classifies the hurricanes of category 3 and more as being major hurricanes . The Joint Typhoon Warning Center classifies the typhoons whose winds reach at least 150 mi/h (241 km/h) as being super typhoons .

The definition of constant winds recommended by the OMM is a ten minutes average. This definition is adopted by the majority of the countries. However, some countries use different definitions: the United States, for example, defines the winds supported under the terms of a one minute average, measured with 10 meters above surface.

The ingredients of a tropical cyclone include a preexistent weather disturbance, hot tropical seas, moisture, and relatively weak winds in altitude. If the requirements persist sufficiently a long time, they can combine to produce the incredible strong winds, waves, the torrential rains, and the Inondation S which are associated with this phenomenon.

There exists a polar counterpart with the tropical cyclone, called the polar Cyclone, whose extreme is the polar Dépression.

Baptism of the cyclones

See also: Nomenclature of the tropical cyclones

The fact of giving a first name to the tropical cyclones goes back to more than two centuries (18th). That meets a need to differentiate each event from the precedents. Thus the Spaniards gave to the cyclone the name of patron saint of the day. The hurricanes having struck Puerto Rico, the September 13rd 1876 then 1928, are called both San Felipe. The last had struck the day before the Guadeloupe and remains called the " Large Cyclone" of 1928.

The American army, of the beginning of the 20th century until the Second world war, was accustomed to using the phonetic alphabet of the military transmissions with the year. In 1949, this system was officialized in the Northern Atlantique. But at the end of three years, in 1953, the repetitive list was replaced by another list using, like often in the army, of the exclusively female first names. In 1954, the preceding list was taken again, but it was decided to change list each year.

Since 1979, following criticisms of the feminist movements, the tropical cyclones are baptized with first names alternatively male and female. A principle of cycles was also established. Based on 6 years and six lists, the even years begin with a male first name and odd a female first name. Thus the list of 2000 is the same one as that of 1994; the list of 2001 shows those of 1989 and 1995.

But at the time of serious cyclones, the names of the latter are removed list and are replaced in order not to shock the population by pointing out too bad memories to him. Thus, in the list 2004, Matthew replaced the name of Mitch. The Ouragan Mitch killed approximately 18.000 people in the Central America in 1998. The first names are first names in English, Spanish and French.

The six lists lay down 21 current first names of has to W but without Q nor U, rather low in first names. Then, it is envisaged to use the Greek letters. In 2005, year of record with 27 cyclones, the list was completely used until Wilma, then to the Greek letter Zeta.

As the tropical cyclones are not limited to the Atlantique basin, of the similar lists are made for the various sectors of the Atlantic Oceans, the Pacific and Indien:

  • In the basin of the Atlantic Ocean, the National Hurricane Center (NHC) of Miami is officially charged to name the cyclones.
  • the basin of the Pacific Ocean is divided between several sectors considering its extent. The NHC of Miami names those of the portion Is, the NHC of Honolulu of center-north, the Japanese center of that north-western and south-west return to the Bureau off Meteorology (BOM) Australian and in the weather centers of Fiji and New Guinea-News-Guinea.
  • the denomination in the Indian Ocean returns with the BOM and the weather center of the Mauritius according to the sector. However, in the sectors north, Indian Sub-continent and Arabia, the cyclones are not named.

Places of formation

Almost all the tropical cyclones are formed with less 30° of the equator and 87% are formed with less 20° of this one. As the Force of Coriolis gives to the cyclones their initial rotation, those are seldom formed with less 10° of the equator (the horizontal component of the force of Coriolis is null at the equator) the formation of a tropical cyclone inside this limit is however possible if another source of initial rotation appears. These conditions are extremely rare and such storms are formed, believes one, less once by century.

The majority of the tropical cyclones are formed in a band of tropical storms which encircles the terrestrial sphere, and which one calls the Zone of intertropical convergence (ZCIT).

All over the world, it is formed on average 80 tropical cyclones per year.

Principal basins

There are seven principal basins of formation of the tropical cyclones:

  • west of the Northern Pacific: the tropical cyclones in this area often affect the China and Taiwan, the Filipino Japan and the . They are called there typhoons (Chinese:　台风 (taifeng)). It is the most active basin by far, cash for the third of all the tropical cyclones in the world. National weather agencies, as well as the Joint Typhoon Warning Center (JTWC) have the responsibility to emit the forecasts and the warnings in this basin.

  • is of the Northern Pacific: it is about the second most active zone in the world, and also densest (the greatest number of storms in a relatively reduced zone of ocean). The storms which are formed in this basin can reach the west of the Mexico, Hawaii and very seldom the California. The Central Pacific Hurricane Center is responsible for the forecasts for the western part of this zone, and the National Hurricane Center is in charge of the part is.
  • is of the Southern Pacific: the cyclones in this area generally affect the Australia and the Oceania. They are followed and envisaged by Australia and New Guinea. They reach sometimes the New Caledonia.
  • the north of the Indian Ocean: one divides this basin into two areas, the Bay of Bengal and the Mer of Arabia. The Bay of Bengal dominates the calculation, with 5 to 6 times more cyclones than the sea of Arabia. The cyclones which are formed in this basin are historically most fatal. Particularly let us note the Cyclone of Bhola of 1970, which made 200.000 victims. The countries affected by this basin include the India, the Bangladesh, the Sri Lanka, the Thailand, the Burma and the Pakistan. Each one of these countries emits forecasts and warnings. On rare occasions, a cyclone coming from this basin can affect the Péninsule of Arabia. As in 1981 when a tropical storm with touched the détoit of Ormuz and the sultanate of Oman and poured completely unusual quantities of water in this area (65 Millimetre S with Mascate).
  • the south-east of the Indian Ocean: the cyclones being formed in this area affect Australia and the Indonesia. They are followed and envisaged by these countries. They also touch the Iles Coconuts and the Christmas island.
  • the south-west of the Indian Ocean: it is about the basin the least best included/understood, because of a lack of historical data. The cyclones being formed here affect Madagascar, the Mozambique, the island of the Meeting, the island Rodrigues, the Mauritius, the the Comoros (of which Mayotte), the Tanzania and the Kenya. The forecasts for these cyclones are emitted by the Specialized Regional Weather Center of the island of the Meeting, service of Weather-France. The baptisms are on the other hand carried out by the weather center of Mauritius and that of Madagascar.
  • North Atlantic: it is the tropical basin more studied. It includes the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. The number of tropical cyclones formed in this basin largely varies from one year to another, between only one and a score. They are called there hurricanes (of Spanish huracàn). The the United States, the Mexico, the Central America, the Caribbean and the Canada can be affected by these cyclones. The forecasts for these cyclones are emitted for all the countries of the area by the National Hurricane Center, based with Miami (Florida); the Canadian Center of forecast of hurricane, based with Halifax (Nova Scotia) emits forecasts and warnings concerning the tropical cyclones which threaten the territory and Canadian water.

Unusual zones of formation

The following zones very seldom produce tropical cyclones:

  • South Atlantic: less hot water, the absence of a zone of intertropical convergence, and the presence of vertical Cisaillement of the wind contribute to make very difficult the formation of cyclones tropical in this area. However two tropical cyclones there were observed: in 1991, a weak tropical storm with broad of the Africa (which with touched the island of Grey waxbill), and the Cyclone Catarina (sometimes also called Aldonça), which struck the Brazilian coast in 2004.

  • the center of the Northern Pacific: shearing in this zone largely limits the chances of development of tropical cyclones. However, this area is often attended by cyclones being formed in the basin much more favorable is of the Northern Pacific.
  • the the Mediterranean: storms which seem related by their structure with tropical cyclones produce sometimes in the Mediterranean basin. Such storms were formed in September 1947, September 1969, January 1982, September 1983 and January 1995. The tropical nature of these storms remains matter with debates.
  • Big lakes (North America): although very in north, the large surface of these lakes can become a ground favourable with the intense convectif development when their temperature is with his maximum and that very cold air of altitude passes there in autumn. A storm in 1996 (see Cyclone of 1996 on Lake Huron) on the Lake Huron had characteristics similar to those of a tropical or subtropical cyclone, of which an eye in the center during a short time.
  • the Southern Pacific: without being an area at the strong risk, the southern Pacific in the east of meridian line 180 is not saved by the disturbances of this type. Between 1831 and 1998 at least 30 cyclones (moderate wind equal or higher than 118 km/h) and approximately 22 tropical storms (90km/h

Seasonal character

On the whole of the sphere, the frequency of the tropical cyclones reaches its maximum towards the end of the summer, whereas water is hottest. Each basin has however its own seasonal characteristics.

In the North Atlantic, one season of the hurricanes dissociated well starts at at the beginning of June and finishes at the end of November, with a strong push at the beginning of September. The North-East of the Pacific has one working life broader but similar to that of the Atlantic. The North-West of the Pacific produces tropical cyclones all the year, with a minimum in February and a point at the beginning of September. In the basin of the north of the Indian Ocean, the cyclones are more frequent from April at December, with points in May and in November.

In the southern hemisphere, the formation of tropical cyclones starts at the end of October and finishes in May. The points occur mid-February and at the beginning of March.

Here a summary table which gives the averages of annual events:

Formation and development

See also: Cyclogénèse tropical

The formation of the tropical cyclones is always a subject of intensive scientific research, and is not yet completely included/understood. Five factors are in general necessary so that the formation of a tropical cyclone is possible:

  1. the temperature of the sea must exceed 26,5 degrees Celsius until a depth of at least 60 meters, with a temperature of surface water reaching or exceeding 28 with 29°C. The warm water is the energy source of the tropical cyclones. When these storms move on the ground or colder water they weaken quickly.

  2. the conditions must be favorable to the formation of Orage S. the atmospheric temperature must decrease quickly with altitude, and the average Troposphère must be relatively wet.
  3. a preexistent atmospheric disturbance. The ascending vertical movement within the disturbance helps with the starting of the tropical cyclone. A relatively weak type of atmospheric disturbance, without rotation, called tropical wave is generally used as starting point with the formation of the tropical cyclones.
  4. a distance of more than 10 degrees of the equator. The Force of Coriolis starts the rotation of the cyclone and contributes to its maintenance. In the surroundings of the equator, the horizontal component of the force of Coriolis is quasi-null (null at the equator), which prohibits the development of cyclones.
  5. Absence of vertical shearing of the wind (a change of force or direction of the wind with altitude). Too much shearing damages or destroys the vertical structure of a tropical cyclone, which prevents or harms its development.

On the occasion, a tropical cyclone can be formed apart from these conditions. In 2001, the Typhon Vamei was formed with only 1,5° in the north of the equator, starting from a preexistent disturbance and relatively fresh atmospheric conditions connected to monsoon. It is estimated that the factors which led to the formation of this typhoon repeat only every 400 years. It also happened that cyclones developed with temperature of sea surface with 25 degrees Celsius or less (e.g. Vince in 2005).

When a tropical cyclone of the Atlantic reaches the average latitudes and takes its race towards the east, it can D-intensify in the form of a depression of the barocline type (also called frontal ). Such depressions of the average latitudes are sometimes violent and can on the occasion preserve wind forces of hurricane when they reach Europe.

Structure

An intense tropical cyclone includes/understands the following elements:

  • Depression: all the tropical cyclones are in rotation around a basic zone Atmospheric pressure on the surface of the Earth. The Pression S measured in the center of the tropical cyclones are among lowest that one can measure with the sea level.

  • a dense central cloud cover: a concentrated zone of Storm S and bands of rain surrounding the central depression. The tropical cyclones with a symmetrical central cover tend to be intense and with good to develop.
  • Eye: an intense tropical cyclone develops in its center a zone of subsidence (movement going down). The conditions in the eye are normally calm and without clouds, although the sea can be extremely agitated. The eye is the coldest place of the cyclone on the surface, but hottest in altitude. It is usually of circular form and its diameter varies from 8 to 200 km. In the cyclones of less intensity, the dense central cloud cover covers the center of the cyclone and there is no eye.
  • Wall of the eye: they are a circular band Convection and intense winds on the immediate edge the eye. One finds there the most violent conditions in a tropical cyclone. In the most intense cyclones, one observes a cycle of replacement of the wall of the eye, in virtue of which concentric walls are formed and replace the wall of the eye. The mechanism at the origin of this phenomenon is still badly included/understood.
  • Écoulement diverges: in the higher levels of a tropical cyclone, the winds move away from the center of rotation and express a anticyclonic rotation. The winds of surface are strongly cyclonic, but weaken with altitude and change direction of rotation close to the top of the storm. This is a single characteristic of the tropical cyclones.

Observation

The intense tropical cyclones pose a particular problem as for their observation. As it is about a dangerous oceanic phenomenon, one seldom has instruments on the site even of the cyclone, except when this one passes on an island or an coastal area, or an unfortunate ship is taken in the storm. Even in these cases, the catch of measurements in real-time is not possible that in periphery of the cyclone, where the conditions are less catastrophic.

The catch of measurements within the cyclone is however possible by plane. Planes especially equipped, generally of large turboprop four-engined planes, can fly in the cyclone, directly take measures or remote, and launch probes there.

One can also color the storm by weather Radar, when relatively close to the coasts, giving information on the structure and the intensity of the Précipitation S. the satellite S geostationary and circumpolar can obtain information in visible Lumière and Infrarouge everywhere above the sphere. One draws from it the thickness from the clouds, their temperature, their organization and the position of the system as well as the Température of sea surface. Certain new satellites with low orbit are even equipped with radars.

Effects

The relaxation of heat in a mature tropical cyclone can exceed 2x1019 Watts. That is equivalent clashing a thermonuclear bomb of 10 megatons every 20 minutes. The tropical cyclones with the big wide cause large waves, strong rain, and strong winds. This disturbs the roads of navigation and runs sometimes ships. However, the effects more the devastators of the tropical cyclones occur when they strike the coast and enter the grounds. In this case, a tropical cyclone can cause damage in 4 ways:

  • Strong winds: wind forces of hurricane can damage or destroy vehicles, buildings, bridges, etc the strong winds can also transform remains into projectiles, which makes the environment external even more dangerous.

  • Wave of storm: the storms of wind, including the tropical cyclones, can cause a rise of the sea level and floods in the coastal areas.
  • strong Rain: the storms and the strong rains cause the formation of torrents, washing the roads and causing landslides. At the end of November 2004, one of these rainy episodes touched the north of Philippines and makes some 500 dead and missings.
  • Tornado S: the storms imbricated in the cyclone often give rise to tornadoes. Although these tornadoes are normally less intense than those of not-tropical origin, they can still cause immense damage.

The side effects of a tropical cyclone are often also destroying:

  • Epidemic S: moist environment and heat in the days which follow the passage of the cyclone, with in more the destruction of the medical infrastructure, make possible of the epidemics which can take lives in danger a long time after the passage of the cyclone.

  • Power cuts: the tropical cyclones often make heavy damage at electrical installations, depriving of current of tens of thousands of people, cutting the communications and harming the Help!.
  • Problems of transport: the tropical cyclones often destroy bridges, viaducts, and roads. This complicates the transport of vivres, drugs and material of help towards the zones which need some.

Paradoxically, or apparently, the fatal and destroying passage of a tropical cyclone can have positive effects on the economy of the affected regions, and the country in general, or rather on its GDP. For example, in October 2004, after one particularly intense cyclone season in the Atlantic, 71  000 jobs were created in the building to repair the undergone damage, in particular in Florida.

Notable cyclones

Historical cyclones

Files

There are hardly data written former to the XIXe century on the American continent relating to weather data specifically. In the Far East, the data are much older and complete and there exists, for example, a register of the typhoons on Philippines who occurred between 1348 and 1934.

There exist however scientific methods making it possible to identify and date from the old events, constituting a paleotempestology , term created in 1996. They are in particular the study of the sediments of the coastal lakes showing the presence of sea sand, relative poverty in Oxygène 18, a heavy isotope, which one can find in the rings of the trees or concretions of the caves.

Atlantic Ocean

  • Hurricane of Galveston, in 1900, one of the most serious catastrophes in the United States
  • Camille in 1969, in the south of the United States
  • Hugo, in 1989 on the the Antilles
  • Andrew, in 1992, Louisiana and Florida
  • Floyd, in 1999, along the American coasts , with a strong impact in North Carolina
  • Katrina which seriously damaged La Nouvelle-Orléans in 2005

Pacific Ocean

  • Cyclone Ingrid
  • Cyclone Larry

Indian Ocean

  • Firinga in 1989 on l´ island of the Meeting

Current events

Cyclone season 2004

See also: Cyclone season 2004 (North Atlantic)

  • the March 26th 2004, the first hurricane of the South Atlantic Catarina touched the coasts of the Brésil.

  • the September 18th 2004, the tropical storm Jeanne devastation Haiti and makes more than 3000 dead.
  • the October 10th 2004, the typhoon My one moves away from Tokyo to the Japan: ten deaths counted. One measured winds of 140 km/h and important Précipitation S. This cyclone was the twenty-second of the Asia-Pacific surface and the ninth to strike Japan since June 2004 directly. The previous week, the Typhoon Meari, had fact 22 died and six missings.
  • In 2004, the Rananim typhoon made 164 died and 1.800 wounded in China. One estimated the economic losses at 18 billion euros.
  • the season of the cyclones from June in October 2004 has been one of most fatal for several years: 23 cyclones were counted in the Asia-Pacific zone. The human account of the 10 cyclones having struck the Japan of 102 died. The material assessment in Japan is also important: at least 155 billion Yen S (1,4 billion dollar) of damage. The typhoons more the violent ones in Japan at the 20th century devastated Muroto in 1934 (3 000 dead) and in the Baie of Ise in 1959 (5 000 dead).

Cyclone season 2005

See also: Cyclone season 2005 (North Atlantic)

  • In July 2005, the Ouragan Refusals causes more than 50 dead and of many damage with Cuba. With winds of 300 km/h, it passed to category 4 of the scale of Saffir-Simpson which counts 5 levels. The early character of this hurricane was underlined. At least 1,5 million people were evacuated by the cuban authorities. It also strongly touched the peninsula of the Yucatan to the Mexico.

  • the July 18th 2005 the Haitang typhoon made four died on the island of Taiwan.
  • the August 29th 2005, the Ouragan Katrina after having made 7 died the August 25th in Florida touched the coasts of Louisiana, flooding 80% of the New-Orleans and devastating the town of Biloxi. The winds would have reached 280 km/h in gust. The victims could amount per thousands and the damage of billion dollars.
  • 4 - September 8th: the Nabi typhoon causes the death and the disappearance of 32 people in South Korea and with the Japan. According to the Japanese police force, 143 people are wounded, and nearly 10.000 houses are flooded. The winds had reached 144 km per hour. Nabi is the 14th typhoon of the season in this area of the Asia-Pacific.
  • the September 10th: the Khanun typhoon passes to broad from Taiwan.
  • the September 24th: the Ouragan Rita touches ground with the Texas and causes indirectly by the rise in the sea level, the rupture of a Digue involving a new flood of the New-Orleans.
  • In October 2005, the Hurricane Stan, classified category 1, made 196 died with the Mexico and in Central America because of the catastrophic floods and the landslides.
  • At the end of October 2005: the Hurricane Wilma, born in the Caribbean Sea, causes important Inondation S in the Péninsule of Yucatan, in Haiti and Jamaica before crossing the Florida.
  • At the end of December 2005: the hurricane Epsilon and the tropical storm Zeta, are the final storms in the North Atlantic cyclone season of 2005.

Other cyclone seasons

See too

Internal bonds

  • weather Alarm
    • Cyclone warning
  • Wind
    • Storm
    • Cyclone
  • Cyclone seasons

External bonds

; Governmental or university:

; Deprived:

  • Cyclone, hurricane, typhoon: who are they? by Futura sciences
  • Followed cyclones on [[Google Earth]]
  • Cyclonextrême: allows to follow in real-time the cyclones of the whole world

Random links:Bléomycine | Leader of the government to the Senate (Canada) | Red Danish | Conjecture of Scholz | Izaak Kolthoff | Comté_d'Edwards,_l'Illinois