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Redirect|Hurricanepp-move-indefA tropical cyclone is a storm|storm system characterized by a low pressure system|low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclone s strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor contained in the moist air. They are fueled by a different heat mechanism than other cyclonic windstorms such as nor'easter s, European windstorm s, and polar low s. The characteristic that separates tropical cyclones from other cyclonic systems is that at any height in the atmosphere, the center of a tropical cyclone will be warmer than its surroundings; a phenomenon called " warm core " storm systems.

The term "tropical" refers both to the geographical origin of these systems, which usually form in tropics|tropical regions of the globe, and to their formation in Air mass#Classification and notation|maritime tropical air masses . The term "cyclone" refers to such storms' cyclonic nature, with Clockwise and counterclockwise|counterclockwise wind flow in the Northern Hemisphere and clockwise wind flow in the Southern Hemisphere . The opposite direction of the wind flow is a result of the Coriolis force . Depending on its location and strength, a tropical cyclone is referred to by names such as #Hurricane or typhoon|hurricane (IPA-en|'h?r?ke?n|, IPA-en|'h?r?k?n|), #Hurricane or typhoon|typhoon , #Tropical storm|tropical storm , cyclonic storm , #Tropical depression|tropical depression , and simply cyclone .

While tropical cyclones can produce extremely powerful winds and torrential rain , they are also able to produce high waves and damaging storm surge as well as spawning tornadoes . They develop over large bodies of warm water, and lose their strength if they move over land due to increased surface friction and loss of the warm ocean as an energy source. This is why 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 ing up to convert|40|km|mi from the coastline. Although their effects on human populations can be devastating, tropical cyclones can relieve drought conditions. They also carry heat energy away from the tropics and transport it toward temperate latitudes , which makes them an important part of the global atmospheric circulation mechanism. As a result, tropical cyclones help to maintain equilibrium in the Earth's troposphere , and to maintain a relatively stable and warm temperature worldwide.

Many tropical cyclones tropical cyclogenesis|develop when the atmospheric conditions around a weak disturbance in the atmosphere are favorable. The background environment is modulated by climatological cycles and patterns such as the Madden-Julian oscillation , El Niño-Southern Oscillation , and the Atlantic multidecadal oscillation . 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 even 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 eventually dissipates. It is not possible to artificially induce the dissipation of these systems with current technology.
Tropicalcyclone

Physical structure


See also|Eye (cyclone)
All tropical cyclones are areas of low pressure area|low atmospheric pressure in the Earth's atmosphere. The pressures recorded at the centers of tropical cyclones are among the lowest that occur on Earth's surface at sea level .cite news|author=Symonds, Steve|title=Highs and Lows|work=Wild Weather|url= http://www.abc.net.au/northcoast/stories/s989385.htm|publisher= Australian Broadcasting Corporation |date=2003-11-17|accessdate=2007-03-23|archiveurl = http://web.archive.org/web/20071011194541/ http://www.abc.net.au/northcoast/stories/s989385.htm |archivedate = October 11, 2007|deadurl=yes Tropical cyclones are characterized and driven by the release of large amounts of latent heat of condensation , which occurs when 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.FAQ A7">cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: What is an extra-tropical cyclone? |publisher= National Oceanic and Atmospheric Administration |accessdate=2007-03-23|url= http://www.aoml.noaa.gov/hrd/tcfaq/A7.html

Eye and center


A strong tropical cyclone will harbor an area of sinking air at the center of circulation. If this area is strong enough, it can develop into a large "eye". Weather in the eye is normally calm and free of clouds, although the sea may be extremely violent.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=2009-05-07|work=JetStream& nbsp;— An Online School for Weather|date=2005-10-19 The eye is normally circular in shape, and is typically convert|30|–|65|km|mi|abbr=in in diameter , though eyes as small as convert|3|km|mi and as large as convert|370|km|mi have been observed.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=2006-09-28|accessdate=2006-12-14cite journal|author=Lander, Mark A.|title=A Tropical Cyclone with a Very Large Eye|url= http://journals.ametsoc.org/doi/full/10.1175/1520-0493%281999%29127%3C0137%3AATCWAV%3E2.0.CO%3B2|format=PDF|journal= Monthly Weather Review |month=January|year=1999|volume=127|issue=1|accessdate=2006-12-14|doi=10.1175/1520-0493(1999)127<0137:ATCWAV>2.0.CO;2|page=137|bibcode = 1999MWRv..127..137L|issn=1520-0493 Intense, mature tropical cyclones can sometimes exhibit an outward curving of the eyewall's top, making it resemble an arena football stadium; this phenomenon is thus sometimes referred to as the Eye (cyclone)#Stadium effect|stadium effect .cite journal|journal= Monthly Weather Review |url= http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281999%29127%3C0581%3AAHSO%3E2.0.CO%3B2|author=Pasch, Richard J. and Lixion Avila|Lixion A. Avila |month=May|year=1999|volume=127|format=PDF|issue=5|title=Atlantic Hurricane Season of 1996|pages=581–610|accessdate=2006-12-14|doi=10.1175/1520-0493(1999)127<0581:AHSO>2.0.CO;2|bibcode = 1999MWRv..127..581P|issn=1520-0493 It is usually coldest in the center.

There are other features that either surround the eye, or cover it. The central dense overcast is the concentrated area of strong thunderstorm activity near the center of a tropical cyclone;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 in weaker tropical cyclones, the CDO may cover the center completely.FAQ A9">cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: What is a "CDO"? |publisher= National Oceanic and Atmospheric Administration |accessdate=2007-03-23|url= http://www.aoml.noaa.gov/hrd/tcfaq/A9.html The eyewall is a circle of strong thunderstorms that surrounds the eye; here is where the greatest wind speeds are found, where clouds reach the highest, and precipitation is the heaviest. The heaviest wind damage occurs where a tropical cyclone's eyewall passes over land. Eye (cyclone)#Eyewall replacement cycles|Eyewall replacement cycles occur naturally in intense tropical cyclones. When cyclones reach peak intensity they usually have an eyewall and radius of maximum wind s that contract to a very small size, around convert|10|to|25|km|mi. Outer rainbands can organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and angular momentum . When the inner eyewall weakens, the tropical cyclone weakens (in other words, the maximum sustained winds weaken and the central pressure rises.) The outer eyewall replaces the inner one completely at the end of the cycle. The storm can be of the same intensity as it was previously or even stronger after the eyewall replacement cycle finishes. The storm may strengthen again as it builds a new outer ring for the next eyewall replacement.FAQ D8">cite web|author=Atlantic Oceanographic and 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= National Oceanic and Atmospheric Administration |accessdate=2006-12-14|url= http://www.aoml.noaa.gov/hrd/tcfaq/D8.html

Size descriptions of tropical cyclones
Type
Less than 2& nbsp;degrees latitude
2 to 3& nbsp;degrees of latitude
3 to 6& nbsp;degrees of latitude
6 to 8& nbsp;degrees of latitude
Over 8& nbsp;degrees of latitude


Size


One measure of the size of a tropical cyclone is determined by measuring the distance from its center of circulation to its outermost closed isobar (meteorology)|isobar , also known as its Radius of outermost closed isobar|ROCI . If the radius is less than two latitude|degrees of latitude or convert|222|km|mi, then the cyclone is "very small" or a "midget". A radius between 3 and 6& nbsp;latitude degrees or convert|333|to|670|km|mi are considered "average-sized". "Very large" tropical cyclones have a radius of greater than 8& nbsp;degrees or convert|888|km|mi. Use of this measure has objectively determined that tropical cyclones in the northwest Pacific Ocean are the largest on earth on average, with Atlantic tropical cyclone s roughly half their size.cite web|url= http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281984%29112%3C1408%3AACOLAS%3E2.0.CO%3B2|title=A comparison of Large and Small Tropical cyclones|last=Merrill|first=Robert T|date=1983-12-14|publisher= American Meteorological Society |accessdate=2009-05-06 Other methods of determining a tropical cyclone's size include measuring the radius of gale force winds and measuring the radius at which its relative vorticity field decreases to 1×10-5 s-1 from its center.cite web|url= http://www.cawcr.gov.au/publications/BMRC_archive/tcguide/ch2/ch2_4.htm|title=Global Guide to Tropical Cyclone Forecasting: chapter 2: Tropical Cyclone Structure|date=2009-05-07|publisher= Bureau of Meteorology (Australia)|Bureau of Meteorology |accessdate=2009-05-06cite journal|author=K. S. Liu and Johnny C. L. Chan|url= http://journals.ametsoc.org/doi/full/10.1175/1520-0493%281999%29127%3C2992%3ASOTCAI%3E2.0.CO%3B2|title=Size of Tropical Cyclones as Inferred from ERS-1 and ERS-2 Data|accessdate=2008-02-24|month=December|year=1999|issue=12|volume=127|journal= Monthly Weather Review |page=2992|doi=10.1175/1520-0493(1999)127<2992:SOTCAI>2.0.CO;2|bibcode = 1999MWRv..127.2992L|issn=1520-0493

Mechanics



A tropical cyclone's primary energy source is the release of the heat of condensation from water vapor condensation|condensing , with solar heating being the initial source for evaporation. 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.cite web|author= National Weather Service |month=September|year=2006|title=Hurricanes... Unleashing Nature's Fury: A Preparedness Guide|publisher= National Oceanic and Atmospheric Administration |accessdate=2006-12-02|format=PDF|url= http://www.srh.noaa.gov/fwd/wcm/hurric.pdf|archiveurl = http://web.archive.org/web/20080226215213/ http://www.srh.noaa.gov/fwd/wcm/hurric.pdf |archivedate = February 26, 2008|deadurl=yes In another way, tropical cyclones could be viewed as a special type of Mesoscale Convective Complex|mesoscale convective complex , which continues to develop over a vast source of relative warmth and moisture. While an initial warm core system, such as an organized thunderstorm complex, is necessary for the formation of a tropical cyclone, a large flux of energy is needed to lower atmospheric pressure more than a few millibars (0.10& nbsp;inch of mercury (element)|mercury ). The inflow (meteorology)|inflow of warmth and moisture from the underlying ocean surface is critical for tropical cyclone strengthening.cite journal|journal=Monthly Weather Review|date=August 1995|title=Evolution of the Inflow Boundary Layer of Hurricane Gilbert (1988)|author=Gary M. Barnes and Mark D. Powell|publisher= American Meteorological Society |url= http://www.aoml.noaa.gov/hrd/Powell/Barnes.pdf|volume=123|page=2348|bibcode = 1995MWRv..123.2348B |doi = 10.1175/1520-0493(1995)123<2348:EOTIBL>2.0.CO;2|issn=1520-0493|year=1995|issue=8 A significant amount of the inflow in the cyclone is in the lowest convert|1|km|ft of the atmosphere.cite web|url= http://www.aoml.noaa.gov/hrd/iwtc/Marks1_1.html|title=Fifth International Workshop on Tropical Cyclones Topic 1 Tropical Cyclone Structure and Structure Change|author=Dr. Frank Marks|date=2003-01-27|accessdate=2009-11-23|publisher= Atlantic Oceanographic and Meteorological Laboratory

Condensation leads to higher wind speeds, as a tiny fraction of the released energy is converted into mechanical energy;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= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/C5c.html 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.cite web|url= http://www.aoml.noaa.gov/hrd/tcfaq/D7.html|title=NOAA FAQ: How much energy does a hurricane release? |month=August|year=2001|accessdate=2009-06-30|publisher= National Oceanic & Atmospheric Administration This positive feedback loop , called the Wind-induced surface heat exchange , continues for as long as conditions are favorable for tropical cyclogenesis|tropical cyclone development . 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.cite web|url= http://www.britannica.com/EBchecked/topic/137646/Coriolis-force|title=Coriolis force (physics).|date=2008-02-25|publisher= Encyclopaedia Britannica |accessdate=2009-05-07cite web|url= http://www.britannica.com/EBchecked/topic/606551/tropical-cyclone#849004.hook|title=Tropical cyclone: Tropical cyclone tracks.|date=2008-02-25|publisher= Encyclopædia Britannica |accessdate=2009-05-07cite web|url= http://www.srh.noaa.gov/jetstream/tropics/tc.htm|author= National Weather Service |publisher= National Oceanic & Atmospheric Administration |title=Tropical Cyclone Introduction|accessdate=2010-09-07|work=JetStream& nbsp;— An Online School for Weather|date=2005-10-19 In the Northern Hemisphere , where the cyclone's wind flow is counterclockwise , the fastest winds relative to the surface of the Earth occur on the eastern side of a northward-moving storm and on the northern side of a westward-moving one; the opposite occurs in the Southern Hemisphere , where the wind flow is clockwise .cite web|url= http://www.usatoday.com/weather/resources/askjack/wfaqhur.htm|title=Are the winds on one side of a hurricane faster than on the other side? |work=Ask the Experts: Hurricanes|publisher= USA Today |date=November 11, 2007|accessdate=September 9, 2011

What primarily distinguishes tropical cyclones from other meteorological phenomena is deep convection as a driving force.cite web|publisher= 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 |archiveurl= http://web.archive.org/web/20080504064129/ http://www.bom.gov.au/weather/wa/cyclone/about/faq/faq_def_6.shtml |archivedate=2008-05-04 Because convection is strongest in a tropical climate , it 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. To continue to drive its heat engine, a tropical cyclone must remain over warm water, which provides the needed atmospheric moisture to keep the positive feedback loop running. When a tropical cyclone passes over land, it is cut off from its heat source and its strength diminishes rapidly.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= National Oceanic & Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/C2.html

The passage of a tropical cyclone over the ocean causes the upper layers of the ocean to cool substantially, which can influence subsequent cyclone development. This cooling is primarily caused by wind-driven mixing of cold water from deeper in the ocean and the warm surface waters. This effect results in a negative feedback process that can inhibit further development or lead to weakening. Additional cooling may come in the form of cold water from falling raindrops (this is because the atmosphere is cooler at higher altitudes). 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.cite web|author=Eric A. D'Asaro and Peter G. Black.|url= http://iop.apl.washington.edu/opd/user/dasaro/DENNIS/HurrConf.pdf|format=PDF|title=J8.4 Turbulence in the Ocean Boundary Layer Below Hurricane Dennis|year=2006|accessdate=2008-02-22|publisher= University of Washington

Scientists estimate that a tropical cyclone releases heat energy at the rate of 50 to 200& nbsp; exajoule s (1018& nbsp;J) per day, equivalent to about 1& nbsp;PW (1015& nbsp;watt). This rate of energy release is equivalent to 70 times the world energy resources and consumption|world energy consumption of humans and 200 times the worldwide electrical generating capacity, or to exploding a 10- TNT equivalent|megaton nuclear bomb every 20& nbsp;minutes.cite web|url= http://www.ucar.edu/news/features/hurricanes/index.jsp|title=Hurricanes: Keeping an eye on weather's biggest bullies.|date=2006-03-31|publisher= University Corporation for Atmospheric Research |accessdate=2009-05-07

In the lower troposphere, the most obvious motion of clouds is toward the center. However 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. This outflow produces high, cirrus cloud s that spiral away from the center. The clouds thin as they move outwards from the center of the system and are evaporated. They may be thin enough for the sun to be visible through them. These high cirrus clouds may be the first signs of an approaching tropical cyclone.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= National Oceanic and Atmospheric Administration |accessdate=2006-07-26|url= http://www.aoml.noaa.gov/hrd/tcfaq/H5.html As air parcels are lifted within the eye of the storm the vorticity is reduced, causing the outflow from a tropical cyclone to have anti-cyclonic motion.

Major basins and related warning centers


Main|Tropical cyclone basins|Regional Specialized Meteorological Center
WMO Monitoring InstitutionsFAQ F1">cite web
Basin !! Responsible RSMCs and TCWCs
North Atlantic
North-East Pacific
North-Central Pacific
North-West Pacific
North Indian Ocean
South-West Indian Ocean
Australian region
Southern Pacific
: Indicates a Tropical Cyclone Warning Center


There are six Regional Specialized Meteorological Center 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. In addition, there are six Tropical Cyclone Warning Center s (TCWCs) that provide information to smaller regions.cite web|publisher= World Meteorological Organization |title=Regional Specialized Meteorological Center|date=2006-04-25|accessdate=2006-11-05|work=Tropical Cyclone Program (TCP)|url= http://severe.worldweather.wmo.int/rsmcs.html The RSMCs and TCWCs are not the only organizations that provide information about tropical cyclones to the public. The Joint Typhoon Warning Center (JTWC) issues advisories in all basins except the Northern Atlantic for the purposes of the United States Government .cite web|url= http://metocph.nmci.navy.mil/jtwc/menu/JTWC_mission.html|title=Joint Typhoon Warning Center Mission Statement.|date=2007-11-09|publisher= Joint Typhoon Warning Center |accessdate=2009-05-07|archiveurl = http://web.archive.org/web/20080409133140/ http://metocph.nmci.navy.mil/jtwc/menu/JTWC_mission.html |archivedate = April 9, 2008|deadurl=yes The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) issues advisories and names for tropical cyclones that approach the Philippines in the Northwestern Pacific to protect the life and property of its citizens.cite web|url= http://www.pagasa.dost.gov.ph/mission.shtml|title=Mission Vision|date=2008-02-24|publisher= Philippine Atmospheric, Geophysical and Astronomical Services Administration |accessdate=2009-05-07 The Canadian Hurricane Center (CHC) issues advisories on hurricanes and their remnants for Canadian citizens when they affect Canada.cite web|url= http://www.atl.ec.gc.ca/weather/hurricane/index_e.html|title=Canadian Hurricane Center|date=2008-02-24|publisher= Canadian Hurricane Center |accessdate=2009-05-07

On 26 March 2004, Cyclone Catarina became the first recorded South Atlantic tropical cyclone|South Atlantic cyclone and subsequently struck southern Brazil with winds equivalent to Category& nbsp;2 on the Saffir-Simpson Hurricane Scale . As the cyclone formed outside the authority of another warning center, Brazilian meteorologists initially treated the system as an extratropical cyclone , although subsequently classified it as tropical.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|year=2004|accessdate=2006-12-24|publisher=Santa Catarina Federal University

Formation


Main|Tropical cyclogenesisWorldwide, tropical cyclone activity peaks in late summer, when the difference between temperatures aloft and sea surface temperatures is 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 while November is the only month with all the tropical cyclone basins active.FAQ G1">cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: When is hurricane season? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/G1.html

Times


In the Northern Atlantic Ocean , a distinct Atlantic hurricane season|cyclone season occurs from June 1 to November 30, sharply peaking from late August through September.FAQ G1"/> The statistical peak of the Atlantic hurricane season is 10 September. The Northeast Pacific Ocean has a broader period of activity, but in a similar time frame to the Atlantic.cite web|author=McAdie, Colin|publisher= National Hurricane Center |title=Tropical Cyclone Climatology|url= http://www.nhc.noaa.gov/pastprofile.shtml|date=2007-05-10|accessdate=2007-06-09 The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and March 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.FAQ G1"/> In the Southern Hemisphere , the tropical cyclone year begins on July 1 and runs all year-round and encompasses the tropical cyclone seasons, which run from November 1 until the end of April, with peaks in mid-February to early March.FAQ G1"/>cite web|url= http://www.wmo.int/pages/prog/www/tcp/documents/TCP24-English2008.pdf|title=Tropical Cyclone Operational Plan for the Southeastern Indian Ocean and the South Pacific Oceans |date=2009-03-10|publisher= World Meteorological Organization |accessdate=2009-05-06


author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division
(>34& nbsp; knot (unit)>knots ) !! Tropical Cyclones
(>63& nbsp;knots)!! Category& nbsp;3+ TCs
(>95& nbsp;knots)
Northwest Pacific
South Indian
Northeast Pacific
North Atlantic
Australia Southwest Pacific
North Indian



Factors



The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood.cite book|last=Ross.|first=Simon|title=Natural Hazards.|publisher=Nelson Thornes|year=1998|edition=Illustrated|page=96|isbn=0748739513, 9780748739516|url= http://books.google.com/? id=JKTDenQB5nAC& pg=PT60& lpg=PT60& dq=formation+of+tropical+cyclones+not+fully+understood|accessdate=2009-05-07 While six factors appear to be generally necessary, tropical cyclones may occasionally form without meeting all of the following conditions. In most situations, Sea surface temperature|water temperatures of at least convert|26.5|C|F are needed down to a depth of at least convert|50|m|abbr=on;FAQ A15">cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: How do tropical cyclones form? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-26|url= http://www.aoml.noaa.gov/hrd/tcfaq/A15.html waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms.FAQ A16">cite web | author = Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: Why do tropical cyclones require convert|80|F|C ocean temperatures to form? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/A16.html Another factor is rapid cooling with height, which allows the release of the heat of condensation that powers a tropical cyclone.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.FAQ A15"/> Low amounts of wind shear are needed, as high shear is disruptive to the storm's circulation.FAQ A15"/> Tropical cyclones generally need to form more than convert|555|km|abbr=on or 5& nbsp;degrees of latitude away from the equator , allowing the Coriolis effect to deflect winds blowing towards the low pressure center and creating a circulation.FAQ A15"/> Lastly, a formative tropical cyclone needs a pre-existing system of disturbed weather, although without a circulation no cyclonic development will take place.FAQ A15"/> Low-latitude and low-level westerly wind bursts associated with the Madden-Julian oscillation can create favorable conditions for tropical cyclogenesis by initiating tropical disturbances.cite journal|url= http://www.soest.hawaii.edu/MET/Faculty/bwang/bw/paper/186_Kikuchi_et_al_Nargis.pdf|journal=Geophysical Research Letters|volume=36|year=2009|doi=10.1029/2009GL037296|author=Kazuyoshi Kikuchi, Bin Wang, and Hironori Fudeyasu|title=Genesis of tropical cyclone Nargis revealed by multiple satellite observations|pages=L06811|bibcode=2009GeoRL..3606811K|issue=6

Locations


Most tropical cyclones form in a worldwide band of thunderstorm activity called by several names: the Intertropical Front (ITF), the Intertropical Convergence Zone (ITCZ), or the monsoon trough .cite web|url= http://www.knmi.nl/~koek/glossary.html#I|title=Marine Meteorological Glossary|author= Fritz Korek|date=2000-11-21|publisher=Marine Knowledge Centre|accessdate=2009-05-06cite web|url= http://www.pagasa.dost.gov.ph/genmet/tropicalcyclone/formation_of_cyclone.html|title=Formation of Tropical Cyclones|year=2008|publisher= Philippine Atmospheric, Geophysical and Astronomical Services Administration |accessdate=2009-05-06cite web|author=DeCaria, Alex|publisher= Millersville University of Pennsylvania|Millersville University |url= http://snowball.millersville.edu/~adecaria/ESCI344/esci344_lesson05_TC_climatology.html|archiveurl= http://web.archive.org/web/20080507051727/ http://snowball.millersville.edu/~adecaria/ESCI344/esci344_lesson05_TC_climatology.html|archivedate=2008-05-07|title=Lesson 5& nbsp;– Tropical Cyclones: Climatology.|work=ESCI 344& nbsp;– Tropical Meteorology|year=2005|accessdate=2008-02-22 Another important source of atmospheric instability is found in tropical wave s, which cause about 85% of intense tropical cyclones in the Atlantic ocean, and become most of the tropical cyclones in the Eastern Pacific basin.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://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281995%29123%3C0887%3AATSO%3E2.0.CO%3B2|format=PDF|accessdate=2006-07-25|doi=10.1175/1520-0493(1995)123<0887:ATSO>2.0.CO;2|first1=Lixion A.|bibcode = 1995MWRv..123..887A|issn=1520-0493 FAQ A4">cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: What is an easterly wave? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/A4.htmlcite journal|author= Chris Landsea|Landsea, Chris |url= http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%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|doi =10.1175/1520-0493(1993)121<1703:ACOIMA>2.0.CO;2|bibcode = 1993MWRv..121.1703L|issn=1520-0493

Tropical cyclones move westward when equatorward of the subtropical ridge , intensifying as they move. Most of these systems form between 10 and 30& nbsp;degrees away of the equator , and 87% form no farther away than 20& nbsp;degrees of latitude, north or south.cite web|publisher= Bureau of Meteorology |url= http://www.cawcr.gov.au/publications/BMRC_archive/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=2006-12-12cite web|url= http://www.aoml.noaa.gov/hrd/Landsea/IPCC/index.html|title=Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment.|coauthors=Henderson-Sellers, H. Zhang, G. Berz, K. Emanuel, William M. Gray|William Gray , Christopher Landsea , Greg Holland, J. Lighthill, S-L. Shieh, P. Webster, and K. McGuffie.|date=2002-10-08|publisher= National Oceanic and Atmospheric Administration |accessdate=2009-05-07 Because the Coriolis effect initiates and maintains tropical cyclone rotation, tropical cyclones rarely form or move within about 5& nbsp;degrees of the equator, where the Coriolis effect is weakest. However, it is possible for tropical cyclones to form within this boundary as Tropical Storm Vamei did in 2001 and Cyclone Agni in 2004.cite web|url= http://australiasevereweather.com/cyclones/2002/summ0112.htm|title=Monthly Global Tropical Cyclone Summary, December 2001|work=Gary Padgett|publisher=Australian Severe Weather Index|accessdate=2009-05-06cite web|url= http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/atcr/2004atcr.pdf|title=Annual Tropical Cyclone Report 2004|year=2006|publisher= Joint Typhoon Warning Center |accessdate=2009-05-06

Movement and track


Steering winds


See also|Prevailing windsAlthough tropical cyclones are large systems generating enormous energy, their movements over the Earth's surface are controlled by large-scale winds—the streams in the Earth's atmosphere. The path of motion is referred to as a tropical cyclone's track and has been compared by Dr. Neil Frank, former director of the National Hurricane Center , to "leaves carried along by a stream".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= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/G6.html

Tropical systems, while generally located equator ward 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.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 African coast and towards the Caribbean Sea, North America, and ultimately into the central Pacific ocean before the waves dampen out.FAQ A4"/> These waves are the precursors to many tropical cyclones within this region. In the Indian Ocean and Western Pacific (both 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.cite web|author=DeCaria, Alex|publisher= Millersville University of Pennsylvania|Millersville University |url= http://snowball.millersville.edu/~adecaria/ESCI344/esci344_lesson05_TC_climatology.html|title = Lesson 5& nbsp;– Tropical Cyclones: Climatology.|work=ESCI 344& nbsp;– Tropical Meteorology|year=2005|accessdate=2008-02-22| archiveurl = http://web.archive.org/web/20080507051727/ http://snowball.millersville.edu/~adecaria/ESCI344/esci344_lesson05_TC_climatology.html| archivedate = May 7, 2008 Tropical cyclones can also be steered by other systems, such as other low pressure systems , high pressure systems , warm front s, and cold front s.

Coriolis effect


The Earth's rotation imparts an acceleration known as the Coriolis effect , Coriolis acceleration , or colloquially, Coriolis force . This acceleration causes cyclonic systems to turn towards the poles in the absence of strong steering currents.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=1997-01-20|accessdate=2006-11-29 The poleward portion of a tropical cyclone contains easterly winds, and the Coriolis effect pulls them slightly more poleward. The westerly winds on the equatorward portion of the cyclone pull slightly towards the equator, but, because the Coriolis effect weakens toward the equator, the net drag on the cyclone is poleward. Thus, tropical cyclones in the Northern Hemisphere usually turn north (before being blown east), and tropical cyclones in the Southern Hemisphere usually turn south (before being blown east) when no other effects counteract the Coriolis effect.

The Coriolis effect also initiates cyclonic rotation, but it is not the driving force that brings this rotation to high speeds& nbsp;– that force is the heat of condensation .

Interaction with the mid-latitude westerlies


See also|WesterliesWhen a tropical cyclone crosses 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. cite web|url= http://www.nrlmry.navy.mil/~chu/chap4/se200.htm|date=2007-04-10|title=Section 2: Tropical Cyclone Motion Terminology|publisher=United States Naval Research Laboratory|accessdate=2009-05-07 A typhoon moving through the Pacific Ocean towards Asia, for example, will recurve offshore of Japan to the north, and then to the northeast, if the typhoon encounters southwesterly winds (blowing northeastward) around a low-pressure system passing over China or Siberia . Many tropical cyclones are eventually forced toward the northeast by extratropical cyclone s in this manner, which move from west to east to the north of the subtropical ridge. An example of a tropical cyclone in recurvature was Hurricane Ioke|Typhoon Ioke in 2006, which took a similar trajectory.cite web|url= http://www.prh.noaa.gov/cphc/summaries/2006.php#ioke | title = Hurricane Ioke: 20–27 August 2006|month=May|year=2007|accessdate=2007-06-09|author=Powell, Jeff, et al.|work=2006 Tropical Cyclones Central North Pacific|publisher= Central Pacific Hurricane Center

Landfall


See also|List of notable tropical cyclones|Tropical cyclogenesis#Unusual areas of formation|l2=Unusual areas of tropical cyclone formationOfficially, 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; in fact, a tropical cyclone can launch its strongest winds over land, yet not make landfall; if this occurs, then it is said that the storm made a direct hit on the coast. As a result of the narrowness of this definition, the landfall area experiences half of a land-bound storm by the time the actual landfall occurs. 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.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

Multiple storm interaction


Main|Fujiwhara effectWhen two cyclones approach one another, their centers will begin orbiting cyclonically about a point between the two systems. The two vortices will be attracted to each other, and eventually spiral into the center point and merge. When the two vortices are of unequal size, the larger vortex will tend to dominate the interaction, and the smaller vortex will orbit around it. This phenomenon is called the Fujiwhara effect, after Sakuhei Fujiwhara .cite news|url= http://www.usatoday.com/weather/wfujiwha.htm|title=Fujiwhara effect describes a stormy waltz|accessdate=2008-02-21|publisher= USA Today |date=2007-11-09

Dissipation


Factors


A tropical cyclone can cease to have tropical characteristics in several different ways. One such way is if it moves over land, thus depriving it of the warm water it needs to power itself, quickly losing strength.cite web|url= http://www.aoml.noaa.gov/hrd/tcfaq/C2.html|title=Subject : C2) Doesn't the friction over land kill tropical cyclones? |date=2008-02-25|work= National Hurricane Center |publisher= National Oceanic and Atmospheric Administration |accessdate=2009-05-07 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 a tropical cyclone could regenerate if it managed to get back over open warm water, such as with Hurricane Ivan . If it remains over mountains for even a short time, weakening will accelerate.cite web|url= http://www.bom.gov.au/weather/wa/cyclone/about/inland_pilbara/index.shtml|title=Tropical Cyclones Affecting Inland Pilbara towns.|publisher= Bureau of Meteorology |accessdate=2009-05-07 Many storm fatalities occur in mountainous terrain, as the dying storm unleashes torrential rainfall,Yuh-Lang Lin, S. Chiao, J. A. Thurman, D. B. Ensley, and J. J. Charney. http://ams.confex.com/ams/10Mountain/techprogram/paper_40695.htm Some Common Ingredients for heavy Orographic Rainfall and their Potential Application for Prediction. Retrieved on 2007-04-26. leading to deadly flood s and mudslide s, similar to those that happened with Hurricane Mitch in 1998.cite web|author=National Hurricane Center|year=1998|title=Hurricane Mitch Tropical Cyclone Report|accessdate=2006-04-20|url= http://www.nhc.noaa.gov/1998mitch.html NHC Mitch Report In addition, dissipation can occur if a storm remains in the same area of ocean for too long, mixing the upper convert|60|m|ft|0 of water, dropping sea surface temperatures more than convert|5|°C-change|0. Joint Typhoon Warning Center . http://www.nrlmry.navy.mil/~chu/chap2/se113.htm 1.13 Local Effects on the Observed Large-scale Circulations. Retrieved on 2008-02-25. Without warm surface water, the storm cannot survive.cite journal|url= http://journals.ametsoc.org/doi/pdf/10.1175/1520-0485%281989%29019%3C0649%3AVSOTOC%3E2.0.CO%3B2|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|doi=10.1175/1520-0485(1989)019<0649:VSOTOC>2.0.CO;2|page=649|bibcode = 1989JPO....19..649S|issn=1520-0485

A tropical cyclone can dissipate when it moves over waters significantly below convert|26.5|C|F. 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.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| archiveurl = http://web.archive.org/web/20070221063429/ http://www.hurricanezone.net/articles/tropical-cyclone-formation.html| archivedate = February 21, 2007 Weakening or dissipation can occur if it experiences vertical wind shear , causing the convection and heat engine to move away from the center; this normally ceases development of a tropical cyclone.cite book|title=East Asian Monsoon|author=Chih-Pei Chang|year=2004|publisher=World Scientific|isbn=9812387692|url= http://books.google.com/? id=N8QYOdqGdgkC& pg=PA484& lpg=PA484|oclc=61353183 In addition, 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& nbsp;days.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=1999-09-23 Even after a tropical cyclone is said to be extratropical or dissipated, it can still have tropical storm force (or occasionally hurricane/typhoon 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 or typhoon-force wind speeds when they reach the west coast of North America. These phenomena can also affect Europe, where they are known as European windstorm s ; Hurricane Iris (1995)|Hurricane Iris's extratropical remnants are an example of such a windstorm from 1995.cite web|author=Rappaport, Edward N.|url= http://www.nhc.noaa.gov/1995iris.html|title=Preliminary Report: Hurricane Iris: 22–4 August September 1995|publisher= National Hurricane Center |date=2000-11-02|accessdate=2006-11-29 In addition, 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. Studies in the 2000s have given rise to the hypothesis that large amounts of dust reduce the strength of tropical cyclones.cite web|url= http://www.npr.org/templates/story/story.php? storyId=94332532|title=African Dust Linked To Hurricane Strength|coauthors=Jon Hamilton|date=2008-09-05|work=All Things Considered|publisher=National Public Radio|accessdate=2009-05-07

Artificial dissipation


In the 1960s and 1970s, the United States government attempted to weaken hurricanes through 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.cite web|url= http://www.aoml.noaa.gov/hrd/hrd_sub/sfury.html|title=Project Stormfury|date=2009-02-07|work=Hurricane Research Division|publisher= National Oceanic and Atmospheric Administration |accessdate=2009-05-07 The winds of Hurricane Debbie (1969)|Hurricane Debbie —a hurricane seeded in Project Stormfury—dropped as much as 31%, but Debbie regained its strength after each of two seeding forays.cite web|url= http://journals.ametsoc.org/doi/pdf/10.1175/1520-0477%281985%29066%3C0505%3APSASC%3E2.0.CO%3B2|title=Project Stormfury: A Scientific Chronicle 1962-1983.|coauthors=H. E. Willoughby, D. P. Jorgensen, R. A. Black, and S. L. Rosenthal.|date=2000-05-23|work= National Oceanic and Atmospheric Administration |publisher= American Meteorological Society |accessdate=2009-05-07 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 .cite book|author=Whipple, Addison|year=1982|title=Storm|location= Alexandria, Virginia|Alexandria, VA |publisher= Time Life|Time Life Books |isbn=0-8094-4312-0|page=151 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% chance of making landfall within 48& nbsp;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.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= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/C5a.html

Other approaches have been suggested over time, including cooling the water under a tropical cyclone by towing iceberg s into the tropical oceans.FAQ C5e"/> Other ideas range from covering the ocean in a substance that inhibits evaporation,FAQ C5b">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 placing a substance on the ocean surface? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/C5b.html dropping large quantities of ice into the eye at very early stages of development (so that the heat of condensation|latent heat is absorbed by the ice, instead of being converted to kinetic energy that would feed the positive feedback loop),FAQ C5e">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 cooling the surface waters with icebergs or deep ocean water? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/C5e.html or blasting the cyclone apart with nuclear weapons.FAQ C5c"/> Project Cirrus even involved throwing dry ice on a cyclone.cite book|author=Scotti, R. A.|title = Sudden Sea: The Great Hurricane of 1938|year=2003|edition=1st|publisher=Little, Brown, and Company|isbn=0-316-73911-1|oclc=51861977|page=47 These approaches all suffer from one flaw above many others: tropical cyclones are simply too large and short-lived for any of the weakening techniques to be practical.FAQ C5f">cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: Why do not we try to destroy tropical cyclones by (fill in the blank)? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/C5i.html

Effects


Main|Effects of tropical cyclonesTropical cyclones out at sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks.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 Tropical cyclones stir up water, leaving a cool wake behind them, which causes the region to be less favorable for subsequent tropical cyclones. On land, strong wind s can damage or destroy vehicles, buildings, bridges, and other outside objects, turning loose debris into deadly flying projectiles. 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.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
The broad rotation of a landfalling tropical cyclone, and vertical wind shear at its periphery, spawns History of tropical cyclone-spawned tornadoes|tornadoes . Tornadoes can also be spawned as a result of eyewall mesovortices , which persist until landfall.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= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/L6.html

Over the past two centuries, tropical cyclones have been responsible for the deaths of about 1.9& nbsp;million people worldwide. Large areas of standing water caused by flooding lead to infection, as well as contributing to mosquito-borne illnesses. Crowded evacuees in Emergency shelter|shelters increase the risk of disease propagation. Tropical cyclones significantly interrupt infrastructure, leading to power outages, bridge destruction, and the hampering of reconstruction efforts.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|format=PDF

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, as they may bring much-needed precipitation to otherwise dry regions. National Oceanic and Atmospheric Administration . http://www.cpc.ncep.noaa.gov/products/Epac_hurr/Epac_hurricane.html 2005 Tropical Eastern North Pacific Hurricane Outlook. Retrieved on 2006-05-02. Tropical cyclones also help maintain the global heat balance by moving warm, moist tropical air to the middle latitudes and polar regions, and by regulating the thermohaline circulation through upwelling .cite journal|last=Emanuel|first=Kerry|title=Contribution of tropical cyclones to meridional heat transport by the oceans|journal= Journal of Geophysical Research |year=2001|month=July|volume=106|issue=D14|pages=14771–14781|doi=10.1029/2000JD900641|bibcode = 2001JGR...10614771E The storm surge and winds of hurricanes may be destructive to human-made structures, but they also stir up the waters of coastal estuary|estuaries , which are typically important fish breeding locales. Tropical cyclone destruction spurs redevelopment, greatly increasing local property values.cite book|author=Christopherson, Robert W.|year=1992|title=Geosystems: An Introduction to Physical Geography|pages=222–224|publisher=Macmillan Publishing Company|location= New York City|New York |isbn=0-02-322443-6

Observation and forecasting


Observation


Main|Tropical cyclone observationIntense tropical cyclones pose a particular observation challenge, as they are a dangerous oceanic phenomenon, and weather station s, being relatively sparse, are rarely available on the site of the storm itself. In general, surface observations are available only if the storm is passing over an island or a coastal area, or if there is a nearby ship. Real-time measurements are usually taken in the periphery of the cyclone, where conditions are less catastrophic and its true strength cannot be evaluated. For this reason, there are teams of meteorologists that move into the path of tropical cyclones to help evaluate their strength at the point of landfall.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 |archiveurl = http://web.archive.org/web/20060503084406/ http://users.ce.ufl.edu/~fcmp/overview/overview.htm |archivedate = May 3, 2006|deadurl=yes

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 Pulse-Doppler radar|Doppler weather radar|radar . Radar plays a crucial role around landfall by showing a storm's location and intensity every several minutes.cite web|url= http://www.prh.noaa.gov/cphc/HAW/observations.php|title=Observations|date=2006-12-09|publisher=Central Pacific Hurricane Center|accessdate=2009-05-07

In situ measurements, in real-time, can be taken by sending specially equipped reconnaissance flights into the cyclone. In the Atlantic basin, these flights are regularly flown by United States government 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 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 Insitu Aerosonde|Aerosonde , a small drone aircraft, was flown through Tropical Storm Ophelia as it passed Virginia's Eastern Shore during the 2005 hurricane season. A similar mission was also completed successfully in the western Pacific ocean. This demonstrated a new way to probe the storms at low altitudes that human pilots seldom dare.cite news|author=Lee, Christopher|title=Drone, Sensors May Open Path Into Eye of Storm|url= http://www.washingtonpost.com/wp-dyn/content/article/2007/10/07/AR2007100700971_pf.html|publisher=The Washington Post|accessdate=2008-02-22


Forecasting


See also|Tropical cyclone track forecasting|Tropical cyclone prediction model|Tropical cyclone rainfall forecastingBecause 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. The deep layer mean flow, or average wind through the depth of the troposphere , is considered the best tool in determining track direction and speed. If storms are significantly sheared, use of wind speed measurements at a lower altitude, such as at the 700& nbsp; mbar|hPa pressure surface (convert|3000|m|ft|disp=s above sea level) will produce better predictions. Tropical forecasters also consider smoothing out short-term wobbles of the storm as it allows them to determine a more accurate long-term trajectory.cite web|publisher= United States Navy |url= http://www.nrlmry.navy.mil/~chu/chap4/se100.htm|title=Influences on Tropical Cyclone Motion|accessdate=2007-04-10 High-speed computers and sophisticated simulation software allow forecasters to produce tropical cyclone prediction model|computer models that predict 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, as well as with a wealth of data from Earth-orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades.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 = 22 May 2006 However, scientists are not as skillful at predicting the intensity of tropical cyclones.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=2006-05-22 The lack of improvement in intensity forecasting is attributed 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 scalesTropical 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|Northeast Pacific Basin , or in Atlantic hurricane|the Atlantic , it is called a hurricane . Neither "hurricane" nor "typhoon" is used in either the Southern Hemisphere or the Indian Ocean. In these Tropical cyclone basins|basins , storms of tropical nature are referred to simply as "cyclones".

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 180th meridian into the Northwest Pacific, becoming typhoons (such as Hurricane Ioke|Hurricane/Typhoon Ioke in 2006); on rare occasions, the reverse will occur.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 It should also be noted that typhoons with sustained winds greater than convert|67|m/s|kn or convert|150|mph|km/h are called Super Typhoons by the Joint Typhoon Warning Center.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|month=April|year=1990|archiveurl = http://web.archive.org/web/20070316162548/ http://metocph.nmci.navy.mil/jtwc/pubref/References/where_have_all_the_super_typhoons_gone.ppt |archivedate = March 16, 2007|deadurl=yes

Tropical depression


A tropical depression is an organized system of clouds and thunderstorms with a defined, closed surface circulation and maximum sustained wind s of less than convert|17|m/s|kn or convert|38|mph|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". 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.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= National Oceanic and Atmospheric Administration |accessdate=2006-12-11|url= http://www.aoml.noaa.gov/hrd/tcfaq/B2.html

Tropical storm


A tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between convert|17|m/s|kn (convert|39|mph|km/h) and convert|32|m/s|kn (convert|73|mph|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 ).

Hurricane or 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 convert|33|m/s|kn or convert|74|mph|km/h. 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 convert|16|km|mi to convert|80|km|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 convert|85|m/s|kn or convert|195|mph|km/h.FAQ E1"/>
Tropical cyclone classification

Origin of storm terms



The word hurricane , used in the North Atlantic and Northeast Pacific, is derived from huracán , the Spanish word for the Carib people|Carib / Taino people|Taino storm god, Juracán . This god is believed by scholars to have been at least partially derived from the Maya peoples|Mayan creator god, Huracan . Huracan was believed by the Maya to have created dry land out of the turbulent waters. The god was also credited with later destroying the "wooden people", the precursors to the " Maya maize god|maize people ", with an immense storm and flood.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=National Oceanic and Atmospheric Administration |accessdate=2006-07-25 |url= http://www.aoml.noaa.gov/hrd/tcfaq/B4.htmlcite book |author=aut|Read, Kay Almere |coauthors=and aut|Jason González |year=2000 |title=Handbook of Mesoamerican Mythology |location=Oxford |publisher= ABC-CLIO |isbn=1-85109-340-0 |page=200 |oclc=43879188 Huracan is also the source of the word orcan , another word for a particularly strong European windstorm .

Naming


Main|Tropical cyclone naming|Lists of tropical cyclone namesStorms 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.cite web|url= http://www.nhc.noaa.gov/aboutnames.shtml|title=Worldwide Tropical Cyclone Names.|year=2009|work= National Hurricane Center |publisher= National Oceanic and Atmospheric Administration |accessdate=2009-05-07 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 that vary from region to region and are usually drafted a few years ahead of time. The lists are decided on, 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. Different countries have different local conventions; for example, in Japan, storms are referred to by number (each year), such as ???9? (Typhoon #9).

Notable tropical cyclones


Main|List of notable tropical cyclones|List of Atlantic hurricanes|List of Pacific hurricanesTropical cyclones that cause extreme destruction are rare, although when they occur, they can cause great amounts of damage or thousands of fatalities.
The 1970 Bhola cyclone is the deadliest tropical cyclone on record, killing more than 300,000& nbsp;peoplecite 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 and potentially as many as 1& nbsp;millioncite news|author=Lawson|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 | date=1999-11-02 after striking the densely populated Ganges Delta region of Bangladesh on 13 November 1970. Its powerful storm surge was responsible for the high death toll. The List of North Indian Ocean cyclone seasons|North Indian cyclone basin has historically been the deadliest basin.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|month=July|year=2005|accessdate=2006-12-14|doi=10.1093/epirev/mxi011|pmid=15958424cite journal|author=Frank, Neil L. and S. A. Husain|title=The Deadliest Tropical Cyclone in History|month=June|url= http://journals.ametsoc.org/doi/pdf/10.1175/1520-0477%281971%29052%3C0438%3ATDTCIH%3E2.0.CO%3B2|format=PDF|journal=Bulletin of the American Meteorological Society|volume=52|issue=6|pages=438–445|accessdate=2006-12-14|doi=10.1175/1520-0477(1971)052<0438:TDTCIH>2.0.CO;2|year=1971|bibcode = 1971BAMS...52..438F|issn=1520-0477 Elsewhere, Typhoon Nina (1975)|Typhoon Nina killed nearly 100,000 in China in 1975 due to a 100-year flood that caused 62& nbsp;dams including the Banqiao Dam to fail.Linda J. Anderson-Berry. http://www.aoml.noaa.gov/hrd/iwtc/AndersonBerry5-1.html Fifth International Workshop on Tropycal Cyclones: Topic 5.1: Societal Impacts of Tropical Cyclones. Retrieved on 2008-02-26. The Great Hurricane of 1780 is the deadliest Atlantic hurricane on record, killing about 22,000& nbsp;people in the Lesser Antilles .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 =1997-04-22|publisher= National Oceanic and Atmospheric Administration 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 ,cite web | url = http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/atcr/1991atcr.pdf|title=Typhoon Thelma (27W)|accessdate=2006-03-31|author= Joint Typhoon Warning Center |work=1991 Annual Tropical Cyclone Report|format=PDF while in 1982, the unnamed tropical depression that eventually became Hurricane Paul (1982)|Hurricane Paul killed around 1,000& nbsp;people in Central America .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://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281983%29111%3C1080%3AENPTCO%3E2.0.CO%3B2 | month=May|year=1983|journal= Monthly Weather Review |format=PDF|volume=111|issue=5|accessdate=2006-03-31|doi=10.1175/1520-0493(1983)111<1080:ENPTCO>2.0.CO;2|page=1080|bibcode = 1983MWRv..111.1080G|issn=1520-0493

Hurricane Katrina is estimated as the costliest tropical cyclone worldwide,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 causing $81.2& nbsp;billion in property damage (2008& nbsp;USD)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=20 December 2005|accessdate=2006-05-30 with overall damage estimates exceeding $100& nbsp;billion (2005& nbsp;USD). Katrina killed at least 1,836& nbsp;people after striking Louisiana and Mississippi as a tropical cyclone scales|major hurricane in August 2005. Hurricane Andrew is the second most destructive tropical cyclone in U.S history, with damages totaling $40.7& nbsp;billion (2008& nbsp;USD), and with damage costs at $31.5& nbsp;billion (2008& nbsp;USD), Hurricane Ike is the third most destructive tropical cyclone in U.S history. The Galveston Hurricane of 1900 is the deadliest natural disaster in the United States, killing an estimated 6,000 to 12,000& nbsp;people in Galveston, Texas . National Hurricane Center . http://www.nhc.noaa.gov/HAW2/english/history.shtml#galveston Galveston Hurricane 1900. Retrieved on 2008-02-24. Hurricane Mitch caused more than 10,000 fatalities in Latin America. Hurricane Iniki in 1992 was the most powerful storm to strike Hawaii in recorded history, hitting Kauai as a Category& nbsp;4 hurricane, killing six people, and causing U.S. $3& nbsp;billion in damage.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 Kauai was also struck by Hurricanes Dot (1959) and Iwa (1982) (see List of Hawaii hurricanes ). Other destructive Eastern Pacific hurricane s include Hurricane Pauline|Pauline and Hurricane Kenna|Kenna , both causing severe damage after striking Mexico as major hurricanes.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=7 November 1997 | accessdate=2006-03-31cite 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=26 December 2002 | accessdate=2006-03-31 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 more than 20& nbsp;years.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

The most intense storm on record was Typhoon Tip in the northwestern Pacific Ocean in 1979, which reached a minimum pressure of 870& nbsp; millibar|mbar (652.5& nbsp; mmHg ) and maximum sustained wind speeds of convert|165|kn|m/s or convert|190|mph|km/h.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| format = PDF | url= http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281980%29108%3C1915%3AAAOSTT%3E2.0.CO%3B2 Typhoon Tip|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.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 = 26 October 1998|archiveurl = http://web.archive.org/web/20070928120128/ http://www.weathermatrix.net/tropical/1998/13/mitch.html |archivedate = September 28, 2007|deadurl=yes Camille was the only storm to actually strike land while at that intensity, making it, with convert|165|kn|m/s or convert|190|mph|km/h sustained winds and convert|183|kn|m/s or convert|210|mph|km/h gusts, the strongest tropical cyclone on record at landfall.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 Typhoon Nancy (1961)|Typhoon Nancy in 1961 had recorded wind speeds of convert|185|kn|m/s or convert|215|mph|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 storm with the highest wind speeds on record.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 Likewise, a surface-level gust caused by Typhoon Paka on Guam was recorded at convert|205|kn|m/s or convert|235|mph|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.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 Hurricane Wilma is the most intense tropical cyclone in the Atlantic Basin and the strongest tropical cyclone in the Western Hemisphere.

In addition to being the most intense tropical cyclone on record, Tip was the largest cyclone on record, with tropical storm-force winds convert|2170|km|mi in diameter. The smallest storm on record, Tropical Storm Marco (2008)|Tropical Storm Marco , formed during October 2008, and made landfall in Veracruz . Marco generated tropical storm-force winds only convert|37|km|mi in diameter.cite web|author=Neal Dorst|publisher=National Hurricane Center|date=May 29, 2009|accessdate=May 29, 2009|title=Subject: E5) Which are the largest and smallest tropical cyclones on record? |url= http://www.aoml.noaa.gov/hrd/tcfaq/E5.html

Hurricane John (1994)|Hurricane John is the longest-lasting tropical cyclone on record, lasting 31& nbsp;days in 1994 Pacific hurricane season|1994 . Before the advent of satellite imagery in 1961, however, many tropical cyclones were underestimated in their durations.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 John is also the longest-tracked tropical cyclone in the Northern Hemisphere on record, which had a path of 7,165& nbsp;miles (13,280& nbsp;km). Reliable data for Southern Hemisphere cyclones is unavailable.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

Changes caused by El Niño-Southern Oscillation


See also|El Niño-Southern OscillationMost tropical cyclones form on the side of the subtropical ridge closer to the equator , then move poleward past the ridge axis before recurving into the main belt of the Westerlies .cite web|author=Joint Typhoon Warning Center|year=2006|url= http://www.nrlmry.navy.mil/forecaster_handbooks/Philippines2/Forecasters%20Handbook%20for%20the%20Philippine%20Islands%20and%20Surrounding%20Waters%20Typhoon%20Forecasting.3.pdf|title=3.3 JTWC Forecasting Philosophies|publisher= United States Navy |accessdate=2007-02-11 When the subtropical ridge position shifts due to El Niño, so will the preferred tropical cyclone tracks. Areas west of Japan and Korea tend to experience much fewer September–November tropical cyclone impacts during El Niño and neutral years. During El Niño years, the break in the subtropical ridge tends to lie near 130th meridian east|130°E which would favor the Japanese archipelago. During El Niño years, Guam 's chance of a tropical cyclone impact is one-third of the long term average.cite web|author=Pacific ENSO Applications Climate Center|url= http://www.soest.hawaii.edu/MET/Enso/peu/2006_4th/guam_cnmi.htm|title=Pacific ENSO Update: 4th Quarter, 2006. Vol. 12 No. 4|accessdate=2008-03-19 The tropical Atlantic ocean experiences depressed activity due to increased vertical wind shear across the region during El Niño years.cite journal|url= http://www.aoml.noaa.gov/general/lib/lib1/nhclib/mwreviews/1997.pdf|title=Atlantic Hurricane Season of 1997|author=Edward N. Rappaport|journal=Monthly Weather Review|volume=127|page=2012|date=September 1999|accessdate=2009-07-18|bibcode = 1999MWRv..127.2012R |doi = 10.1175/1520-0493(1999)127<2012:AHSO>2.0.CO;2|issn=1520-0493|year=1999|issue=9 During La Niña years, the formation of tropical cyclones, along with the subtropical ridge position, shifts westward across the western Pacific ocean, which increases the landfall threat to China .cite journal|author=M. C. Wu, W. L. Chang, and W. M. Leung|year=2003|url= http://ams.allenpress.com/perlserv/? request=get-document& doi=10.1175%2F1520-0442(2004)017%3C1419:IOENOE%3E2.0.CO%3B2|title=Impacts of El Niño-Southern Oscillation Events on Tropical Cyclone Landfalling Activity in the Western North Pacific|volume=17|journal=Journal of Climate|pages=1419–1428|accessdate=2007-02-11|doi=10.1175/1520-0442(2004)017<1419:IOENOE>2.0.CO;2|issue=6|bibcode = 2004JCli...17.1419W|issn=1520-0442

Long-term activity trends


:See also|Atlantic hurricane reanalysisWhile the number of storms in the Atlantic has increased since 1995, there is no obvious global trend; the annual number of tropical cyclones worldwide remains about 87& nbsp;±& nbsp;10 (Between 77 and 97 tropical cyclones annually). However, the ability of climatologists to make long-term data analysis in certain basins is limited by the lack of reliable historical data in some basins, primarily in the Southern Hemisphere.cite journal|author=Chris Landsea|title=Can We Detect Trends in Extreme Tropical Cyclones? |url= http://www.aoml.noaa.gov/hrd/Landsea/landseaetal-science06.pdf|journal= Science (journal)|Science |format=PDF|volume=313|pages=452–454|date=2006-07-28|accessdate=2007-06-09|doi=10.1126/science.1128448|pmid=16873634|issue=5786|author-separator=,|author2=Chris|display-authors=2|last3=Hoarau|first3=K|last4=Knaff|first4=JA In spite of that, there is some evidence that the intensity of hurricanes is increasing. Kerry Emanuel stated, "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& nbsp;years or so, corresponding to about a 15% increase in the maximum wind speed and a 60% increase in storm lifetime."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|month=January|year=2006

Atlantic storms are becoming more destructive financially, since five of the ten List of costliest Atlantic hurricanes#Listed by cost (United States only)|most expensive storms in United States history have occurred since 1990. According to the World Meteorological Organization , “recent increase in societal impact from tropical cyclones has been caused largely by rising concentrations of population and infrastructure in coastal regions.”cite press release|title=Summary Statement on Tropical Cyclones and Climate Change|publisher= World Meteorological Organization |date=2006-12-04|url= http://www.wmo.int/pages/prog/arep/press_releases/2006/pdf/iwtc_summary.pdf|format=PDF|accessdate=2009-05-07 Pielke et al. (2008) normalized mainland U.S. hurricane damage from 1900–2005 to 2005 values and found no remaining trend of increasing absolute damage. The 1970s and 1980s were notable because of the extremely low amounts of damage compared to other decades. The decade 1996–2005 was the second most damaging among the past 11 decades, with only the decade 1926–1935 surpassing its costs. The most damaging single storm is the 1926 Miami hurricane , with $157& nbsp;billion of normalized damage.cite journal|last=Pielke|first=Roger A., Jr.|year=2008|title=Normalized Hurricane Damage in the United States: 1900–2005|journal=Natural Hazards Review|volume=9|issue=1|pages=29–42 | doi=10.1061/(ASCE)1527-6988(2008)9:1(29)|url= http://forecast.mssl.ucl.ac.uk/shadow/docs/Pielkeetal2006a.pdf|format=PDF|accessdate=2009-05-07|display-authors=1|last2=Gratz|first2=Joel|last3=Landsea|first3=Christopher W.|last4=Collins|first4=Douglas|last5=Saunders|first5=Mark A.|last6=Musulin|first6=Rade

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.cite web|publisher= Bureau of Meteorology |url= http://www.cawcr.gov.au/publications/BMRC_archive/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

The number and strength of Atlantic hurricanes may undergo a 50–70& nbsp;year cycle, also known as the Atlantic Multidecadal Oscillation . Nyberg et al. reconstructed Atlantic major hurricane activity back to the early 18th century and found five periods averaging 3–5 major hurricanes per year and lasting 40–60& nbsp;years, and six other averaging 1.5–2.5 major hurricanes per year and lasting 10–20& nbsp;years. These periods are associated with the Atlantic multidecadal oscillation. Throughout, a decadal oscillation related to solar irradiance was responsible for enhancing/dampening the number of major hurricanes by 1–2 per year.cite journal|last=Nyberg|first=J.|coauthors=Winter, A.; Malmgren, B. A.|year=2005|title=Reconstruction of Major Hurricane Activity|journal=Eos Trans. AGU|volume=86|issue=52, Fall Meet. Suppl.|pages=Abstract PP21C–1597|url= http://www.agu.org/cgi-bin/SFgate/SFgate? & listenv=table& multiple=1& range=1& directget=1& application=fm05& database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm05%2Ffm05& maxhits=200& =%22PP21C-1597%22|accessdate=2009-05-07

Although more common since 1995, few above-normal hurricane seasons occurred during 1970–94.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.|month=March|year=2006|accessdate=2006-11-30 Destructive hurricanes struck frequently from 1926–60, including many major New England hurricanes. Twenty-one Atlantic tropical storms formed in 1933 Atlantic hurricane season|1933 , a record only recently exceeded in 2005 Atlantic hurricane season|2005 , which saw 28 storms. Tropical hurricanes occurred infrequently during the seasons of 1900–25; however, many intense storms formed during 1870–99. During the 1887 Atlantic hurricane season|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 19th century, including a 1821 Norfolk and Long Island hurricane|1821 storm that made a direct hit on New York City . Some historical weather experts say these storms may have been as high as Saffir-Simpson Hurricane Scale|Category 4 in strength.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|archiveurl = http://web.archive.org/web/20070102092224/ http://www.ccsr.columbia.edu/information/hurricanes/ |archivedate = January 2, 2007|deadurl=yes

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 reconnaissance aircraft encountered one, a ship reported a voyage through the storm, or a storm hit land in a populated area. 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.

Proxy records based on paleotempestology|paleotempestological research have revealed that major hurricane activity along the Gulf of Mexico coast varies on timescales of centuries to millennia.cite conference|first=Kam-biu|last=Liu|title=Millennial-scale variability in catastrophic hurricane landfalls along the Gulf of Mexico coast|conference=23rd Conference on Hurricanes and Tropical Meteorology|publisher=American Meteorological Society|year=1999|location=Dallas, Texas, United States of America|url=|pages=374–377cite journal|last=Liu|first=Kam-biu|coauthors=Fearn, Miriam L.|year=2000|title=Reconstruction of Prehistoric Landfall Frequencies of Catastrophic Hurricanes in Northwestern Florida from Lake Sediment Records|journal=Quaternary Research|volume=54|issue=2|pages=238–245|doi=10.1006/qres.2000.2166|bibcode = 2000QuRes..54..238L Few major hurricanes struck the Gulf coast during 3000–1400 BC and again during the most recent millennium. These quiescent intervals were separated by a hyperactive period during 1400 BC and 1000 AD, when the Gulf coast was struck frequently by catastrophic hurricanes and their landfall probabilities increased by 3–5 times. This millennial-scale variability has been attributed to long-term shifts in the position of the Azores High , which may also be linked to changes in the strength of the North Atlantic Oscillation .cite journal|last=Elsner|first=James B.|coauthors=Liu, Kam-biu; Kocher, Bethany|year=2000|title=Spatial Variations in Major U.S. Hurricane Activity: Statistics and a Physical Mechanism |journal=Journal of Climate |volume=13|issue=13|pages=2293–2305|doi=10.1175/1520-0442(2000)013<2293:SVIMUS>2.0.CO;2|bibcode = 2000JCli...13.2293E|issn=1520-0442

According to the Azores High hypothesis, an anti-phase pattern is expected to exist between the Gulf of Mexico coast and the Atlantic coast. During the quiescent periods, a more northeasterly position of the Azores High would result in more hurricanes being steered towards the Atlantic coast. During the hyperactive period, more hurricanes were steered towards the Gulf coast as the Azores High was shifted to a more southwesterly position near the Caribbean. Such a displacement of the Azores High is consistent with paleoclimatic evidence that shows an abrupt onset of a drier climate in Haiti around 3200 Radiocarbon dating|14C years BP,cite journal|last=Higuera-Gundy|first=Antonia|year=1999|title=A 10,300 14C yr Record of Climate and Vegetation Change from Haiti |journal=Quaternary Research|volume=52|issue=2|pages=159–170|doi=10.1006/qres.1999.2062|bibcode = 1999QuRes..52..159H|display-authors=1|author2=|last3=Hodell|first3=David A.|last4=Curtis|first4=Jason H.|last5=Leyden|first5=Barbara W.|last6=Binford|first6=Michael W. and a change towards more humid conditions in the Great Plains during the late-Holocene as more moisture was pumped up the Mississippi Valley through the Gulf coast. Preliminary data from the northern Atlantic coast seem to support the Azores High hypothesis. A 3000-year proxy record from a coastal lake in Cape Cod suggests that hurricane activity increased significantly during the past 500–1000& nbsp;years, just as the Gulf coast was amid a quiescent period of the last millennium.

Global warming



:See also|Effects of global warming|Hurricane Katrina and global warming:
The U.S. National Oceanic and Atmospheric Administration Geophysical Fluid Dynamics Laboratory performed a simulation to determine if there is a statistics|statistical Periodic trends|trend in the frequency or strength of tropical cyclones over time. 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".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

In an article in Nature (journal)|Nature , meteorology professor 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 climate oscillation|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".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 | doi = 10.1038/nature03906 | year = 2005 | pmid = 16056221|bibcode = 2005Natur.436..686E In more recent work published by Emanuel (in the March 2008 issue of the Bulletin of the American Meteorological Society ), he states that new climate modeling data indicates “global warming should reduce the global frequency of hurricanes.”cite journal|last=Emanuel|first=Kerry|coauthors=Sundararajan, Ragoth, Williams, John|title=Hurricanes and Global Warming: Results from Downscaling IPCC AR4 Simulations|journal=Bulletin of the American Meteorological Society|year=2008|month=March|volume=89|issue=3|pages=347–367|doi=10.1175/BAMS-89-3-347|authorlink=Kerry Emanuel|bibcode = 2008BAMS...89..347E According to the Houston Chronicle, the new work suggests that, even in a dramatically warming world, hurricane frequency and intensity may not substantially rise during the next two centuries.cite newspaper |url= http://www.chron.com/disp/story.mpl/front/5693436.html |title=Hurricane expert reconsiders global warming's impact |newspaper= Houston Chronicle |accessdate=2010-07-31 |first=Eric |last=Berger |date=2008-04-12

Likewise, P.J. Webster and others published an article in Science (journal)|Science examining the "changes in tropical cyclone number, duration, and intensity" over the past 35& nbsp;years, the period when satellite data has been available. Their 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.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 = 16 September 2005 | volume = 309 | issue = 5742 | pages = 1844–1846 | accessdate = 2006-03-20|doi = 10.1126/science.1116448 | pmid = 16166514|bibcode = 2005Sci...309.1844W

Costliest U.S. Atlantic hurricanes by wealth normalization|align=rightThe strength of the reported effect is surprising in light of modeling studiescite journal|author = Knutson, Thomas R. and Robert E. Tuleya|title= Impact of CO2-Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization|journal=Journal of Climate|volume=17|issue=18|year=2004|pages=3477–3494|doi= 10.1175/1520-0442(2004)017<3477:IOCWOS>2.0.CO;2|bibcode = 2004JCli...17.3477K|issn = 1520-0442 that predict only a one-half category increase in storm intensity as a result of a ~2& nbsp;°C (3.6& nbsp;°F) global warming. Such a response would have predicted only a ~10% increase in Emanuel's potential destructiveness index during the 20th century rather than the ~75–120% increase he reported.Emanuel 2005"/> Second, after adjusting for changes in population and inflation, and despite a more than 100% increase in Emanuel's potential destructiveness index, no statistically significant increase in the monetary damages resulting from Atlantic hurricanes has been found.cite journal|author=Pielke, R. A. Jr|journal=Nature|doi=10.1038/nature04426|year=2005|title=Meteorology: Are there trends in hurricane destruction? |pages=E11|volume=438|pmid=16371954|issue=7071|bibcode = 2005Natur.438E..11P

Sufficiently warm sea surface temperatures are considered vital to the development of tropical cyclones.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 Although neither study can directly link hurricanes with global warming, the increase in sea surface temperatures is believed to be due to both global warming and natural variability, e.g. the hypothesized Atlantic Multidecadal Oscillation (AMO), although an exact attribution has not been defined. However, recent temperatures are the warmest ever observed for many ocean basins.Emanuel 2005"/>

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, among others. The report concluded the observed increase in tropical cyclone intensity is larger than climate models predict. In addition, the report considered that it is likely that storm intensity will continue to increase through the 21st century, and declared it more likely than not that there has been some human contribution to the increases in tropical cyclone intensity.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/publications_and_data/ar4/wg1/en/contents.html However, there is no universal agreement about the magnitude of the effects anthropogenic global warming has on tropical cyclone formation, track, and intensity. For example, critics such as Chris Landsea assert that man-made effects would be "quite tiny compared to the observed large natural hurricane variability".FAQ G3">cite web | author = Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division | title = Frequently Asked Questions: What may happen with tropical cyclone activity due to global warming? | publisher = NOAA | accessdate = 2007-06-02 | url = http://www.aoml.noaa.gov/hrd/tcfaq/G3.html A statement by the American Meteorological Society on 1 February 2007 stated that trends in tropical cyclone records offer "evidence both for and against the existence of a detectable anthropogenic signal" in tropical cyclogenesis .cite journal | title= Climate Change: An Information Statement of the American Meteorological Society | author = American Meteorological Society | date = 2007-02-01 | journal = Bulletin of the American Meteorological Society | page = 5 | url = http://www.ametsoc.org/POLICY/2007climatechange.pdf | format = PDF | volume = 88 | accessdate = 2007-06-03 | doi= 10.1175/BAMS-88-7-Kelleher | last2= Droegemeier | first2= Kelvin K. | last3= Levit | first3= Jason J. | last4= Sinclair | first4= Carl | last5= Jahn | first5= David E. | last6= Hill | first6= Scott D. | last7= Mueller | first7= Lora | last8= Qualley | first8= Grant | last9= Crum | first9= Tim D.|bibcode = 2007BAMS...88....5K | issue= 7 Although many aspects of a link between tropical cyclones and global warming are still being "hotly debated", a point of agreement is that no individual tropical cyclone or season can be attributed to global warming.cite web | author = Stefan Rahmstorf , Michael E. Mann , Rasmus Benestad, Gavin Schmidt and William Connolley | url = http://www.realclimate.org/index.php/archives/2005/09/hurricanes-and-global-warming/ | title = Hurricanes and Global Warming& nbsp;— Is There a Connection? | publisher = RealClimate | date = 2 September 2005 | accessdate = 2006-03-20cite web|author = World Meteorological Organization | title = Statement on Tropical Cyclones and Climate Change | page = 6 | url = http://www.wmo.ch/pages/themes/wmoprod/documents/iwtc_statement.pdf | format = PDF | date = 11 December 2006 | accessdate = 2007-06-02 Research reported in the 3 September 2008 issue of Nature found that the strongest tropical cyclones are getting stronger, in particular over the North Atlantic and Indian oceans. Wind speeds for the strongest tropical storms increased from an average of convert|140|mph|km/h in 1981 to convert|156|mph|km/h in 2006, while the ocean temperature, averaged globally over the all regions where tropical cyclones form, increased from convert|28.2|°C|°F to convert|28.5|°C|°F during this period. http://www.nature.com/news/2008/080903/full/news.2008.1079.html Hurricanes are getting fiercer Nature, Retrieved on 4 September 2008. http://newswise.com/articles/view/543977/ Warmer Seas Linked to Strengthening Hurricanes: Study Fuels Global Warming Debate Newswise, Retrieved on 4 September 2008.

Related cyclone types


See also|Cyclone|Extratropical cyclone|Subtropical cycloneIn 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.cite web|url= http://www.aoml.noaa.gov/hrd/iwtc/Lander4-1.html|title=Fifth International Workshop on Tropical Cyclones|coauthors=Mark A. Lander, N. Davidson, H. Rosendal, J. Knaff, and R. Edson, J. Evans, R. Hart.|date=2003-08-03|publisher= World Meteorological Organization |accessdate=2009-05-06 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; although not as frequently, an extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone.cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division|title=Frequently Asked Questions: What is an extra-tropical cyclone? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/A7.html From space, extratropical storms have a characteristic " comma (punctuation)|comma -shaped" cloud pattern.cite web|url= http://profhorn.meteor.wisc.edu/wxwise/satmet/lesson14/Satextracyclone.html|title=Lesson 14: Background: Synoptic Scale|date=2008-02-25|publisher= University of Wisconsin–Madison |accessdate=2009-05-06 Extratropical cyclones can also be dangerous when their low-pressure centers cause powerful winds and high seas.cite web|url= http://pubs.usgs.gov/of/2003/of03-337/winter.html|title=An Overview of Coastal Land Loss: With Emphasis on the Southeastern United States.|year=2008|publisher= United States Geological Survey |accessdate=2009-05-06

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 s, from the equator to 50°. Although subtropical storms rarely have hurricane-force winds, they may become tropical in nature as their cores warm.FAQ A6">cite web|author= Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division | title = Frequently Asked Questions: What is a sub-tropical cyclone? |publisher= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/A6.html From an operational standpoint, a tropical cyclone is usually not considered to become subtropical during its extratropical transition.cite web|author=Padgett, Gary|url= http://australiasevereweather.com/cyclones/2001/summ0012.htm|title=Monthly Global Tropical Cyclone Summary for December 2000|year=2001|accessdate=2006-03-31

Tropical cyclones in popular culture


Main|Tropical cyclones in popular cultureIn popular culture , tropical cyclones have made appearances in different types of media, including films, books, television, music, and electronic game s. The media can have tropical cyclones that are entirely fiction al, or can be based on real events.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= National Oceanic and Atmospheric Administration |accessdate=2006-07-25|url= http://www.aoml.noaa.gov/hrd/tcfaq/J4.html 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.cite web|author=Heidorn, Keith C|url= http://www.webcitation.org/5gZwFiLzF|title=George Stewart's Storm: Remembering A Classic.|accessdate=2006-12-10|publisher=The Weather Doctor Another example is the hurricane in The Perfect Storm (film)|The Perfect Storm , which describes the sinking of the Andrea Gail by the 1991 Perfect Storm .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=2004-12-13|accessdate=2007-02-04 Also, Tropical cyclones in popular culture|hypothetical hurricanes have been featured in parts of the plots of series such as Hurricane Neddy|The Simpsons , Invasion (TV series)|Invasion , One If by Clam, Two If by Sea|Family Guy , The Checks|Seinfeld , '' Dawson's Creek , and CSI: Miami (season 2)|CSI: Miami ''.FAQ J4"/>cite web|url= http://www.webcitation.org/5gZwJxocj|title=Hurricane Neddy& nbsp;– Episode Overview|publisher= Yahoo& #33; TV|accessdate=2008-02-26cite web|url= http://www.webcitation.org/5gZwSoAsA|title=Family Guy: One if by Clam, Two if by Sea& nbsp;– Summary|publisher=starpulse.com|accessdate=2008-02-26cite web|url= http://www.webcitation.org/5gZw0SALq|title=Dawson's Creek& nbsp;– Hurricane|publisher="Yahoo& #33; TV|accessdate=2008-02-25cite web|title=The Checks (Seinfeld Episode Script)|author=TheNewsGuy(Mike)|url= http://www.webcitation.org/5gZwWynCE|publisher=Seinfeldscripts.com|accessdate=2007-02-25cite web|url= http://www.webcitation.org/5gZwe9J9x|title=CSI: Miami Episodes& nbsp;– Episode Detail: Hurricane Anthony|publisher=TV Guide|accessdate=2008-02-25 The 2004 film The Day After Tomorrow includes several mentions of actual tropical cyclones as well as featuring fantastical "hurricane-like" non-tropical Arctic storms.cite web|publisher=Tribute.ca|url= http://www.webcitation.org/5gZwqK4ej|title=The Day After Tomorrow Movie Synopsis|accessdate=2008-02-26cite news|url= http://movies.nytimes.com/movie/281154/The-Day-After-Tomorrow/trailers|accessdate=2008-02-26|title=The Day After Tomorrow (2004)|publisher=The New York Times

See also


multicol
  • Outline of tropical cyclones

  • Cyclone

  • Disaster preparedness

  • HURDAT (online database)

  • Hurricane Alley

  • Saffir–Simpson Hurricane Scale

  • multicol-breakPortal|Tropical cyclones
  • Hypercane

  • List of wettest tropical cyclones by country

  • Secondary flow#Tropical cyclones|Secondary flow in tropical cyclones

  • multicol-end
    Col-beginCol-2;Annual seasons
  • List of Atlantic hurricane seasons ( CURRENTYEAR Atlantic hurricane season|current )

  • List of North Indian Ocean cyclone seasons ( CURRENTYEAR North Indian Ocean cyclone season|current )

  • List of Pacific hurricane seasons ( CURRENTYEAR Pacific hurricane season|current )

  • List of Pacific typhoon seasons ( CURRENTYEAR Pacific typhoon season|current )

  • List of South-West Indian Ocean cyclone seasons ( #ifexpr:#time:n>6|#time:Y-#time:y|+1 year|#time:Y|-1 year-#time:y South-West Indian Ocean cyclone season|current )

  • List of Australian region cyclone seasons ( #ifexpr:#time:n>6|#time:Y-#time:y|+1 year|#time:Y|-1 year-#time:y Australian region cyclone season|current )

  • List of South Pacific cyclone seasons ( #ifexpr:#time:n>6|#time:Y-#time:y|+1 year|#time:Y|-1 year-#time:y South Pacific cyclone season|current )

  • Col-2;Forecasting and preparation
  • Catastrophe modeling

  • Hurricane engineering

  • Hurricane preparedness

  • Hurricane-proof building

  • ITyphoon|iTyphoon ndash A mobile application used to provide information about typhoons in the Philippines.

  • Tropical cyclone watches and warnings

  • Col-end

    References


    Reflist|colwidth=25em

    External links


    WiktionaryCommons category|Tropical cyclones
    ;Regional Specialized Meteorological Centers
  • http://www.nhc.noaa.gov/ US National Hurricane Center& nbsp;– North Atlantic, Eastern Pacific

  • http://www.prh.noaa.gov/hnl/cphc/ Central Pacific Hurricane Center& nbsp;– Central Pacific

  • http://www.jma.go.jp/en/typh/ Japan Meteorological Agency& nbsp;– NW Pacific

  • http://www.imd.gov.in/ India Meteorological Department& nbsp;– Bay of Bengal and the Arabian Sea

  • http://www.meteo.fr/temps/domtom/La_Reunion/ Météo-France& nbsp;– La Reunion& nbsp;– South Indian Ocean from 30°E to 90°E

  • http://www.met.gov.fj/ Fiji Meteorological Service& nbsp;– South Pacific west of 160°E, north of 25° S


  • ;Tropical Cyclone Warning Centers
  • http://maritim.bmg.go.id Indonesian Meteorological Department& nbsp;– South Indian Ocean from 90°E to 125°E, north of 10°S

  • http://www.bom.gov.au/weather/cyclone/index.shtml Australian Bureau of Meteorology (TCWC's Perth, Darwin & Brisbane).& nbsp;– South Indian Ocean & South Pacific Ocean from 90°E to 160°E, south of 10°S

  • http://metservice.com/national/ Meteorological Service of New Zealand Limited& nbsp;– South Pacific west of 160°E, south of 25°S


  • ;Reference
  • http://www.a-z-dictionaries.com/Hurricane_glossary.html Hurricane Glossary of Terms


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    ca:Cicló tropical
    cv:Ç??-?a?a?
    ceb:Bagyo
    cs:Tropická cyklóna
    cy:Corwynt
    da:Orkan
    de:Tropischer Wirbelsturm
    et:Orkaan
    el:???p???? ??????a?
    es:Ciclón tropical
    eo:Uragano
    eu:Zikloi tropikal
    fa:?????
    fr:Cyclone tropical
    fy:Orkaan
    gl:Furacán
    ko:?? ???
    haw:Makani Pahili
    hi:???????????? ???????
    hr:Tropska oluja
    id:Siklon tropis
    is:Fellibylur
    it:Ciclone tropicale
    he:???? ??????
    jv:Siklon tropis
    kn:????????
    ka:????????? ???????
    kk:????????? ?????????
    sw:Kimbunga
    ht:Siklòn twopikal
    la:Typhon marinus
    lv:Viesulvetra
    lt:Uraganas
    jbo:vlile carna xamsi brife
    hu:Trópusi ciklon
    mk:??????? ??????
    ms:Taufan
    cdo:Hung-tai
    nl:Tropische cycloon
    ja:?????
    no:Tropisk syklon
    nn:Tropisk syklon
    oc:Ciclon tropical
    om:Tropical cyclone
    pnb:????
    pap:Tormenta tropikal
    pl:Cyklon tropikalny
    pt:Ciclone tropical
    ro:Ciclon tropical
    qu:Hatun pillunkuy
    ru:??????????? ??????
    sa:????????
    sq:Uragani
    simple:Tropical cyclone
    sk:Hurikán
    sl:Tropski ciklon
    sr:??????
    sh:Tropski ciklon
    fi:Trooppinen hirmumyrsky
    sv:Tropisk cyklon
    tl:Bagyo
    ta:?????
    th:???????????????
    tr:Kasirga
    uk:????????? ??????
    ur:?????
    ug:?????? ?????? ???????
    vi:Xoáy thu?n nhi?t d?i
    fiu-vro:Marupöörüs
    war:Bagyo
    yi:?????? ?????
    yo:Ìjìláyípo Il?`-Olóoru
    zh-yue:????
    zh:????

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