Editing Cyclone (section)

==Synoptic scale==
[[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.

===Surface-based types===
{{See also|Low-pressure area}}
There are three main types of surface-based cyclones: [[extratropical cyclone]]s, [[subtropical cyclone]]s and [[tropical cyclone]]s.

====Extratropical cyclone====
{{main|Extratropical cyclone}}

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 [[Surface weather analysis|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&nbsp;– Extratropical Cyclones
 |author =  DeCaria
 |publisher = Department of Earth Sciences, Millersville University, Millersville, Pennsylvania
 |date = 2005-12-07
 |url = http://www.atmos.millersville.edu/~adecaria/ESCI241/esci241_lesson16_cyclones.html
 |access-date = 2006-10-21 |archive-url = https://web.archive.org/web/20060903093420/http://www.atmos.millersville.edu/~adecaria/ESCI241/esci241_lesson16_cyclones.html |archive-date = September 3, 2006}}</ref>

"[[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.<ref name="ExtraLessonMillUni"/><ref name="ExtratropicalPhases">{{cite web
 |title = Synoptic Composites of the Extratropical Transition Lifecycle of North Atlantic TCs as Defined Within Cyclone Phase Space
 |author1 = Robert Hart
 |author2 = Jenni Evans
 |publisher = American Meteorological Society
 |year = 2003
 |url = http://ams.confex.com/ams/pdfpapers/70524.pdf
 |access-date = 2006-10-03
 |archive-date = 2011-06-09
 |archive-url = https://web.archive.org/web/20110609164448/http://ams.confex.com/ams/pdfpapers/70524.pdf
 |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.

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]]''.

==== 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]]
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 {{citation needed|reason=As far as I know, the Arctic and Antarctic oceans are both warmer than the air above, at about the freezing point, and the air over the ocean is generally colder in the Antarctic due to the katabatic winds sweeping off the continent|date=July 2015}}. However, vigorous polar lows can be found over the Southern Ocean. 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 17&nbsp;m/s.<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====
[[File:Alex 2016-01-13 1530Z.jpg|thumb|right|[[Hurricane Alex (2016)|Subtropical Storm Alex]] in the north Atlantic Ocean in January [[2016 Atlantic hurricane season|2016]]]]

{{main|Subtropical cyclone}}
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"/> 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]] 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">{{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>

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&nbsp;degrees Celsius (73&nbsp;°F) for their formation, which is  three degrees Celsius (5&nbsp;°F) lower than for tropical cyclones.<ref name="HistSubTropCyclones">{{cite web
 |title = A Fifty year History of Subtropical Cyclones
 |author = David Mark Roth
 |publisher = Hydrometeorological Prediction Center
 |date = 2002-02-15
 |url = http://www.wpc.ncep.noaa.gov/research/roth/Subpreprint.pdf
 |access-date = 2006-10-04
 |archive-date = 2021-04-17
 |archive-url = https://web.archive.org/web/20210417020816/https://www.wpc.ncep.noaa.gov/research/roth/Subpreprint.pdf
 |url-status = live
 }}</ref> 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.<ref name = "AOML FAQ A6">{{cite web|author = Chris Landsea|publisher = [[NOAA]]|title = Frequently Asked Questions: What is a sub-tropical cyclone?|access-date = 2009-12-27|date = 2009-02-06|url = http://www.aoml.noaa.gov/hrd/tcfaq/A6.html|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>

====Tropical====
{{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]]]]
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"/>

While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and a damaging [[storm surge]].<ref name="oxfo">{{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> 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,<ref name="AOML FAQ A15">{{cite web|author=Chris Landsea |title=Frequently Asked Questions: How do tropical cyclones form? |date=2009-02-06 |publisher=[[NOAA]] |access-date=2006-07-26 |url=http://www.aoml.noaa.gov/hrd/tcfaq/A15.html |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> and hence lose their strength if they move over land.<ref>{{cite web|author=Sim Aberson|publisher=[[National Hurricane Center]]|url=http://www.aoml.noaa.gov/hrd/tcfaq/C2.html|title=Subject : C2) Doesn't the friction over land kill tropical cyclones?|access-date=2008-02-25|date=2009-02-06|archive-date=2012-07-31|archive-url=https://web.archive.org/web/20120731202853/http://www.aoml.noaa.gov/hrd/tcfaq/C2.html|url-status=live}}</ref> This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from strong winds.<ref name="laserfocusworld.com"/> Heavy rains, however, can produce significant flooding inland.<ref name="laserfocusworld.com"/> 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 {{convert|40|km|mi}} from the coastline.<ref name="laserfocusworld.com"/> Although their effects on human populations can be devastating, tropical cyclones can also relieve [[drought]] conditions.<ref name="2005 EPac outlook">[[National Oceanic and Atmospheric Administration]]. [http://www.cpc.ncep.noaa.gov/products/Epac_hurr/Epac_hurricane.html 2005 Tropical Eastern North Pacific Hurricane Outlook.] {{Webarchive|url=https://web.archive.org/web/20090614024616/http://www.cpc.ncep.noaa.gov/products/Epac_hurr/Epac_hurricane.html |date=2009-06-14 }} Retrieved on 2006-05-02.</ref> They also carry heat and energy away from the tropics and transport it toward [[temperate]] [[latitudes]],<ref name="laserfocusworld.com"/> 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]].<ref name="laserfocusworld.com"/>

Many tropical cyclones [[tropical cyclogenesis|develop]] when the atmospheric conditions around a weak disturbance in the atmosphere are favorable.<ref name="laserfocusworld.com"/> 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. A tropical cyclone can become extratropical as it moves toward higher latitudes if its energy source changes from heat released by condensation to differences in temperature between air masses.<ref name = "AOML FAQ A7"/> A tropical cyclone is usually not considered to become subtropical during its extratropical transition.<ref name=PadgetDecember2000>{{cite web|author = Padgett, Gary|url = http://australiasevereweather.com/cyclones/2001/summ0012.htm|title = Monthly Global Tropical Cyclone Summary for December 2000|year = 2001|access-date = 2006-03-31|archive-date = 2014-11-29|archive-url = https://web.archive.org/web/20141129070208/http://www.australiasevereweather.com/cyclones/2001/summ0012.htm|url-status = live}}</ref>

===Upper level types===

====Polar cyclone====
{{main|Polar cyclone}}
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====
{{Main|Upper tropospheric cyclonic vortex}}
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>