Cyclone: Difference between revisions
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In [[meteorology]], a '''cyclone''' ({{IPAc-en|ˈ|s|aɪ|.|k|l|oʊ|n}}) is a large [[air mass]] that rotates around a strong center of low [[atmospheric pressure]], counterclockwise in the [[Northern Hemisphere]] and clockwise in the [[Southern Hemisphere]] as viewed from above (opposite to an [[anticyclone]]).<ref name="AMSCcDef">{{cite web|title = Cyclonic circulation|author = Glossary of Meteorology|date = June 2000|publisher = [[American Meteorological Society]]|url = http://glossary.ametsoc.org/wiki/Cyclonic_circulation|access-date = 2008-09-17|archive-date = 2018-12-25|archive-url = https://web.archive.org/web/20181225164334/http://glossary.ametsoc.org/wiki/Cyclonic_circulation|url-status = live}}</ref><ref name="AMSCycDef">{{cite web|title = Cyclone|date = June 2000|author = Glossary of Meteorology|publisher = [[American Meteorological Society]]|url = http://glossary.ametsoc.org/wiki/Cyclone|access-date = 2008-09-17|archive-date = 2018-12-25|archive-url = https://web.archive.org/web/20181225164340/http://glossary.ametsoc.org/wiki/Cyclone|url-status = live}}</ref> Cyclones are characterized by inward-spiraling winds that rotate about a zone of [[low pressure]].<ref name="BBCCycDef">{{cite web |author = BBC Weather Glossary |title = Cyclone|date= July 2006|publisher= [[BBC]]|url = http://www.bbc.co.uk/weather/weatherwise/glossary/c.shtml|access-date = 2006-10-24|archive-url = https://web.archive.org/web/20060829214837/http://www.bbc.co.uk/weather/weatherwise/glossary/c.shtml |archive-date = 2006-08-29}}</ref><ref name="UCARCycDef">{{cite web |title = UCAR Glossary — Cyclone |publisher = University Corporation for Atmospheric Research |url = http://meted.ucar.edu/satmet/goeschan/glossary.htm#c |access-date = 2006-10-24 |archive-date = 2018-12-25 |archive-url = https://web.archive.org/web/20181225164339/https://www.meted.ucar.edu/sign_in.php?go_back_to=%2Fsatmet%2Fgoeschan%2Fglossary.htm#c |url-status = live | In [[meteorology]], a '''cyclone''' ({{IPAc-en|ˈ|s|aɪ|.|k|l|oʊ|n}}) is a large [[air mass]] that rotates around a strong center of low [[atmospheric pressure]], counterclockwise in the [[Northern Hemisphere]] and clockwise in the [[Southern Hemisphere]] as viewed from above (opposite to an [[anticyclone]]).<ref name="AMSCcDef">{{cite web |title = Cyclonic circulation |author = Glossary of Meteorology |date = June 2000 |publisher = [[American Meteorological Society]] |url = http://glossary.ametsoc.org/wiki/Cyclonic_circulation |access-date = 2008-09-17 |archive-date = 2018-12-25 |archive-url = https://web.archive.org/web/20181225164334/http://glossary.ametsoc.org/wiki/Cyclonic_circulation |url-status = live}}</ref><ref name="AMSCycDef">{{cite web |title = Cyclone |date = June 2000 |author = Glossary of Meteorology |publisher = [[American Meteorological Society]] |url = http://glossary.ametsoc.org/wiki/Cyclone |access-date = 2008-09-17 |archive-date = 2018-12-25 |archive-url = https://web.archive.org/web/20181225164340/http://glossary.ametsoc.org/wiki/Cyclone |url-status = live }}</ref> Cyclones are characterized by inward-spiraling winds that rotate about a zone of [[low pressure]].<ref name="BBCCycDef">{{cite web |author = BBC Weather Glossary |title = Cyclone|date= July 2006|publisher= [[BBC]]|url = http://www.bbc.co.uk/weather/weatherwise/glossary/c.shtml|access-date = 2006-10-24 |archive-url = https://web.archive.org/web/20060829214837/http://www.bbc.co.uk/weather/weatherwise/glossary/c.shtml |archive-date = 2006-08-29}}</ref><ref name="UCARCycDef">{{cite web |title = UCAR Glossary — Cyclone |publisher = University Corporation for Atmospheric Research |url = http://meted.ucar.edu/satmet/goeschan/glossary.htm#c |access-date = 2006-10-24 |archive-date = 2018-12-25 |archive-url = https://web.archive.org/web/20181225164339/https://www.meted.ucar.edu/sign_in.php?go_back_to=%2Fsatmet%2Fgoeschan%2Fglossary.htm#c |url-status = live }}</ref> | ||
Cyclones have also been seen on planets other than the Earth, such as [[Mars]], [[Jupiter]], and [[Neptune]].<ref name="Brand" /><ref name="WIZ">{{cite web |publisher=[[NASA]] |author=Samantha Harvey |date=2006-10-02 |url=http://solarsystem.nasa.gov/educ/themes/display.cfm?Item=hurricane |title=Historic Hurricanes |access-date=2008-06-14 |archive-url=https://web.archive.org/web/20080415120400/http://solarsystem.nasa.gov/educ/themes/display.cfm?Item=hurricane |archive-date=2008-04-15 |url-status=dead }}</ref> [[Cyclogenesis]] is the process of cyclone formation and intensification.<ref name="Arc">{{cite web |author=Nina A. Zaitseva |year=2006 |publisher=[[National Snow and Ice Data Center]] |url=http://nsidc.org/arcticmet/glossary/cyclogenesis.html |title=Cyclogenesis |access-date=2006-12-04 |url-status=dead |archive-url=https://web.archive.org/web/20060830135741/http://www.nsidc.org/arcticmet/glossary/cyclogenesis.html |archive-date=2006-08-30 }}</ref> | |||
[[Extratropical cyclones]] begin as waves in large regions of enhanced mid-latitude temperature contrasts called [[baroclinity|baroclinic zones]]. These zones contract and form [[weather front]]s as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones [[occluded front|occlude]] as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical [[jet stream]]. | |||
Weather fronts mark the boundary between two masses of air of different [[temperature]], [[humidity]], and [[densities]], and are associated with the most prominent [[meteorological phenomena]]. Strong cold fronts typically feature narrow bands of [[thunderstorm]]s and [[severe weather]], and may on occasion be preceded by [[squall line]]s or [[dry line]]s. Such fronts form west of the circulation center and generally move from west to east; [[warm front]]s form east of the cyclone center and are usually preceded by [[Stratus cloud|stratiform]] [[precipitation]] and [[fog]]. Warm fronts move [[Geographical pole|poleward]] ahead of the cyclone path. Occluded fronts form late in the cyclone life cycle near the center of the cyclone and often wrap around the storm center. | Weather fronts mark the boundary between two masses of air of different [[temperature]], [[humidity]], and [[densities]], and are associated with the most prominent [[meteorological phenomena]]. Strong cold fronts typically feature narrow bands of [[thunderstorm]]s and [[severe weather]], and may on occasion be preceded by [[squall line]]s or [[dry line]]s. Such fronts form west of the circulation center and generally move from west to east; [[warm front]]s form east of the cyclone center and are usually preceded by [[Stratus cloud|stratiform]] [[precipitation]] and [[fog]]. Warm fronts move [[Geographical pole|poleward]] ahead of the cyclone path. Occluded fronts form late in the cyclone life cycle near the center of the cyclone and often wrap around the storm center. | ||
[[Tropical cyclogenesis]] describes the process of development of tropical cyclones. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core.<ref>{{cite web |title=Tropical cyclogenesis |url=http://www-das.uwyo.edu/~geerts/cwx/notes/chap13/trop_cyclogenesis.html |website=www-das.uwyo.edu |access-date=12 January 2021 |archive-date=17 May 2021 |archive-url=https://web.archive.org/web/20210517035428/http://www-das.uwyo.edu/~geerts/cwx/notes/chap13/trop_cyclogenesis.html |url-status=live }}</ref><ref name = "AOML FAQ A7">{{cite web|publisher = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division|title = Frequently Asked Questions: What is an extra-tropical cyclone?|author = Stan Goldenberg|date = 2004-08-13|access-date = 2007-03-23|url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|archive-date = 2007-02-09|archive-url = https://web.archive.org/web/20070209121005/http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|url-status = live}}</ref> Cyclones can transition between extratropical, subtropical, and tropical phases.<ref>{{cite journal |last1=Evans |first1=Clark |last2=Wood |first2=Kimberly M. |last3=Aberson |first3=Sim D. |last4=Archambault |first4=Heather M. |last5=Milrad |first5=Shawn M. |last6=Bosart |first6=Lance F. |last7=Corbosiero |first7=Kristen L. |last8=Davis |first8=Christopher A. |last9=Pinto |first9=João R. Dias |last10=Doyle |first10=James |last11=Fogarty |first11=Chris |last12=Galarneau |first12=Thomas J. |last13=Grams |first13=Christian M. |last14=Griffin |first14=Kyle S. |last15=Gyakum |first15=John |last16=Hart |first16=Robert E. |last17=Kitabatake |first17=Naoko |last18=Lentink |first18=Hilke S. |last19=McTaggart-Cowan |first19=Ron |last20=Perrie |first20=William |last21=Quinting |first21=Julian F. D. |last22=Reynolds |first22=Carolyn A. |last23=Riemer |first23=Michael |last24=Ritchie |first24=Elizabeth A. |last25=Sun |first25=Yujuan |last26=Zhang |first26=Fuqing |title=The Extratropical Transition of Tropical Cyclones. Part I: Cyclone Evolution and Direct Impacts |journal=Monthly Weather Review |date=1 November 2017 |volume=145 |issue=11 |pages=4317–4344 |doi=10.1175/MWR-D-17-0027.1 | [[Tropical cyclogenesis]] describes the process of development of tropical cyclones. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core.<ref>{{cite web |title=Tropical cyclogenesis |url=http://www-das.uwyo.edu/~geerts/cwx/notes/chap13/trop_cyclogenesis.html |website=www-das.uwyo.edu |access-date=12 January 2021 |archive-date=17 May 2021 |archive-url=https://web.archive.org/web/20210517035428/http://www-das.uwyo.edu/~geerts/cwx/notes/chap13/trop_cyclogenesis.html |url-status=live }}</ref><ref name = "AOML FAQ A7">{{cite web|publisher = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division|title = Frequently Asked Questions: What is an extra-tropical cyclone?|author = Stan Goldenberg|date = 2004-08-13|access-date = 2007-03-23|url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|archive-date = 2007-02-09|archive-url = https://web.archive.org/web/20070209121005/http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|url-status = live}}</ref> Cyclones can transition between extratropical, subtropical, and tropical phases.<ref>{{cite journal |last1=Evans |first1=Clark |last2=Wood |first2=Kimberly M. |last3=Aberson |first3=Sim D. |last4=Archambault |first4=Heather M. |last5=Milrad |first5=Shawn M. |last6=Bosart |first6=Lance F. |last7=Corbosiero |first7=Kristen L. |last8=Davis |first8=Christopher A. |last9=Pinto |first9=João R. Dias |last10=Doyle |first10=James |last11=Fogarty |first11=Chris |last12=Galarneau |first12=Thomas J. |last13=Grams |first13=Christian M. |last14=Griffin |first14=Kyle S. |last15=Gyakum |first15=John |last16=Hart |first16=Robert E. |last17=Kitabatake |first17=Naoko |last18=Lentink |first18=Hilke S. |last19=McTaggart-Cowan |first19=Ron |last20=Perrie |first20=William |last21=Quinting |first21=Julian F. D. |last22=Reynolds |first22=Carolyn A. |last23=Riemer |first23=Michael |last24=Ritchie |first24=Elizabeth A. |last25=Sun |first25=Yujuan |last26=Zhang |first26=Fuqing |title=The Extratropical Transition of Tropical Cyclones. Part I: Cyclone Evolution and Direct Impacts |journal=Monthly Weather Review |date=1 November 2017 |volume=145 |issue=11 |pages=4317–4344 |doi=10.1175/MWR-D-17-0027.1 |bibcode=2017MWRv..145.4317E |s2cid=38114516 |url=https://escholarship.mcgill.ca/concern/articles/gf06g709j |hdl=1959.4/unsworks_47895 |hdl-access=free }}</ref> Mesocyclones form as warm core cyclones over land, and can lead to [[tornado]] formation.<ref name="FoN">Forces of Nature. [http://library.thinkquest.org/C003603/english/tornadoes/themesocyclone.shtml Tornadoes : the mesocyclone.] {{webarchive|url=https://web.archive.org/web/20080616154710/http://library.thinkquest.org/C003603/english/tornadoes/themesocyclone.shtml|date=2008-06-16}} Retrieved on 2008-06-15.</ref> [[Waterspout]]s can also form from mesocyclones, but more often develop from environments of high instability and low vertical [[wind shear]].<ref name = "NWS"/> In the Atlantic and the northeastern Pacific oceans, a tropical cyclone is generally referred to as a [[hurricane]] (from the name of the ancient Central American deity of wind, [[Huracan]]), in the Indian and south Pacific oceans it is called a cyclone, and in the northwestern Pacific it is called a [[typhoon]].<ref>{{cite web |url=http://www.aoml.noaa.gov/hrd/tcfaq/A1.html |title=Frequently asked questions |work=Hurricane Research Division |access-date=2006-04-08 |archive-date=2011-03-09 |archive-url=https://web.archive.org/web/20110309163143/http://www.aoml.noaa.gov/hrd/tcfaq/A1.html |url-status=live }}</ref> | ||
The growth of instability in the vortices is not universal. For example, the size, intensity, moist-convection, surface evaporation, the value of potential temperature at each potential height can affect the nonlinear evolution of a vortex.<ref>{{cite journal |last1=Rostami |first1=Masoud |last2=Zeitlin |first2=Vladimir |title=An improved moist-convective rotating shallow-water model and its application to instabilities of hurricane-like vortices |journal=Quarterly Journal of the Royal Meteorological Society |date=July 2018 |volume=144 |issue=714 |pages=1450–1462 |doi=10.1002/qj.3292 |bibcode=2018QJRMS.144.1450R |url=http://hal.sorbonne-universite.fr/hal-01755718/file/Improved_mcRSW_PrePrint.pdf }}</ref> | The growth of instability in the vortices is not universal. For example, the size, intensity, moist-convection, surface evaporation, the value of potential temperature at each potential height can affect the nonlinear evolution of a vortex.<ref>{{cite journal |last1=Rostami |first1=Masoud |last2=Zeitlin |first2=Vladimir |title=An improved moist-convective rotating shallow-water model and its application to instabilities of hurricane-like vortices |journal=Quarterly Journal of the Royal Meteorological Society |date=July 2018 |volume=144 |issue=714 |pages=1450–1462 |doi=10.1002/qj.3292 |bibcode=2018QJRMS.144.1450R |url=http://hal.sorbonne-universite.fr/hal-01755718/file/Improved_mcRSW_PrePrint.pdf }}</ref> | ||
== | ==Name== | ||
[[Henry Piddington]] published | |||
The term ''cyclone'' comes from the [[Greek language|Greek]] word {{lang|el|κύκλος}} ({{transliteration|el|kýklos}}, meaning "circle" or "ring" in [[Ancient Greek]]), due to the spiraling nature of a cyclone's winds.<ref>{{cite web|url=https://www.nesdis.noaa.gov/news/hurricanes-cyclones-and-typhoons-whats-name|title=Hurricanes, Cyclones and Typhoons: What's in a Name?|date=May 28, 2025|work=National Environmental Satellite, Data, and Information Service|publisher=National Oceanic and Atmospheric Administration|access-date=October 8, 2025}}</ref> The word was coined by [[Henry Piddington]], an official in the [[British East India Company]] who published 40 papers dealing with [[tropical storms]] from [[Calcutta]] between 1836 and 1855 in ''[[The Journal of the Asiatic Society]]''.<ref>{{cite ODNB|author=Blyth, Caroline |chapter=Piddington, Henry (1797–1858)| title= Oxford Dictionary of National Biography|year= 2004 |doi=10.1093/ref:odnb/22221 }}</ref> | |||
==Structure== | ==Structure== | ||
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There are a number of structural characteristics common to all cyclones. A cyclone is a [[low-pressure area]].<ref name="FAQ eye">{{cite web|author=[[Chris Landsea]] and Sim Aberson|title=Subject: A11) What is the "eye"? How is it formed and maintained ? What is the "eyewall"? What are "spiral bands"?|url=http://www.aoml.noaa.gov/hrd/tcfaq/A11.html|date=August 13, 2004|publisher=[[Atlantic Oceanographic and Meteorological Laboratory]]|access-date=2009-12-28|archive-date=2006-06-14|archive-url=https://web.archive.org/web/20060614205417/http://www.aoml.noaa.gov/hrd/tcfaq/A11.html|url-status=live}}</ref> A cyclone's center (often known in a mature tropical cyclone as the [[eye (cyclone)|eye]]), is the area of lowest atmospheric pressure in the region.<ref name="FAQ eye"/> Near the center, the [[pressure gradient force]] (from the pressure in the center of the cyclone compared to the pressure outside the cyclone) and the [[force]] from the [[Coriolis effect]] must be in an approximate balance, or the cyclone would collapse on itself as a result of the difference in pressure.<ref>{{cite web|url=http://homepages.abdn.ac.uk/wpe001/meteo/metoh8.pdf|title=The Atmosphere in Motion|publisher=[[University of Aberdeen]]|access-date=2011-09-11|url-status=dead|archive-url=https://web.archive.org/web/20121018224041/http://homepages.abdn.ac.uk/wpe001/meteo/metoh8.pdf|archive-date=2012-10-18}}</ref> | There are a number of structural characteristics common to all cyclones. A cyclone is a [[low-pressure area]].<ref name="FAQ eye">{{cite web|author=[[Chris Landsea]] and Sim Aberson|title=Subject: A11) What is the "eye"? How is it formed and maintained ? What is the "eyewall"? What are "spiral bands"?|url=http://www.aoml.noaa.gov/hrd/tcfaq/A11.html|date=August 13, 2004|publisher=[[Atlantic Oceanographic and Meteorological Laboratory]]|access-date=2009-12-28|archive-date=2006-06-14|archive-url=https://web.archive.org/web/20060614205417/http://www.aoml.noaa.gov/hrd/tcfaq/A11.html|url-status=live}}</ref> A cyclone's center (often known in a mature tropical cyclone as the [[eye (cyclone)|eye]]), is the area of lowest atmospheric pressure in the region.<ref name="FAQ eye"/> Near the center, the [[pressure gradient force]] (from the pressure in the center of the cyclone compared to the pressure outside the cyclone) and the [[force]] from the [[Coriolis effect]] must be in an approximate balance, or the cyclone would collapse on itself as a result of the difference in pressure.<ref>{{cite web|url=http://homepages.abdn.ac.uk/wpe001/meteo/metoh8.pdf|title=The Atmosphere in Motion|publisher=[[University of Aberdeen]]|access-date=2011-09-11|url-status=dead|archive-url=https://web.archive.org/web/20121018224041/http://homepages.abdn.ac.uk/wpe001/meteo/metoh8.pdf|archive-date=2012-10-18}}</ref> | ||
Because of the [[Coriolis effect]], the wind flow around a large cyclone is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.<ref>{{cite web|author=Chris Landsea|date=2009-02-06|url=http://www.aoml.noaa.gov/hrd/tcfaq/D3.html|title=Subject: D3) Why do tropical cyclones' winds rotate counterclockwise (clockwise) in the Northern (Southern) Hemisphere?|access-date=2009-12-28|publisher=[[Atlantic Oceanographic and Meteorological Laboratory]]|author-link=Chris Landsea|archive-date=2009-01-06|archive-url=https://web.archive.org/web/20090106113522/http://www.aoml.noaa.gov/hrd/tcfaq/D3.html|url-status=live}}</ref> In the Northern Hemisphere, the fastest winds relative to the surface of the Earth therefore occur on the eastern side of a northward-moving cyclone and on the northern side of a westward-moving one; the opposite occurs in the Southern Hemisphere.<ref>{{cite web|url=https://www.usatoday.com/weather/resources/askjack/wfaqhur.htm|title=Are the winds on one side of a hurricane faster than on the other side?|series=Ask the Experts: Hurricanes|work=[[USA Today]]|date=November 11, 2007|access-date=September 9, 2011|archive-date=October 12, 2011|archive-url=https://web.archive.org/web/20111012204835/http://www.usatoday.com/weather/resources/askjack/wfaqhur.htm|url-status=dead}}</ref> | Because of the [[Coriolis effect]], the wind flow around a large cyclone is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.<ref>{{cite web|author=Chris Landsea|date=2009-02-06|url=http://www.aoml.noaa.gov/hrd/tcfaq/D3.html|title=Subject: D3) Why do tropical cyclones' winds rotate counterclockwise (clockwise) in the Northern (Southern) Hemisphere?|access-date=2009-12-28|publisher=[[Atlantic Oceanographic and Meteorological Laboratory]]|author-link=Chris Landsea|archive-date=2009-01-06|archive-url=https://web.archive.org/web/20090106113522/http://www.aoml.noaa.gov/hrd/tcfaq/D3.html|url-status=live}}</ref> In the Northern Hemisphere, the fastest winds relative to the surface of the Earth therefore occur on the eastern side of a northward-moving cyclone and on the northern side of a westward-moving one; the opposite occurs in the Southern Hemisphere.<ref>{{cite web|url=https://www.usatoday.com/weather/resources/askjack/wfaqhur.htm|title=Are the winds on one side of a hurricane faster than on the other side?|series=Ask the Experts: Hurricanes|work=[[USA Today]]|date=November 11, 2007|access-date=September 9, 2011|archive-date=October 12, 2011|archive-url=https://web.archive.org/web/20111012204835/http://www.usatoday.com/weather/resources/askjack/wfaqhur.htm|url-status=dead}}</ref> | ||
==Formation== | ==Formation== | ||
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{{main|Cyclogenesis|Tropical cyclogenesis}} | {{main|Cyclogenesis|Tropical cyclogenesis}} | ||
Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere.<ref name="Arc"/> Cyclogenesis is an umbrella term for several different processes that all result in the development of some sort of cyclone.<ref>{{cite web |title=Cyclogenesis {{!}} meteorology |url=https://www.britannica.com/science/cyclogenesis |website=Encyclopædia Britannica |access-date=13 January 2021 |archive-date=14 January 2021 |archive-url=https://web.archive.org/web/20210114004348/https://www.britannica.com/science/cyclogenesis |url-status=live }}</ref> | Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere.<ref name="Arc"/> Cyclogenesis is an umbrella term for several different processes that all result in the development of some sort of cyclone.<ref>{{cite web |title=Cyclogenesis {{!}} meteorology |url=https://www.britannica.com/science/cyclogenesis |website=Encyclopædia Britannica |access-date=13 January 2021 |archive-date=14 January 2021 |archive-url=https://web.archive.org/web/20210114004348/https://www.britannica.com/science/cyclogenesis |url-status=live }}</ref> | ||
Tropical cyclones form as a result of significant convective activity, and are warm core.<ref name = "AOML FAQ A7"/> Mesocyclones form as warm core cyclones over land, and can lead to tornado formation.<ref name = "FoN"/> [[Waterspout]]s can also form from mesocyclones, but more often develop from environments of high instability and low vertical [[wind shear]].<ref name="NWS">[[National Weather Service]] Key West [https://web.archive.org/web/20050211013703/http://www.srh.noaa.gov/eyw/HTML/spoutweb.htm summary of waterspout types]</ref> Cyclolysis is the opposite of cyclogenesis, and is the high-pressure system equivalent, which deals with the formation of [[high-pressure area]]s—[[anticyclogenesis]].<ref name="CyclogenesisDef">{{cite web|publisher = [[American Meteorological Society]]|author = Glossary of Meteorology|title = Cyclogenesis|date = June 2000|url = http://glossary.ametsoc.org/wiki/Cyclogenesis|access-date = 2009-12-28|archive-date = 2014-01-15|archive-url = https://web.archive.org/web/20140115065635/http://glossary.ametsoc.org/wiki/Cyclogenesis|url-status = live}}</ref> | Tropical cyclones form as a result of significant convective activity, and are warm core.<ref name = "AOML FAQ A7"/> Mesocyclones form as warm core cyclones over land, and can lead to tornado formation.<ref name = "FoN"/> [[Waterspout]]s can also form from mesocyclones, but more often develop from environments of high instability and low vertical [[wind shear]].<ref name="NWS">[[National Weather Service]] Key West [https://web.archive.org/web/20050211013703/http://www.srh.noaa.gov/eyw/HTML/spoutweb.htm summary of waterspout types]</ref> Cyclolysis is the opposite of cyclogenesis, and is the high-pressure system equivalent, which deals with the formation of [[high-pressure area]]s—[[anticyclogenesis]].<ref name="CyclogenesisDef">{{cite web|publisher = [[American Meteorological Society]]|author = Glossary of Meteorology|title = Cyclogenesis|date = June 2000|url = http://glossary.ametsoc.org/wiki/Cyclogenesis|access-date = 2009-12-28|archive-date = 2014-01-15|archive-url = https://web.archive.org/web/20140115065635/http://glossary.ametsoc.org/wiki/Cyclogenesis|url-status = live}}</ref> | ||
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A surface low can form in a variety of ways. Topography can create a surface low. [[Mesoscale convective system]]s can spawn surface lows that are initially warm-core.<ref>{{cite journal|author1=Raymond D. Menard |author2=J.M. Fritsch |title=A Mesoscale Convective Complex-Generated Inertially Stable Warm Core Vortex|date=June 1989|journal=Monthly Weather Review|pages=1237–1261|volume=117|issue=6|doi=10.1175/1520-0493(1989)117<1237:AMCCGI>2.0.CO;2|bibcode = 1989MWRv..117.1237M |doi-access=free}}</ref> The disturbance can grow into a wave-like formation along the [[Surface weather analysis|front]] and the low is positioned at the crest. Around the low, the flow becomes cyclonic. This rotational flow moves polar air towards the equator on the west side of the low, while warm air move towards the pole on the east side. A cold front appears on the west side, while a warm front forms on the east side. Usually, the cold front moves at a quicker pace than the warm front and "catches up" with it due to the slow erosion of higher density air mass out ahead of the cyclone. In addition, the higher density air mass sweeping in behind the cyclone strengthens the higher pressure, denser cold air mass. The cold front over takes the warm front, and reduces the length of the warm front.<ref>{{cite web|author=Glenn Elert|year=2006|work=The Physics Factbook|url=http://hypertextbook.com/facts/2000/RachelChu.shtml|title=Density of Air|access-date=2010-01-01|archive-date=2010-01-02|archive-url=https://web.archive.org/web/20100102035928/http://hypertextbook.com/facts/2000/RachelChu.shtml|url-status=live}}</ref> At this point an [[occluded front]] forms where the warm air mass is pushed upwards into a trough of warm air aloft, which is also known as a [[trowal]].<ref>{{cite web|author=St. Louis University|url=http://www.eas.slu.edu/CIPS/Presentations/Conferences/NWA2002/Snow_NWA_02/tsld003.htm|publisher=[[National Weather Association]]|title=What is a trowal?|access-date=2010-01-01|date=2004-09-06|archive-url = https://web.archive.org/web/20080608235916/http://www.eas.slu.edu/CIPS/Presentations/Conferences/NWA2002/Snow_NWA_02/tsld003.htm |archive-date = June 8, 2008|url-status=dead}}</ref> | A surface low can form in a variety of ways. Topography can create a surface low. [[Mesoscale convective system]]s can spawn surface lows that are initially warm-core.<ref>{{cite journal|author1=Raymond D. Menard |author2=J.M. Fritsch |title=A Mesoscale Convective Complex-Generated Inertially Stable Warm Core Vortex|date=June 1989|journal=Monthly Weather Review|pages=1237–1261|volume=117|issue=6|doi=10.1175/1520-0493(1989)117<1237:AMCCGI>2.0.CO;2|bibcode = 1989MWRv..117.1237M |doi-access=free}}</ref> The disturbance can grow into a wave-like formation along the [[Surface weather analysis|front]] and the low is positioned at the crest. Around the low, the flow becomes cyclonic. This rotational flow moves polar air towards the equator on the west side of the low, while warm air move towards the pole on the east side. A cold front appears on the west side, while a warm front forms on the east side. Usually, the cold front moves at a quicker pace than the warm front and "catches up" with it due to the slow erosion of higher density air mass out ahead of the cyclone. In addition, the higher density air mass sweeping in behind the cyclone strengthens the higher pressure, denser cold air mass. The cold front over takes the warm front, and reduces the length of the warm front.<ref>{{cite web|author=Glenn Elert|year=2006|work=The Physics Factbook|url=http://hypertextbook.com/facts/2000/RachelChu.shtml|title=Density of Air|access-date=2010-01-01|archive-date=2010-01-02|archive-url=https://web.archive.org/web/20100102035928/http://hypertextbook.com/facts/2000/RachelChu.shtml|url-status=live}}</ref> At this point an [[occluded front]] forms where the warm air mass is pushed upwards into a trough of warm air aloft, which is also known as a [[trowal]].<ref>{{cite web|author=St. Louis University|url=http://www.eas.slu.edu/CIPS/Presentations/Conferences/NWA2002/Snow_NWA_02/tsld003.htm|publisher=[[National Weather Association]]|title=What is a trowal?|access-date=2010-01-01|date=2004-09-06|archive-url = https://web.archive.org/web/20080608235916/http://www.eas.slu.edu/CIPS/Presentations/Conferences/NWA2002/Snow_NWA_02/tsld003.htm |archive-date = June 8, 2008|url-status=dead}}</ref> | ||
Tropical cyclogenesis is the development and strengthening of a [[tropical cyclone]].<ref name="CYCDEF">{{cite web|author=Nina A. Zaitseva |year=2006 |url=http://nsidc.org/arcticmet/glossary/cyclogenesis.html |title=Definition for Cyclogenesis |publisher=National Snow and Ice Data Center |access-date=2006-10-20 |url-status=dead |archive-url=https://web.archive.org/web/20060830135741/http://www.nsidc.org/arcticmet/glossary/cyclogenesis.html |archive-date=2006-08-30 }}</ref> The mechanisms by which tropical cyclogenesis occurs are distinctly different from those that produce mid-[[latitude]] cyclones. Tropical cyclogenesis, the development of a [[Tropical cyclone#Mechanics|warm-core]] cyclone, begins with significant [[convection]] in a favorable atmospheric environment. There are | Tropical cyclogenesis is the development and strengthening of a [[tropical cyclone]].<ref name="CYCDEF">{{cite web|author=Nina A. Zaitseva |year=2006 |url=http://nsidc.org/arcticmet/glossary/cyclogenesis.html |title=Definition for Cyclogenesis |publisher=National Snow and Ice Data Center |access-date=2006-10-20 |url-status=dead |archive-url=https://web.archive.org/web/20060830135741/http://www.nsidc.org/arcticmet/glossary/cyclogenesis.html |archive-date=2006-08-30 }}</ref> The mechanisms by which tropical cyclogenesis occurs are distinctly different from those that produce mid-[[latitude]] cyclones. Tropical cyclogenesis, the development of a [[Tropical cyclone#Mechanics|warm-core]] cyclone, begins with significant [[convection]] in a favorable atmospheric environment. There are two main requirements for tropical cyclogenesis: sufficiently warm [[sea surface temperature]]s,<ref>[http://www.thethermograpiclibrary.org/index.php?title=Fichier:Water_cooling.jpg Cyclon in a board] {{Webarchive|url=https://web.archive.org/web/20130614225446/http://www.thethermograpiclibrary.org/index.php?title=Fichier:Water_cooling.jpg |date=2013-06-14 }}. thethermograpiclibrary.org</ref> and low vertical [[wind shear]].<ref name="A15">{{cite web|author=Chris Landsea |url=http://www.aoml.noaa.gov/hrd/tcfaq/A15.html |title=Subject: A15) How do tropical cyclones form ? |publisher=[[Atlantic Oceanographic and Meteorological Laboratory]] |access-date=2010-01-01 |date=2009-02-06 |url-status=dead |archive-url=https://web.archive.org/web/20090827030639/http://www.aoml.noaa.gov/hrd/tcfaq/A15.html |archive-date=2009-08-27 |author-link=Chris Landsea }}</ref> | ||
An average of 86 tropical cyclones of tropical storm intensity form annually worldwide,<ref>{{cite journal |last1=Shultz |first1=James M. |last2=Russell |first2=Jill |last3=Espinel |first3=Zelde |title=Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development |journal=Epidemiologic Reviews |date=July 2005 |volume=27 |issue=1 |pages=21–35 |doi=10.1093/epirev/mxi011 |pmid=15958424 }}</ref> with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones (at least Category 3 intensity on the [[Saffir–Simpson hurricane scale]]).<ref>{{cite web|author = Chris Landsea|url = http://www.aoml.noaa.gov/hrd/Landsea/climvari/table.html|title = Climate Variability table — Tropical Cyclones|publisher = [[Atlantic Oceanographic and Meteorological Laboratory]]|date = 2000-01-04|access-date = 2006-10-19|author-link = Chris Landsea|archive-date = 2012-10-02|archive-url = https://web.archive.org/web/20121002045230/http://www.aoml.noaa.gov/hrd/Landsea/climvari/table.html|url-status = live}}</ref> | An average of 86 tropical cyclones of tropical storm intensity form annually worldwide,<ref>{{cite journal |last1=Shultz |first1=James M. |last2=Russell |first2=Jill |last3=Espinel |first3=Zelde |title=Epidemiology of Tropical Cyclones: The Dynamics of Disaster, Disease, and Development |journal=Epidemiologic Reviews |date=July 2005 |volume=27 |issue=1 |pages=21–35 |doi=10.1093/epirev/mxi011 |pmid=15958424 }}</ref> with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones (at least Category 3 intensity on the [[Saffir–Simpson hurricane scale]]).<ref>{{cite web|author = Chris Landsea|url = http://www.aoml.noaa.gov/hrd/Landsea/climvari/table.html|title = Climate Variability table — Tropical Cyclones|publisher = [[Atlantic Oceanographic and Meteorological Laboratory]]|date = 2000-01-04|access-date = 2006-10-19|author-link = Chris Landsea|archive-date = 2012-10-02|archive-url = https://web.archive.org/web/20121002045230/http://www.aoml.noaa.gov/hrd/Landsea/climvari/table.html|url-status = live}}</ref> | ||
==Synoptic | ==Synoptic types== | ||
[[File:UK-Cyclone.gif|thumb|A fictitious synoptic chart of an extratropical cyclone affecting the UK and Ireland. The blue arrows between [[isobar (meteorology)|isobars]] indicate the direction of the wind, while the "L" symbol denotes the centre of the "low". Note the occluded, cold and warm [[Surface weather analysis|frontal boundaries]].]] | [[File:UK-Cyclone.gif|thumb|A fictitious synoptic chart of an extratropical cyclone affecting the UK and Ireland. The blue arrows between [[isobar (meteorology)|isobars]] indicate the direction of the wind, while the "L" symbol denotes the centre of the "low". Note the occluded, cold and warm [[Surface weather analysis|frontal boundaries]].]] | ||
The following types of cyclones are identifiable in synoptic charts. | The following types of cyclones are identifiable in synoptic charts.<ref name=scale>{{cite journal|author=I. Orlanski|year=1975|title=A rational subdivision of scales for atmospheric processes |journal=Bulletin of the American Meteorological Society |volume=56 |pages=527–530 |issue=5 |bibcode=1975BAMS...56..527. |doi=10.1175/1520-0477-56.5.527 |doi-access=free }}</ref> | ||
===Surface-based types=== | ===Surface-based types=== | ||
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{{main|Extratropical cyclone}} | {{main|Extratropical cyclone}} | ||
An | An extratropical cyclone is a [[synoptic scale]] [[Low-pressure area|low-pressure]] weather system that does not have [[tropical cyclone|tropical]] characteristics,<ref>{{cite book |doi=10.1016/B978-0-444-53199-5.00027-0 |chapter=Precipitation |title=Treatise on Water Science |date=2011 |last1=Koutsoyiannis |first1=D. |last2=Langousis |first2=A. |pages=27–77 |isbn=978-0-444-53199-5 }}</ref> as it is connected with [[Weather fronts|fronts]] and horizontal [[gradients]] (rather than vertical) in [[temperature]] and [[dew point]] otherwise known as "baroclinic zones".<ref name="ExtraLessonMillUni">{{cite web | ||
|title = ESCI 241 – Meteorology; Lesson 16 – Extratropical Cyclones | |title = ESCI 241 – Meteorology; Lesson 16 – Extratropical Cyclones | ||
|author = DeCaria | |author = DeCaria | ||
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|archive-url = https://web.archive.org/web/20110609164448/http://ams.confex.com/ams/pdfpapers/70524.pdf | |archive-url = https://web.archive.org/web/20110609164448/http://ams.confex.com/ams/pdfpapers/70524.pdf | ||
|url-status = live | |url-status = live | ||
}}</ref> They are often described as "depressions" or "lows" by weather forecasters and the general public. These are the everyday phenomena that, along with [[anticyclone]]s, drive weather over much of the Earth. | }}</ref> They are often described as "depressions" or "lows" by weather forecasters and the general public.<ref> | ||
{{cite web |year=2008 |title=Cyclone |url=http://amsglossary.allenpress.com/glossary/search?id=cyclone1 |archive-url=https://web.archive.org/web/20081004114152/http://amsglossary.allenpress.com/glossary/search?id=cyclone1 |archive-date=4 October 2008 |access-date=August 29, 2025 |website=amsglossary.allenpress.com |series=Glossary of Meteorology |publisher=Allen Press |department=[[American Meteorological Society]]}} | |||
</ref> These are the everyday phenomena that, along with [[anticyclone]]s, drive weather over much of the Earth.<ref>{{cite web |title=Weather Conditions |url=https://www.metoffice.gov.uk/weather/learn-about/weather/how-weather-works/high-and-low-pressure/weather-conditions |publisher=Met Office |access-date=7 November 2024}}</ref> | |||
Although extratropical cyclones are almost always classified as [[baroclinic]] since they form along zones of temperature and dewpoint gradient within the [[westerlies]], they can sometimes become [[barotropic]] late in their life cycle when the temperature distribution around the cyclone becomes fairly uniform with radius.<ref>{{cite web|author=Ryan N. Maue|year=2008|url=http://www.coaps.fsu.edu/~maue/cyclone_ch3.html|title=Chapter 3: Cyclone Paradigms and Extratropical Transition Conceptualizations|access-date=2008-06-15|publisher=[[Florida State University]]|archive-url=https://web.archive.org/web/20080510210146/http://www.coaps.fsu.edu/~maue/cyclone_ch3.html |archive-date=2008-05-10}}</ref> An extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone, if it dwells over warm waters sufficient to warm its core, and as a result develops central convection.<ref name = "AOML FAQ A7-2">{{cite web|author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division|title = Frequently Asked Questions: What is an extra-tropical cyclone?|publisher = [[NOAA]]|access-date = 2006-07-25|url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|archive-date = 2007-02-09|archive-url = https://web.archive.org/web/20070209121005/http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|url-status = live}}</ref> A particularly intense type of extratropical cyclone that strikes during winter is known colloquially as a | Although extratropical cyclones are almost always classified as [[baroclinic]] since they form along zones of temperature and dewpoint gradient within the [[westerlies]], they can sometimes become [[barotropic]] late in their life cycle when the temperature distribution around the cyclone becomes fairly uniform with radius.<ref>{{cite web|author=Ryan N. Maue|year=2008|url=http://www.coaps.fsu.edu/~maue/cyclone_ch3.html|title=Chapter 3: Cyclone Paradigms and Extratropical Transition Conceptualizations|access-date=2008-06-15|publisher=[[Florida State University]]|archive-url=https://web.archive.org/web/20080510210146/http://www.coaps.fsu.edu/~maue/cyclone_ch3.html |archive-date=2008-05-10}}</ref> An extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone, if it dwells over warm waters sufficient to warm its core, and as a result develops central convection.<ref name = "AOML FAQ A7-2">{{cite web|author = [[Atlantic Oceanographic and Meteorological Laboratory]], Hurricane Research Division|title = Frequently Asked Questions: What is an extra-tropical cyclone?|publisher = [[NOAA]]|access-date = 2006-07-25|url = http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|archive-date = 2007-02-09|archive-url = https://web.archive.org/web/20070209121005/http://www.aoml.noaa.gov/hrd/tcfaq/A7.html|url-status = live}}</ref> A particularly intense type of extratropical cyclone that strikes during winter is known colloquially as a [[nor'easter]].<ref>{{cite web|url=http://www.noaa.gov/features/03_protecting/noreasters.html|archive-url=https://web.archive.org/web/20160214123432/http://www.noaa.gov/features/03_protecting/noreasters.html|archive-date=February 14, 2016|title=Know the dangers of nor'easters|publisher=National Oceanic and Atmospheric Administration|date=February 7, 2013}}</ref> | ||
==== Polar low ==== | ==== Polar low ==== | ||
{{Main|Polar low}} | {{Main|Polar low}} | ||
[[File:Sea of Japan polar low 2009-12-20 0213Z.jpg|thumb|A polar low over the [[Sea of Japan]] in December 2009]] | [[File:Sea of Japan polar low 2009-12-20 0213Z.jpg|thumb|A polar low over the [[Sea of Japan]] in December 2009]] | ||
A | A polar low is a small-scale, short-lived atmospheric [[low-pressure system]] (depression) that is found over the ocean areas poleward of the main [[polar front]] in both the Northern and Southern Hemispheres. Polar lows were first identified on the meteorological satellite imagery that became available in the 1960s, which revealed many small-scale cloud vortices at high latitudes. The most active polar lows are found over certain ice-free maritime areas in or near the Arctic during the winter, such as the [[Norwegian Sea]], [[Barents Sea]], [[Labrador Sea]] and [[Gulf of Alaska]]. Polar lows dissipate rapidly when they make landfall. Antarctic systems tend to be weaker than their northern counterparts since the air-sea temperature differences around the continent are generally smaller. However, vigorous polar lows can be found over the Southern Ocean.<ref>{{Cite journal |last1=Moreno-Ibáñez |first1=Marta |last2=Laprise |first2=René |last3=Gachon |first3=Philippe |date=2021-01-01 |title=Recent advances in polar low research: current knowledge, challenges and future perspectives |journal=Tellus A: Dynamic Meteorology and Oceanography |language=en |volume=73 |issue=1 |pages=1–31 |doi=10.1080/16000870.2021.1890412 |s2cid=233807634 |issn=1600-0870|doi-access=free |bibcode=2021TellA..7390412M }}</ref> | ||
During winter, when cold-core lows with temperatures in the mid-levels of the troposphere reach {{convert|-45|C|F}} move over open waters, deep convection forms, which allows polar low development to become possible.<ref>{{cite book|url=https://books.google.com/books?id=-tBa1DWYoDIC&pg=PA227|title=Polar lows: mesoscale weather systems in the polar regions|page=224|author1=Erik A. Rasmussen |author2=John Turner |year=2003|publisher=Cambridge University Press|access-date=2011-01-27|isbn=978-0-521-62430-5}}</ref> The systems usually have a horizontal length scale of less than {{convert|1000|km|mi}} and exist for no more than a couple of days. They are part of the larger class of [[mesoscale meteorology|mesoscale]] weather systems. Polar lows can be difficult to detect using conventional weather reports and are a hazard to high-latitude operations, such as shipping and gas and oil platforms. Polar lows have been referred to by many other terms, such as polar mesoscale vortex, Arctic hurricane, Arctic low, and cold air depression. Today the term is usually reserved for the more vigorous systems that have near-surface winds of at least {{convert|17|m/s|mph km/h|abbr=on}}.<ref>{{cite book|author1=E. A. Rasmussen |author2=J. Turner |year=2003|title=Polar Lows: Mesoscale Weather Systems in the Polar Regions|publisher=Cambridge University Press|page=612|isbn=978-0-521-62430-5}}</ref> | |||
====Subtropical==== | ====Subtropical==== | ||
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{{main|Subtropical cyclone}} | {{main|Subtropical cyclone}} | ||
A | 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 between the equator and the 50th parallel.<ref name="A6">{{cite web|author=Chris Landsea|url=http://www.aoml.noaa.gov/hrd/tcfaq/A6.html|title=Subject: A6) What is a sub-tropical cyclone?|access-date=2009-12-27|date=2009-02-06|publisher=[[Atlantic Oceanographic and Meteorological Laboratory]]|author-link=Chris Landsea|archive-date=2011-10-11|archive-url=https://web.archive.org/web/20111011042947/http://www.aoml.noaa.gov/hrd/tcfaq/A6.html|url-status=live}}</ref> As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical cyclones or extratropical cyclones, and used terms such as quasi-tropical and semi-tropical to describe the cyclone hybrids.<ref>{{cite journal |doi=10.1175/1520-0493(1973)101<0380:R>2.3.CO;2 |title=Reply |date=1973 |last1=Spiegler |first1=David B. |journal=Monthly Weather Review |volume=101 |issue=4 |page=380 |bibcode=1973MWRv..101..380S |doi-access=free }}</ref> By 1972, the [[National Hurricane Center]] in the United States officially recognized this cyclone category.<ref>{{cite journal |doi=10.1175/1520-0493(1973)101<0323:AHSO>2.3.CO;2 |title=Atlantic Hurricane Season of 1972 |date=1973 |last1=Simpson |first1=R. H. |last2=Hebert |first2=Paul J. |journal=Monthly Weather Review |volume=101 |issue=4 |pages=323–333 |bibcode=1973MWRv..101..323S |doi-access=free }}</ref> Subtropical cyclones began to receive names off the [[Tropical cyclone naming|official tropical cyclone list]] in the Atlantic Basin in 2002.<ref name = "A6"/> They have broad wind patterns with maximum sustained winds located farther from the center than typical tropical cyclones, and exist in areas of weak to moderate temperature gradient.<ref name="A6"/> | ||
Since they form from extratropical cyclones, which have colder temperatures aloft than normally found in the tropics, the sea surface temperatures required is around 23 degrees Celsius (73 °F) for their formation, which is three degrees Celsius (5 °F) lower than for tropical cyclones.<ref name="HistSubTropCyclones">{{cite web | Since they form from extratropical cyclones, which have colder temperatures aloft than normally found in the tropics, the sea surface temperatures required is around 23 degrees Celsius (73 °F) for their formation, which is three degrees Celsius (5 °F) lower than for tropical cyclones.<ref name="HistSubTropCyclones">{{cite web | ||
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{{main|Tropical cyclone}} | {{main|Tropical cyclone}} | ||
[[File:Dramatic Views of Hurricane Florence from the International Space Station From 9 12 (42828603210) (cropped).jpg|thumb|[[Hurricane Florence]] viewed from the [[International Space Station]]]] | [[File:Dramatic Views of Hurricane Florence from the International Space Station From 9 12 (42828603210) (cropped).jpg|thumb|[[Hurricane Florence]] viewed from the [[International Space Station]]]] | ||
A | A tropical cyclone is a [[storm system]] characterized by a [[Low-pressure area|low-pressure]] center and numerous [[thunderstorm]]s that produce strong winds and flooding rain.<ref name="StackPath">{{cite web |title=StackPath |url=https://www.laserfocusworld.com/home/article/14192224/tropical-cyclone#:~:text=View%20Image%20Gallery-,A%20tropical%20cyclone%20is%20a%20storm%20system%20characterized%20by%20a,contained%20in%20the%20moist%20air. |website=www.laserfocusworld.com | date=10 August 2011 |access-date=13 January 2021 |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414230334/https://www.laserfocusworld.com/home/article/14192224/tropical-cyclone#:~:text=View%20Image%20Gallery-,A%20tropical%20cyclone%20is%20a%20storm%20system%20characterized%20by%20a,contained%20in%20the%20moist%20air. |url-status=live }}</ref> A tropical cyclone feeds on heat released when moist air rises, resulting in [[condensation]] of [[water vapour]] contained in the moist air.<ref name="StackPath"/> They are fueled by a different heat mechanism than other cyclonic windstorms such as [[nor'easter]]s, [[European windstorm]]s, and [[polar low]]s, leading to their classification as "warm core" storm systems.<ref name="StackPath"/><ref name = "AOML FAQ A7"/> | ||
The term "tropical" refers to both the geographic origin of these systems, which form almost exclusively in [[Tropics|tropical]] regions of the globe,<ref name="laserfocusworld.com">{{cite web |title=StackPath |url=https://www.laserfocusworld.com/home/article/14192224/tropical-cyclone#:~:text=View%20Image%20Gallery-,A%20tropical%20cyclone%20is%20a%20storm%20system%20characterized%20by%20a,contained%20in%20the%20moist%20air |website=www.laserfocusworld.com | date=10 August 2011 |access-date=14 January 2021 |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414230334/https://www.laserfocusworld.com/home/article/14192224/tropical-cyclone#:~:text=View%20Image%20Gallery-,A%20tropical%20cyclone%20is%20a%20storm%20system%20characterized%20by%20a,contained%20in%20the%20moist%20air |url-status=live }}</ref> and their dependence on [[Air mass#Classification and notation|Maritime Tropical air masses]] for their formation. The term "cyclone" refers to the storms' cyclonic nature, with [[counterclockwise]] rotation in the [[Northern Hemisphere]] and clockwise rotation in the [[Southern Hemisphere]].<ref name="laserfocusworld.com"/> Depending on their location and strength, tropical cyclones are referred to by other names, such as [[hurricane]], [[typhoon]], [[tropical storm]], [[cyclonic storm]], [[tropical depression]], or simply as a cyclone.<ref name="laserfocusworld.com"/> | The term "tropical" refers to both the geographic origin of these systems, which form almost exclusively in [[Tropics|tropical]] regions of the globe,<ref name="laserfocusworld.com">{{cite web |title=StackPath |url=https://www.laserfocusworld.com/home/article/14192224/tropical-cyclone#:~:text=View%20Image%20Gallery-,A%20tropical%20cyclone%20is%20a%20storm%20system%20characterized%20by%20a,contained%20in%20the%20moist%20air |website=www.laserfocusworld.com | date=10 August 2011 |access-date=14 January 2021 |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414230334/https://www.laserfocusworld.com/home/article/14192224/tropical-cyclone#:~:text=View%20Image%20Gallery-,A%20tropical%20cyclone%20is%20a%20storm%20system%20characterized%20by%20a,contained%20in%20the%20moist%20air |url-status=live }}</ref> and their dependence on [[Air mass#Classification and notation|Maritime Tropical air masses]] for their formation. The term "cyclone" refers to the storms' cyclonic nature, with [[counterclockwise]] rotation in the [[Northern Hemisphere]] and clockwise rotation in the [[Southern Hemisphere]].<ref name="laserfocusworld.com"/> Depending on their location and strength, tropical cyclones are referred to by other names, such as [[hurricane]], [[typhoon]], [[tropical storm]], [[cyclonic storm]], [[tropical depression]], or simply as a cyclone.<ref name="laserfocusworld.com"/> | ||
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====Polar cyclone==== | ====Polar cyclone==== | ||
{{main|Polar cyclone}} | {{main|Polar cyclone}} | ||
A | A polar, sub-polar, or Arctic cyclone (also known as a [[polar vortex]])<ref name = "glossvortex"/> is a vast area of low pressure that strengthens in the winter and weakens in the summer.<ref>{{cite web|author=Halldór Björnsson |date=2005-01-19 |url=http://andvari.vedur.is/~halldor/HB/Met210old/GlobCirc.html |title=Global circulation |publisher=Veðurstofa Íslands |access-date=2008-06-15 |url-status=dead |archive-url=https://web.archive.org/web/20110807132251/http://andvari.vedur.is/~halldor/HB/Met210old/GlobCirc.html |archive-date=2011-08-07 }}</ref> A polar cyclone is a low-pressure [[weather system]], usually spanning {{convert|1000|km|mi}} to {{convert|2000|km|mi}},<ref>{{cite web |last1=Garima |first1=Khera |title=A vortex of winds-Cyclones – Geography and You |url=https://geographyandyou.com/a-vortex-of-winds-cyclones/ |access-date=14 January 2021 |archive-date=2 March 2021 |archive-url=https://web.archive.org/web/20210302232449/https://geographyandyou.com/a-vortex-of-winds-cyclones/ |url-status=live }}</ref> in which the air circulates in a counterclockwise direction in the northern hemisphere, and a clockwise direction in the southern hemisphere. The Coriolis acceleration acting on the air masses moving poleward at high altitude, causes a counterclockwise circulation at high altitude. The poleward movement of air originates from the air circulation of the [[atmospheric circulation#Latitudinal circulation features|Polar cell]]. The polar low is not driven by convection as are tropical cyclones, nor the cold and warm air mass interactions as are extratropical cyclones, but is an artifact of the global air movement of the Polar cell. The base of the polar low is in the mid to upper troposphere. In the Northern Hemisphere, the polar cyclone has two centers on average. One center lies near Baffin Island and the other over northeast Siberia.<ref name="glossvortex">{{cite web|author=Glossary of Meteorology|date=June 2000|url=http://glossary.ametsoc.org/wiki/Polar_vortex|title=Polar vortex|access-date=2008-06-15|publisher=[[American Meteorological Society]]|archive-date=2019-07-18|archive-url=https://web.archive.org/web/20190718200838/http://glossary.ametsoc.org/wiki/Polar_vortex|url-status=live}}</ref> In the southern hemisphere, it tends to be located near the edge of the [[Ross ice shelf]] near 160 west longitude.<ref>{{cite journal |last1=Chen |first1=Rui-Rong |last2=Boyer |first2=Don L. |last3=Tao |first3=Lijun |title=Laboratory Simulation of Atmospheric Motions in the Vicinity of Antarctica |journal=Journal of the Atmospheric Sciences |date=December 1993 |volume=50 |issue=24 |pages=4058–4079 |doi=10.1175/1520-0469(1993)050<4058:LSOAMI>2.0.CO;2 |bibcode=1993JAtS...50.4058C |doi-access=free }}</ref> When the polar vortex is strong, its effect can be felt at the surface as a westerly wind (toward the east). When the polar cyclone is weak, significant cold outbreaks occur.<ref>{{cite web|author=James E. Kloeppel|url=http://www.news.uiuc.edu/scitips/01/12weather.html |date=2001-12-01|publisher=[[University of Illinois at Urbana–Champaign]] via the Internet Wayback Machine|title=Stratospheric polar vortex influences winter freezing, researchers say|access-date=2009-12-27 |archive-url = https://web.archive.org/web/20011224094138/http://www.news.uiuc.edu/scitips/01/12weather.html |archive-date=2001-12-24}}</ref> | ||
====TUTT cell==== | ====TUTT cell==== | ||
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Under specific circumstances, upper level cold lows can break off from the base of the tropical upper tropospheric trough (TUTT), which is located mid-ocean in the Northern Hemisphere during the summer months. These upper tropospheric cyclonic vortices, also known as TUTT cells or TUTT lows, usually move slowly from east-northeast to west-southwest, and their bases generally do not extend below {{convert|20,000|ft|m}} in altitude. A weak inverted surface trough within the [[trade wind]] is generally found underneath them, and they may also be associated with broad areas of high-level clouds. Downward development results in an increase of [[cumulus cloud]]s and the appearance of a surface vortex. In rare cases, they become warm-core [[tropical cyclone]]s. Upper cyclones and the upper troughs that trail tropical cyclones can cause additional outflow channels and aid in their intensification. Developing tropical disturbances can help create or deepen upper troughs or upper lows in their wake due to the outflow jet emanating from the developing tropical disturbance/cyclone.<ref name="CLARK">{{cite web|author = Clark Evans|url = http://flhurricane.com/cyclone/showflat.php?Cat=0&Number=64429&an=0&page=0|title = Favorable trough interactions on tropical cyclones|publisher = Flhurricane.com|date = January 5, 2006|access-date = 2006-10-20|archive-url = https://web.archive.org/web/20061017001243/http://flhurricane.com/cyclone/showflat.php?Cat=0&Number=64429&an=0&page=0|archive-date = October 17, 2006|url-status = dead}}</ref><ref name="AMSPAPER">{{cite journal|author1=Deborah Hanley |author2=John Molinari |author3=Daniel Keyser |title = A Composite Study of the Interactions between Tropical Cyclones and Upper-Tropospheric Troughs|date=October 2001|journal = [[Monthly Weather Review]]|publisher = [[American Meteorological Society]]|volume = 129|issue = 10|pages = 2570–84|doi = 10.1175/1520-0493(2001)129<2570:ACSOTI>2.0.CO;2|bibcode = 2001MWRv..129.2570H |doi-access = free}}</ref> | Under specific circumstances, upper level cold lows can break off from the base of the tropical upper tropospheric trough (TUTT), which is located mid-ocean in the Northern Hemisphere during the summer months. These upper tropospheric cyclonic vortices, also known as TUTT cells or TUTT lows, usually move slowly from east-northeast to west-southwest, and their bases generally do not extend below {{convert|20,000|ft|m}} in altitude. A weak inverted surface trough within the [[trade wind]] is generally found underneath them, and they may also be associated with broad areas of high-level clouds. Downward development results in an increase of [[cumulus cloud]]s and the appearance of a surface vortex. In rare cases, they become warm-core [[tropical cyclone]]s. Upper cyclones and the upper troughs that trail tropical cyclones can cause additional outflow channels and aid in their intensification. Developing tropical disturbances can help create or deepen upper troughs or upper lows in their wake due to the outflow jet emanating from the developing tropical disturbance/cyclone.<ref name="CLARK">{{cite web|author = Clark Evans|url = http://flhurricane.com/cyclone/showflat.php?Cat=0&Number=64429&an=0&page=0|title = Favorable trough interactions on tropical cyclones|publisher = Flhurricane.com|date = January 5, 2006|access-date = 2006-10-20|archive-url = https://web.archive.org/web/20061017001243/http://flhurricane.com/cyclone/showflat.php?Cat=0&Number=64429&an=0&page=0|archive-date = October 17, 2006|url-status = dead}}</ref><ref name="AMSPAPER">{{cite journal|author1=Deborah Hanley |author2=John Molinari |author3=Daniel Keyser |title = A Composite Study of the Interactions between Tropical Cyclones and Upper-Tropospheric Troughs|date=October 2001|journal = [[Monthly Weather Review]]|publisher = [[American Meteorological Society]]|volume = 129|issue = 10|pages = 2570–84|doi = 10.1175/1520-0493(2001)129<2570:ACSOTI>2.0.CO;2|bibcode = 2001MWRv..129.2570H |doi-access = free}}</ref> | ||
== | ==Non-synoptic types== | ||
The following types of cyclones are not identifiable in synoptic charts. | The following types of cyclones are not identifiable in synoptic charts.<ref name="scale" /> | ||
===Mesocyclone=== | ===Mesocyclone=== | ||
{{Main|Mesocyclone}} | {{Main|Mesocyclone}} | ||
A | A mesocyclone is a [[vortex]] of air, {{convert|2.0|km|mi}} to {{convert|10|km|mi}} in diameter (the [[mesoscale meteorology|mesoscale of meteorology]]), within a [[convection|convective]] storm.<ref name="MesocyloneDef">{{cite web|title=Mesocyclone|author=Glossary of Meteorology|publisher=[[American Meteorological Society]]|date=June 2000|url=http://glossary.ametsoc.org/wiki/Mesocyclone|access-date=2006-12-07|archive-date=2014-05-17|archive-url=https://web.archive.org/web/20140517225409/http://glossary.ametsoc.org/wiki/Mesocyclone|url-status=live}}</ref> Air rises and rotates around a vertical axis, usually in the same direction as low-pressure systems<ref name="skybrary.aero">{{cite web |title=Mesocyclone – SKYbrary Aviation Safety |url=https://www.skybrary.aero/index.php/Mesocyclone |website=www.skybrary.aero |access-date=13 January 2021 |archive-date=14 January 2021 |archive-url=https://web.archive.org/web/20210114104249/https://www.skybrary.aero/index.php/Mesocyclone |url-status=live }}</ref> in both northern and southern hemisphere. They are most often cyclonic, that is, associated with a localized low-pressure region within a [[supercell]].<ref name="skybrary.aero"/><ref>{{cite web|author=[[National Weather Service]] Forecast Office State College, Pennsylvania|url=http://www.erh.noaa.gov/ctp/features/2006/07_10/|title=Splitting Storm and Anti-cyclonic Rotating Mesocyclone in a Thunderstorm over Elk County July 10th, 2006|date=2006-07-16|access-date=2008-06-15|archive-date=2009-01-14|archive-url=https://web.archive.org/web/20090114220647/http://www.erh.noaa.gov/ctp/features/2006/07_10/|url-status=live}}</ref> Such storms can feature strong surface winds and severe [[hail]].<ref name="skybrary.aero"/> Mesocyclones often occur together with updrafts in [[supercell]]s, where [[tornado]]es may form.<ref name="skybrary.aero"/> About 1,700 mesocyclones form annually across the United States, but only half produce tornadoes.<ref name="FoN">Forces of Nature. [http://library.thinkquest.org/C003603/english/tornadoes/themesocyclone.shtml Tornadoes : the mesocyclone.] {{webarchive|url=https://web.archive.org/web/20080616154710/http://library.thinkquest.org/C003603/english/tornadoes/themesocyclone.shtml|date=2008-06-16}} Retrieved on 2008-06-15.</ref> | ||
===Dust devil=== | ===Dust devil=== | ||
{{main|Dust devil}} | {{main|Dust devil}} | ||
A [[dust devil]] is a | A [[dust devil]] is a type of vortex that involves [[debris]] such as dust being lifted upward into the air.<ref name="dd2" /><ref name="Dust Devils">{{cite web |title=Dust Devils |url=https://www.crystalinks.com/dustdevils.html |website=www.crystalinks.com |access-date=13 January 2021 |archive-date=25 January 2021 |archive-url=https://web.archive.org/web/20210125094338/https://www.crystalinks.com/dustdevils.html |url-status=live }}</ref> Most dust devils are between {{convert|10|ft|m|abbr=on}} and {{convert|300|ft|m|abbr=on}} wide, and between {{convert|500|ft|m|abbr=on}} and {{convert|1000|ft|m|abbr=on}} tall, although the strongest can be several thousand feet tall. Wind speed varies depending on the size of the dust devil; larger ones have winds of at least {{convert|60|mph|km/h|abbr=on}}, reaching up to {{convert|75|mph|km/h|abbr=on}}. Dust devils form from a warm surface during sunny days, often in an area where surface types change, and require the surrounding air to be unstable, dissipating when conditions become more stable; they therefore often from in [[desert]]s. They usually dissipate after only a few minutes, but stronger dust devils can last over an hour. Dust devils are smaller than [[tornado]]es and are usually harmless, though stronger ones can destroy small structures. Dust devils have been found on Mars as well as on Earth.<ref name="dd2">{{cite web|url=https://www.weather.gov/fgz/DustDevil|title=Dust Devils in Northern Arizona|publisher=National Weather Service|access-date=October 17, 2025}}</ref> | ||
===Waterspout=== | ===Waterspout=== | ||
{{main|Waterspout}} | {{main|Waterspout}} | ||
A waterspout is a columnar vortex forming over water that is, in its most common form, a non-[[supercell]] [[tornado]] over water that is connected to a [[cumuliform cloud]]. While it is often weaker than most of its land counterparts, stronger versions spawned by [[mesocyclones]] do occur. | A waterspout is a columnar vortex forming over water that is, in its most common form, a non-[[supercell]] [[tornado]] over water that is connected to a [[cumuliform cloud]]. While it is often weaker than most of its land counterparts, stronger versions spawned by [[mesocyclones]] do occur.<ref>{{cite web |url= https://www.geographic.org/climate/w.html#waterspout |title=A Comprehensive Glossary of Weather: Waterspout definition |website=geographic.org |access-date=10 July 2014 |url-status=live |archive-url=https://web.archive.org/web/20220208114424/https://www.geographic.org/climate/w.html#waterspout |archive-date=8 February 2022}}</ref> | ||
===Steam devil=== | ===Steam devil=== | ||
{{main|Steam devil}} | {{main|Steam devil}} | ||
A gentle vortex over calm water or wet land made visible by rising water vapour. | A steam devil is a gentle vortex over calm water or wet land that is made visible by rising water vapour.<ref>{{cite web|url=https://cloudatlas.wmo.int/en/steam-devil.html |title=Steam Devil |publisher=[[World Meteorological Organisation]] |access-date=28 August 2025}}</ref> | ||
===Fire whirl=== | ===Fire whirl=== | ||
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{{Main|Extraterrestrial vortex}} | {{Main|Extraterrestrial vortex}} | ||
[[File:Mars cyclone.jpg|thumb|right|350px|Cyclone on Mars, imaged by the [[Hubble Space Telescope]]]] | [[File:Mars cyclone.jpg|thumb|right|350px|Cyclone on Mars, imaged by the [[Hubble Space Telescope]]]] | ||
Cyclones are not unique to Earth. Cyclonic storms are common on [[giant planet]]s, such as the [[Small Dark Spot]] on [[Neptune]].<ref>{{cite web |title=TCFAQ H6) Are there hurricanes on other planets ? |url=https://www.aoml.noaa.gov/hrd/tcfaq/H6.html#:~:text=Subject%3A%20H6)%20Are%20there%20hurricanes%20on%20other%20planets%20%3F&text=There%20are%20no%20other%20planets,and%20Saturn%20exhibits%20such%20storms. |website=www.aoml.noaa.gov |access-date=13 January 2021 |archive-date=19 March 2021 |archive-url=https://web.archive.org/web/20210319065453/https://www.aoml.noaa.gov/hrd/tcfaq/H6.html#:~:text=Subject%3A%20H6)%20Are%20there%20hurricanes%20on%20other%20planets%20%3F&text=There%20are%20no%20other%20planets,and%20Saturn%20exhibits%20such%20storms. |url-status=live }}</ref> It is about one third the diameter of the [[Great Dark Spot]] and received the nickname "Wizard's Eye" because it looks like an eye. This appearance is caused by a white cloud in the middle of the Wizard's Eye.<ref name="WIZ"/> [[Mars]] has also exhibited cyclonic storms.<ref name="Brand">{{cite web|author=David Brand|url=https://www.news.cornell.edu/releases/May99/mars.cyclone.deb.html|title=Colossal cyclone swirling near Martian north pole is observed by Cornell-led team on Hubble telescope|access-date=2008-06-15|date=1999-05-19|publisher=[[Cornell University]]|archive-url = https://web.archive.org/web/20070613133949/http://www.news.cornell.edu/releases/May99/mars.cyclone.deb.html |archive-date = June 13, 2007|url-status=dead}}</ref> Jovian storms like the [[Great Red Spot]] are usually mistakenly named as giant hurricanes or cyclonic storms. However, this is inaccurate, as the Great Red Spot is, in fact, the inverse phenomenon, an [[anticyclone]].<ref name="HaydPlan">{{cite web | |||
Cyclones are not unique to Earth. Cyclonic storms are common on [[giant planet]]s, such as the [[Small Dark Spot]] on [[Neptune]].<ref>{{cite web |title=TCFAQ H6) Are there hurricanes on other planets ? |url=https://www.aoml.noaa.gov/hrd/tcfaq/H6.html#:~:text=Subject%3A%20H6)%20Are%20there%20hurricanes%20on%20other%20planets%20%3F&text=There%20are%20no%20other%20planets,and%20Saturn%20exhibits%20such%20storms. |website=www.aoml.noaa.gov |access-date=13 January 2021 |archive-date=19 March 2021 |archive-url=https://web.archive.org/web/20210319065453/https://www.aoml.noaa.gov/hrd/tcfaq/H6.html#:~:text=Subject%3A%20H6)%20Are%20there%20hurricanes%20on%20other%20planets%20%3F&text=There%20are%20no%20other%20planets,and%20Saturn%20exhibits%20such%20storms. |url-status=live }}</ref> It is about one third the diameter of the [[Great Dark Spot]] and received the nickname "Wizard's Eye" because it looks like an eye. This appearance is caused by a white cloud in the middle of the Wizard's Eye.<ref name="WIZ"/> [[Mars]] has also exhibited cyclonic storms.<ref name="Brand">{{cite web|author=David Brand|url= | |||
|title = Jupiter's Great Red Spot | |title = Jupiter's Great Red Spot | ||
|year = 2009 | |year = 2009 | ||
| Line 173: | Line 166: | ||
|archive-date = 2007-08-08 | |archive-date = 2007-08-08 | ||
}}</ref> | }}</ref> | ||
{{clr}} | |||
==See also== | ==See also== | ||
Latest revision as of 12:30, 18 October 2025
Template:Short description Script error: No such module "about". Template:Pp-semi-indef Template:Pp-move-indef
In meteorology, a cyclone (Template:IPAc-en) is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an anticyclone).[1][2] Cyclones are characterized by inward-spiraling winds that rotate about a zone of low pressure.[3][4]
Cyclones have also been seen on planets other than the Earth, such as Mars, Jupiter, and Neptune.[5][6] Cyclogenesis is the process of cyclone formation and intensification.[7]
Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.
Weather fronts mark the boundary between two masses of air of different temperature, humidity, and densities, and are associated with the most prominent meteorological phenomena. Strong cold fronts typically feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. Such fronts form west of the circulation center and generally move from west to east; warm fronts form east of the cyclone center and are usually preceded by stratiform precipitation and fog. Warm fronts move poleward ahead of the cyclone path. Occluded fronts form late in the cyclone life cycle near the center of the cyclone and often wrap around the storm center.
Tropical cyclogenesis describes the process of development of tropical cyclones. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core.[8][9] Cyclones can transition between extratropical, subtropical, and tropical phases.[10] Mesocyclones form as warm core cyclones over land, and can lead to tornado formation.[11] Waterspouts can also form from mesocyclones, but more often develop from environments of high instability and low vertical wind shear.[12] In the Atlantic and the northeastern Pacific oceans, a tropical cyclone is generally referred to as a hurricane (from the name of the ancient Central American deity of wind, Huracan), in the Indian and south Pacific oceans it is called a cyclone, and in the northwestern Pacific it is called a typhoon.[13] The growth of instability in the vortices is not universal. For example, the size, intensity, moist-convection, surface evaporation, the value of potential temperature at each potential height can affect the nonlinear evolution of a vortex.[14]
Name
The term cyclone comes from the Greek word Script error: No such module "Lang". (Template:Transliteration, meaning "circle" or "ring" in Ancient Greek), due to the spiraling nature of a cyclone's winds.[15] The word was coined by Henry Piddington, an official in the British East India Company who published 40 papers dealing with tropical storms from Calcutta between 1836 and 1855 in The Journal of the Asiatic Society.[16]
Structure
There are a number of structural characteristics common to all cyclones. A cyclone is a low-pressure area.[17] A cyclone's center (often known in a mature tropical cyclone as the eye), is the area of lowest atmospheric pressure in the region.[17] Near the center, the pressure gradient force (from the pressure in the center of the cyclone compared to the pressure outside the cyclone) and the force from the Coriolis effect must be in an approximate balance, or the cyclone would collapse on itself as a result of the difference in pressure.[18]
Because of the Coriolis effect, the wind flow around a large cyclone is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.[19] In the Northern Hemisphere, the fastest winds relative to the surface of the Earth therefore occur on the eastern side of a northward-moving cyclone and on the northern side of a westward-moving one; the opposite occurs in the Southern Hemisphere.[20]
Formation
Script error: No such module "Labelled list hatnote". Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere.[7] Cyclogenesis is an umbrella term for several different processes that all result in the development of some sort of cyclone.[22]
Tropical cyclones form as a result of significant convective activity, and are warm core.[9] Mesocyclones form as warm core cyclones over land, and can lead to tornado formation.[11] Waterspouts can also form from mesocyclones, but more often develop from environments of high instability and low vertical wind shear.[12] Cyclolysis is the opposite of cyclogenesis, and is the high-pressure system equivalent, which deals with the formation of high-pressure areas—anticyclogenesis.[23]
A surface low can form in a variety of ways. Topography can create a surface low. Mesoscale convective systems can spawn surface lows that are initially warm-core.[24] The disturbance can grow into a wave-like formation along the front and the low is positioned at the crest. Around the low, the flow becomes cyclonic. This rotational flow moves polar air towards the equator on the west side of the low, while warm air move towards the pole on the east side. A cold front appears on the west side, while a warm front forms on the east side. Usually, the cold front moves at a quicker pace than the warm front and "catches up" with it due to the slow erosion of higher density air mass out ahead of the cyclone. In addition, the higher density air mass sweeping in behind the cyclone strengthens the higher pressure, denser cold air mass. The cold front over takes the warm front, and reduces the length of the warm front.[25] At this point an occluded front forms where the warm air mass is pushed upwards into a trough of warm air aloft, which is also known as a trowal.[26]
Tropical cyclogenesis is the development and strengthening of a tropical cyclone.[27] The mechanisms by which tropical cyclogenesis occurs are distinctly different from those that produce mid-latitude cyclones. Tropical cyclogenesis, the development of a warm-core cyclone, begins with significant convection in a favorable atmospheric environment. There are two main requirements for tropical cyclogenesis: sufficiently warm sea surface temperatures,[28] and low vertical wind shear.[29]
An average of 86 tropical cyclones of tropical storm intensity form annually worldwide,[30] with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones (at least Category 3 intensity on the Saffir–Simpson hurricane scale).[31]
Synoptic types
The following types of cyclones are identifiable in synoptic charts.[32]
Surface-based types
Script error: No such module "Labelled list hatnote". There are three main types of surface-based cyclones: extratropical cyclones, subtropical cyclones and tropical cyclones.
Extratropical cyclone
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An extratropical cyclone is a synoptic scale low-pressure weather system that does not have tropical characteristics,[33] as it is connected with fronts and horizontal gradients (rather than vertical) in temperature and dew point otherwise known as "baroclinic zones".[34]
"Extratropical" is applied to cyclones outside the tropics, in the middle latitudes. These systems may also be described as "mid-latitude cyclones" due to their area of formation, or "post-tropical cyclones" when a tropical cyclone has moved (extratropical transition) beyond the tropics.[34][35] They are often described as "depressions" or "lows" by weather forecasters and the general public.[36] These are the everyday phenomena that, along with anticyclones, drive weather over much of the Earth.[37]
Although extratropical cyclones are almost always classified as baroclinic since they form along zones of temperature and dewpoint gradient within the westerlies, they can sometimes become barotropic late in their life cycle when the temperature distribution around the cyclone becomes fairly uniform with radius.[38] An extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone, if it dwells over warm waters sufficient to warm its core, and as a result develops central convection.[39] A particularly intense type of extratropical cyclone that strikes during winter is known colloquially as a nor'easter.[40]
Polar low
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A polar low is a small-scale, short-lived atmospheric low-pressure system (depression) that is found over the ocean areas poleward of the main polar front in both the Northern and Southern Hemispheres. Polar lows were first identified on the meteorological satellite imagery that became available in the 1960s, which revealed many small-scale cloud vortices at high latitudes. The most active polar lows are found over certain ice-free maritime areas in or near the Arctic during the winter, such as the Norwegian Sea, Barents Sea, Labrador Sea and Gulf of Alaska. Polar lows dissipate rapidly when they make landfall. Antarctic systems tend to be weaker than their northern counterparts since the air-sea temperature differences around the continent are generally smaller. However, vigorous polar lows can be found over the Southern Ocean.[41]
During winter, when cold-core lows with temperatures in the mid-levels of the troposphere reach Template:Convert move over open waters, deep convection forms, which allows polar low development to become possible.[42] The systems usually have a horizontal length scale of less than Template:Convert and exist for no more than a couple of days. They are part of the larger class of mesoscale weather systems. Polar lows can be difficult to detect using conventional weather reports and are a hazard to high-latitude operations, such as shipping and gas and oil platforms. Polar lows have been referred to by many other terms, such as polar mesoscale vortex, Arctic hurricane, Arctic low, and cold air depression. Today the term is usually reserved for the more vigorous systems that have near-surface winds of at least Template:Convert.[43]
Subtropical
Script error: No such module "Labelled list hatnote". 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 between the equator and the 50th parallel.[44] As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical cyclones or extratropical cyclones, and used terms such as quasi-tropical and semi-tropical to describe the cyclone hybrids.[45] By 1972, the National Hurricane Center in the United States officially recognized this cyclone category.[46] Subtropical cyclones began to receive names off the official tropical cyclone list in the Atlantic Basin in 2002.[44] They have broad wind patterns with maximum sustained winds located farther from the center than typical tropical cyclones, and exist in areas of weak to moderate temperature gradient.[44]
Since they form from extratropical cyclones, which have colder temperatures aloft than normally found in the tropics, the sea surface temperatures required is around 23 degrees Celsius (73 °F) for their formation, which is three degrees Celsius (5 °F) lower than for tropical cyclones.[47] This means that subtropical cyclones are more likely to form outside the traditional bounds of the hurricane season. Although subtropical storms rarely have hurricane-force winds, they may become tropical in nature as their cores warm.[48]
Tropical
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A tropical cyclone is a storm system characterized by a low-pressure center and numerous thunderstorms that produce strong winds and flooding rain.[49] A tropical cyclone feeds on heat released when moist air rises, resulting in condensation of water vapour contained in the moist air.[49] They are fueled by a different heat mechanism than other cyclonic windstorms such as nor'easters, European windstorms, and polar lows, leading to their classification as "warm core" storm systems.[49][9]
The term "tropical" refers to both the geographic origin of these systems, which form almost exclusively in tropical regions of the globe,[50] and their dependence on Maritime Tropical air masses for their formation. The term "cyclone" refers to the storms' cyclonic nature, with counterclockwise rotation in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere.[50] Depending on their location and strength, tropical cyclones are referred to by other names, such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply as a cyclone.[50]
While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and a damaging storm surge.[51] Their winds increase the wave size, and in so doing they draw more heat and moisture into their system, thereby increasing their strength. They develop over large bodies of warm water,[52] and hence lose their strength if they move over land.[53] This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from strong winds.[50] Heavy rains, however, can produce significant flooding inland.[50] Storm surges are rises in sea level caused by the reduced pressure of the core that in effect "sucks" the water upward and from winds that in effect "pile" the water up. Storm surges can produce extensive coastal flooding up to Template:Convert from the coastline.[50] Although their effects on human populations can be devastating, tropical cyclones can also relieve drought conditions.[54] They also carry heat and energy away from the tropics and transport it toward temperate latitudes,[50] 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.[50]
Many tropical cyclones develop when the atmospheric conditions around a weak disturbance in the atmosphere are favorable.[50] Others form when other types of cyclones acquire tropical characteristics. Tropical systems are then moved by steering winds in the troposphere; if the conditions remain favorable, the tropical disturbance intensifies, and can even develop an 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. 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.[9] A tropical cyclone is usually not considered to become subtropical during its extratropical transition.[55]
Upper level types
Polar cyclone
Script error: No such module "Labelled list hatnote". A polar, sub-polar, or Arctic cyclone (also known as a polar vortex)[56] is a vast area of low pressure that strengthens in the winter and weakens in the summer.[57] A polar cyclone is a low-pressure weather system, usually spanning Template:Convert to Template:Convert,[58] in which the air circulates in a counterclockwise direction in the northern hemisphere, and a clockwise direction in the southern hemisphere. The Coriolis acceleration acting on the air masses moving poleward at high altitude, causes a counterclockwise circulation at high altitude. The poleward movement of air originates from the air circulation of the Polar cell. The polar low is not driven by convection as are tropical cyclones, nor the cold and warm air mass interactions as are extratropical cyclones, but is an artifact of the global air movement of the Polar cell. The base of the polar low is in the mid to upper troposphere. In the Northern Hemisphere, the polar cyclone has two centers on average. One center lies near Baffin Island and the other over northeast Siberia.[56] In the southern hemisphere, it tends to be located near the edge of the Ross ice shelf near 160 west longitude.[59] When the polar vortex is strong, its effect can be felt at the surface as a westerly wind (toward the east). When the polar cyclone is weak, significant cold outbreaks occur.[60]
TUTT cell
Script error: No such module "Labelled list hatnote". Under specific circumstances, upper level cold lows can break off from the base of the tropical upper tropospheric trough (TUTT), which is located mid-ocean in the Northern Hemisphere during the summer months. These upper tropospheric cyclonic vortices, also known as TUTT cells or TUTT lows, usually move slowly from east-northeast to west-southwest, and their bases generally do not extend below Template:Convert in altitude. A weak inverted surface trough within the trade wind is generally found underneath them, and they may also be associated with broad areas of high-level clouds. Downward development results in an increase of cumulus clouds and the appearance of a surface vortex. In rare cases, they become warm-core tropical cyclones. Upper cyclones and the upper troughs that trail tropical cyclones can cause additional outflow channels and aid in their intensification. Developing tropical disturbances can help create or deepen upper troughs or upper lows in their wake due to the outflow jet emanating from the developing tropical disturbance/cyclone.[61][62]
Non-synoptic types
The following types of cyclones are not identifiable in synoptic charts.[32]
Mesocyclone
Script error: No such module "Labelled list hatnote". A mesocyclone is a vortex of air, Template:Convert to Template:Convert in diameter (the mesoscale of meteorology), within a convective storm.[63] Air rises and rotates around a vertical axis, usually in the same direction as low-pressure systems[64] in both northern and southern hemisphere. They are most often cyclonic, that is, associated with a localized low-pressure region within a supercell.[64][65] Such storms can feature strong surface winds and severe hail.[64] Mesocyclones often occur together with updrafts in supercells, where tornadoes may form.[64] About 1,700 mesocyclones form annually across the United States, but only half produce tornadoes.[11]
Dust devil
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A dust devil is a type of vortex that involves debris such as dust being lifted upward into the air.[66][67] Most dust devils are between Template:Convert and Template:Convert wide, and between Template:Convert and Template:Convert tall, although the strongest can be several thousand feet tall. Wind speed varies depending on the size of the dust devil; larger ones have winds of at least Template:Convert, reaching up to Template:Convert. Dust devils form from a warm surface during sunny days, often in an area where surface types change, and require the surrounding air to be unstable, dissipating when conditions become more stable; they therefore often from in deserts. They usually dissipate after only a few minutes, but stronger dust devils can last over an hour. Dust devils are smaller than tornadoes and are usually harmless, though stronger ones can destroy small structures. Dust devils have been found on Mars as well as on Earth.[66]
Waterspout
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A waterspout is a columnar vortex forming over water that is, in its most common form, a non-supercell tornado over water that is connected to a cumuliform cloud. While it is often weaker than most of its land counterparts, stronger versions spawned by mesocyclones do occur.[68]
Steam devil
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A steam devil is a gentle vortex over calm water or wet land that is made visible by rising water vapour.[69]
Fire whirl
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A fire whirl – also colloquially known as a fire devil, fire tornado, firenado, or fire twister – is a whirlwind induced by a fire and often made up of flame or ash.
Other planets
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Cyclones are not unique to Earth. Cyclonic storms are common on giant planets, such as the Small Dark Spot on Neptune.[70] It is about one third the diameter of the Great Dark Spot and received the nickname "Wizard's Eye" because it looks like an eye. This appearance is caused by a white cloud in the middle of the Wizard's Eye.[6] Mars has also exhibited cyclonic storms.[5] Jovian storms like the Great Red Spot are usually mistakenly named as giant hurricanes or cyclonic storms. However, this is inaccurate, as the Great Red Spot is, in fact, the inverse phenomenon, an anticyclone.[71]
See also
Template:Stack Template:Col div
- Tropical cyclone
- Subtropical cyclone
- Extratropical cyclone
- Tornado
- Storm
- Atlantic hurricane
- Australian region tropical cyclone
- Space hurricane
- Space tornado
References
External links
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- ↑ a b c Forces of Nature. Tornadoes : the mesocyclone. Template:Webarchive Retrieved on 2008-06-15.
- ↑ a b National Weather Service Key West summary of waterspout types
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