Tropical cyclone

• High winds - Hurricane strength winds can damage or destroy vehicles, buildings, bridges, etc. High winds also turn loose debris into flying projectiles, making the outdoor environment even more dangerous.
• Storm surge - Tropical cyclones cause an increase in sea level, which can flood coastal communities. This is the worst effect, as historically cyclones claimed 80% of their victims when they first strike shore.
• Heavy rain - The thunderstorm activity in a tropical cyclone causes intense rainfall. Rivers and streams flood, roads become impassable, and landslides can occur. Inland areas are particularly vulnerable to freshwater flooding, due to residents not preparing adequately.[National Hurricane Preparedness Week: Inland Flooding] accessed March 31, 2006
• Tornado activity - The broad rotation of a hurricane often spawns tornadoes. Also, tornadoes can be spawned as a result of eyewall mesovortices which persist until landfall. While these tornadoes are normally not as strong as their non-tropical counterparts, they can still cause tremendous damage.[FAQ: Hurricanes, typhoons and tropical cyclones] accessed April 24, 2006

The aftermath of Hurricane Katrina in Gulfport, Mississippi. Katrina was the costliest tropical cyclone in United States history.

Often, the secondary effects of a tropical cyclone are equally damaging. These include:

• Disease - The wet environment in the aftermath of a tropical cyclone, combined with the destruction of sanitation facilities and a warm tropical climate, can induce epidemics of disease which claim lives long after the storm passes. One of the most common post-hurricane injuries is stepping on a nail in storm debris, leading to a risk of tetanus or other infection. Infections of cuts and bruises can be greatly amplified by wading in sewage-polluted water. Large areas of standing water caused by flooding also contribute to mosquito-borne illnesses.
• Power outages - Tropical cyclones often knock out power to tens or hundreds of thousands of people (or occasionally millions if a large urban area is affected), prohibiting vital communication and hampering rescue efforts.
• Transportation difficulties - Tropical cyclones often destroy key bridges, overpasses, and roads, complicating efforts to transport food, clean water, and medicine to the areas that need it.

Beneficial effects of tropical cyclones

Hurricanes also help to maintain global heat balance by moving warm, moist tropical air to the mid-latitudes and polar regions.[link] Were it not for the movement of heat poleward (through other means as well as hurricanes), the tropical regions would be unbearably hot. The storm surges and winds of hurricanes may be destructive to human-made structures, but they also stir up the waters of coastal estuaries, which are typically important fish breeding locales.

In addition, the destruction caused by Camille on the Gulf coast spurred redevelopment as well, greatly increasing local property values. On the other hand, disaster response officials point out that redevelopment encourages more people to live in clearly dangerous areas subject to future deadly storms. Hurricane Katrina is the most obvious example, as it devastated the region that had been revitalized after Hurricane Camille. Of course, many former residents and businesses do relocate to inland areas away from the threat of future hurricanes as well.

At sea, tropical cyclones can stir up water, leaving a cool wake behind them. This can cause the region to be less favourable for a subsequent tropical cyclone. On rare occasions, tropical cyclones may actually do the opposite. 2005's Hurricane Dennis blew warm water behind it, contributing to the unprecedented intensity of the close-following Hurricane Emily.[Tropical Storm Emily Discussion 8] accessed May 2, 2006

Long term trends in cyclone activity

Atlantic storms are certainly becoming more destructive financially, since five of the ten most expensive storms in United States history have occurred since 1990. This can, to a large extent, be attributed to the number of people living in susceptible coastal area, and massive development in the region since the last surge in Atlantic hurricane activity in the 1960s.

Often in part because of the threat of hurricanes, many coastal regions had sparse population between major ports until the advent of automobile tourism; therefore, the most severe portions of hurricanes striking the coast often went unmeasured. The combined effects of ship destruction and remote landfall severely limit the number of intense hurricanes in the official record before the era of hurricane reconnaissance aircraft and satellite meteorology. Although the record shows a distinct increase in the number and strength of intense hurricanes, therefore, experts regard the early data as suspect.

The number and strength of Atlantic hurricanes may undergo a 50-70-year cycle. Although more common since 1995, few above-normal hurricane seasons occurred during 1970-1994. Destructive hurricanes struck frequently from 1926-60, including many major New England hurricanes. A record 21 Atlantic tropical storms formed in 1933, only recently exceeded in 2005. Tropical hurricanes occurred infrequently during the seasons of 1900-1925; however, many intense storms formed 1870-1899. During the 1887 season, 19 tropical storms formed, of which a record 4 occurred after 1 November and 11 strengthened into hurricanes. Few hurricanes occurred in the 1840s to 1860s; however, many struck in the early 1800s, including an 1821 storm that made a direct hit on New York City which some historical weather experts say may have been as high as Category 4 in strength.

These unusually active hurricane seasons predated satellite coverage of the Atlantic basin that now enables forecasters to see all tropical cyclones. Before the satellite era began in 1961, tropical storms or hurricanes went undetected unless a ship reported a voyage through the storm. The official record, therefore, probably misses many storms in which no ship experienced gale-force winds, recognized it as a tropical storm (as opposed to a high-latitude extra-tropical cyclone, a tropical wave, or a brief squall), returned to port, and reported the experience.

Global warming

Regarding strength, a similar conclusion was the prevailing consensus, until recently, when it was questioned by Kerry Emanuel. In an article in Nature,[Nature Vol. 436, pp 686–688] accessed March 20, 2006 Emanuel states that the potential hurricane destructiveness, a measure which combines strength, duration, and frequency of hurricanes, "is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multidecadal oscillations in the North Atlantic and North Pacific, and global warming." K. Emanuel further predicts "a substantial increase in hurricane-related losses in the twenty-first century."[Preprint of a paper by Kerry Emanuel] accessed March 20, 2006

Along similar lines, P.J. Webster and others published an article[Webster Science 2005 Hurricanes] accessed March 20, 2006 in Science[Science. Volume 309, pp 1844-1846] examining "changes in tropical cyclone number, duration, and intensity" over the last 35 years, a period where satellite data is available. The main finding is that while the number of cyclones "decreased in all basins except the North Atlantic during the past decade" there is a "large increase in the number and proportion of hurricanes reaching categories 4 and 5." That is, while the number of cyclones decreased overall, the number of very strong cyclones increased.

Both Emanuel and Webster et al., consider the sea surface temperature as of key importance in the development of cyclones. The question then becomes: what caused the observed increase in sea surface temperatures? In the Atlantic, it could be due to the Atlantic Multidecadal Oscillation (AMO), a 50–70 year pattern of temperature variability. Emanuel, however, found the recent temperature increase was outside the range of previous oscillations. So, both a natural variation (such as the AMO) and global warming could have made contributions to the warming of the tropical Atlantic over the past decades, but an exact attribution is so far impossible to make.

While Emanuel analyzes total annual energy dissipation, Webster et al. analyze the slightly less relevant percentage of hurricanes in the combined categories 4 and 5, and find that this percentage has increased in each of six distinct hurricane basins: North Atlantic, North East and North West Pacific, South Pacific, and North and South Indian. Because each individual basin may be subject to intra-basin oscillations similar to the AMO, any single-basin statistic remains open to question. But if the local oscillations are not synchronized by some as-yet-unidentified global oscillation, the independence of the basins allows joint statistical tests that are more powerful than any set of individual basin tests. Unfortunately Webster et al. do not undertake any such test.

Under the assumption that the six basins are statistically independent except for the effect of global warming,[Zfacts] accessed March 20, 2006 has carried out the obvious paired t-test and found that the null-hypothesis of no impact of global warming on the percentage of Category 4 and 5 hurricanes can be rejected at the 0.1% level. Thus, there is only a 1 in 1000 chance of simultaneously finding the observed six increases in the percentages of Category 4 or 5 hurricanes. This statistic needs refining because the variables being tested are not normally distributed with equal variances, but it may provide the best evidence yet that the impact of global warming on hurricane intensity has been detected.

Observation and forecasting

Observation

Sunset view of Hurricane Isidore's rainbands photographed at 7,000 feet.

Intense tropical cyclones pose a particular observation challenge. As they are a dangerous oceanic phenomenon, weather stations are rarely available on the site of the storm itself. Surface level observations are generally available only if the storm is passing over an island or a coastal area, or it has overtaken an unfortunate ship. Even in these cases, real-time measurement taking is generally possible only in the periphery of the cyclone, where conditions are less catastrophic.

It is however possible to take in-situ measurements, in real-time, by sending specially equipped reconnaissance flights into the cyclone. In the Atlantic basin, these flights are regularly flown by United States government hurricane hunters. [Hurricane Hunters homepage] accessed March 30, 2006 The aircraft used are WC-130 Hercules and WP-3D Orions, both four-engine turboprop cargo aircraft. These aircraft fly directly into the cyclone and take direct and remote-sensing measurements. The aircraft also launch GPS dropsondes inside the cyclone. These sondes measure temperature, humidity, pressure, and especially winds between flight level and the ocean's surface.

A new era in hurricane observation began when a remotely piloted Aerosonde, a small drone aircraft, was flown through Tropical Storm Ophelia as it passed Virginia's Eastern Shore during the 2005 hurricane season. This demonstrated a new way to probe the storms at low altitudes that human pilots seldom dare.Bowman, L. "Drones defy heart of storm." [South Mississippi Sun-Herald] accessed March 30, 2006

Tropical cyclones far from land are tracked by weather satellites capturing visible and infrared images from space, usually at half-hour to quarter-hour intervals. As a storm approaches land, it can be observed by land-based Doppler radar. Radar plays a crucial role around landfall because it shows a storm's location and intensity minute by minute.

Recently, academic researchers have begun to deploy mobile weather stations fortified to withstand hurricane-force winds. The two largest programs are the Florida Coastal Monitoring Program [Florida Coastal Monitoring Program project overview] accessed March 30, 2006 and the Wind Engineering Mobile Instrumented Tower Experiment. [WEMITE homepage] accessed March 30, 2006 During landfall, the NOAA Hurricane Research Division compares and verifies data from reconnaissance aircraft, including wind speed data taken at flight level and from GPS dropwindsondes and stepped-frequency microwave radiometers, to wind speed data transmitted in real time from weather stations erected near or at the coast. The National Hurricane Center uses the data to evaluate conditions at landfall and to verify forecasts.

Forecasting

Hurricane Epsilon organized and strengthened despite extremely unfavorable conditions.

Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high- and low-pressure areas, and predicting how those areas will change during the life of a tropical system.

With their understanding of the forces that act on tropical cyclones, and a wealth of data from earth-orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades. High-speed computers and sophisticated simulation software allow forecasters to produce computer models that forecast tropical cyclone tracks based on the future position and strength of high- and low-pressure systems. But while track forecasts have become more accurate than 20 years ago, scientists say they are less skillful at predicting the intensity of tropical cyclones. They attribute the lack of improvement in intensity forecasting to the complexity of tropical systems and an incomplete understanding of factors that affect their development.

Classifications, Terminology and Naming

Intensity classifications

Tropical Depression 19, which formed during the 2005 Atlantic hurricane season, showing the lack of organization in tropical depressions when compared to stronger cyclones.

Tropical cyclones are classified into three main groups, based on intensity: tropical depressions, tropical storms, and a third group of more intense storms, whose name depends on the region.

A tropical depression is an organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds of less than 17 m/s (33 kt, 38 mph, or 62 km/h). It has no eye, and does not typically have the organization or the spiral shape of more powerful storms. It is already a low-pressure system, however, hence the name "depression."

A tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 17 and 32 m/s (34–63 kt, 39–73 mph, or 62–117 km/h). At this point, the distinctive cyclonic shape starts to develop, though an eye is usually not present. Government weather services assign first names to systems that reach this intensity (thus the term named storm).

A tropical cyclone (or hurricane or typhoon) is a system with sustained winds greater than 33 m/s (64 kt, 74 mph, or 118 km/h). A tropical cyclone tends to develop an eye, an area of relative calm (and lowest atmospheric pressure) at the center of circulation. The eye is often visible in satellite images as a small, circular, cloud-free spot. Surrounding the eye is the eyewall, an area about 10–50 mi (16–80 km) wide in which the strongest thunderstorms and winds circulate around the storm's center.

The circulation of clouds around a cyclone's center imparts a distinct spiral shape to the system. Bands or arms may extend over great distances as clouds are drawn toward the cyclone. The direction of the cyclonic circulation depends on the hemisphere; it is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Maximum sustained winds in the strongest tropical cyclones have been measured at more than 85 m/s (165 kt, 190 mph, 305 km/h). Intense, mature hurricanes can sometimes exhibit an inward curving of the eyewall top that resembles a football stadium: this phenomenon is thus sometimes referred to as the stadium effect.

Eyewall replacement cycles naturally occur in intense tropical cyclones. When cyclones reach peak intensity they usually - but not always - have an eyewall and radius of maximum winds that contract to a very small size, around 5 to 15 miles. At this point, some of the outer rainbands may organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and momentum. During this phase, the tropical cyclone is weakening (i.e. the maximum winds die off a bit and the central pressure goes up). Eventually the outer eyewall replaces the inner one completely and the storm can be the same intensity as it was previously or, in some cases, even stronger.

Categories and ranking

Hurricanes are ranked according to their maximum winds using the Saffir-Simpson Hurricane Scale. A Category 1 storm has the lowest maximum winds (74-95 mph, 119-153 km/h), a Category 5 hurricane has the highest (> 155 mph, 249 km/h). The U.S. National Hurricane Center classifies hurricanes of Category 3 and above as major hurricanes.

The U.S. Joint Typhoon Warning Center classifies West Pacific typhoons as tropical cyclones with winds greater than 73 mph (118 km/h). Typhoons with wind speeds of at least 150 mph (67 m/s or 241 km/h, equivalent to a strong Category 4 hurricane) are dubbed Super Typhoons.

The Australian Bureau of Meteorology uses a 1-5 scale called tropical cyclone severity categories. Unlike the Saffir-Simpson Hurricane Scale, severity categories are based on estimated maximum wind gusts. A category 1 storm features gusts less than 126 km/h (78 mph), while gusts in a category 5 cyclone are at least 280 km/h (174 mph).

Meteorologists in the United States use maximum 1-minute average sustained winds 10 meters above the ground to determine tropical cyclone strength. Other countries use the maximum 10-minute average, as suggested by the World Meteorological Organization. Maximum wind speeds are typically about 12% lower with the 10-minute method than with the 1-minute method. http://www.weather.gov/directives/sym/pd01006004curr.pdf

The rankings are not absolute in terms of damage and other effects. Lower-category storms can inflict greater damage than higher-category storms, depending on factors such as local terrain and total rainfall. For instance, a Category 2 hurricane that strikes a major urban area will likely do more damage than a large Category 5 hurricane that strikes a mostly rural region. In fact, tropical systems of minimal strength can produce significant damage and human casualties from flooding and landslides.

Regional terminology

Eye of Typhoon Odessa, Pacific Ocean, August 1985.

Terms used in weather reports for tropical cyclones that have surface winds over 64 knots (73.6 mph) or 32 m/s vary by region:

• Hurricane: Atlantic basin and North Pacific Ocean east of the International date line
• Typhoon: Northwest Pacific west of the dateline
• Severe tropical cyclone: Southwest Pacific west of 160°E and the southeast Indian Ocean east of 90°E
• Very severe cyclonic storm: North Indian Ocean
• Tropical cyclone: Southwest Indian Ocean and the South Pacific east of 160°E.
• Cyclone (unofficially): South Atlantic Ocean

Origin of storm terms

• From the Chinese 大風 (daaih fūng (Cantonese); dà fēng (Mandarin)) which means "great wind." (The Chinese term as 颱風 táifēng, and 台風 taifu in Japanese, has an independent origin traceable variously to 風颱, 風篩 or 風癡 hongthai, going back to Song 宋 (960-1278) and Yuan 元(1260-1341) dynasties. The first record of the character 颱 appeared in 1685's edition of Summary of Taiwan 臺灣記略).#redirect [[Template:Fact]]
• From Urdu, Persian or Arabic ţūfān (طوفان) < Greek tuphōn (Τυφών).#redirect [[Template:Fact]]

The word hurricane is derived from the name of a native Caribbean Amerindian storm god, Huracan, via Spanish huracán.[NHC Tropical Cyclone FAQ Subject B4] accessed April 15, 2006

The word cyclone was coined by a Captain Henry Piddington, who used it to refer to the storm that blew a freighter in circles in Mauritius in February of 1845.Whipple, p. 53 Tropical cyclones are then circular wind storms that form in the tropics.

Naming of tropical cyclones

Main article: Lists of tropical cyclone names

Each year, the names of particularly destructive storms (if there are any) are "retired" and new names are chosen to take their place.

Naming schemes

In the North Atlantic and Northeastern Pacific regions, feminine and masculine names are alternated in alphabetic order during a given season. The gender of the season's first storm also alternates year to year. Six lists of names are prepared in advance, and each list is used once every six years. Five letters — "Q," "U," "X," "Y" and "Z" — are omitted in the North Atlantic; only "Q" and "U" are omitted in the Northeastern Pacific. This allows for 21 names in the North Atlantic and 24 names in Northeastern Pacific. Names of storms may be retired by request of affected countries if they have caused extensive damage. The affected countries then decide on a replacement name of the same gender, and if possible, the same language as the name being retired. If there are more than 21 named storms in an Atlantic season or 24 named storms in an Eastern Pacific season, the rest are named as letters from the Greek alphabet. This was first necessary during the 2005 season when the list was exhausted. There is no precedent for a storm named with a Greek letter causing enough damage to justify retirement; how this situation would be handled is unknown.

In the Central North Pacific region, the name lists are maintained by the Central Pacific Hurricane Center in Honolulu, Hawaii. Four lists of Hawaiian names are selected and used in sequential order without regard to year.

In the Northwestern Pacific, name lists are maintained by the WMO Typhoon Committee. Five lists of names are used, with each of the 14 nations on the Typhoon Committee submitting two names to each list. Names are used in the order of the countries' English names, sequentially without regard to year. Since 1981, the numbering system had been the primary system to identify tropical cyclone among Typhoon Committee members and it is still in use. International numbers are assigned by Japan Meteorological Agency on the order that a tropical storm forms while different internal numbers may be assigned by different NMCs. The Typhoon "Songda" in September 2004 was internally called the typhoon number 18 in Japan but typhoon number 19 in China. Internationally, it is recorded as the TY Sonda (0418) with "04" taken from the year. Names are rarely retired from these lists, and only at the request of the nation that submitted the name.

The Australian Bureau of Meteorology maintains three lists of names, one for each of the Western, Northern and Eastern Australian regions. These lists are in alphabetical order and alternate gender, but are used sequentially rather than switched each year. There are also Fiji region and Papua New Guinea region names.

The Seychelles Meteorological Service maintains a list for the Southwestern Indian Ocean. There, a new list is created each year, so names are not retired.

Renaming of tropical cyclones

1. A tropical storm enters the southwestern Indian Ocean from the east
2. :In the southwestern Indian Ocean, Metéo France in Réunion names a tropical storm once it crosses 90°E from the east, even though it has been named. In this case, the Joint Typhoon Warning Center (JTWC) will put two names together with a hyphen. Examples include Cyclone Adeline-Juliet in early 2005 and Cyclone Bertie-Alvin in late 2005.
3. A tropical storm crosses from the Atlantic into the Pacific, or vice versa, before 2001
4. :It was the policy of National Hurricane Center (NHC) to rename a tropical storm which crossed from Atlantic into Pacific, or vice versa. Examples include Hurricane Cesar-Douglas in 1996 and Hurricane Joan-Miriam in 1988.[NHC Tropical Cyclone FAQ Subject E15] accessed March 30, 2006
5. :In 2001, when Iris moved across Central America, NHC mentioned that Iris would retain its name if it regenerated in the Pacific. However, the Pacific tropical depression developed from the remnants of Iris was called Fifteen-E instead. The depression later became tropical storm Manuel.
6. :NHC explained that Iris had dissipated as a tropical cyclone prior to entering the eastern North Pacific basin; the new depression was properly named Fifteen-E, rather than Iris.[NHC Tropical Storm Manuel Report] accessed March 31, 2006
7. :In 2003, when Larry was about to move across Mexico, NHC attempted to provide greater clarity:
8. ::"Should Larry remain a tropical cyclone during its passage over Mexico into the Pacific, it would retain its name. However, a new name would be given if the surface circulation dissipates and then regenerates in the Pacific."[NHC Tropical Storm Larry Discussion Number 16] accessed March 31, 2006
9. :Up to now, there has been no tropical cyclone retaining its name during the passage from Atlantic to Pacific, or vice versa.
10. Uncertainties of the continuation
11. :When the remnants of a tropical cyclone redevelop, the redeveloping system will be treated as a new tropical cyclone if there are uncertainties of the continuation, even though the original system may contribute to the forming of the new system. One example is Tropical Depression 10-Tropical Depression 12 (which became Hurricane Katrina) from 2005.
12. Human errors
13. :Sometimes, there may be human faults leading to the renaming of a tropical cyclone. This is especially true if the system is poorly organized or if it passes from the area of responsibility of one forecaster to another. Examples include Tropical Storm Ken-Lola in 1989[JTWC Ken-Lola Report] accessed March 30, 2006 and Tropical Storm Upana-Chanchu in 2000Padgett, G. [Monthly Global Tropical Cyclone Summary for July 2000] accessed March 30, 2000

History of tropical cyclone naming

The practice of giving storms people's names was introduced by Clement Lindley Wragge, an Anglo-Australian meteorologist at the end of the 19th century. He used girls' names, the names of politicians who had offended him, and names from history and mythology.[NHC Tropical Cyclone FAQ Subject B1] accessed March 30, 2006[Bureau of Meteorology FAQ Question 13] accessed March 31, 2006

During World War II, tropical cyclones were given feminine names, mainly for the convenience of the forecasters and in a somewhat ad hoc manner. In addition, George R. Stewart's 1941 novel Storm help to popularize the concept of giving names to tropical cyclones.[NHC Tropical Cyclones FAQ Subject J4] accessed March 31, 2006

From 1950 to 1953, names from the Joint Army/Navy Phonetic Alphabet were used. The modern naming convention came about in response to the need for unambiguous radio communications with ships and aircraft. As transportation traffic increased and meteorological observations improved in number and quality, several typhoons, hurricanes or cyclones might have to be tracked at any given time. To help in their identification, beginning in 1953 the practice of systematically naming tropical storms and hurricanes was initiated by the United States National Hurricane Center. Naming is now maintained by the World Meteorological Organization.

In keeping with the common English language practice of referring to named inanimate objects such as boats, trains, etc., using the female pronoun "she," names used were exclusively feminine. The first storm of the year was assigned a name beginning with the letter "A", the second with the letter "B", etc. However, since tropical storms and hurricanes are primarily destructive, some considered this practice sexist. The World Meteorological Organization responded to these concerns in 1979 with the introduction of masculine names to the nomenclature. It was also in 1979 that the practice of preparing a list of names before the season began. The names are usually of English, French or Spanish origin in the Atlantic basin, since these are the three predominant languages of the region which the storms typically affect. In the southern hemisphere, male names were given to cyclones starting in 1975.

Notable cyclones

Main article: List of notable tropical cyclones

The deadliest tropical cyclone on record hit the densely populated Ganges Delta region of Bangladesh on November 13, 1970, likely as a Category 3 tropical cyclone. It killed an estimated 500,000 people. The North Indian basin has historically been the deadliest, with several storms since 1900 killing over 100,000 people, each in Bangladesh.[Encarta Online] accessed March 31, 2006

In the Atlantic basin, at least three storms have killed more than 10,000 people. Hurricane Mitch during the 1998 Atlantic hurricane season caused severe flooding and mudslides in Honduras, killing about 18,000 people and changing the landscape enough that entirely new maps of the country were needed.[NHC Mitch Report] accessed March 31, 2006 The Galveston Hurricane of 1900, which made landfall at Galveston, Texas as an estimated Category 4 storm, killed 8,000 to 12,000 people, and remains the deadliest natural disaster in the history of the United States.National Hurricane Center [The Deadliest Atlantic Tropical Cyclones, 1492-1996] accessed March 31, 2006 The deadliest Atlantic storm on record was the Great Hurricane of 1780, which killed about 22,000 people in the Antilles.

The relative sizes of Typhoon Tip, Tropical Cyclone Tracy, and the United States.

The most intense storm on record was Typhoon Tip in the northwestern Pacific Ocean in 1979, which had a minimum pressure of only 870 mbar and maximum sustained wind speeds of 190 mph (305 km/h). It weakened before striking Japan. Tip does not hold the record for fastest sustained winds in a cyclone alone; Typhoon Keith in the Pacific, and Hurricane Camille and Hurricane Allen in the North Atlantic currently share this record as well,Weatherwatchers[Weatherwatchers page on Hurricane Mitch] accessed March 30, 2006 although recorded wind speeds that fast are suspect since most monitoring equipment is likely to be destroyed by such extreme conditions. Camille was the only storm to actually strike land while at that intensity, making it, with 190 mph (305 km/h) sustained winds and 210 mph (335 km/h) gusts, the strongest tropical cyclone on record at landfall. For comparison, these speeds are encountered at the center of a strong tornado, but Camille, like all tropical cyclones, was much larger and long-lived than any tornado.

Typhoon Nancy in 1961 had recorded wind speeds of 215 mph (345 km/h), but recent research indicates that wind speeds from the 1940s to the 1960s were gauged too high, and this is no longer considered the fastest storm on record.[NHC Tropical Cyclone FAQ Subject E1] accessed March 30, 2006 Similarly, a surface-level gust caused by Typhoon Paka on Guam was recorded at 236 mph (380 km/h); had it been confirmed, this would be the strongest non-tornadic wind ever recorded at the Earth's surface, but the reading had to be discarded since the anemometer was damaged by the storm.National Weather Service [Super Typhoon Paka's (1997) Surface Winds Over Guam] accessed March 30, 2006

Tip was also the largest cyclone on record, with a circulation of tropical storm-force winds 1,350 miles (2,170 km) wide. The average tropical cyclone is only 300 miles (480 km) wide. The smallest storm on record, 1974's Cyclone Tracy, which devastated Darwin, Australia, was roughly 60 miles (100 km) wide.[NHC Tropical Cyclone FAQ Subject E5] accessed March 30, 2006

Hurricane Iniki in 1992 was the most powerful storm to strike Hawaii in recorded history, hitting Kauai as a Category 4 hurricane, killing six and causing $3 billion in damage.[Central Pacific Hurricane Center Iniki report] accessed March 31, 2006 Other destructive Pacific hurricanes include Pauline[NHC Pauline Report] accessed March 31, 2006 and Kenna.[NHC Kenna Report] accessed March 31, 2006

The first recorded South Atlantic hurricane, Cyclone Catarina from 2004.

On March 26, 2004, Cyclone Catarina became the first recorded South Atlantic hurricane. Previous South Atlantic cyclones in 1991 and 2004 reached only tropical storm strength. Tropical cyclones may have formed there before 1960 but were not observed until weather satellites began monitoring the Earth's oceans in that year.

A tropical cyclone need not be particularly strong to cause memorable damage; Tropical Storm Thelma, in November 1991 killed thousands in the Philippines even though it never became a typhoon; the damage from Thelma was mostly due to flooding, not winds or storm surge.[Joint Typhoon Center Thelma report] accessed March 31, 2006 In 1982, the unnamed tropical depression that eventually became Hurricane Paul caused the deaths of around 1,000 people in Central America due to the effects of its rainfall.American Meteorological Society "Eastern North Pacific Tropical Cyclones of 1982" [May 1983 Monthly Weather Review] accessed March 31, 2006

On August 29 2005, Hurricane Katrina made landfall in Louisiana and Mississippi. The U.S. National Hurricane Center, in its August review of the tropical storm season stated that Katrina was probably the worst natural disaster in U.S. history.[August 2005 Atlantic Tropical Weather Summary] accessed March 31, 2006 Currently, its death toll is at least 1,836, mainly from flooding and the aftermath in New Orleans, Louisiana. It is also estimated to have caused $75 billion in damages. Before Katrina, the costliest system in monetary terms had been 1992's Hurricane Andrew, which caused an estimated $39 billion (2005 USD) in damage in Florida.[NHC Katrina Report] accessed March 31, 2006

Other storm systems

Many other forms of cyclone can form in nature. Two of these relate to the formation or dissipation of tropical cyclones.

Extratropical cyclone

Main article: Extratropical cyclone

Subtropical storm

Main article: Subtropical cyclone

See also

Current seasons

• 2006 Pacific typhoon season
• 2006 Atlantic hurricane season
• 2006 Pacific hurricane season
• 2006 North Indian cyclone season
• 2005-06 Southern Hemisphere tropical cyclone season

Meteorology

Forecasting and preparation

• Catastrophe modeling
• Hurricane proof building
• Hurricane preparedness
• Hong Kong Tropical Cyclone Warning Signals

Categories

1. redirect[[Template:Portal]]

Notes

External links

1. redirect [[Template:Commonscat]]

Learning resources

• [WMO guide on cyclone terminology]
• [Summary of cyclone terminology from NOAA FAQ]
• [Create-a-Cane] Interactive fun site from NOAA, allows to specify conditions and see how they impact storm formation
• [NASA Hurricane Web Page] - Data, research, science & multimedia resources from NASA
• [NOVA scienceNOW: Hurricanes]
• [Mariner's Guide for Hurricane Awareness (pdf)]
• [The Hurricane Hut] - Information on tropical cyclones, as well as information on hurricane naming, and all Atlantic storms 1950-2005
• [The Hurricane Newspaper Archive]
• [Hurricanes: A Primer on Formation, Structure, Intensity Change and Frequency], by Dr. Robert Hart

Tracking and warning

• [World Meteorological Organization Severe Weather Information Center] - Shows all current tropical systems worldwide and their tracks
• [Joint Typhoon warning Center] - Western Pacific
• [MetService, New Zealand] - Tasman Sea, South Pacific south of 25° S
• [Australian Bureau of Meteorology] - Southern hemisphere from 90° E to 160° E
• [