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Tropical cyclone

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[[Image:Cyclone Catarina from the ISS on March 26 2004.JPG|thumb|250px|[[Cyclone Catarina]], a rare [[South Atlantic tropical cyclone]] viewed from the [[International Space Station]] on [[March 26]] [[2004]]]]
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'''Tropical cyclone''' is the [[meteorology|meterological]] term for a type of storm system characterized by a [[low pressure]] center and [[thunderstorms]], producing strong wind and flooding rain. A tropical cyclone feeds on the heat released when moist air rises and the water vapor [[condensation|condenses]]. The adjective "tropical" refers to both the geographic origin of these systems, which form almost exclusively in [[tropics|tropical]] regions of the globe, and their formation in tropical, or more precisely, 'maritime tropical' air masses. The term "Cyclone" refers to such storms' [[cyclone|cyclonic]] nature, with [[Clockwise and counterclockwise|counterclockwise]] rotation in the [[Northern Hemisphere]] and clockwise rotation in the [[Southern Hemisphere]]. Tropical cyclones are distinguished from other cyclonic windstorms such as [[nor'easter]]s, [[European windstorm]]s, and [[polar low]]s by the heat mechanism that fuels them, which makes them "warm core" storm systems. Depending on their location and strength, there are various terms by which tropical cyclones are known, such as '''hurricane''', '''typhoon''', '''tropical storm''', '''cyclonic storm''', and '''tropical depression'''.

Tropical cyclones can produce extremely strong and powerful winds, [[tornado]]es, torrential [[rain]], high waves, and [[storm surge]]. They are born and sustained over large bodies of warm water, and lose their strength over land. This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from receiving strong winds. Heavy rains, however, can produce significant flooding inland, and storm surges can produce extensive coastal [[flood|flooding]] up to 25&nbsp;[[mile|mi]] (40&nbsp;[[kilometre|km]]) inland. Although their effects on human populations can be devastating, tropical cyclones can also relieve [[drought]] conditions. They carry heat away from the tropics, an important mechanism of the global [[atmospheric circulation]] that helps maintain equilibrium in the Earth's [[troposphere]].

Many tropical cyclones [[tropical cyclogenesis|develop]] when the atmospheric conditions around a weak disturbance in the atmosphere are favorable. Others form when [[#Related cyclone types|other types of cyclones]] acquire tropical characteristics. Tropical systems are then moved by [[#Steering winds|steering winds]] in the [[troposphere]]; if the conditions remain favorable, the tropical disturbance intensifies, and can develop an [[eye (cyclone)|eye]]. On the other end of the spectrum, if the conditions around the system deteriorate, or the tropical cyclone makes landfall, the system weakens and dissipates.

==Physical structure==
[[Image:Hurricane structure graphic.jpg|thumb|250px|right|Structure of a tropical cyclone]]
All tropical cyclones rotate around an area of [[low pressure area|low]] [[atmospheric pressure]] near the Earth's surface. The pressures recorded at the centers of tropical cyclones are among the lowest that occur on Earth's surface at [[sea level]].<ref name="ABC pressures">{{cite news | author = Symonds, Steve |title = Highs and Lows | work = Wild Weather | publisher = [[Australian Broadcasting Corporation]] | date = [[November 17]], [[2003]] | accessdate = 2007-03-23 | url = http://www.abc.net.au/northcoast/stories/s989385.htm}}</ref> Tropical cyclones are characterized and driven by the release of large amounts of latent [[heat of condensation]] as moist air is carried upwards and its water vapor condenses. This heat is distributed vertically, around the center of the storm. Thus, at any given altitude (except close to the surface where water temperature dictates air temperature) the environment inside the cyclone is warmer than its outer surroundings.<ref name = "AOML FAQ A7">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an extra-tropical cyclone? | publisher = [[NOAA]] | accessdate = 2007-03-23 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html}}</ref> [[Rainbands]] are bands of showers and thunderstorms that spiral cyclonically toward the storm center. High wind gusts and heavy downpours often occur in individual rainbands, with relatively calm weather between bands. Tornadoes often form in the rainbands of landfalling tropical cyclones.<ref name="JetStream structure">{{cite web | url = http://www.srh.noaa.gov/jetstream/tropics/tc_structure.htm | author = [[National Weather Service]] | publisher = [[National Oceanic & Atmospheric Administration]] | title = Tropical Cyclone Structure | accessdate = 2006-12-14 | work = JetStream - An Online School for Weather | date = [[October 19]], [[2005]]}}</ref> [[Annular hurricane]]s are distinctive for their lack of rainbands.<ref name="KnaffJournal">{{cite journal | url = http://www.ssec.wisc.edu/~kossin/articles/annularhurr.pdf | title = Annular Hurricanes | accessdate = 2006-07-23 | last = Knaff | first = John A. | coauthors = James P. Kossin, and Mark DeMaria | year = 2003 | month = April | format = PDF | journal = Weather and Forecasting | publisher = American Meteorological Society | pages = 204–223 | volume = 18 | issue = 2}}</ref> While all surface low pressure areas require divergence aloft to continue deepening, the divergence over tropical cyclones is in all directions away from the center. The upper levels of a tropical cyclone feature winds headed away from the center of the storm with an [[anticyclonic]] rotation, due to the [[Coriolis force]]. [[Wind]]s at the surface are strongly cyclonic, weaken with height, and eventually reverse themselves. Tropical cyclones owe this unique characteristic to requiring a relative lack of vertical [[wind shear]] to maintain the warm core at the center of the storm.<ref>{{citeweb|publisher=[[University of Illinois]]|url=http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/grow/home.rxml |title=Hurricanes|accessdate= 2006-10-21}}</ref><ref>{{citebook|title=Flood Geomorphology |author= R. Craig. Kochel, Victor R. Baker, Peter C. Patton|year= 1988|publisher=Wiley-Interscience|id=ISBN 0471625582|url= http://books.google.com/books?vid=ISBN0471625582&id=snLfvo2w-ngC&pg=PA18&lpg=PA18&ots=chABkSpKQ9&dq=%22Tropical+Cyclone%22+%22wind+shear%22&ie=ISO-8859-1&output=html&sig=av-CZCexGMtTR2KVVtbXryYzr68}}</ref>

A strong tropical cyclone will harbor an area of sinking air at the center of circulation, developing into an [[eye (cyclone)|eye]]. Weather in the eye is normally calm and free of clouds, however, the sea may be extremely violent.<ref name="JetStream structure"/> The eye is normally circular in shape, and may range in size from 3 to 370&nbsp;km (2–230&nbsp;miles) in diameter.<ref name="WilmaTCR">{{cite web|last=Pasch|first=Richard J.|coauthors=Eric S. Blake, Hugh D. Cobb III, and David P. Roberts | url=http://www.nhc.noaa.gov/pdf/TCR-AL252005_Wilma.pdf | format=PDF | title= Tropical Cyclone Report: Hurricane Wilma: 15-25 October 2005 | publisher=[[National Hurricane Center]] | date=[[September 28]], [[2006]]|accessdate=2006-12-14}}</ref><ref name="MWR Lander 1999">{{cite journal | author = Lander, Mark A. | title = A Tropical Cyclone with a Very Large Eye | url = http://ams.allenpress.com/archive/1520-0493/127/1/pdf/i1520-0493-127-1-137.pdf | format =PDF | journal = [[Monthly Weather Review]] | date = January 1999 | volume = 127 | issue = 1 | accessdate=2006-12-14}}</ref> 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]].<ref name="MWR 1996 AHS summary">{{cite journal | author = Pasch, Richard J. and [[Lixion Avila|Lixion A. Avila]] | title = Atlantic Hurricane Season of 1996 | journal = [[Monthly Weather Review]] | pages = 581–610 | url = http://ams.allenpress.com/archive/1520-0493/127/5/pdf/i1520-0493-127-5-581.pdf | format = PDF | date = May 1999 | volume = 127 | issue = 5 | accessdate = 2006-12-14}}</ref>

There are other features that either surround the eye, or cover it. The [[central dense overcast]] is the shield of cirrus clouds produced by the eyewall thunderstorms;<ref name="CDO AMS">{{cite web|author = [[American Meteorological Society]] | url = http://amsglossary.allenpress.com/glossary/browse?s=c&p=19 | title = AMS Glossary: C | work = Glossary of Meteorology | accessdate=2006-12-14 | publisher = [[Allen Press]]}}</ref> in weaker tropical cyclones, the CDO may cover the eye completely.<ref name = "AOML FAQ A9">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is a "CDO"? | publisher = [[NOAA]] | accessdate = 2007-03-23 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A9.html}}</ref> The [[eyewall]] is a band around the eye, in which the greatest wind speeds are found, and where clouds reach the highest and precipitation is the heaviest. The heaviest wind damage occurs where a hurricane's eyewall passes over land.<ref name="JetStream structure"/> Associated with eyewalls are [[Eye (cyclone)#Eyewall replacement cycle|eyewall replacement cycles]], which occur naturally in intense tropical cyclones. When cyclones reach peak intensity they usually - but not always - have an eyewall and [[radius of maximum wind]]s that contract to a very small size, around 5 to 15 miles (10&ndash;25&nbsp;km). 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 [[angular momentum]]. During this phase, the tropical cyclone weakens (i.e. the maximum winds die off a bit and the central pressure goes up), but eventually the outer eyewall replaces the inner one completely. The storm can be of the same intensity as it was previously or, in some cases, it can be even stronger after the eyewall replacement cycle. Even if the cyclone is weaker at the end of the cycle, the fact that it has just undergone one and will not undergo another one soon will allow it to strengthen further, if other conditions allow it to do so.<ref name = "AOML FAQ D8">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What are "concentric eyewall cycles" (or "eyewall replacement cycles") and why do they cause a hurricane's maximum winds to weaken? | publisher = [[NOAA]] | accessdate = 2006-12-14 | url = http://www.aoml.noaa.gov/hrd/tcfaq/D8.html}}</ref>

===Mechanics===
[[Image:Hurricane profile graphic.gif|thumb|250px|right|Tropical cyclones form when the energy released by the condensation of moisture in rising air causes a [[positive feedback loop]] over warm ocean waters.]]

Structurally, a tropical cyclone is a large, rotating system of [[cloud]]s, [[wind]], and [[thunderstorm]]s. Its primary [[energy]] source is the release of the [[heat of condensation]] from water vapor [[condensation|condensing]] at high altitudes, the heat being ultimately derived from the [[sun]]. Therefore, a tropical cyclone can be visualized as a giant vertical [[heat engine]] supported by mechanics driven by physical forces such as the [[rotation]] and [[gravity]] of the [[Earth]].<ref name = "NOAA preparedness">{{cite web | author = [[National Weather Service]] | date = September 2006 | title = Hurricanes... Unleashing Nature's Fury: A Preparedness Guide | publisher = [[NOAA]] | accessdate = 2006-12-02 | format = PDF | url = http://www.weather.gov/os/hurricane/pdfs/Hurricane_unleashing06.pdf}}</ref> In another way, tropical cyclones could be viewed as a special type of [[Mesoscale Convective Complex]], which continues to develop over a vast source of relative warmth and moisture. Condensation leads to higher wind speeds, as a tiny fraction of the released energy is converted into mechanical energy;<ref name = "AOML FAQ C5c">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by nuking them? | publisher = [[NOAA]] | accessdate = 2006-07-25|url = http://www.aoml.noaa.gov/hrd/tcfaq/C5c.html}}</ref> the faster winds and lower pressure associated with them in turn cause increased surface evaporation and thus even more condensation. Much of the released energy drives [[vertical draft|updrafts]] that increase the height of the storm clouds, speeding up condensation.<ref name="NOAA Question of the Month">{{cite web | author = [[National Oceanic & Atmospheric Administration]] | url = http://www.noaa.gov/questions/question_082900.html | title = NOAA Question of the Month: How much energy does a hurricane release? | date = August 2000 | accessdate=2006-03-31 | publisher = [[NOAA]]}}</ref> This gives rise to factors that provide the system with enough energy to be self-sufficient and cause a [[positive feedback loop]], where it can draw more energy as long as the source of heat, warm water, remains. Factors such as a continued lack of equilibrium in air mass distribution would also give supporting energy to the cyclone. The rotation of the Earth causes the system to spin, an effect known as the [[Coriolis effect]], giving it a cyclonic characteristic and affecting the trajectory of the storm.

The factors to form a tropical cyclone include a pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds aloft. If the right conditions persist and allow it to create a feedback loop by maximizing the energy intake possible &ndash; for example, such as high winds to increase the rate of evaporation &ndash; they can combine to produce the violent winds, incredible waves, torrential rains, and floods associated with this phenomenon.

Deep convection as a driving force is what primarily distinguishes tropical cyclones from other meteorological phenomena.<ref name="BOM Question 6">{{cite web | author = [[Bureau of Meteorology]] | work = Frequently Asked Questions | title = How are tropical cyclones different to mid-latitude cyclones? | url = http://www.bom.gov.au/weather/wa/cyclone/about/faq/faq_def_6.shtml | accessdate = 2006-03-31}}</ref> Because this is strongest in a [[tropical climate]], this defines the initial domain of the tropical cyclone. By contrast, [[mid-latitude cyclone]]s draw their energy mostly from pre-existing horizontal temperature [[gradient]]s in the atmosphere.<ref name="BOM Question 6"/> To continue to drive its heat engine, a tropical cyclone must remain over warm water, which provides the needed atmospheric moisture. The evaporation of this moisture is accelerated by the high winds and reduced atmospheric pressure in the storm, resulting in a positive feedback loop. As a result, when a tropical cyclone passes over land, its strength diminishes rapidly.<ref name = "AOML FAQ C2">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Doesn't the friction over land kill tropical cyclones?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C2.html}}</ref>

[[Image:GulfMexTemps 2005Hurricanes.gif|thumb|180px|Chart displaying the drop in surface temperature in the [[Gulf of Mexico]] as Hurricanes [[Hurricane Katrina|Katrina]] and [[Hurricane Rita|Rita]] passed over]]
The passage of a tropical cyclone over the ocean can cause the upper ocean to cool substantially, which can influence subsequent cyclone development. Cooling is primarily caused by upwelling of cold water from below due to the wind stresses the tropical cyclone itself induces upon the upper layers of the ocean. Additional cooling may come from cold water from falling raindrops. Cloud cover may also play a role in cooling the ocean by shielding the ocean surface from direct sunlight before and slightly after the storm passage. All these effects can combine to produce a dramatic drop in sea surface temperature over a large area in just a few days.<ref name="NASA Cooling">{{cite web | author = Earth Observatory | url = http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17164 | title = Passing of Hurricanes Cools Entire Gulf | year = 2005 | accessdate = 2006-04-26 | publisher = [[NASA|National Aeronautics and Space Administration]]}}</ref>

Scientists at the [[National Center for Atmospheric Research]] estimate that a tropical cyclone releases heat energy at the rate of 50 to 200 [[trillion]] [[joule]]s per day.<ref name="NOAA Question of the Month"/> For comparison, this rate of energy release is equivalent to exploding a 10-megaton [[nuclear bomb]] every 20 minutes<ref name="UCAR">[[University Corporation for Atmospheric Research]] [http://www.ucar.edu/news/features/hurricanes/index.jsp Hurricanes: Keeping an eye on weather's biggest bullies] accessed March 31, 2006</ref> or 200 times the world-wide electrical generating capacity per day.<ref name="NOAA Question of the Month"/>

While the most obvious motion of clouds is toward the center, tropical cyclones also develop an upper-level (high-altitude) outward flow of clouds. These originate from air that has released its moisture and is expelled at high altitude through the "chimney" of the storm engine.<ref name = "NOAA preparedness"/> This outflow produces high, thin [[cirrus cloud]]s that spiral away from the center. The high cirrus clouds may be the first signs of an approaching tropical cyclone.<ref name = "AOML FAQ H5">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What's it like to go through a hurricane on the ground? What are the early warning signs of an approaching tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-26 | url = http://www.aoml.noaa.gov/hrd/tcfaq/H5.html}}</ref>

==Major basins and related warning centers==
{{main|Tropical cyclone basins|Regional Specialized Meteorological Centre|Tropical Cyclone Warning Centre}}
{| style="float: right; clear: right; background-color: transparent; margin-left: 0em"
|
{|class="wikitable" style="float: right; font-size: 92%; margin-right: 0px;"
! colspan=2 style="background: #ccf;" | Basins and [[World Meteorological Organization|WMO]] Monitoring Institutions<ref name = "AOML FAQ F1">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What regions around the globe have tropical cyclones and who is responsible for forecasting there?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/F1.html}}</ref>
|-
! Basin !! Responsible RSMCs and TCWCs
|-
| Northern Atlantic || [[National Hurricane Center]]
|-
| Northeastern Pacific || [[National Hurricane Center]]
|-
| North central Pacific || [[Central Pacific Hurricane Center]]
|-
| Northwestern Pacific || [[Japan Meteorological Agency]]
|-
| Northern Indian || [[Indian Meteorological Department]]
|-
| Southwestern Indian || [[Météo-France]]
|-
| South and<br/>Southwestern Pacific || [[Fiji Meteorological Service]]<br/>[[Meteorological Service of New Zealand]]<sup>†</sup><br/>Papua New Guinea National Weather Service<sup>†</sup><br/>[[Bureau of Meteorology]]<sup>†</sup> (Australia)
|-
| Southeastern Indian || [[Bureau of Meteorology]]<sup>†</sup> (Australia)
|-
! colspan=2 style="font-size: 92%; text-align: right;" | <sup>†</sup>: '''''Indicates a Tropical Cyclone Warning Centre'''''
|}
|-
|
[[Image:Global tropical cyclone tracks-edit2.jpg|thumb|right|372px|Map of the cumulative tracks of all tropical cyclones during the 1985–2005 time period. The [[Pacific Ocean]] west of the [[International Date Line]] sees more tropical cyclones than any other basin, while there is almost no activity in the [[Atlantic Ocean]] south of the [[Equator]].]]
|-
|}
=== Warning centers ===
There are six [[Regional Specialised Meteorological Centre]]s (RSMCs) worldwide. These organizations are designated by the [[World Meteorological Organization]] and are responsible for tracking and issuing bulletins, warnings, and advisories about tropical cyclones in their designated areas of responsibility. Additionally, there are five [[Tropical Cyclone Warning Centre]]s (TCWCs) that provide information to smaller regions.<ref name="WMO RSMC list">{{cite web | author = [[World Meteorological Organization]] | title = RSMCs | date = [[April 25]], [[2006]] | accessdate = 2006-11-05 | work = Tropical Cyclone Programme (TCP) | url = http://www.wmo.ch/web/www/TCP/rsmcs.html}}</ref> The RSMCs and TCWCs, however, are not the only organizations that provide information about tropical cyclones to the public. The [[Joint Typhoon Warning Center]] (JTWC) issues informal advisories in all basins except the Northern Atlantic and Northeastern Pacific. The [[Philippine Atmospheric, Geophysical and Astronomical Services Administration]] (PAGASA) issues informal advisories, as well as names, for tropical cyclones that approach the [[Philippines]] in the Northwestern Pacific. The [[Canadian Hurricane Centre]] (CHC) issues advisories on hurricanes and their remnants that affect Canada.

On [[March 26]], [[2004]], [[Cyclone Catarina]] became the first recorded [[South Atlantic tropical cyclone|South Atlantic cyclone]] and subsequently struck southern [[Brazil]] as the equivalence of a Category 2 hurricane on the [[Saffir-Simpson Hurricane Scale]]. As the cyclone formed outside of the authority of another warning center, Brazilian meteorologists initially treated the system as an [[extratropical cyclone]], though subsequently classified it as tropical.<ref name="Emerson Marcelino">{{cite web | author = Marcelino, Emerson Vieira; Isabela Pena Viana de Oliveira Marcelino; Frederico de Moraes Rudorff | title = Cyclone Catarina: Damage and Vulnerability Assessment | url = http://www.dsr.inpe.br/geu/Rel_projetos/Relatorio_IAI_Emerson_Marcelino.pdf | format = PDF | date = 2004 | accessdate = 2006-12-24 | publisher = Santa Catarina Federal University}}</ref>

===Times of formation===
Worldwide, tropical cyclone activity peaks in late [[summer]] when the difference between temperatures aloft and sea surface temperatures are the greatest. However, each particular basin has its own seasonal patterns. On a worldwide scale, May is the least active month, while September is the most active.<ref name = "AOML FAQ G1">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: When is hurricane season?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/G1.html}}</ref>

In the North [[Atlantic Ocean|Atlantic]], a distinct hurricane season occurs from [[June 1]] to [[November 30]], sharply peaking from late August through September. The statistical peak of the North Atlantic hurricane season is [[September 10]]. The Northeast Pacific has a broader period of activity, but in a similar time frame to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November.<ref name = "AOML FAQ G1"/>

In the [[Southern Hemisphere]], tropical cyclone activity begins in late October and ends in May. Southern Hemisphere activity peaks in mid-February to early March.<ref name = "AOML FAQ G1"/>

<center>
{|class="wikitable" style="font-size: 92%;"
! colspan=6 style="background: #ccf;" | Season Lengths and Seasonal Averages<ref name = "AOML FAQ E10">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What are the average, most, and least tropical cyclones occurring in each basin? | publisher = [[NOAA]] | accessdate = 2006-11-30 | url = http://www.aoml.noaa.gov/hrd/tcfaq/E10.html}}</ref><ref name = "AOML FAQ G1"/>
|-
! Basin !! Season Start !! Season End !! Tropical Storms<br/>(>34 knots) !! Tropical Cyclones<br/>(>63 knots)!! Category 3+ TCs<br/>(>95 knots)
|-
| Northwest Pacific || April || January || 26.7 || 16.9 || 8.5
|-
| South Indian || October || May || 20.6 || 10.3 || 4.3
|-
| Northeast Pacific || May || November || 16.3 || 9.0 || 4.1
|-
| North Atlantic || June || November || 10.6 || 5.9 || 2.0
|-
| Australia Southwest Pacific || October || May || 10.6 || 4.8 || 1.9
|-
| North Indian || April || December || 5.4 || 2.2 || 0.4
|}
</center>

==Formation==
===Factors in formation===
[[Image:Atlantic hurricane graphic.gif|thumb|180px|right|Waves in the trade winds in the Atlantic Ocean—areas of converging winds that move along the same track as the prevailing wind—create instabilities in the atmosphere that may lead to the formation of hurricanes.]]
{{main|Tropical cyclogenesis}}

The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood. Six factors appear to be generally necessary, although tropical cyclones may occasionally form without meeting all of these conditions. [[Sea surface temperature|Water temperatures]] of at least 26.5&nbsp;°C (80°F) are needed<ref name = "AOML FAQ A15">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: How do tropical cyclones form? | publisher = [[NOAA]] | accessdate = 2006-07-26 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A15.html}}</ref> down to a depth of at least 50&nbsp;m (150&nbsp;feet). Waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms.<ref name = "AOML FAQ A16">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why do tropical cyclones require 80°F (26.5°C) ocean temperatures to form?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A16.html}}</ref> Another factor is rapid cooling with height. This allows the release of [[latent heat]], which is the source of energy in a tropical cyclone.<ref name = "AOML FAQ A15"/> High humidity is needed, especially in the lower-to-mid [[troposphere]]; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop.<ref name = "AOML FAQ A15"/> Low amounts of [[wind shear]] are needed, as when shear is high, the convection in a cyclone or disturbance will be disrupted, preventing formation of the feedback loop.<ref name = "AOML FAQ A15"/> Tropical cyclones generally need to form over 500&nbsp;km (310&nbsp;miles) or 5 degrees from the [[equator]]. This allows the [[Coriolis force]] to deflect winds blowing towards the low pressure center, causing a circulation.<ref name = "AOML FAQ A15"/> Lastly, a formative tropical cyclone needs pre-existing system of disturbed weather. The system must have some sort of circulation as well as a low pressure center.<ref name = "AOML FAQ A15"/>

===Locations of formation===
Most tropical cyclones form in a worldwide band of thunderstorm activity called by several names: the Intertropical Discontinuity (ITD), the [[Intertropical Convergence Zone]] (ITCZ), or the [[monsoon trough]]. Another important source of atmospheric instability is found in [[tropical wave]]s, which cause about 85% of intense tropical cyclones in the Atlantic ocean,<ref name="MWR Avila 1995">{{cite journal | last = [[Lixion Avila|Avila, Lixion]] | coauthors = Richard Pasch | year = 1995 | month = March | title = Atlantic tropical systems of 1993 | journal = [[Monthly Weather Review]] | volume = 123 | issue = 3 | pages = 887-896 | url = http://ams.allenpress.com/perlserv/?request=res-loc&uri=urn%3Aap%3Apdf%3Adoi%3A10.1175%2F1520-0493%281995%29123%3C0887%3AATSO%3E2.0.CO%3B2 | format = PDF | accessdate = 2006-07-25 }}</ref> and which most of the tropical cyclones in the Eastern Pacific basin.<ref name = "AOML FAQ A4">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an easterly wave? | publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A4.html}}</ref><ref name="Landsea 1993">{{cite journal | author = [[Chris Landsea|Landsea, Chris]] | url = http://ams.allenpress.com/perlserv/?request=res-loc&uri=urn%3Aap%3Apdf%3Adoi%3A10.1175%2F1520-0493%281993%29121%3C1703%3AACOIMA%3E2.0.CO%3B2 | format = PDF | title = A Climatology of Intense (or Major) Atlantic Hurricanes | journal = [[Monthly Weather Review]] | volume = 121 | issue = 6 | year = 1993 | month = June | accessdate = 2006-03-25 | pages = 1703-1713}}</ref>

Tropical cyclones form where sea temperatures are high, usually at about 27 degrees celsius. They originate on the eastern side of oceans, but move west, intensifying as they move. Most of these systems form between 10 and 30 degrees of the [[equator]] and 87% form within 20 degrees of it. Because the [[Coriolis effect]] initiates and maintains tropical cyclone rotation, tropical cyclones rarely form or move within about 5 degrees of the equator, where the Coriolis effect is weakest.<ref name=BOMmap>{{cite web | publisher = [[Bureau of Meteorology]] | url = http://www.bom.gov.au/bmrc/pubs/tcguide/ch1/figures_ch1/figure1.9.htm | title = Worldwide Tropical Cyclone Tracks 1979-88 | author = Neumann, Charles J. | work = Global Guide to Tropical Cyclone Forecasting | accessdate = 2006-12-12}}</ref> However, it is possible for tropical cyclones to form within this boundary as did [[Typhoon Vamei]] in 2001 and [[Cyclone Agni]] in 2004.

==Movement and track==
===Steering winds===
Although tropical cyclones are large systems generating enormous energy, their movements over the Earth's surface are controlled by large-scale winds&mdash;the streams in the Earth's atmosphere. The path of motion is referred to as a tropical cyclone's ''track'' and has been analogized by Dr. Neil Frank, former director of the [[National Hurricane Center]], to "leaves carried along by a stream."<ref name = "AOML FAQ G6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What determines the movement of tropical cyclones?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/G6.html}}</ref>

Tropical systems, while generally located [[Equator|equatorward]] of the 20th parallel, are steered primarily westward by the east-to-west winds on the equatorward side of the [[subtropical ridge]], a persistent high pressure area over the world's oceans.<ref name = "AOML FAQ G6"/> In the tropical North Atlantic and Northeast Pacific oceans, [[trade winds]], another name for the westward-moving wind currents, steer [[tropical waves]] westward from the [[Africa|African]] coast and towards the Caribbean Sea, North America, and ultimately into the central Pacific ocean before the waves dampen out.<ref name = "AOML FAQ A4">{{ cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an easterly wave? | publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A4.html}}</ref> These waves are the precursors to many tropical cyclones within this region.<ref name="MWR Avila 1995">{{cite journal | last = [[Lixion Avila|Avila, Lixion]] | coauthors = Richard Pasch | year = 1995 | month = March | title = Atlantic tropical systems of 1993 |journal = [[Monthly Weather Review]] | volume = 123 | issue = 3 | pages = 887-896 | url = http://ams.allenpress.com/pdfserv/10.1175%2F1520-0493(1995)123%3C0887:ATSO%3E2.0.CO%3B2 | format = PDF | accessdate = 2006-07-25 }}</ref> In the Indian Ocean and Western Pacific (north and south of the equator), tropical cyclogenesis is strongly influenced by the seasonal movement of the [[Intertropical Convergence Zone]] and the [[monsoon trough]], rather than by easterly waves.<ref name="MILLER7">{{cite web | author = DeCaria, Alex | publisher = [[Millersville University of Pennsylvania|Millersville University]] | url = http://www.atmos.millersville.edu/~adecaria/ESCI344/esci344_lesson08_TC_climatology.html | title = Lesson 7 – Tropical Cyclones: Climatology. | work = ESCI 344 – Tropical Meteorology | year = 2005 | accessdate = 2006-11-26}}</ref>

===Coriolis effect===
[[Image:Cyclone_Monica.gif|thumb|180px|right|Infrared image of [[Cyclone Monica]] near peak intensity, showing [[clockwise]] rotation due to the [[Coriolis effect]].]]
The Earth's rotation imparts an acceleration known as the ''Coriolis Acceleration'' or ''[[Coriolis Effect]].'' This acceleration causes cyclonic systems to turn towards the poles in the absence of strong steering currents.<ref name="Paleoglossary Cn-Cz">{{cite web | author = Baum, Steven K. | url = http://stommel.tamu.edu/~baum/paleo/paleogloss/node10.html | title = The Glossary: Cn-Cz. | work = Glossary of Oceanography and the Related Geosciences with References | publisher = [[Texas A&M University]] | date = [[January 20]], [[1997]] | accessdate = 2006-11-29}}</ref> The poleward portion of a tropical cyclone has winds blowing towards the west, and the Coriolis acceleration pulls them slightly more poleward. The winds blowing towards the east on the equatorward portion of the cyclone are pulled slightly towards the equator. But because the Coriolis acceleration is increasingly weak as you move toward the equator, the net drag on the cyclone is poleward. Thus, tropical cyclones in the [[Northern Hemisphere]] normally turn north (before being blown east), and tropical cyclones in the [[Southern Hemisphere]] normally turn south (before being blown east), if no strong pressure systems counteract the Coriolis acceleration.

The Coriolis acceleration also initiates cyclonic rotation, but it is not the driving force that brings this rotation to high speeds. These speeds instead result from the [[conservation of angular momentum]]. This means that air is drawn in from an area much larger than the cyclone such that the tiny rotational speed (originally imparted by the Coriolis acceleration) is magnified greatly as the air is drawn into the low pressure center.<ref name="Angular Momentum">{{cite web | publisher = [[University of Tennessee]] | url = http://csep10.phys.utk.edu/astr161/lect/solarsys/angmom.html | title = Conservation of Angular Momentum | work = Astronomy 161 Lectures | accessdate = 2006-11-29}}</ref>

===Interaction with the mid-latitude westerlies===
When a tropical cyclone moves into higher latitudes to the north of the [[subtropical ridge]] axis, its general track around the high-pressure area is deflected significantly by winds moving towards the general low-pressure area to its north. When the cyclone track becomes strongly poleward with an easterly component, the cyclone has begun ''recurvature.'' A typhoon moving through the Pacific Ocean towards [[Asia]], for example, will recurve to the north and then northeast offshore of [[Japan]] if the typhoon encounters winds blowing northeastward toward a low-pressure system passing over [[China]] or [[Siberia]]. Many tropical cyclones are eventually forced toward the northeast by low-pressure areas, which move from west to east when they are north of the subtropical ridge.

===Landfall===
Officially, "[[landfall (meteorology)|landfall]]" is when a storm's center (the center of its circulation, not its edge) crosses the coastline. Storm conditions may be experienced on the coast and inland hours before landfall. For a storm moving inland, the landfall area experiences half the storm by the time of actual landfall. For emergency preparedness, actions should be timed from when a certain wind speed or intensity of rainfall will reach land, not from when landfall will occur.<ref name="NHC glossary">{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/aboutgloss.shtml | year = 2005 | title = Glossary of NHC/TPC Terms | accessdate= 2006-11-29 | publisher = [[National Oceanic and Atmospheric Administration]]}}</ref> For a list of notable and unusual landfalling tropical cyclones, see [[list of notable tropical cyclones]]. For a list of unusual formation areas, see [[Tropical cyclogenesis#Unusual areas of formation|Unusual areas of formation]].

==Dissipation==
=== Factors ===
[[Image:TropicalStormFranklin05.jpg|thumb|right|180px|[[Tropical Storm Franklin (2005)|Tropical Storm Franklin]], an example of a strongly [[windshear|sheared]] tropical cyclone in the [[Atlantic hurricane|Atlantic Basin]] during [[2005 Atlantic hurricane season|2005]]]]
A tropical cyclone can cease to have tropical characteristics in several ways. One such way is if it moves over land, thus depriving it of the warm water it needs to power itself, and quickly loses strength. Most strong storms lose their strength very rapidly after landfall and become disorganized areas of low pressure within a day or two, or evolve into [[extratropical cyclone]]s. There is a chance they could regenerate if they manage to get back over open warm water. If a storm is over mountains for even a short time, it can rapidly lose its structure. Many storm fatalities occur in mountainous terrain, as the dying storm unleashes torrential rainfall which can lead to deadly [[flood]]s and [[mudslide]]s, as happened with [[Hurricane Mitch]] in 1998. Additionally, dissipation can occur if a storm remains in the same area of ocean for too long, mixing the upper 100&nbsp;feet (30&nbsp;meters) of water, which draws up colder water due to [[upwelling]] and becomes too cool to support the storm. Without warm surface water, the storm cannot survive.<ref name="Shays et al 1989">{{cite journal | url = http://ams.allenpress.com/archive/1520-0485/19/5/pdf/i1520-0485-19-5-649.pdf | author = Shay, Lynn K., Russell L. Elsberry and Peter G. Black | title = Vertical Structure of the Ocean Current Response to a Hurricane | month = May | year = 1989 | accessdate = 2006-12-12 | format = PDF | journal = Journal of Physical Oceanography | volume = 19 | issue = 5}}</ref>

A tropical cyclone can dissipate when it moves over waters significantly below 26°C. This will cause the storm to lose its tropical characteristics (i.e. thunderstorms near the center and warm core) and become a remnant low pressure area, which can persist for several days. This is the main dissipation mechanism in the Northeast Pacific ocean.<ref name="Edwards genesis">{{cite web | author = Edwards, Jonathan | url = http://www.hurricanezone.net/articles/tropical-cyclone-formation.html | title = Tropical Cyclone Formation | accessdate = 2006-11-30 | publisher = HurricaneZone.net}}</ref> Weakening or dissipation can occur if it experiences vertical [[wind shear]], causing the convection and heat engine to move away from the center which normally ceases development of a tropical cyclone.<ref name="EAM">{{citebook|title=East Asian Monsoon |author= Chih-Pei Chang|year= 2004|publisher=World Scientific|id=ISBN 9812387692 |url=http://books.google.com/books?vid=ISBN9812387692&id=N8QYOdqGdgkC&pg=PA484&lpg=PA484&ots=jH3lLnS6LHie=ISO-8859-1&output=html&sig=Dxv5vz1f9RSR-VHJPygruiitADo}}</ref> Additionally, its interaction with the main belt of the Westerlies, by means of merging with a nearby frontal zone, can cause tropical cyclones to evolve into [[extratropical cyclones]]. This transition can take 1-3 days.<ref name = "JWTC intensity">{{cite web | url = http://www.nrlmry.navy.mil/~chu/chap6/se300.htm | author = [[United States Naval Research Laboratory]] | work = Tropical Cyclone Forecasters' Reference Guide| title = Tropical Cyclone Intensity Terminology | accessdate = 2006-11-30 | date = [[September 23]], [[1999]]}}</ref> Even after a tropical cyclone is said to be extratropical or dissipated, it can still have tropical storm force (or occasionally hurricane force) winds and drop several inches of rainfall. In the [[Pacific ocean]] and [[Atlantic ocean]], such tropical-derived cyclones of higher latitudes can be violent and may occasionally remain at hurricane-force wind speeds when they reach the west coast of [[North America]] or Europe, where they are known as [[European windstorm]]s. The extratropical remnants of [[Hurricane Iris (1995)|Hurricane Iris]] in [[1995]] became such a windstorm.<ref name="IrisTCR">{{cite web| author = Rappaport, Edward N. | url= http://www.nhc.noaa.gov/1995iris.html | title=Preliminary Report: Hurricane Iris: 22 August-4 September 1995 | publisher=[[National Hurricane Center]] | date=[[November 2]], [[2000]]|accessdate=2006-11-29}}</ref>

A hurricane can weaken if an outer eye wall forms (typically around 50-100&nbsp;miles from the center of the storm), choking off the convection within the inner eye wall. Such weakening is called an [[eyewall replacement cycle]], and is usually temporary.<ref name="AOML FAQ D8"/> Additionally, a cyclone can merge with another area of low pressure, becoming a larger area of low pressure. This can strengthen the resultant system, although it may no longer be a tropical cyclone.<ref name="EAM"/>

===Artificial dissipation===
In the 1960s and 1970s, the United States government attempted to weaken hurricanes in its [[Project Stormfury]] by [[cloud seeding|seeding]] selected storms with [[silver iodide]]. It was thought that the seeding would cause supercooled water in the outer rainbands to freeze, causing the inner eyewall to collapse and thus reducing the winds. The winds of [[1969 Atlantic hurricane season#Hurricane Debbie|Hurricane Debbie]] dropped as much as 30 percent, but then regained their strength after each of two seeding forays. In an earlier episode in [[1947]], disaster struck when a hurricane east of [[Jacksonville, Florida]] promptly changed its course after being seeded, and smashed into [[Savannah, Georgia]].<ref name="Whipple 151">{{cite book | author = Whipple, Addison | year = 1982 | title = Storm | pages = 151 | location = [[Alexandria, Virginia|Alexandria, VA]] | publisher = [[Time Life|Time Life Books]] | id = ISBN 0-8094-4312-0}}</ref> Because there was so much uncertainty about the behavior of these storms, the federal government would not approve seeding operations unless the hurricane had a less than 10 percent chance of making landfall within 48 hours, greatly reducing the number of possible test storms. The project was dropped after it was discovered that [[eye (cyclone)#eyewall replacement cycles|eyewall replacement cycles]] occur naturally in strong hurricanes, casting doubt on the result of the earlier attempts. Today, it is known that silver iodide seeding is not likely to have an effect because the amount of supercooled water in the rainbands of a tropical cyclone is too low.<ref name = "AOML FAQ C5a">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by seeding them with silver iodide?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C5a.html}}</ref>

Other approaches have been suggested over time, including cooling the water under a tropical cyclone by towing [[iceberg]]s into the tropical oceans, dropping large quantities of ice into the eye at very early stages so that latent heat is absorbed by ice at the entrance (storm cell perimeter bottom) instead of heat energy being converted to kinetic energy at high altitudes vertically above, covering the ocean in a substance that inhibits evaporation, or blasting the cyclone apart with nuclear weapons. Project Cirrus even involved throwing dry ice on a cyclone.<ref name="Sudden Sea">{{cite book | author = Scotti, R. A. | title = Sudden Sea: the Great Hurricane of 1938 | year = 2003 | pages=47 | edition = 1st ed. | publisher = Little, Brown, and Company | id = ISBN 0-316-73911-1}}</ref> These approaches all suffer from the same flaw: tropical cyclones are simply too large for any of them to be practical.<ref name = "AOML FAQ C5f">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Why don't we try to destroy tropical cyclones by (fill in the blank)?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/C5f.html}}</ref>

==Effects==
{{seealso|Tropical cyclone rainfall climatology}}
[[Image:cyclone Deaths.svg|thumb|right|180px|Pie graph of American tropical cyclone casualties by cause from 1970-1999]]
A mature tropical cyclone can release heat at a rate upwards of 6x10<sup>14</sup> watts.<ref name="NOAA Question of the Month"/> Tropical cyclones on the open sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks.<ref name="18cva">{{cite web|author=David Roth and Hugh Cobb|year=2001|title=Eighteenth Century Virginia Hurricanes|publisher=NOAA|accessdate=2007-02-24|url=http://www.hpc.ncep.noaa.gov/research/roth/va18hur.htm}}</ref> However, the most devastating effects of a tropical cyclone occur when they cross coastlines, making landfall. Strong [[wind]]s can damage or destroy vehicles, buildings, bridges, and other outside objects, turning loose debris into deadly flying projectiles. In the [[United States]], [[tropical cyclone scales|major hurricanes]] comprise just 21% of all landfalling tropical cyclones, though account for 83% of all damage.<ref name="faqd5">{{cite web|author=Chris Landsea|year=1998|title=How does the damage that hurricanes cause increase as a function of wind speed?|publisher=Hurricane Research Division|accessdate=2007-02-24|url=http://www.aoml.noaa.gov/hrd/tcfaq/D5.html}}</ref> The [[storm surge]], or the increase in sea level due to the cyclone, is typically the worst effect from landfalling tropical cyclones, historically resulting in 90% of tropical cyclone deaths.<ref name="oxfo">{{cite web|author=James M. Shultz, Jill Russell and Zelde Espinel|year=2005|title=Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development|publisher=Oxford Journal|accessdate=2007-02-24|url=http://epirev.oxfordjournals.org/cgi/content/full/27/1/21}}</ref>
The [[thunderstorm]] activity in a tropical cyclone produces intense [[rain]]fall, potentially resulting in flooding or mudslides. Inland areas are particularly vulnerable to freshwater [[flooding]], due to residents not preparing adequately.<ref name=NHCFlooding>{{cite web | author = Rappaport, Ed | url = http://www.nhc.noaa.gov/HAW2/english/inland_flood.shtml | work = National Hurricane Preparedness Week | publisher = [[National Hurricane Center]] | title = Inland Flooding | date = May 2006 | accessdate = 2006-03-31}}</ref> The broad rotation of a landfalling tropical cyclone often spawns [[History of tropical cyclone-spawned tornadoes|tornadoes]]. While these tornadoes are normally not as strong as their non-tropical counterparts, heavy damage or loss of life can still occur. Tornadoes can also be spawned
as a result of [[Eye (cyclone)#Eyewall mesovortices|eyewall mesovortices]], which persist until landfall.
<ref name = "AOML FAQ L6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Are TC tornadoes weaker than midlatitude tornadoes?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/L6.html}}</ref>
[[Image:Hurricane katrina damage gulfport mississippi.jpg|thumb|180px|right|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. 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.<ref name="Shultz Epid Reviews 2005"/> Overall, in the last two centuries, tropical cyclones have been responsible for the deaths of about 1.9&nbsp;million persons worldwide. 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. Furthermore, crowded evacuees in [[shelter]]s increase the risk of disease propagation.<ref name="Shultz Epid Reviews 2005"/> Tropical cyclones often knock out power to tens or hundreds of thousands of people, preventing vital communication and hampering rescue efforts.<ref name="Power failures">{{cite news|author=Staff Writer|date=2005-08-30|title=Hurricane Katrina Situation Report #11|publisher=Office of Electricity Delivery and Energy Reliability (OE) [[United States Department of Energy]]|accessdate=2007-02-24|url=http://www.oe.netl.doe.gov/docs/katrina/katrina_083005_1600.pdf}}</ref> Tropical cyclones often destroy key bridges, overpasses, and roads, complicating efforts to transport food, clean water, and medicine to the areas that need it. Furthermore, the damage caused by tropical cyclones to buildings and dwellings can result in economic damage to a region, and to a [[diaspora]] of the population of the region.<ref name="Shultz Epid Reviews 2005"/>

===Beneficial effects of tropical cyclones===
Although cyclones take an enormous toll in lives and personal property, they may be important factors in the [[precipitation (meteorology)|precipitation]] regimes of places they impact and bring much-needed precipitation to otherwise dry regions. Hurricanes in the eastern north Pacific often supply moisture to the [[Southwestern United States]] and parts of Mexico.<ref name="2005 EPac outlook">[[National Oceanic and Atmospheric Administration]] [http://www.cpc.ncep.noaa.gov/products/Epac_hurr/Epac_hurricane.html 2005 Tropical Eastern North Pacific Hurricane Outlook] accessed May 2, 2006</ref> [[Japan]] receives over half of its rainfall from typhoons.<ref name="Whipple 54">{{cite book | author = Whipple, Addison | year = 1982 | title = Storm | pages = 54 | location = [[Alexandria, Virginia|Alexandria, VA]] | publisher = [[Time Life|Time Life Books]] | id = ISBN 0-8094-4312-0}}</ref> [[Hurricane Camille]] averted drought conditions and ended water deficits along much of its path,<ref name="Christopherson">{{cite book | author = Christopherson, Robert W. | date = 1992 | title = Geosystems: An Introduction to Physical Geography | pages = 222–224 | publisher = Macmillan Publishing Company | location = [[New York City|New York]] | id = ISBN 0-02-322443-6}}</ref> though it also killed 259 people and caused $9.14&nbsp;billion (2005 [[USD]]) in damage.

Hurricanes also help to maintain the global heat balance by moving warm, moist tropical air to the mid-latitudes and polar regions.<ref name="Zurich">{{cite web | publisher = Zurich Financial Services | url = http://www.zurich.com/main/productsandsolutions/industryinsight/2005/july2005/industryinsight20050711_004.htm | title = Living With an Annual Disaster | date = July/August 2005 | accessdate = 2006-11-29}}</ref> 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.<ref name="Christopherson"/> 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.<ref name="NASA Cooling"/> 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 (2005)|Hurricane Emily]].<ref name="NHC Emily disc 8">{{cite web | url = http://www.nhc.noaa.gov/archive/2003/dis/al172003.discus.016.shtml | author = [[James Franklin (meteorologist)|Franklin, James]] | title = Tropical Storm Emily Discussion No. 8, 5:00 p.m. EDT | date = [[July 12]], [[2005]] | accessdate = 2006-05-02 | publisher = [[National Hurricane Center]]}}</ref>

==Observation and forecasting==
===Observation===
{{main|Tropical cyclone observation}}
[[Image:Isidore091902-p3sunset.jpg|right|thumb|180px|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 station]]s 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 if it has overtaken an unfortunate ship. Even in these cases, real-time measurements are 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]].<ref name="Hurricane Hunters">{{cite web | author = 403rd Wing | url = http://www.hurricanehunters.com | title = The Hurricane Hunters | publisher = [[Hurricane Hunters|53rd Weather Reconnaissance Squadron]] | accessdate = 2006-03-30}}</ref> 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 dropsonde]]s 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.<ref name="SunHerald">{{cite news | author = Bowman, Lee | title = Drones defy heart of storm | url = http://www.sunherald.com/mld/sunherald/12699210.htm | publisher = [[The Sun Herald]] | accessdate = 2006-03-30}}</ref>

Tropical cyclones far from land are tracked by [[weather satellite]]s capturing [[visible light|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<ref name="FCMP">{{cite web | url = http://users.ce.ufl.edu/~fcmp/overview/overview.htm | author = Florida Coastal Monitoring Program | title = Project Overview | accessdate = 2006-03-30 | publisher = [[University of Florida]]}}</ref> and the Wind Engineering Mobile Instrumented Tower Experiment.<ref name="WEMITE">{{cite web | url = http://www.atmo.ttu.edu/WEMITE/introduction.htm | author= Hurricane Research Team | title = Texas Tech Hurricane Research Team Project History and Information | publisher = [[Texas Tech University]] | accessdate = 2006-03-30}}</ref> 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.

[[Image:NHC_Atlantic_Forecast_Error_Trends.gif|thumb|right|180px|A general decrease in error trends in tropical cyclone path prediction is evident since the 1970s]]

===Forecasting===
{{seealso|Tropical cyclone prediction model}}
{{seealso|Tropical cyclone rainfall forecasting}}
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. High-speed computers and sophisticated simulation software allow forecasters to produce [[tropical cyclone prediction model|computer models]] that forecast tropical cyclone tracks based on the future position and strength of high- and low-pressure systems. Combining forecast models with increased 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.<ref name="NHC forecast verifications models">{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/verification/verify6.shtml?#FIG1 | work = National Hurricane Center Forecast Verification | title = Annual average model track errors for Atlantic basin tropical cyclones for the period 1994-2005, for a homogeneous selection of "early" models | accessdate = 2006-11-30 | publisher = [[National Oceanic and Atmospheric Administration]] | date = [[May 22]], [[2006]]}}</ref> However, scientists say they are less skillful at predicting the intensity of tropical cyclones.<ref name="NHC forecast verifications Atlantic">{{cite web | author = [[National Hurricane Center]] | work = National Hurricane Center Forecast Verification | url = http://www.nhc.noaa.gov/verification/verify5.shtml? | title = Annual average official track errors for Atlantic basin tropical cyclones for the period 1989-2005, with least-squares trend lines superimposed | accessdate = 2006-11-30 | publisher = [[National Oceanic and Atmospheric Administration]] | date = [[May 22]], [[2006]]}}</ref> 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===
{{main|Tropical cyclone scales}}
[[Image:Typhoon saomai 060807.jpg|thumb|right|180px|Three tropical cyclones at different stages of development. The weakest, on the left, demonstrates only the most basic circular shape. The storm at the top right, which is stronger, demonstrates [[rainbands|spiral banding]] and increased centralization, while the storm in the lower right, the strongest, has developed an [[eye (cyclone)|eye]].]]
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. For example, if a [[#Tropical Storm|tropical storm]] in the Northwestern Pacific reaches hurricane-strength winds on the [[Beaufort scale]], it is referred to as a ''typhoon''; if a tropical storm passes the same benchmark in the [[Pacific hurricane|North-East Pacific Ocean]], or in [[Atlantic hurricane|the Atlantic]], it is called a ''hurricane''.<ref name="NHC glossary"/> Neither term is used in the South Pacific.

Additionally, as indicated in the table below, each basin uses a separate [[Tropical cyclone scales|system of terminology]], making comparisons between different basins difficult. In the Pacific Ocean, hurricanes from the Central North Pacific sometimes cross the [[International Date Line]] into the Northwest Pacific, becoming typhoons (such as [[Hurricane Ioke|Hurricane/Typhoon Ioke]] in 2006); on rare occasions, the reverse will occur.<ref name="CPHC John TCR">{{cite web | author=[[Central Pacific Hurricane Center]] | title=Hurricane John Preliminary Report | publisher=[[National Oceanic and Atmospheric Administration]] | url=http://www.prh.noaa.gov/cphc/summaries/1994.php#John | year= 2004 | accessdate=2007-03-23}}</ref> It should also be noted that typhoons with sustained winds greater than 130&nbsp;[[knot (speed)|knots]] (240&nbsp;[[kilometres per hour|km/h]] or 150&nbsp;[[miles per hour|mph]]) are called ''Super Typhoons'' by the Joint Typhoon Warning Center.<ref name="SUPERDUPER">{{cite web | author = Bouchard, R. H. | url = http://metocph.nmci.navy.mil/jtwc/pubref/References/where_have_all_the_super_typhoons_gone.ppt | title = A Climatology of Very Intense Typhoons: Or Where Have All the Super Typhoons Gone? | format = [[Microsoft PowerPoint|PPT]] | accessdate = 2006-12-05 | date = April 1990}}</ref>

<span id="Tropical depression" />A '''tropical depression''' is an organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds of less than 17&nbsp;[[metre per second|m/s]] (33&nbsp;[[knot (speed)|kt]], 38&nbsp;[[miles per hour|mph]], or 62&nbsp;[[kilometres per hour|km/h]]). It has no [[eye (cyclone)|eye]] and does not typically have the organization or the spiral shape of more powerful storms. However, it is already a low-pressure system, hence the name "depression."<ref name = "NOAA preparedness"/> The practice of the [[Philippines]] is to name tropical depressions from their own naming convention when the depressions are within the Philippines' area of responsibility.<ref name="AOML FAQ B2">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What are the upcoming tropical cyclone names? | publisher = [[NOAA]] | accessdate = 2006-12-11 | url = http://www.aoml.noaa.gov/hrd/tcfaq/B2.html}}</ref>

<span id="Tropical storm" />A '''tropical storm''' is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 17 and 32&nbsp;m/s (34&ndash;63&nbsp;kt, 39&ndash;73&nbsp;mph, or 62&ndash;117&nbsp;km/h). At this point, the distinctive cyclonic shape starts to develop, although an eye is not usually present. Government weather services, other than the Philippines, first assign names to systems that reach this intensity (thus the term ''named storm'').<ref name = "NOAA preparedness"/>

<span id="Hurricane" /><span id="Typhoon" />A '''hurricane''' or '''typhoon''' (sometimes simply referred to as a tropical cyclone, as opposed to a depression or storm) is a system with sustained winds of at least 33&nbsp;m/s (64&nbsp;kt, 74&nbsp;mph, or 118&nbsp;km/h).<ref name = "NOAA preparedness"/> A cyclone of this intensity 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 16&ndash;80&nbsp;[[kilometre|km]] (10&ndash;50&nbsp;[[mile|mi]]) wide in which the strongest [[thunderstorm]]s and winds circulate around the storm's center. Maximum sustained winds in the strongest tropical cyclones have been estimated at about 85&nbsp;m/s (165&nbsp;kt, 190&nbsp;mph, 305&nbsp;km/h).<ref name = "AOML FAQ E1"/>
{| class=wikitable style="font-size:92%;"
! colspan=9 style="background: #ccf;" | '''Tropical Cyclone Classifications (all winds are 10-minute averages)'''
|-
! [[Beaufort scale]]
! 10-minute sustained winds (knots)
! N Indian Ocean<br>[[Indian Meteorological Department|IMD]]
! SW Indian Ocean<br>[[Météo-France|MF]]
! Australia<br>[[Bureau of Meteorology (Australia)|BOM]]
! SW Pacific<br>[[Fiji Meteorological Service|FMS]]
! NW Pacific<br>[[Japan Meteorological Agency|JMA]]
! NW Pacific<br>[[Joint Typhoon Warning Center|JTWC]]
! NE Pacific &<br>N Atlantic<br>[[National Hurricane Center|NHC]] & [[Central Pacific Hurricane Center|CPHC]]
|-
| 0–6
| <28
| Depression
| Trop. Disturbance
|rowspan="3"| Tropical Low
|rowspan="3"| Tropical Depression
|rowspan="3"| Tropical Depression
|rowspan="2"| Tropical Depression
|rowspan="2"| Tropical Depression
|-
|rowspan="2"| 7
| 28-29
|rowspan="2"| Deep Depression
|rowspan="2"| Tropical Depression
|-
| 30-33
|rowspan="3"| Tropical Storm
|rowspan="3"| Tropical Storm
|-
| 8–9
| 34–47
| Cyclonic Storm
| Moderate Tropical Storm
| Trop. Cyclone (1)
|rowspan="11"| Tropical Cyclone
| Tropical Storm
|-
| 10
| 48–55
|rowspan="2"| Severe Cyclonic Storm
|rowspan="2"| Severe Tropical Storm
|rowspan="2"| Tropical Cyclone (2)
|rowspan="2"| Severe Tropical Storm
|-
| 11
| 56–63
|rowspan="7"| Typhoon
|rowspan="2"| Hurricane (1)
|-
|rowspan="8"| 12
| 64–72
|rowspan="7"| Very Severe Cyclonic Storm
|rowspan="3"| Tropical Cyclone
|rowspan="2"| Severe Tropical Cyclone (3)
|rowspan="8"| Typhoon
|-
| 73–85
| Hurricane (2)
|-
| 86–89
|rowspan="3"| Severe Tropical Cyclone (4)
|rowspan="2"| Major Hurricane (3)
|-
| 90–99
|rowspan="3"| Intense Tropical Cyclone
|-
| 100–106
|rowspan="3"| Major Hurricane (4)
|-
| 107-114
|rowspan="3"| Severe Tropical Cyclone (5)
|-
| 115–119
|rowspan="2"| Very Intense Tropical Cyclone
|rowspan="2"| Super Typhoon
|-
| >120
| Super Cyclonic Storm
| Major Hurricane (5)
|}

===Origin of storm terms===
The word ''typhoon'', used today in the Northwest Pacific, has two possible and equally plausible origins. The first is from the [[Chinese Language|Chinese]] 大風 ([[Cantonese language|Cantonese]]: daaih fūng; [[Mandarin language|Mandarin]]: dà fēng) which means "great [[wind]]."<ref name = "EO lib names">{{cite web | author = Earth Observatory | title = Hurricanes: The Greatest Storms on Earth | accessdate = 2006-07-19|publisher = [[NASA|National Aeronautics and Space Administration]] | url = http://earthobservatory.nasa.gov/Library/Hurricanes/printall.php}}</ref> (The Chinese term as 颱風 or 台风 táifēng, and 台風 ''taifū'' 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).<ref name="CWB Taiwan typhoon">{{cite web | url=http://photino.cwb.gov.tw/rdcweb/lib/cd/cd01conf/cd_00002.htm | title=臺灣百年來之颱風 | date=[[2002-12-10]] | accessdate=2006-12-13 | author=Taiwan Ministry of Communications/[[Central Weather Bureau]] | publisher=Government of the Republic of China | language={{zh icon}}}}</ref> Alternatively, the word may be derived from [[Urdu language|Urdu]], [[Persian language|Persian]] and [[Arabic language|Arabic]] ''ţūfān''<ref name="CWB Taiwan typhoon"/> (طوفان), which in turn originates from [[Greek language|Greek]] ''[[Typhon|tuphōn]]'' (Τυφών), a monster in [[Greek mythology]] responsible for hot winds.<ref name="Greek typhoon">{{cite encyclopedia | encyclopedia = [[The American Heritage Dictionary of the English Language]] | year = 2004 | publisher = [[Dictionary.com]] | url = http://dictionary.reference.com/browse/typhoon | accessdate = 2006-12-14 | title = Typhoon | edition = 4th ed.}}</ref> The related [[Portuguese language|Portuguese]] word ''tufão'', used in Portuguese for any tropical cyclone, is also derived from Greek ''tuphōn''.

The word ''hurricane'', used in the North Atlantic and Northeast Pacific, is derived from the name of a native [[Caribbean]] [[Amerindian]] storm [[god]], [[Huracan]], via [[Spanish language|Spanish]] ''huracán''.<ref name = "AOML FAQ B4">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is the origin of the word "hurricane"?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/B4.html}}</ref> (Huracan is also the source of the word ''Orcan'', another word for the [[European windstorm]]. These events should not be confused.)

===Naming===
{{main|Tropical cyclone naming|Lists of tropical cyclone names}}
Storms reaching tropical storm strength were initially given names to eliminate confusion when there are multiple systems in any individual basin at the same time which assists in warning people of the coming storm.<ref>National Hurricane Center. [http://www.nhc.noaa.gov/aboutnames.shtml Worldwide Tropical Cyclone Names.] Retrieved on [[2006-12-28]].</ref> In most cases, a tropical cyclone retains its name throughout its life; however, under [[Tropical cyclone naming#Renaming of tropical cyclones|special circumstances]], tropical cyclones may be renamed while active. These names are taken from lists which vary from region to region and are drafted a few years ahead of time. The lists are decided upon, depending on the regions, either by committees of the [[World Meteorological Organization]] (called primarily to discuss many other issues), or by national weather offices involved in the forecasting of the storms. Each year, the names of particularly destructive storms (if there are any) are "retired" and new names are chosen to take their place.

==Notable tropical cyclones==
{{main|List of notable tropical cyclones|List of notable Atlantic hurricanes|List of notable Pacific hurricanes}}
Tropical cyclones that cause extreme destruction are rare, though when they occur, then can cause great amounts of damage or thousands of fatalities.

The [[1970 Bhola cyclone]] is the deadliest tropical cyclone on record, killing over 300,000 people<ref name="faqe9">{{cite web|author=Chris Landsea|year=1993|title=Which tropical cyclones have caused the most deaths and most damage?|publisher=Hurricane Research Division|accessdate=2007-02-23|url=http://www.aoml.noaa.gov/hrd/tcfaq/E9.html}}</ref> and potentially as many as 1 million<ref name="1970death">{{cite news|author=Lawson|year=1999|title=South Asia: A history of destruction|publisher=[[BBC|British Broadcasting Corporation]]|accessdate=2007-02-23|url=http://news.bbc.co.uk/1/hi/world/south_asia/503139.stm}}</ref> after striking the densely population [[Ganges Delta]] region of [[Bangladesh]] on [[November 13]], [[1970]]. Its powerful storms surge was responsible for the high death toll.<ref name="faqe9"/> The [[List of North Indian cyclone seasons|North Indian cyclone basin]] has historically been the deadliest basin, with several cyclones since [[1900]] killing over 100,000 people, each in Bangladesh.<ref name="Shultz Epid Reviews 2005">{{cite journal | author = Shultz, James M., Jill Russell and Zelde Espinel | title = Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development | journal = Epidemiologic Reviews | volume = 27 | issue = 1 | pages = 21–25 | url = http://epirev.oxfordjournals.org/cgi/content/full/27/1/21 | date = July 2005 | accessdate=2006-12-14}}</ref><ref name="Deadliest cyclone">{{cite journal | author = Frank, Neil L. and S. A. Husain | title = The Deadliest Tropical Cyclone in History | date = June 1971 | url = http://ams.allenpress.com/archive/1520-0477/52/6/pdf/i1520-0477-52-6-438.pdf | format = PDF | journal = Bulletin of the American Meteorological Society | volume = 52 | issue = 6 | pages = 438–445 | accessdate = 2006-12-14}}</ref> Elsewhere, [[Typhoon Nina (1975)|Typhoon Nina]] killed 29,000 in [[China]] due to [[100-year flood|2000-year flooding]] which caused 62 dams along the [[Banqiao Dam]] to fail, with another 145,000 killed during subsequent famine and epidemic.<ref name="nina75">{{cite web|author=Hydrology Department of Henan Province|year=2006|title=Flood and drought disaster|language=Chinese|accessdate=2007-02-23|url=http://www.hnsl.gov.cn/look0/article.php?L_Type=1&id=297}}</ref> The [[Great Hurricane of 1780]] is the deadliest [[Atlantic hurricane]] on record, killing about 22,000 people in the [[Lesser Antilles]].
<ref name=NHCPastDeadly>{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/pastdeadlyapp1.shtml? | title = The Deadliest Atlantic Tropical Cyclones, 1492-1996 | accessdate = 2006-03-31 | date = [[April 22]], [[1997]] | publisher = [[National Oceanic and Atmospheric Administration]]}}</ref> A tropical cyclone does need not be particularly strong to cause memorable damage, primarily if the deaths are from rainfall or mudslides. [[Tropical Storm Thelma]] in November [[1991]] killed thousands in the [[Philippines]],<ref name="JTWCThelma">{{cite web | url = https://metocph.nmci.navy.mil/jtwc/atcr/1991atcr/pdf/wnp/27w.pdf | title = Typhoon Thelma (27W) | accessdate = 2006-03-31 | author = [[Joint Typhoon Warning Center]] | work = 1991 Annual Tropical Cyclone Report | format = PDF}}</ref> while in 1982, the unnamed tropical depression that eventually became [[Hurricane Paul (1982)|Hurricane Paul]] killed around 1,000 people in [[Central America]].<ref name="MWR Paul 1982">{{cite journal | author = Gunther, E. B., R.L. Cross, and R.A. Wagoner | title = Eastern North Pacific Tropical Cyclones of 1982 | url = http://ams.allenpress.com/archive/1520-0493/111/5/pdf/i1520-0493-111-5-1080.pdf | month = May | year = 1983 | journal = [[Monthly Weather Review]] | format = PDF | volume = 111 | issue = 5 | accessdate = 2006-03-31}}</ref>

[[Hurricane Katrina]] is estimated as the costliest tropical cyclone worldwide,<ref name="epi">{{cite web|author=Earth Policy Institute|year=2006|title=Hurricane Damages Sour to New Levels|publisher=United States Department of Commerce|accessdate=2007-02-23|url=http://www.earth-policy.org/Updates/2006/Update58_data.htm}}</ref> causing $81.2 billion in property damage (2005 USD)<ref name="KatrinaTCR">{{cite web|author = Knabb, Richard D., Jamie R. Rhome and Daniel P. Brown | url=http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf | format=PDF | title=Tropical Cyclone Report: Hurricane Katrina: 23-30 August 2005 | publisher=[[National Hurricane Center]] | date=[[December 20]], [[2005]] | accessdate=2006-05-30}}</ref> and estimates beginning at at over $100 billion (2005 USD).<ref name="epi"/> The [[National Hurricane Center]] in [[Miami, Florida]] considered Katrina as the worst natural disaster in [[History of the United States|United States history]],<ref name="NHC Atlantic Monthly Report for August 2005">{{cite web | author = [[National Hurricane Center]] | url = http://www.nhc.noaa.gov/archive/2005/tws/MIATWSAT_aug.shtml? | title = Monthly Tropical Weather Summary for the North Altantic, Caribbean Sea and the Gulf of Mexico | accessdate = 2006-03-31 | publisher = [[National Oceanic and Atmospheric Administration]] | date = August 2005}}</ref> killing at least 1,836 after striking [[Louisiana]] and [[Mississippi]] as a [[tropical cyclone scales|major hurricane]] in [[August 2005]]. Prior to Katrina, the costliest tropical cyclone was [[Hurricane Andrew]] in [[August 1992]], which caused an estimated $39 billion (2005 [[USD]]) in damage in [[Florida]].<ref name="KatrinaTCR">{{cite web|author = Knabb, Richard D., Jamie R. Rhome and Daniel P. Brown | url=http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf | format=PDF | title=Tropical Cyclone Report: Hurricane Katrina: 23-30 August 2005 | publisher=[[National Hurricane Center]] | date=[[December 20]], [[2005]] | accessdate=2006-05-30}}</ref> [[Hurricane Iniki]] in [[1992]] was the most powerful storm to strike [[Hawaii]] in recorded history, hitting [[Kauai]] as a Category 4 hurricane, killing six people, and causing U.S. $3 billion in damage.<ref name="InikiTCR">{{cite web|publisher = [[National Oceanic and Atmospheric Administration]] | url= http://www.prh.noaa.gov/cphc/summaries/1992.php#Iniki | title=Hurricane Iniki Natural Disaster Survey Report |author=[[Central Pacific Hurricane Center]]| accessdate=2006-03-31}}</ref> Other destructive Eastern [[Pacific hurricane]]s include [[Hurricane Pauline|Pauline]] and [[Hurricane Kenna|Kenna]], both causing severe damage after striking [[Mexico]] as a major hurricane.<ref name="PaulineTCR">{{cite web | last=Lawrence | first=Miles B. | url=http://www.nhc.noaa.gov/1997pauline.html | title=Preliminary Report: Hurricane Pauline: 5-10 October 1997 | publisher=[[National Hurricane Center]] | date=[[November 7]], [[1997]] | accessdate=2006-03-31}}</ref><ref name="KennaTCR">{{cite web | author = [[James Franklin (meteorologist)|Franklin, James L]]. | url=http://www.nhc.noaa.gov/2002kenna.shtml | title=Tropical Cyclone Report: Hurricane Kenna: 22-26 October 2002 | publisher=[[National Hurricane Center]] | date=[[December 26]], [[2002]] | accessdate=2006-03-31}}</ref> In [[March 2004]], [[Cyclone Gafilo]] struck northeastern [[Madagascar]] as a powerful cyclone, killing 74, affecting more than 200,000, and becoming the worst cyclone to affect the nation for over 20 years.<ref name="gafilo">{{cite web|author=World Food Programme|year=2004|title=WFP Assists Cyclone And Flood Victims in Madagascar|accessdate=2007-02-24|url=http://www.sidsnet.org/archives/other-newswire/2004/msg00182.html}}</ref>

[[Image:Typhoonsizes.jpg|right|frame|The relative sizes of [[Typhoon Tip]], [[Cyclone Tracy]], and the United States.]]
The most intense storm on record was [[Typhoon Tip]] in the northwestern Pacific Ocean in [[1979]], which reached a minimum pressure of 870 [[millibar|mbar]] and maximum sustained wind speeds of 190 mph (305 km/h).<ref name="jtwc">{{cite web|author=George M. Dunnavan & John W. Dierks|year=1980|title=An Analysis of Super Typhoon Tip (October 1979)|publisher=Joint Typhoon Warning Center|accessdate=2007-01-24|url=http://ams.allenpress.com/archive/1520-0493/108/11/pdf/i1520-0493-108-11-1915.pdf}}</ref> Tip, however, does not solely hold the record for fastest sustained winds in a cyclone. [[1997 Pacific typhoon season#Typhoon Keith|Typhoon Keith]] in the Pacific and Hurricanes [[Hurricane Camille|Camille]] and [[Hurricane Allen|Allen]] in the North Atlantic currently share this record with Tip.<ref name="Weathermatrix Mitch">{{cite web | author = Ferrell, Jesse | publisher = Weathermatrix.net | url = http://www.weathermatrix.net/tropical/1998/13/mitch.html | title = Hurricane Mitch | accessdate = 2006-03-30 | date = [[October 26]], [[1998]]}}</ref> 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.<ref name="hurdat">{{cite web|author=NHC Hurricane Research Division|date=2006-02-17|title=Atlantic hurricane best track ("HURDAT")|publisher=NOAA|accessdate=2007-02-22|url=http://www.aoml.noaa.gov/hrd/hurdat/easyhurdat_5105.html#0_0}}</ref> [[Typhoon Nancy (1961)|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.<ref name = "AOML FAQ E1">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Which is the most intense tropical cyclone on record? | publisher = [[NOAA]] | accessdate = 2006-07-25|url = http://www.aoml.noaa.gov/hrd/tcfaq/E1.html}}</ref> Similarly, a surface-level gust caused by [[Typhoon Paka]] on [[Guam]] was recorded at 236 mph (380 km/h). Had it been confirmed, it would be the strongest non-[[tornado|tornadic]] wind ever recorded on the [[Earth]]'s surface, but the reading had to be discarded since the [[anemometer]] was damaged by the storm.<ref name="NWSPaka">{{cite web | author = Houston, Sam, Greg Forbes and Arthur Chiu | publisher = [[National Weather Service]] | date = [[17 August]], [[1998]] | url = http://www.aoml.noaa.gov/hrd/project98/sh_proj1.html | title = Super Typhoon Paka's (1997) Surface Winds Over Guam | accessdate = 2006-03-30}}</ref>

In addition to being the most intense tropical cyclone on record, Tip was the largest cyclone on record, with tropical storm-force winds 1,350 miles (2,170 km) in diameter. The smallest storm on record, [[Cyclone Tracy]], was roughly 60 miles (100 km) wide before striking [[Darwin, Northern Territory|Darwin]], [[Australia]] in [[1974]].<ref name = "AOML FAQ E5">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: Which are the largest and smallest tropical cyclones on record?|publisher = [[NOAA]] | accessdate= 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/E5.html}}</ref>

[[Hurricane John (1994)|Hurricane John]] is the longest-lasting tropical cyclone on record, lasting 31 days in [[1994 Pacific hurricane season|1994]]. Prior to the advent of satellite imagery in 1961, however, many tropical cyclones were underestimated in their durations.<ref name="john94">{{cite web|author=Neal Dorst|year=2006|title=Which tropical cyclone lasted the longest?|publisher=Hurricane Research Division|accessdate=2007-02-23|url=http://www.aoml.noaa.gov/hrd/tcfaq/E6.html}}</ref> John is the second longest-tracked tropical cyclone in the Northern Hemisphere on record, behind [[1960 Pacific typhoon season#Typhoon Ophelia|Typhoon Ophelia]] of 1960 which had a path of 8500 miles (12500 km). Reliable data for Southern Hemisphere cyclones are unavailable.<ref name="faqe7">{{cite web|author=Neal Dorst|year=2006|url=http://www.aoml.noaa.gov/hrd/tcfaq/E7.html|accessdate=2007-02-23|title=What is the farthest a tropical cyclone has traveled ?|publisher=Hurricane Research Division}}</ref>

In [[popular culture]], tropical cyclones have made appearances in different types of media, including [[film]]s, [[book]]s, [[television]], [[music]], and [[electronic game]]s. The media can have tropical cyclones that are entirely [[fiction]]al, or can be based on real events.<ref name = "AOML FAQ J4">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What fictional books, plays, and movies have been written involving tropical cyclones? | publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/J4.html}}</ref> For example, [[George Rippey Stewart]]'s ''[[Storm (novel)|Storm]]'', a [[best-seller]] published in [[1941]], is thought to have influenced meteorologists into giving female names to Pacific tropical cyclones.<ref>{{cite web | author = Heidorn, Keith C. | url = http://www.islandnet.com/~see/weather/arts/storm.htm | title = George Stewart's Storm: Remembering A Classic. | accessdate = 2006-12-10 | publisher = The Weather Doctor}}</ref> Another example is the hurricane in ''[[The Perfect Storm (film)|The Perfect Storm]]'', which describes the sinking of the ''[[Andrea Gail]]'' by the [[1991 Halloween Nor'easter]].<ref name="1991 Perfect Storm">{{cite web | author = McCown, Sean | title = Unnamed Hurricane 1991 | work = Satellite Events Art Gallery: Hurricanes | url = http://www.ncdc.noaa.gov/oa/satellite/satelliteseye/hurricanes/unnamed91/unnamed91.html | publisher = [[National Climatic Data Center]] | date = [[December 13]], [[2004]] | accessdate = 2007-02-04}}</ref> Also, [[Tropical cyclones in popular culture|hypothetical hurricanes]] have also been featured in parts of the plots of series such as ''[[The Simpsons]]'', ''[[Invasion (TV series)|Invasion]]'', ''[[Family Guy]]'', ''[[Seinfeld]]'', and ''[[CSI Miami]]''.

== Long term trends in cyclone activity ==
[[Image:NOAA ACE index 1950-2004 RGB.svg|thumb|right|250px|Atlantic Multidecadal Cycle since 1950, using accumulated cyclone energy (ACE)]]
:{{seealso|Atlantic hurricane reanalysis}}
While the number of storms in the Atlantic has increased since 1995, there is no obvious global trend; the annual global number of tropical cyclones remains about 87&nbsp;±&nbsp;10. However, there is some evidence that the intensity of hurricanes is increasing. "Records of hurricane activity worldwide show an upswing of both the maximum wind speed in and the duration of hurricanes. The energy released by the average hurricane (again considering all hurricanes worldwide) seems to have increased by around 70% in the past 30 years or so, corresponding to about a 15% increase in the maximum wind speed and a 60% increase in storm lifetime."<ref name="EmanuelHomepage">{{cite web | url = http://wind.mit.edu/~emanuel/anthro2.htm | author = [[Kerry Emanuel|Emanuel, Kerry]] | title = Anthropogenic Effects on Tropical Cyclone Activity | accessdate = 2006-03-30 | date = January 2006}}</ref>

Atlantic storms are becoming more destructive financially, since five of the ten most expensive storms in [[United States]] history have occurred since [[1990]]. This can be attributed to the increased intensity and duration of hurricanes striking North America,<ref name="EmanuelHomepage"/> and to a greater degree, the number of people living in susceptible coastal area following increased 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 may have gone unmeasured in some instances. 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.<ref name="BOM TC Guide 1.3">{{cite web | publisher = [[Bureau of Meteorology]] | url = http://www.bom.gov.au/bmrc/pubs/tcguide/ch1/ch1_3.htm | title = 1.3: A Global Climatology | author = Neumann, Charles J. | work = Global Guide to Tropical Cyclone Forecasting | accessdate = 2006-11-30}}</ref>

The number and strength of Atlantic hurricanes may undergo a 50-70 year cycle, also known as a multi-decadal cycle. Although more common since 1995, few above-normal hurricane seasons occurred during 1970-1994.<ref name="RMS activity">{{cite web | author = [[Risk Management Solutions]] | url = http://www.rms.com/Publications/60HUActivityRates_whitepaper.pdf | format = PDF | title = U.S. and Caribbean Hurricane Activity Rates. | date = March 2006 | accessdate = 2006-11-30}}</ref> 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.<ref name="Columbia CCSR">{{cite web | author = Center for Climate Systems Research | title = Hurricanes, Sea Level Rise, and New York City | url = http://www.ccsr.columbia.edu/information/hurricanes/ | publisher = [[Columbia University]] | accessdate = 2006-11-29}}</ref>

These active hurricane seasons predated satellite coverage of the Atlantic basin. Before the satellite era began in 1960, tropical storms or hurricanes went undetected unless a ship reported a voyage through the storm or a storm hit land in a populated area.<ref name="BOM TC Guide 1.3"/> The official record, therefore, could miss 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===
Most [[climatologist]]s agree that a single storm, or even a single season, cannot clearly be attributed to a single cause such as [[global warming]] or natural variation.<ref name="realclimate">{{cite web | author = [[Stefan Rahmstorf|Rahmstorf, Stefan]], [[Michael Mann]], Rasmus Benestad, [[Gavin Schmidt]] and [[William Connolley]] | url = http://www.realclimate.org/index.php?p=181 | title = Hurricanes and Global Warming - Is There a Connection? | publisher = [[RealClimate]] | date = [[September 2]], [[2005]] | accessdate = 2006-03-20}}</ref> The [[United States|U.S.]] [[National Oceanic and Atmospheric Administration]] [[Geophysical Fluid Dynamics Laboratory]] performed a simulation to determine if there is a [[statistics|statistical]] [[trend]] in the frequency or strength of cyclones. The simulation concluded "the strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century as the earth's climate is warmed by increasing levels of greenhouse gases in the atmosphere."<ref name="GFDL warming">{{cite web | author = [[Geophysical Fluid Dynamics Laboratory]] | url = http://www.oar.noaa.gov/spotlite/archive/spot_gfdl.html | title = Global Warming and Hurricanes | accessdate = 2006-11-29 | publisher = [[National Oceanic and Atmospheric Administration]]}}</ref> In an article in ''[[Nature (journal)|Nature]]'', [[Kerry Emanuel]] stated that potential hurricane destructiveness, a measure combining hurricane strength, duration, and frequency, "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." Emanuel predicted "a substantial increase in hurricane-related losses in the twenty-first century."<ref name="Nature Emanuel 2005">{{cite journal | url = ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdf | format = PDF | author = [[Kerry Emanuel|Emanuel, Kerry]] | journal =[[Nature (journal)|Nature]] | volume = 436 | issue = 7051 | pages = 686–688 | accessdate = 2006-03-20 | title = Increasing destructiveness of tropical cyclones over the past 30 years}}</ref>

Similarly, P.J. Webster and others published an article in ''[[Science (journal)|Science]]'' examining the "changes in tropical cyclone number, duration, and intensity" over the last 35 years, the period when satellite data has been available. The main finding was although the number of cyclones decreased throughout the planet excluding the north [[Atlantic Ocean]], there was a great increase in the number and proportion of very strong cyclones.<ref name="Webster et al. 2005">{{cite journal | author = Webster, P. J., G. J. Holland, J. A. Curry and H.-R. Chang | url = http://www.sciencemag.org/cgi/reprint/309/5742/1844.pdf | title = Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment | format = PDF | journal = [[Science (journal)|Science]] | date = [[September 16]], [[2005]] | volume = 309 | issue = 5742 | pages = 1844-1846 | accessdate = 2006-03-20}}</ref> Both Emanuel and Webster et al. consider [[sea surface temperatures]] to be vital in the development of cyclones. The increase in temperatures is believed to be due to global warming and the hypothesized [[Atlantic Multidecadal Oscillation]] (AMO), a possible 50&ndash;70 year pattern of temperature variability. However, Emanuel observed the recent temperature increase as outside the range of previous sea surface temperature peaks. Thus, both global warming and a natural variation such as the AMO could have contributed to the warming of the tropical Atlantic over the past decades, though an exact attribution has not been defined.<ref name=realclimate/>

In [[February 2007]], the [[United Nations]] [[Intergovernmental Panel on Climate Change]] released its [[IPCC Fourth Assessment Report|fourth assessment report]] on [[climate change]]. The report noted many observed changes in the climate including atmospheric composition, global average temperatures, ocean conditions, and other climate changes. The report concluded the observed increase in hurricane intensity is larger than climate models predict. Additionally, the report considered it likely that hurricane intensity will continue to increase through the 21st century, and declared it more likely than not that there have been some human contribution to the increases in hurricane intensity.<ref name="ipcc">{{cite web|author=Richard Alley, et. al|year=2007|title=Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change|publisher=United Nations|accessdate=2007-02-23|url=http://www.ipcc.ch/SPM2feb07.pdf}}</ref>

==Related cyclone types==
[[Image:Gustav 09 sep 2002 1805Z.jpg|thumb|180px|right|[[Hurricane Gustav (2002)|Subtropical Storm Gustav]] in [[2002 Atlantic hurricane season|2002]]]]
{{seealso|Cyclone|Extratropical cyclone|Subtropical cyclone}}
In addition to tropical cyclones, there are two other classes of cyclones within the spectrum of cyclone types. These kinds of cyclones, known as [[extratropical cyclone]]s and [[subtropical cyclone]]s, can be stages a tropical cyclone passes through during its [[tropical cyclogenesis|formation]] or dissipation.<ref>Mark A. Lander, N. Davidson, H. Rosendal, J. Knaff, and R. Edson, J. Evans, R. Hart. [http://www.aoml.noaa.gov/hrd/iwtc/Lander4-1.html FIFTH INTERNATIONAL WORKSHOP on TROPICAL CYCLONES.] Retrieved on [[2006-12-14]].</ref>

An ''extratropical cyclone'' is a storm that derives energy from horizontal temperature differences, which are typical in higher latitudes. A tropical cyclone can become extratropical as it moves toward higher latitudes if its energy source changes from heat released by condensation to differences in temperature between air masses;<ref name = "AOML FAQ A7">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is an extra-tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html}}</ref> additionally, although not as frequently, an extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone. From space, extratropical storms have a characteristic "[[comma (punctuation)|comma]]-shaped" cloud pattern. Extratropical cyclones can also be dangerous when their low-pressure centers cause powerful winds and very high seas.

A ''subtropical cyclone'' is a [[weather]] system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. They can form in a wide band of [[latitude]], from the [[equator]] to 50°. Although subtropical storms rarely have hurricane-force winds, they may become tropical in nature as their cores warm.<ref name = "AOML FAQ A6">{{cite web | author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division | title = Frequently Asked Questions: What is a sub-tropical cyclone?|publisher = [[NOAA]] | accessdate = 2006-07-25 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A6.html}}</ref> From an operational standpoint, a tropical cyclone is usually not considered to become subtropical during its extratropical transition.<ref name=PadgetDecember2000>{{cite web | author = Padgett, Gary | url = http://australiasevereweather.com/cyclones/2001/summ0012.txt | title = Monthly Global Tropical Cyclone Summary for December 2000 | year = 2001 | accessdate = 2006-03-31}}</ref> At this time, subtropical cyclones are handled operationally similarly to tropical cyclones only in the northern half of the Western Hemisphere and the southwest Indian Ocean.

==See also==
{{tcportal}}
;Current seasons
* [[2007 Atlantic hurricane season]]
* [[2007 North Indian cyclone season]]
* [[2007 Pacific hurricane season]]
* [[2007 Pacific typhoon season]]
* [[2006-07 Southern Hemisphere tropical cyclone season]]

;Meteorology
*[[Lists of tropical cyclone names]]
*[[Mesoscale Convective Complex]]
*[[Tropical cyclogenesis]]

;Forecasting and preparation
* [[Catastrophe modeling]]
* [[Hong Kong Tropical Cyclone Warning Signals]]
* [[Hurricane preparedness]]
* [[Hurricane proof building]]
* [[Tropical cyclone watches and warnings]]

;Categories
* [[:Category:Lists of tropical cyclones]]
* [[:Category:Tropical cyclones by basin]]
* [[:Category:Tropical cyclones by region]]
* [[:Category:Tropical cyclones by season]]
* [[:Category:Tropical cyclones by strength]]

{{Cyclones}}

==Notes==
<div class="references-small">
<references />
</div>

==External links==
{{wiktionary}}
{{commonscat|Tropical cyclones}}

;Learning resources
*[http://www.bom.gov.au/bmrc/pubs/tcguide/ch1/ch1_3.htm WMO guide on cyclone terminology]
*[http://www.aoml.noaa.gov/hrd/tcfaq/A1.html Summary of cyclone terminology from NOAA FAQ]
*[http://www.pbs.org/wgbh/nova/teachers/viewing/3204_02_nsn.html NOVA scienceNOW: Hurricanes]
*{{PDF|[http://www.nhc.noaa.gov/marinersguide.pdf Mariner's Guide for Hurricane Awareness]|1.23&nbsp;[[Mebibyte|MiB]]<!-- application/pdf, 1290745 bytes -->}}
*[http://severe.worldweather.org/ World Meteorological Organization Severe Weather Information Center] - Shows all current tropical systems worldwide and their tracks
*[http://www.solar.ifa.hawaii.edu/Tropical/tropical.html Tropical Storms Worldwide] - by Hawaii University
*[http://www.fema.gov/kids/hurr.htm FEMA for Kids: Hurricanes]

;Regional specialised meteorological centers
*[http://www.nhc.noaa.gov/ US National Hurricane Center] - North Atlantic, Eastern Pacific
*[http://www.prh.noaa.gov/hnl/cphc/ Central Pacific Hurricane Center] - Central Pacific
*[http://www.jma.go.jp/en/typh/ Japan Meteorological Agency] - NW Pacific
*[http://www.imd.gov.in/ India Meteorological Department] - [[Bay of Bengal]] and the [[Arabian Sea]]
*[http://www.meteo.fr/temps/domtom/La_Reunion/ Météo-France - La Reunion] - South Indian Ocean from Africa to 90° E
*[http://www.met.gov.fj/advisories.html Fiji Meteorological Service] - South Pacific east of 160°, north of 25° S

;Past storms
*[http://www.bom.gov.au/bmrc/pubs/tcguide/ch1/ch1_3.htm Global climatology of tropical cyclones]
*[http://www.metoffice.com/weather/tropicalcyclone/images.html Tropical cyclone images and movies, from the United Kingdom Met Office]
*[http://weather.unisys.com/hurricane/ Unisys historical and contemporary hurricane track data]
*[http://www.hpc.ncep.noaa.gov/tropical/rain/tcrainfall.html United States Tropical Cyclone Rainfall Climatology] - Nearly 30 years of tropical cyclone histories with an emphasis on storm total rainfall, in color, up to present. Broken up by year, region, by point of landfall, and North American countries impacted
*[http://www.ncdc.noaa.gov/oa/rsad/gibbs/gibbs.html Global ISCCP B1 Browse System Satellite Archive]

[[Category:Tropical cyclone meteorology| ]]
[[Category:Tropical cyclones| ]]
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