Editing Cyclone (section)

==Formation==
[[File:Baroclinicleafphasecyclogenesiscropped.gif|thumb|The initial extratropical low-pressure area forms at the location of the red dot on the image. It is usually perpendicular (at a right angle to) the leaf-like cloud formation seen on satellite during the early stage of cyclogenesis. The location of the axis of the upper level [[jet stream]] is in light blue.]]
[[File:Hurricane profile.svg|thumb|Tropical cyclones form when the energy released by the condensation of moisture in rising air causes a [[positive feedback loop]] over warm ocean waters.<ref>{{cite web|author=Kerry Emanuel|url=http://wind.mit.edu/~emanuel/anthro2.htm|title=Anthropogenic Effects on Tropical Cyclone Activity|access-date=2008-02-25|date=January 2006|publisher=[[Massachusetts Institute of Technology]]|author-link=Kerry Emanuel|archive-date=2012-07-17|archive-url=https://web.archive.org/web/20120717074958/http://wind.mit.edu/~emanuel/anthro2.htm|url-status=live}}</ref>]]

{{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> It can occur at various scales, from the microscale to the synoptic scale.

Extratropical cyclones begin as waves along [[weather fronts]] before occluding later in their life cycle as cold-core systems. However, some intense extratropical cyclones can become warm-core systems when a  [[warm seclusion]] occurs.

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>

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 six 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> 
# atmospheric instability, 
# high [[humidity]] in the lower to middle levels of the [[troposphere]]
# enough [[Coriolis force]] to develop a low-pressure center
# a preexisting low-level focus or disturbance
# 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&nbsp;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&nbsp;— 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>