Extratropical cyclone: Difference between revisions

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{{short description|Type of cyclone}}

[[Image:UK-Cyclone.gif|thumb|right|250px|A ficticious synoptic chart of an extratropical cyclone affecting the UK. The blue arrows between [[isobars]] indicate the direction of the wind, while the "L" symbol denotes the center of the "low". Note the occluded, cold and warm [[Surface weather analysis|frontal boundaries]].]]

{{Redirect-distinguish|Wave cyclone|Tropical wave}}

[[Image:Storm_of_the_century_satellite.gif|thumb|right|250px|An image from a [[weather satellite]] of the [[1993 North American storm complex|Great Blizzard of 1993]]. This is a classic extratropical cyclone structure, with the [[low pressure area]] over [[Georgia (U.S. state)|Georgia]] and [[Alabama]], the [[surface weather analysis|cold front]] extending down into [[Central America]], and an occlusion extending up into southern [[Canada]].]]

[[File:Extratropical Cyclone over North Atlantic 2022-03-20.jpg|upright=1.35|thumb|A powerful extratropical cyclone over the North [[Atlantic Ocean]] in March 2022]]

An '''extratropical cyclone''', sometimes called a '''mid-latitude cyclone''' or a '''[[cyclone]]''', is a [[Synoptic scale meteorology|synoptic scale]] [[Low pressure area|low pressure]] weather system that has neither [[tropical cyclone|tropical]] or [[polar cyclone|polar]] characteristics, and is connected with [[Surface weather analysis|fronts]] and horizontal [[gradients]] in [[temperature]] and [[dew point]] otherwise known as "baroclinic zones".<ref name="ExtraLessonMillUni"> {{cite web| title = ESCI 241 – Meteorology; Lesson 16 – Extratropical Cyclones| author = Dr. DeCaria| publisher = [http://muweb.millersville.edu/~esci/ Department of Earth Sciences, Millersville University, Millersville, Pennsylvania]| date = [[2005-12-07]]| url = http://www.atmos.millersville.edu/~adecaria/ESCI241/esci241_lesson16_cyclones.html| accessdate = 2006-10-21 }} </ref> Extratropical cyclones are the everyday phenomena which, along with [[anticyclone]]s, drive the weather over much of the Earth, producing weather ranging from cloudiness and mild [[rain|shower]]s, to heavy gales and thunderstorms.

{{Weather}}

'''Extratropical cyclones''', sometimes called '''mid-latitude cyclones''' or '''wave cyclones''', are [[low-pressure area]]s which, along with the [[anticyclone]]s of [[high-pressure area]]s, drive the weather over much of the Earth. Extratropical [[cyclone]]s are capable of producing anything from cloudiness and mild [[rain|showers]] to severe [[hail]], [[thunderstorm]]s, [[blizzard]]s, and [[tornado]]es. These types of cyclones are defined as [[Synoptic scale meteorology|large scale (synoptic)]] [[Low-pressure area|low pressure]] [[weather system]]s that occur in the [[middle latitudes]] of the Earth. In contrast with [[tropical cyclone]]s, extratropical cyclones produce rapid changes in temperature and [[dew point]] along broad lines, called [[weather front]]s, about the center of the cyclone.<ref name="ExtraLessonMillUni">{{cite web| title = ESCI 241&nbsp;– Meteorology; Lesson 16&nbsp;– Extratropical Cyclones | author = DeCaria| publisher = Department of Earth Sciences, [[Millersville University]]| date = 2005-12-07| url = http://www.atmos.millersville.edu/~adecaria/ESCI241/esci241_lesson16_cyclones.html | access-date = 2009-06-21 |archive-url = https://web.archive.org/web/20080208224320/http://www.atmos.millersville.edu/~adecaria/ESCI241/esci241_lesson16_cyclones.html |archive-date = 2008-02-08}}</ref>

==Terminology==

[[File:Strong Extratropical Cyclone Over the US Midwest.OGG|thumb|This animation shows [[October 2010 North American storm complex|an extratropical cyclone]] developing over the United States, starting late on October 25 and running through October 27, 2010.]]

An extratropical cyclone is a class of storms described by many different names. While they are occasionally referred to just as "[[cyclone]]s", this is incorrect, as cyclone is a broader term covering many other types of weather phenomena. The descriptor "extratropical" signifies that this type of cyclone generally occurs outside of the tropics, in the middle [[latitude]]s of the planet. These systems may also be described as "mid-latitude cyclones" due to their area of formation, or "post-tropical cyclones" where [[#Extratropical transition|extratropical transition]] has occured.<ref name="ExtraLessonMillUni">ExtraLessonMillUni</ref><ref name="ExtratropicalPhases">{{cite web| title = Synoptic Composites of the Extratropical Transition Lifecycle of North Atlantic TCs as Defined Within Cyclone Phase Space| author = Robert Hart and Jenni Evans| publisher = [http://ams.confex.com/ American Meteorological Society]| date = 2003 | url = http://ams.confex.com/ams/pdfpapers/70524.pdf| accessdate = 2006-10-03 }}</ref> They are often described as "depressions" or "lows" by weather forecasters and the general public.

The term "[[cyclone]]" applies to numerous types of low pressure areas, one of which is the extratropical cyclone. The descriptor ''extratropical'' signifies that this type of cyclone generally occurs outside the tropics and in the middle [[latitude]]s of Earth between 30° and 60° latitude. They are termed ''mid-latitude cyclones'' if they form within those latitudes, or [[post-tropical cyclone]]s if a tropical cyclone has intruded into the mid latitudes.<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 |author-link2=Jenni L. Evans| publisher = [[American Meteorological Society]]| year = 2003 | url = http://ams.confex.com/ams/pdfpapers/70524.pdf| access-date = 2006-10-03 }}</ref> Weather forecasters and the general public often describe them simply as "[[Depression (weather)|depressions]]" or "lows". Terms like frontal cyclone, frontal depression, frontal low, extratropical low, non-tropical low and hybrid low are often used as well.{{Citation needed|date=January 2021}}

Although extratropical cyclones are almost always classified as [[baroclinic]] because they form along zones of temperature and dewpoint [[gradient]], they can sometimes become [[barotropic]] late in their life cycle when the distibution of heat around the cyclone becomes fairly uniform with radius.

Extratropical cyclones are classified mainly as [[baroclinity|baroclinic]], because they form along zones of temperature and dewpoint [[gradient]] known as [[weather fronts|frontal zones]]. They can become [[barotropic]] late in their life cycle, when the distribution of heat around the cyclone becomes fairly uniform with its radius.<ref>{{cite web|author=Ryan N. Maue |date=2004-12-07 |url=http://www.coaps.fsu.edu/~maue/cyclone_ch3.html |title=Chapter 3: Cyclone Paradigms and Extratropical Transition Conceptualizations |access-date=2008-06-15 |archive-url=https://web.archive.org/web/20080510210146/http://www.coaps.fsu.edu/~maue/cyclone_ch3.html |archive-date=2008-05-10}}</ref>

==Formation==

[[ImageFile:Extratropical formation areas.jpg|thumb|250px|rightleft|Approximate areas of extratropical cyclone formation worldwide]]

[[ImageFile:Jetstreak.gifpng|thumb|right|250pxleft|An upper -level jet streak. DIV areas are regions of divergence aloft, which will lead to surface convergence and aid cyclogenesis.]]

Extratropical cyclones form anywhere within the extratropical regions of the Earth (usually between 30° and 60° latitude from the [[equator]]), either through [[cyclogenesis]] or extratropical transition. In a climatology study with two different cyclone algorithms, a total of 49,745–72,931 extratropical cyclones in the [[Northern Hemisphere]] and 71,289–74,229 extratropical cyclones in the [[Southern Hemisphere]] were detected between 1979 and 2018 based on reanalysis data.<ref name=":0">{{Cite journal|last1=Messmer|first1=Martina|last2=Ian Simmonds|date=2021|title=Global analysis of cyclone-induced compound precipitation and wind extreme events|journal=Weather and Climate Extremes|language=en|volume=32|page=100324|doi=10.1016/j.wace.2021.100324|bibcode=2021WCE....3200324M |issn=2212-0947|doi-access=free}}</ref> A study of extratropical cyclones in the Southern Hemisphere shows that between the [[30th parallel south|30th]] and [[70th parallel south|70th parallels]], there are an average of 37 cyclones in existence during any 6-hour period.<ref name="VarSouthCyc">{{cite journal | title = Variability of Southern Hemisphere Extratropical Cyclone Behavior, 1958–97 |author1=Ian Simmonds |author2=Kevin Keay | date = February 2000 | pages = 550–561 | journal = Journal of Climate | volume = 13 | issue=3 | doi = 10.1175/1520-0442(2000)013<0550:VOSHEC>2.0.CO;2 | issn = 1520-0442 |bibcode = 2000JCli...13..550S | doi-access =free }}</ref> A separate study in the Northern Hemisphere suggests that approximately 234 significant extratropical cyclones form each winter.<ref name="WinterStormsNorth">{{cite journal | journal=Climate Dynamics | volume = 17| pages=795–809 | title = Winter Storms in the Northern Hemisphere (1958–1999) |author1=S. K. Gulev |author2=O. Zolina |author3=S. Grigoriev | year = 2001 |bibcode = 2001ClDy...17..795G |doi = 10.1007/s003820000145 | issue=10 | s2cid = 129364159}}</ref>

Extratropical cyclones form anywhere within the extratropical regions of the Earth (usually between 30° and 60° [[latitude]] from the [[equator]]) in one of two ways; either through cyclogenesis or extratropical transition. A study of extratropical cyclones in the Southern Hemisphere shows that on average, there are an average of 37 in existance during any 6 hour period between the 30th and 70th parallels.<ref name="VarSouthCyc"> {{cite web

| title = Variability of Southern Hemisphere Extratropical Cyclone Behavior, 1958–97

| author = Ian Simmonds and Kevin Keay

| publisher = [http://ams.allenpress.com/ American Meteorology Society (Allenpress Inc)]

| date = 2000-02

| url = http://ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2F1520-0442(2000)013%3C0550:VOSHEC%3E2.0.CO%3B2#I1520-0442-13-3-550-F04

| accessdate = 2006-10-20 }}</ref> A seperate study in the northern hemisphere suggests that approximately 234 significant extratropical cyclones form each [[winter]].<ref name="WinterStormsNorth"> {{cite web

| title = Winter Storms in the Northern Hemisphere (1958-1999)

| author = S.K. Gulev, O. Zolina, and S. Grigoriev

| publisher = [http://www.co2science.org/ CO₂ Science]

| date = 2001

| url = http://www.co2science.org/scripts/CO2ScienceB2C/articles/V4/N37/C2.jsp

| accessdate = 2006-10-20 }}</ref>

===Cyclogenesis===

{{main|Cyclogenesis}}

Extratropical cyclones form along linear bands of temperature/dewpointdew point gradient with significant vertical [[wind shear]], and are thus classified as [[baroclinic cyclone]]scyclones. Initially, [[cyclogenesis]], or low pressure formation, occurs along [[Surface weather analysis|frontal zones]] near a favorable quadrant of a maximum in the [[Jetstream|upper level jetstream]], known as a jet streak. The favorable quadrants are usually beingat the right rear and left front quadrants, where [[divergence]] ensues.<ref>{{cite Thisjournal |author1=Carlyle H. Wash |author2=Stacey H. Heikkinen |author3=Chi-Sann Liou |author4=Wendell A. Nuss |title=A Rapid Cyclogenesis Event during GALE IOP 9 |volume=118 |issue=2 |date=February 1990 |journal=Monthly Weather Review |pages=234–257 |doi=10.1175/1520-0493(1990)118<0375:ARCEDG>2.0.CO;2 |issn=1520-0493 |bibcode=1990MWRv..118..375W |doi-access=free }}</ref> The divergence causes air to rush out from the top of the air column. As whichmass in turnthe forcescolumn is reduced, [[convergenceatmospheric pressure]] inat thesurface low-level wind(the fieldweight andof increasedthe upwardair motioncolumn) withinis the columnreduced. The increasedlowered upwardpressure motionstrengthens causesthe surfacecyclone pressures(a tolow lowerpressure assystem). theThe upwardlowered airpressure motionacts counteractsto gravity,draw lesseningin theair, weightcreating of the atmosphere ([[atmosphericConvergence pressurezone|surface pressureconvergence]]) in thatthe ___location,low-level wind field. Low-level convergence and thusupper-level strengtheningdivergence imply upward motion within the cyclone.column, making cyclones cloudy. As the cyclone strengthens, the cold front sweeps towards the [[equator]] and moves around the back of the cyclone. Meanwhile, its associated [[surface weather analysis#Warm front|warm front]] progresses more slowly, as the cooler air ahead of the system is [[density|denser]], and therefore more difficult to dislodge. Later, the cyclones [[Surface weather analysis#Occluded fronts.2Ftrowalsfront|occlude]] as the poleward portion of the cold front overtakes a section of the warm front, forcing a tongue, or [[trowal]], of warm air aloft. Eventually, the cyclone will become barotropically cold and begin to weaken.{{Citation needed|date=January 2021}}

[[Atmospheric pressure]] can fall very rapidly when there are strong upper level forces on the system. When pressures fall more than {{convert|1|mbar|inHg|3|lk=on}} per hour, the process is called explosive cyclogenesis, and the cyclone can be described as a [[Bomb (meteorology)|bomb]].<ref name="BombNWAtlantic">{{cite web | title = Bomb cyclones ravage northwestern Atlantic | author = Jack Williams | publisher = USA Today | date = 2005-05-20 | url = https://www.usatoday.com/weather/tg/wnoreast/wbombs.htm | access-date = 2006-10-04 }}</ref><ref name="BombDef">{{cite web | title = Bomb | author= Glossary of Meteorology | publisher = American Meteorological Society | date = June 2000 | url = http://amsglossary.allenpress.com/glossary/search?id=bomb1 | access-date = 2009-06-21 }}</ref><ref name = "Bomb Ref">{{cite journal | title = Synoptic-Dynamic Climatology of the "Bomb" |date=October 1980 | volume = 108 | issue = 10 |author1=Frederick Sanders |author2=John R. Gyakum | journal = [[Monthly Weather Review]]|page=1589 |doi=10.1175/1520-0493(1980)108<1589:SDCOT>2.0.CO;2 |bibcode=1980MWRv..108.1589S |doi-access=free }}</ref> These bombs rapidly drop in pressure to below {{convert|980|mbar|inHg|2}} under favorable conditions such as near a natural [[temperature gradient]] like the [[Gulf Stream]], or at a preferred quadrant of an upper-level jet streak, where upper level divergence is best. The stronger the upper level divergence over the cyclone, the deeper the cyclone can become. Hurricane-force extratropical cyclones are most likely to form in the northern Atlantic and northern Pacific oceans in the months of December and January.<ref name="HurrForceExtraTropCyc">{{cite web | title = Hurricane Force Extratropical Cyclones |author1=Joseph M. Sienkiewicz |author2=Joan M. Von Ahn |author3=G. M. McFadden | publisher = American Meteorology Society | date = 2005-07-18 | url = http://ams.confex.com/ams/pdfpapers/94332.pdf | access-date = 2006-10-21 }}</ref> On 14 and 15 December 1986, an extratropical cyclone near Iceland deepened to below {{convert|920|mbar|inHg}},<ref>{{cite web | title = Great weather events&nbsp;— A record-breaking Atlantic weather system | publisher = U.K. Met Office | url = http://www.metoffice.gov.uk/corporate/pressoffice/anniversary/recordlow1986.html | archive-url = https://web.archive.org/web/20080707080905/http://www.metoffice.gov.uk/corporate/pressoffice/anniversary/recordlow1986.html | archive-date = 2008-07-07 | access-date = 2009-05-26 }}</ref> which is a pressure equivalent to a [[Saffir-Simpson Hurricane Scale|category 5 hurricane]]. In the [[Arctic Ocean|Arctic]], the average pressure for cyclones is {{convert|980|mbar|inHg|2}} during the winter, and {{convert|1000|mbar|inHg|2}} during the summer.<ref name="ArcticCycloneStats">{{cite journal | title = A cyclone statistics for the Arctic based on European Centre re-analysis data (Abstract) |author1=Brümmer B. |author2=Thiemann S. |author3=Kirchgässner A. | journal = Meteorology and Atmospheric Physics | volume = 75 | pages=233–250 | url = http://cat.inist.fr/?aModele=afficheN&cpsidt=861335 | access-date = 2006-10-04 | doi = 10.1007/s007030070006 | year = 2000 | issn= 0177-7971 | issue= 3–4 |bibcode = 2000MAP....75..233B |s2cid=119849630 | url-access = subscription }}</ref>

A rapidly-falling [[atmospheric pressure]] is possible due to strong upper level forces on the system, and such a cyclone is sometimes referred to as a bomb.<ref name="BombNWAtlantic">{{cite web

| title = Bomb cyclones ravage northwestern Atlantic

| author = Jack Williams

| publisher = [http://www.USATODAY.com USA Today]

| date = [[2005-05-20]]

| url = http://www.usatoday.com/weather/tg/wnoreast/wbombs.htm

| accessdate = 2006-10-04 }}</ref><ref name="BombDef>

{{cite web

| title = American Meteorological Society Glossary - Bomb

| publisher = [http://www.allenpress.com Allen Press Inc.]

| date = 2000-06

| url = http://amsglossary.allenpress.com/glossary/search?id=bomb1

| accessdate = 2006-10-03 }}</ref> These bombs rapidly drop in pressure to below 980&nbsp;[[millibars]] (980&nbsp;[[hectopascal|hPa]], 28.94&nbsp;[[inHg]]) under favorable conditions such as near a natural temperature gradient like the the Gulf Stream, or at a preferred quadrant of an upper level jet streak, where upper level divergence is best. The stronger the upper level divergence over the cyclone, the deeper the cyclone can become. Hurricane-force extratropical cyclones are most likely to form in the northern Atlantic and northern Pacific oceans in the months of December and January.<ref name="HurrForceExtraTropCyc"> {{cite web

| title = Hurricane Force Extratropical Cyclones

| author = Joseph M. Sienkiewicz, Joan M. Von Ahn, and G. M. McFadden

| publisher = [http://ams.confex.com/ American Meteorology Society]

| date = [[2005-07-18]]

| url = http://ams.confex.com/ams/pdfpapers/94332.pdf

| accessdate = 2006-10-21 }}</ref> The lowest pressure measured from an extratropical cyclone in the [[United States]] was 951.7&nbsp;[[hPa]] on [[March 1]], [[1914]] in Bridgehampton, [[New York]]. Between [[January 4]] and [[January 5]], [[1989]], an extratropical cyclone south of Atlantic Canada deepened to 928&nbsp;[[hPa]].<ref name="JeffMastersNoreaster">{{cite web

| title = Flying into a record Nor'easter

| author = JeffMasters

| publisher = [http://www.wunderground.com/blog/JeffMasters/ JeffMasters' Blog] on [http://www.wunderground.com Wunderground.Com]

| date = [[2006-02-15]]

| url = http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=304&tstamp=200602

| accessdate = 2006-10-04 }}</ref> In the [[Arctic Ocean|Arctic]], the average pressure for cyclones is 988&nbsp;[[hPa]] (29.18&nbsp;[[inHg]]) during the winter, and 1000&nbsp;[[hPa]] (29.53&nbsp;[[inHg]]) during the summer.<ref name="ArcticCycloneStats">{{cite web

| title = A cyclone statistics for the Arctic based on European Centre re-analysis data (Abstract)

| Author = BRÜMMER B.; THIEMANN S.; KIRCHGÄSSNER A.;

| publisher = Springer, Wien, AUTRICHE (1986)

| url = http://cat.inist.fr/?aModele=afficheN&cpsidt=861335

| accessdate = 2006-10-04 }}</ref> A rapidly-falling [[atmospheric pressure]] is possible due to strong upper level forces on the system, and such a cyclone is sometimes referred to as a bomb.<ref name="BombNWAtlantic">{{cite web

| title = Bomb cyclones ravage northwestern Atlantic

| author = Jack Williams

| publisher = [http://www.USATODAY.com USA Today]

| date = [[2005-05-20]]

| url = http://www.usatoday.com/weather/tg/wnoreast/wbombs.htm

| accessdate = 2006-10-04 }}</ref>

===Extratropical transition===

[[ImageFile:ETSCristobal FlorenceAug 200629 2014 1615Z.jpg|thumb|Cyclone[[Hurricane FlorenceCristobal (2014)]] in the north Atlantic after completing its transition from a hurricane to an extratropical cyclone from a hurricane.]]

[[Tropical cyclone]]s often transform into extratropical cyclones at the end of their tropical existence, usually between 30° and 40° latitude, where there is sufficient [[Earth's atmosphere (Meteorology)|forcing]] from upper-level troughs or [[Shortwave (meteorology)|shortwaves]] riding the [[Westerlies]] for the process of extratropical transition to begin. During extratropical transition, the cyclone begins to tilt back into the colder airmass with height, and the cyclone's primary energy source converts from the release of latent [[heat of condensation|heat from condensation]] (from thunderstorms near the center) to baroclinic processes. The low pressure system eventually loses its warm core and becomes a cold-core system. During this process, a cyclone in extratropical transition (known in [[Canada]] as the post-tropical stage)<ref name="CanHurrCenterGlossaryETClimo">{{cite webjournal

| title = A climatology of extratropical transition of tropical cyclones in the North Atlantic

|author1=Robert E. Hart |author2=Jenni L. Evans | journal = Journal of Climate

|volume=14 |issue=4 | date = February 2001

| pages = 546–564

| doi = 10.1175/1520-0442(2001)014<0546:ACOTET>2.0.CO;2

|bibcode = 2001JCli...14..546H |doi-access = free}}</ref> During this process, a cyclone in extratropical transition (known across the eastern North Pacific and North Atlantic oceans as the post-tropical stage),<ref name="CanHurrCenterGlossary">{{cite web

| title = Glossary of Hurricane Terms

| publisher = [http://www.atl.ec.gc.ca/weather/hurricane/index_e.html Canadian Hurricane Center]

| date = [[2003-07-10]]

| url = http://www.atl.ec.gc.ca/weather/hurricane/hurricanes9.html

| accessdateaccess-date = 2006-10-04 |archive-url = https://web.archive.org/web/20061002040835/http://www.atl.ec.gc.ca/weather/hurricane/hurricanes9.html |archive-date = 2006-10-02}}</ref><ref>{{cite web|url=http://www.nhc.noaa.gov/aboutgloss.shtml#p|author=National Hurricane Center|publisher=[[National Oceanic and Atmospheric Administration]]|date=2011-07-11|access-date=2011-07-23|title=Glossary of NHC Terms: P|author-link=National Hurricane Center}}</ref> will invariably form or connect with nearby fronts and/or troughs consistent with a baroclinic system. Due to this, the size of the system will usually appear to increase, while the core weakens. However, after transition is complete, the storm may re-stengthenstrengthen due to baroclinic energy, depending on the environmental conditions surrounding the system.<ref name="ETClimo"/> The cyclone will also distort in shape, becoming less symmetric with time.<ref name="CPS-ET"/><ref name="CPS1">{{cite journal

| title = A Cyclone Phase Space Derived from Thermal Wind and Thermal Asymmetry

| author = Robert E. Hart

| journal = Monthly Weather Review

| volume = 131

| issue = 4

| date = April 2003

| pages = 585–616

| doi = 10.1175/1520-0493(2003)131<0585:ACPSDF>2.0.CO;2

|bibcode = 2003MWRv..131..585H | s2cid = 3753455

| doi-access = free

}}</ref><ref name="ETCompositesHEE"/>

During extratropical transition, the cyclone begins to tilt back into the colder airmass with height, and the cyclone's primary energy source converts from the release of latent [[heat of condensation|heat from condensation]] (from thunderstorms near the center) to [[Baroclinity|baroclinic]] processes. The low pressure system eventually loses its warm core and becomes a [[cold-core low|cold-core system]].<ref name="ETCompositesHEE">{{cite journal

On rare occasions, an extratropical cyclone can transition into a tropical cyclone if it reaches an area of ocean with warmer waters and an environment with less vertical wind shear. The peak time of [[Subtropical cyclone|subtropical]] cyclogenesis (the midpoint of this transition) is in the months of September and October, when the difference between the temperature of the air aloft and the [[sea surface temperature]] is the greatest, leading to the greatest potential for instability.<ref name="HistSubTropCyclones">{{cite web

| title = Synoptic composites of the extratropical transition lifecycle of North Atlantic tropical cyclones: Factors determining post-transition evolution

|author1=Robert E. Hart |author2=Clark Evans |author3=Jenni L. Evans | journal = Monthly Weather Review

|volume=134 |issue=2 | date = February 2006

| pages = 553–578

| doi = 10.1175/MWR3082.1

|bibcode = 2006MWRv..134..553H |citeseerx=10.1.1.488.5251 |s2cid=3742254 }}</ref><ref name="CPS-ET">{{cite journal

| title = Objective indicators of the life cycle evolution of extratropical transition for Atlantic tropical cyclones

|author1=Jenni L. Evans |author2=Robert E. Hart | journal = Monthly Weather Review

|volume=131 |issue=5 | date = May 2003

| pages = 909–925

| doi = 10.1175/1520-0493(2003)131<0909:OIOTLC>2.0.CO;2

|bibcode = 2003MWRv..131..909E |s2cid=3744671 }}</ref>

The peak time of [[Subtropical cyclone|subtropical]] cyclogenesis (the midpoint of this transition) in the North Atlantic is in the months of September and October, when the difference between the temperature of the air aloft and the [[sea surface temperature]] is the greatest, leading to the greatest potential for instability.<ref name="NAtlSTClimo">{{cite journal

| title = Atlantic Subtropical Storms. Part II: Climatology

|author1=Mark P. Guishard |author2=Jenni L. Evans |author3=Robert E. Hart |s2cid=51435473 | journal = Journal of Climate

|volume=22 |issue=13 | date = July 2009

| pages = 3574–3594

| doi = 10.1175/2008JCLI2346.1

|bibcode = 2009JCli...22.3574G |doi-access=free }}</ref> On rare occasions, an extratropical cyclone can transform into a tropical cyclone if it reaches an area of ocean with warmer waters and an environment with less vertical wind shear.<ref name="NAtlSTCases">{{cite journal

| title = Atlantic Subtropical Storms. Part I: Diagnostic Criteria and Composite Analysis

|author1=Jenni L. Evans |author2=Mark P. Guishard | journal = Monthly Weather Review

|volume=137 |issue=7 | date = July 2009

| pages = 2065–2080

| doi = 10.1175/2009MWR2468.1

|bibcode = 2009MWRv..137.2065E |doi-access = free}}</ref> An example of this happening is in the [[1991 Perfect Storm]].<ref name="HistSubTropCyclones">{{cite web

| title = A Fifty year History of Subtropical Cyclones

| author = David MarkM. Roth

| publisher = [http://www.hpc.ncep.noaa.gov/ Hydrometeorological Prediction Center]

| date = [[2002-02-15]]

| url = http://www.hpcwpc.ncep.noaa.gov/research/roth/Subpreprint.pdf

| access-date = 2006-10-04 }}</ref> The process known as "tropical transition" involves the usually slow development of an extratropically cold core vortex into a tropical cyclone.<ref name="TropicalTransition">{{cite web

| accessdate = 2006-10-04 }}</ref>

| title = Cyclogenesis and Tropical Transition in decaying frontal zones

|author=Michelle L. Stewart |author2=M. A. Bourassa

| date = 2006-04-25

| url = http://ams.confex.com/ams/27Hurricanes/techprogram/paper_108880.htm

| access-date = 2006-10-24 }}</ref><ref name="TropicalTransition2">{{cite journal

| title = The TT Problem&nbsp;— Forecasting the Tropical Transition of Cyclones

|author1=Christopher A. Davis |author2=Lance F. Bosart |s2cid=122903747 | journal = [[Bulletin of the American Meteorological Society]]

|volume=85 |issue=11 | date = November 2004

| pages = 1657–1662

| doi = 10.1175/BAMS-85-11-1657

|bibcode = 2004BAMS...85.1657D |doi-access = free }}</ref>

The [[Joint Typhoon Warning Center]] uses the extratropical transition (XT) technique to subjectively estimate the intensity of tropical cyclones becoming extratropical based on visible and infrared [[Weather satellite|satellite imagery]]. Loss of central convection in transitioning tropical cyclones can cause the [[Dvorak technique]] to fail;<ref>{{cite journal |author=Velden, C. |date=Aug 2006 |title=The Dvorak Tropical Cyclone Intensity Estimation Technique: A Satellite-Based Method that Has Endured for over 30 Years |journal=[[Bulletin of the American Meteorological Society]] |volume=87 |issue=9 |pages=1195–1210 |doi=10.1175/BAMS-87-9-1195 |url=http://www.nhc.noaa.gov/pdf/06velden.pdf |access-date=2008-11-07|bibcode = 2006BAMS...87.1195V |display-authors=etal|citeseerx=10.1.1.669.3855 |s2cid=15193271 }}</ref> the loss of convection results in unrealistically low estimates using the Dvorak technique.<ref>{{cite journal |last=Lander |first=Mark A. |year=2004 |title=Monsoon depressions, monsoon gyres, midget tropical cyclones, TUTT cells, and high intensity after recurvature: Lessons learned from the use of Dvorak's techniques in the world's most prolific tropical-cyclone basin |journal=26th Conference on Hurricanes and Tropical Meteorology |url=http://ams.confex.com/ams/pdfpapers/75346.pdf |access-date=2008-11-08 }}</ref> The system combines aspects of the Dvorak technique, used for estimating tropical cyclone intensity, and the Hebert-Poteat technique, used for estimating [[subtropical cyclone]] intensity.<ref>{{cite web|url=http://home1.gte.net/anstett/XT_Pg01.htm |title=JTWC TN 97/002 Page 1 |archive-url=https://web.archive.org/web/20120208085744/http://home1.gte.net/anstett/XT_Pg01.htm |archive-date=2012-02-08}}</ref> The technique is applied when a tropical cyclone interacts with a [[Surface weather analysis#Fronts|frontal boundary]] or loses its central convection while maintaining its forward speed or accelerating.<ref name=autogenerated2>{{cite web|url=http://home1.gte.net/anstett/XT_Pg08.htm |title=JTWC TN 97/002 Page 8 |archive-url=https://web.archive.org/web/20120208085747/http://home1.gte.net/anstett/XT_Pg08.htm |archive-date=2012-02-08}}</ref> The XT scale corresponds to the Dvorak scale and is applied in the same way, except that "XT" is used instead of "T" to indicate that the system is undergoing extratropical transition.<ref name=autogenerated1>{{cite web|url=http://home1.gte.net/anstett/XT_Pg02.htm |title=JTWC TN 97/002 Page 2 |archive-url=https://web.archive.org/web/20120208085752/http://home1.gte.net/anstett/XT_Pg02.htm |archive-date=2012-02-08}}</ref> Also, the XT technique is only used once extratropical transition begins; the Dvorak technique is still used if the system begins dissipating without transition.<ref name=autogenerated2 /> Once the cyclone has completed transition and become [[cold-core low|cold-core]], the technique is no longer used.<ref name=autogenerated1 />

==Structure==

{{see also|Weather fronts}}

=== Surface pressure/Wind distribution ===

[[Image:Quikscatcyclone.jpg|thumb|right|250 px|[[QuikSCAT]] image of typical extratropical cyclones over the ocean. Note the maximum winds are on the outside of the occlusion.]]

[[File:Quikscatcyclone.jpg|thumb|[[QuikSCAT]] image of typical extratropical cyclones over the ocean. Note the maximum winds are on the outside of the occlusion.]]

The windfield of an extratropical cyclone constricts with distance in relation to surface level pressure, with the highest winds and lowest pressure being found near the center; typically just on the cold/poleward side of warm fronts and occlusions and just behind cold fronts (where [[pressure gradient force]] is highest.) <ref name="ww2010PGF">{{cite web

=== Surface pressure and wind distribution ===

The windfield of an extratropical cyclone constricts with distance in relation to surface level pressure, with the lowest pressure being found near the center, and the highest winds typically just on the cold/poleward side of warm fronts, occlusions, and [[cold front]]s, where the [[pressure gradient force]] is highest.<ref name="ww2010PGF">{{cite web

| title = WW2010 - Pressure Gradient Force

| publisher = [http://ww2010.atmos.uiuc.edu/(Gh)/abt/home.rxml University of Illinois]

| date = [[1999-09-02]]

| url = http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/pgf.rxml

| access-date = 2006-10-11 }}</ref> The area poleward and west of the cold and warm fronts connected to extratropical cyclones is known as the cold sector, while the area equatorward and east of its associated cold and warm fronts is known as the warm sector.{{Citation needed|date=January 2021}}

| accessdate = 2006-10-11 }}</ref>

Near this center, the pressure gradient force (from the pressure at the center of the cyclone compared to the pressure outside the cyclone) and the [[Coriolis effect|Coriolis]] force must be in an approximate balance for the cyclone to avoid collapsing in on itself as a result of the difference in pressure. The central pressure of the cyclone will lower with increasing maturity, while outside of the cyclone, the [[sea-level pressure]] is not very low; its typical value is below 1013.2&nbsp;[[mbar]] (1013.2&nbsp;[[hPa]], 29.92&nbsp;[[inHg]]), which is the average sea level pressure for Earth. In most extratropical cyclones, the part of the cold front ahead of the cyclone will develop into a [[warm front]], giving the frontal zone (as drawn on [[Surface weather analysis|surface weather maps]]) a wave-like shape. Due to this appearance in their early life cycles, extratropical cyclones can also be referred to as frontal waves. In the [[United States]], an old name for such a system is "warm wave".<ref name="GlobalAverageSLP">{{cite web

| title = The Atmosphere in motion: Pressure & mass

| publisher = [http://www.sbs.ohio-state.edu/ Ohio State University]

| date = [[2006-04-26]]

| url = http://geog-www.sbs.ohio-state.edu/courses/G520/bmark/Lecture%2013-Chp9,%20Atmosphere%20in%20motion-P&mass.pdf#search=%22average%20surface%20atmosphere%20pressure%20distribution%22

| accessdate = 2006-10-04 }}</ref>

[[File:Extratropical cyclone off Australia 2016-12-28 0230Z.jpg|thumb|left|Extratropical cyclones spin clockwise in the Southern Hemisphere, just like tropical cyclones.]]

===Rotation===

The wind flow around an extratropical cyclone is [[clockwise and counterclockwise|counterclockwise]] in the northern hemisphere, and clockwise in the southern hemisphere, due to the [[Coriolis effect]] (this manner of rotation is generally referred to as ''cyclonic''). Near this center, the pressure gradient force (from the pressure at the center of the cyclone compared to the pressure outside the cyclone) and the Coriolis force must be in an approximate balance for the cyclone to avoid collapsing in on itself as a result of the difference in pressure.<ref>{{cite web|url=http://www.abdn.ac.uk/~wpe001/meteo/metoh8.pdf |title=The Atmosphere in Motion |publisher=[[University of Aberdeen]] |access-date=2011-09-11 |archive-url=https://web.archive.org/web/20130907053250/http://www.abdn.ac.uk/~wpe001/meteo/metoh8.pdf |archive-date=2013-09-07}}</ref> The central pressure of the cyclone will lower with increasing maturity, while outside of the cyclone, the [[Mean sea level pressure|sea-level pressure]] is about average. In most extratropical cyclones, the part of the cold front ahead of the cyclone will develop into a warm front, giving the frontal zone (as drawn on [[Surface weather analysis|surface weather maps]]) a wave-like shape. Due to their appearance on satellite images, extratropical cyclones can also be referred to as frontal waves early in their life cycle. In the [[United States]], an old name for such a system is "warm wave".<ref name="GlobalAverageSLP">{{cite web| title = The Atmosphere in motion: Pressure & mass| publisher = [[Ohio State University]]| date = 2006-04-26| url = http://geog-www.sbs.ohio-state.edu/courses/G520/bmark/Lecture+13-Chp9,+Atmosphere+in+motion-P&mass.pdf| access-date = 2009-06-21| archive-url = https://web.archive.org/web/20060905234506/http://geog-www.sbs.ohio-state.edu/courses/G520/bmark/Lecture%2013-Chp9%2C%20Atmosphere%20in%20motion-P%26mass.pdf| archive-date = 2006-09-05}}</ref>

The wind flow around a large cyclone, generally referred to as cyclonic, is [[counterclockwise]] in the northern hemisphere, and [[Clockwise and counterclockwise|clockwise]] in the southern hemisphere, due to the [[Coriolis effect]].

In the northern hemisphere, once a cyclone occludes, a trough of warm air aloft—or "trowal" for short—will be caused by strong southerly winds on its eastern periphery rotating aloft around its northeast, and ultimately into its northwestern periphery (also known as the warm conveyor belt), forcing a surface trough to continue into the cold sector on a similar curve to the occluded front. The trowal creates the portion of an occluded cyclone known as its '''comma head''', due to the [[comma (punctuation)|comma]]-like shape of the mid-tropospheric cloudiness that accompanies the feature. It can also be the focus of locally heavy precipitation, with thunderstorms possible if the atmosphere along the trowal is unstable enough for convection.<ref name="TROW">{{cite web

| title = What is a TROWAL?

| publisher = [[St. Louis University]]

| date = 2003-08-04

| url = http://www.eas.slu.edu/CIPS/Presentations/Conferences/NWA2002/Snow_NWA_02/tsld003.htm

| access-date = 2006-11-02 |archive-url = https://web.archive.org/web/20060916052440/http://www.eas.slu.edu/CIPS/Presentations/Conferences/NWA2002/Snow_NWA_02/tsld003.htm |archive-date = 2006-09-16}}</ref>

===Vertical structure===

Extratropical cyclones slant back into colder air masses and strengtheningstrengthen with height, sometimes exceeding 30,000&nbsp;feet (approximately 109&nbsp;[[km]]) in depth.<ref name="MidLatVertStructure">{{cite web

| title = Mid-Latitude Cyclones: Vertical Structure

| author = Andrea Lang

| publisher = [http://www.aos.wisc.edu/ University of Wisconsin-Madison Department of Atmospheric and Oceanic Sciences]

| date = [[2006-04-20]]

| url = http://www.aos.wisc.edu/~aalopez/aos101/wk14.html

| accessdateaccess-date = 2006-10-03 }}</ref>

| archive-url = https://web.archive.org/web/20060903120723/http://www.aos.wisc.edu/~aalopez/aos101/wk14.html

Above the surface of the earth, the air temperature near the center of the cyclone is increasingly colder than the surrounding environment. These characteristics are the direct opposite of those found in their [[tropical cyclone]]s, and they are sometimes called "cold-core lows" for these reasons.<ref name="AnlFcastHelp">{{cite web

| archive-date = 2006-09-03}}</ref>

Above the surface of the earth, the air temperature near the center of the cyclone is increasingly colder than the surrounding environment. These characteristics are the direct opposite of those found in their counterparts, [[tropical cyclone]]s; thus, they are sometimes called "cold-core lows".<ref name="AnlFcastHelp">{{cite web

| title = Cyclone Phase Analysis and Forecast: Help Page

| author = Robert Hart

| publisher = [http://moe.met.fsu.edu Florida State University Department of Meteorology]

| date = [[2003-02-18]]

| url = http://moe.met.fsu.edu/cyclonephase/help.html

| accessdateaccess-date = 2006-10-03 }}</ref> Various charts can be examined to check the characteristics of a cold-core system with height, such as the {{convert|700&nbsp;[[millibar|mbar]] ([[hPa]])|inHg|2}} chart, which is at about {{convert|10,000|ft|m|0|abbr=off|sp=us}} feet or 3,000 meters in heightaltitude. Cyclone [[phase diagram|phase space diagrams]] are used to tell whether a cyclone is tropical, subtropical, or extratropical.<ref name="CycPhaseEvolution"> {{cite web

| title = Cyclone phase evolution: Analyses & Forecasts

| author = Robert HartHarthi

| publisher = [http://moe.met.fsu.edu Florida State University Department of Meteorology]

| date = [[2006-10-04]]

| url = http://moe.met.fsu.edu/cyclonephase/

| accessdateaccess-date = 2006-10-03 }}</ref>

==Cyclone evolution==

[[File:Alex 2016-01-10 1635Z.jpg|thumb|A hurricane-force extratropical cyclone in the north Atlantic in January 2016 with a distinct eye-like feature, caused by a warm seclusion. This system would later undergo [[tropical cyclogenesis]] and become [[Hurricane Alex (2016)|Hurricane Alex]].]]

[[Image:Cyclonemodels.gif|thumb|right|250px|Norwegian cyclone and Shapiro-Keyser model differences in frontal structure.]]

There are two models of cyclone development and lifecycleslife cycles in common use: - Thethe Norwegian model and the Shapiro-KeyserShapiro–Keyser Modelmodel. <ref name="UnifiedSurfaceAnalysisManual">{{cite web

| title = Unified Surface Analysis Manual

| author = DrothDavid M. Roth

| publisher = [http://www.hpc.ncep.noaa.gov/ Hydrometeorological Prediction Center (NOAA)]

| date = [[2005-12-15]]

| url = http://www.hpcwpc.ncep.noaa.gov/sfc/UASfcManualVersion1.pdf

| accessdateaccess-date = 2006-10-11 }}</ref>

===Norwegian cyclone model===

{{main|Norwegian cyclone model}}

Of the two theories on extratropical cyclone structure and life cycle, the oldest is the Norwegian Cyclone Model, developed during World War I. In this theory, cyclones develop as they move up and along a frontal boundary, eventually [[Occlusion|occluding]] and ending up in a barotropically cold envirnoment.<ref name="NorCycMod">{{cite web

Of the two theories on extratropical cyclone structure and life cycle, the older is the Norwegian Cyclone Model, developed during [[World War I]]. In this theory, cyclones develop as they move up and along a frontal boundary, eventually [[occluded front|occluding]] and reaching a barotropically cold environment.<ref name="NorCycMod">{{cite web

| title = The Norwegian Cyclone Model

| author = Shaye Johnson

| publisher = [http://weather.ou.edu/ University of Oklahoma, School of Meteorology]

| date = [[2001-09-25]]

| url = http://weather.ou.edu/~metr4424/Files/Norwegian_Cyclone_ModelNorwegian_Cyclone_Modle.pdf#search=%22norwegian%20cyclone%20model%22

| accessdateaccess-date = 2006-10-11 |archive-url = https://web.archive.org/web/20060901163934/http://weather.ou.edu/~metr4424/Files/Norwegian_Cyclone_Model.pdf#search=%22norwegian%20cyclone%20model%22 |archive-date = 2006-09-01}}</ref> It was developed completely from surface-based weather observations, including descriptions of clouds found near frontal boundaries. This theory still retains merit, as it is a good description for extratropical cyclones over continental landmasses.{{Citation needed|date=January 2021}}

===Shapiro-KeyserShapiro–Keyser model===

A second competing theory for extratropical cyclone development over the oceans is the Shapiro-KeyserShapiro–Keyser model, developed in 1990.<ref name="CIMMSStrucEvoTLF"> {{cite web

| title = Determining Midlatitude Cyclone Structure and Evolution from the Upper-Level Flow

| author author1= David M. Schultz and |author2=Heini Werli | publisher = Cooperative Institute for Mesoscale Meteorological Studies

| date = 2001-01-05

| publisher = [http://www.cimms.ou.edu/ Cooperative Institute for Mesoscale Meteorological Studies]

| date = [[2001-01-05]]

| url = http://www.cimms.ou.edu/~schultz/papers/marwealog.html

| accessdateaccess-date = 2006-10-09 }}</ref> Its main differences with the Norwegian Cyclone Model are the fracture of the cold front, treating warm-type occlusions and warm fronts as the same, and allowing the cold front to progress through the warm sector [[perpendicular]] to the warm front. This model was based on oceanic cyclones and their frontal structure, as seen in surface observations and in previous projects which used [[Fixed-wing aircraft|planes]] to determine the vertical structure of fronts across the northwest Atlantic.{{Citation needed|date=January 2021}}

====Warm seclusion====

A warm seclusion is the mature phase of the extratropical cyclone lifecyclelife cycle. This was conceptualized after the [[ERICA (Meteorology)|ERICA]] field experiment of the late 1980s., The experimentwhich produced observations of intense marine cyclones that indicated an anomalously warm low-level thermal structure, secluded (or surrounded) by a bent-back warm front and a coincident [[chevron]]-shaped band of intense surface winds.<ref name="WarmSeclusionCycMet"> {{cite web

| title = Warm seclusion cyclone climatology

| author = Ryan N. Maue

| publisher = [http://ams.confex.com/ American Meteorological Society Conference]

| date = [[2006-04-25]]

| url = http://ams.confex.com/ams/27Hurricanes/techprogram/paper_108776.htm

| accessdateaccess-date = 2006-10-06 }}</ref> The [[Norwegian cyclone model|Norwegian Cyclone Model]], as developed by the [[Bergen School of Meteorology]], largely observed cyclones at the tail end of their lifecycle and used the term occlusion to identify the decaying stages.<ref{{Citation nameneeded|date="WindThrowDamages">January {{cite web2021}}

| title = Wind Throw Damages on Forests - Frequency and Associated Pressure Patterns 1961-1990 and in a Future Climate Scenario

| author = Lars Bärring

| publisher = [http://www.natgeo.lu.se/English/homeines.asp Department of Geography and Ecosystems Analysis, Lund University

| date = [[2003-12-11]]

| url = http://www.natgeo.lu.se/ex-jobb/exj_97.pdf#search=occlusion

| accessdate = 2006-10-30 }}</ref>

Warm seclusions may have cloud-free, [[eye (cyclone)|eye]]-like features at their center (reminiscent of [[tropical cyclone]]s), significant pressure falls, hurricane -force winds, and moderate to strong [[convection]]. The most intense warm seclusions often attain pressures less than 950&nbsp;[[millibar|mbar]]millibars (28.05&nbsp;inHg) with a definitive lower to mid-level warm core structure.<ref name="WarmSeclusionCycMet">Ref</ref> A warm seclusion is, the result of a baroclinic lifecycle and, occurs at latitudes well poleward of the tropics.{{Citation The process known as "tropical transition" involves the usually slow development of an extratropically cold core vortex into a tropical cyclone.<ref nameneeded|date="TropicalTransition"> {{citeJanuary web2021}}

| title = Cyclogenesis and Tropical Transition in decaying frontal zones

| author = Michelle L. Stewart, COAPS, Tallahassee, FL; and M. A. Bourassa

| publisher = [http://ams.confex.com/ American Meteorological Society Conference]

| date = [[2006-04-25]]

| url = http://ams.confex.com/ams/27Hurricanes/techprogram/paper_108880.htm

| accessdate = 2006-10-24 }}</ref><ref name="TropicalTransition2"> {{cite web

| title = The TT Problem - Forecasting the Tropical Transition of Cyclones

| author = Christopher A. Davis ; Lance F. Bosart

| publisher = [http://ams.allenpress.com/ American Meteorological Society Journals Online]

| date = 2004-11

| url = http://ams.allenpress.com/archive/1520-0477/85/11/pdf/i1520-0477-85-11-1657.pdf

| accessdate = 2006-10-24 }}</ref>

As latent heat [[flux]] releases are important for their development and intensification, a vast majority ofmost warm seclusion events occur over the world's [[ocean]]s; andthey may impact coastal nations with hurricane force [[wind]]s and torrential [[rain]].<ref name="MidLatStrucULFCIMMSStrucEvoTLF"/><ref name="Blizzicanes">{{cite web

| title = Determining Midlatitude Cyclone Structure and Evolution from the Upper-Level Flow

| author = David M. Schultz ; Heini Wernli

| publisher = [http://www.cimms.ou.edu/ Cooperative Institute for Mesoscale Meteorological Studies]

| date = [[2001-01-05]]

| url = http://www.cimms.ou.edu/~schultz/papers/marwealog.html

| accessdate = 2006-11-01 }}</ref><ref name="Blizzicanes"> {{cite web

| title = Blizzicanes

| author = Jeff Masters

| publisher = [http://www.wunderground.com/blog/JeffMasters/ JeffMasters' Blog] on [http://www.wunderground.com Wunderground.Com]

| date = [[2006-02-14]]

| url = http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=303&tstamp=200602

| accessdateaccess-date = 2006-11-01 }}</ref> Climatologically, the Northern Hemisphere sees warm seclusions during the cold season months, while the Southern Hemisphere may see a strong cyclone event such as this during all times of the year.{{Citation needed|date=January 2021}}

In all tropical basins, except the Northern Indian Ocean, the extratropical transition of a tropical cyclone may result in reintensification into a warm seclusion. For example, Hurricane [[Hurricane Maria (2005)|Hurricane Maria]] of (2005) and [[Hurricane Cristobal]] (2014) each reintensifiedre-intensified into a strong baroclinic system and achieved warm seclusion status at maturity (or lowest pressure).<ref name="Maria">{{cite webreport| title=Tropical Cyclone Report: Hurricane Maria| author1=Richard J. Pasch| author2=Eric S. Blake| date=February 8, 2006| publisher=National Hurricane Center| ___location=Miami Florida| url=https://www.nhc.noaa.gov/data/tcr/AL142005_Maria.pdf| access-date=July 21, 2021}}</ref><ref>{{cite magazine|last=Fontaine|first=Andie Sophia|title=Stormy Weather Is Hurricane Cristobal Petering Out|date=September 1, 2014|url=https://grapevine.is/news/2014/09/01/stormy-weather-is-hurricane-cristobal-petering-out/|magazine=[[The Reykjavík Grapevine]]|access-date=July 21, 2021}}</ref>

| title = Tropical Cyclone Report - Hurricane Maria

| author = Richard J. Pasch; Eric S. Blake

| publisher = [http://www.nhc.noaa.gov National Hurricane Center (NOAA)]

| date = [[2006-02-08]]

| url = http://www.nhc.noaa.gov/pdf/TCR-AL142005_Maria.pdf

| accessdate = 2006-10-30 }}</ref>

==Motion==

[[ImageFile:Zonalflow.gif|thumb|right|250 px300px|A zonal flow regime. Note the dominant west-to-east flow as shown in the 500 hPa height pattern.]]

[[File:Feb242007 blizzard.gif|thumb|300px|right|A February 24, 2007 radar image of a large extratropical cyclonic storm system at its peak over the central United States.]]

Extratropical cyclones are generally driven, or "steered", by deep westerly winds in a general west to east motion across both the Northern and Southern hemispheres of the Earth. This general motion of atmospheric flow is known as "zonal".<ref name="ZonalFlowDef"> {{cite web| title = American Meteorological Society Glossary - Zonal Flow

Extratropical cyclones are generally driven, or "steered", by deep westerly winds in a general west to east motion across both the Northern and Southern hemispheres of the Earth. This general motion of atmospheric flow is known as "zonal".<ref name="ZonalFlowDef">{{cite web | title = Zonal Flow | author = Glossary of Meteorology | publisher = American Meteorological Society | date = June 2000 | url = http://amsglossary.allenpress.com/glossary/search?id=zonal-flow1 | access-date = 2006-10-03 | archive-url = https://web.archive.org/web/20070313084248/http://amsglossary.allenpress.com/glossary/search?id=zonal-flow1 | archive-date = 2007-03-13 }}</ref> Where this general trend is the main steering influence of an extratropical cyclone, it is known as a "[[zonal flow|zonal flow regime]]".{{Citation needed|date=January 2021}}

| publisher = [http://www.allenpress.com Allen Press Inc.]

| date = 2000-06

| url = http://amsglossary.allenpress.com/glossary/search?id=zonal-flow1

| accessdate = 2006-10-03 }}</ref> Where this general trend is the main steering influence of an extratropical cyclone, it is known as a "[[zonal flow|zonal flow regime]]".

When the general flow pattern buckles from a zonal pattern to the meridional pattern,<ref name="MeridonialFlow">{{cite web | title = Meridional Flow | publisher = American Meteorological Society | author = Glossary of Meteorology | date = June 2000 | url = http://amsglossary.allenpress.com/glossary/search?id=meridional-flow1 | access-date = 2006-10-03 | archive-url = https://web.archive.org/web/20061026100131/http://amsglossary.allenpress.com/glossary/search?id=meridional-flow1 | archive-date = 2006-10-26 }}</ref> a slower movement in a north or southward direction is more likely. [[Meridional flow]] patterns feature strong, amplified troughs and ridges, generally with more northerly and southerly flow.{{Citation needed|date=January 2021}}

When the general flow pattern buckles from a zonal pattern to the meridional pattern,<ref name="MeridonialFlow">{{cite web

| title = American Meteorological Society Glossary - Meridional Flow

| publisher = [http://www.allenpress.com Allen Press Inc.]

| date = 2000-06

| url = http://amsglossary.allenpress.com/glossary/search?id=meridional-flow1

| accessdate = 2006-10-03 }}</ref> a slower movement in a north or southward direction is more likely. [[Meridional flow]] patterns feature strong, amplified troughs and ridges, generally with more northerly and southerly flow.

Changes in direction of this nature are most commonly observed as a result of a cylonecyclone's interaction with other [[low pressure system]]s, [[Troughtrough (meteorology)|troughs]], [[Ridgeridge (meteorology)|ridges]], or with [[anticyclone]]s. A strong and stationary [[anticyclone]] can effectively block the path of an extratropical cyclone. Such [[Blockingblocking anticyclone|blocking patterns]] are quite normal, and will generally result in a weakening of the cyclone, the weakening of the anticyclone, a diversion of the cyclone towards the anticyclonesanticyclone's periphery, or a combination of all three to some extent depending on the precise conditions. It is also common for an extratropical cyclone to strengthen as the blocking anticyclone or ridge weakens in these circumstances.<ref name="AnticycBlocking"> {{cite webjournal

| title = The Interactions between a Midlatitude Blocking Anticyclone and Synoptic-Scale Cyclones That Occurred during the Summer Season

| author author1= Anthony R. Lupo ; |author2=Phillip J. Smith | date = February 1998 | volume=126| issue=2 |journal=Monthly Weather Review |pages =502–515

| doi = 10.1175/1520-0493(1998)126<0502:TIBAMB>2.0.CO;2

| publisher = [http://www.purdue.edu/eas/ Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana]

| dateissn = [[19971520-05-02]]0493

|bibcode = 1998MWRv..126..502L |hdl=10355/2398 |hdl-access=free }}</ref>

| url = http://ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2F1520-0493(1998)126%3C0502:TIBAMB%3E2.0.CO%3B2#S4

| accessdate = 2006-10-21 }} </ref>

Where an extratropical cyclone encounters another extratropical cyclone (or almost any other kind of cyclonic [[vortex]] in the atmosphere), the two may combine to become a "Binarybinary cyclone", where the vorticiesvortices of the two cyclones rotate around each other (known as the "[[Fujiwhara effect]]".). This most often results in a merging of the two low pressure systems into a single extratropical cyclone, or can less commonly result in a mere change of direction of either one or both of the cyclones.<ref name="ExtraFujiwhara"> {{cite webjournal

| title = Theoretical and Applied Climatology -&nbsp;— Rotation of mid-latitude binary cyclones: a potential vorticity approach

|author1=B. Ziv |author2=P. Alpert |issn=0177-798X|volume=76|date=December 2003|doi=10.1007/s00704-003-0011-x|pages=189–202| journal = Theoretical and Applied Climatology|issue=3–4 |bibcode = 2003ThApC..76..189Z |s2cid=54982309 }}</ref> The precise results of such interactions depend on factors such as the size of the two cyclones, their strength, their distance from each other, and the prevailing atmospheric conditions around them.{{Citation needed|date=January 2021}}

| author = B. Ziv ; P. Alpert

| publisher = Springer Wien (ISSN 0177-798X (Print) 1434-4483 (Online))

| date = [[2003-11-20]]

| url = http://www.springerlink.com/content/nhlkqm3ckujgm106/

| accessdate = 2006-10-21 }} </ref> The precise results of such interactions depend on a number of factors including the size of the two cyclones, their strength, the distance between the two cyclones, and the prevailing atmospheric conditions around them.

{{clear}}

==Effects==

[[File:Snowcsi.gif|thumb|right|300px|Preferred region of snowfall in an extratropical cyclone]]

[[File:SL 96P 2021-02-22 0165Z.jpg|thumb|250px|An [[Australian east coast low|east coast low]] approaching southeastern Australia]]

===General===

Extratropical cyclones can bring little rain and surface [[wind]]s of {{convert|15|–|30|km/h|mph|abbr=on|round=5}}, or they can be dangerous with torrential rain and winds exceeding {{convert|119|km/h|mph|abbr=on}},<ref name="MarinersWeatherLog">{{cite web

[[Image:Snowcsi.gif|thumb|right|250 px|Preferred region of snowfall in an extratropical cyclone.]]

Extratropical cyclones can bring mild weather with a little rain and surface [[wind]]s of 7-15 knots, or they can be cold and dangerous with torrential rain and winds exceeding 64 knots,<ref name="MarinersWeatherLog">{{cite web

| title = Mariners Weather Log, Vol 49, No. 1

| author author1= Joan Von Ahn; |author2=Joe Sienkiewicz; |author3=Greggory McFadden; | publisher = Voluntary Observing Ship Program

| date = April 2005

| publisher = [http://www.vos.noaa.gov/ Voluntary Observing Ship Program]

| date = 2005-04

| url = http://www.vos.noaa.gov/MWL/april_05/cyclones.shtml

| accessdateaccess-date = 2006-10-04 }}</ref> (and so they are sometimes referred to as [[European windstorm|windstorms]] in Europe.) The band of [[precipitation (meteorology)|precipitation]] that is associated with the [[warm front]] is often extensive. In mature extratropical cyclones, an area known as the '''comma head''' on the northwest periphery of the surface low can be a region of heavy precipitation, frequent [[thunderstorm]]s, and [[thundersnow]]s. Cyclones tend to move along a predictable path at a moderate rate of progress. During late [[autumn|fall]], [[winter]], and [[spring]], the atmosphere over continents can be cold enough through the depth of the [[troposphere]] to cause snowfall.{{Citation needed|date=January 2021}}

===Severe Weatherweather===

Squall lines, or solid linesbands of strong thunderstorms, can form ahead of cold fronts and [[Trough (meteorology)#Lee_troughLee trough|lee trough]]s due to the presence of significant atmospheric moisture coupled withand strong upper level divergence, leading to [[hail]] and high winds.<ref name="SquallLines"> {{cite web

| title = WW2010 - Squall Lines

| publisher = [http://ww2010.atmos.uiuc.edu/(Gh)/abt/home.rxml University of Illinois]

| date = [[1999-09-02]]

| url = http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/type/mline/home.rxml

| accessdateaccess-date = 2006-10-21 }}</ref> When significant directional wind shear exists in the atmosphere ahead of a cold front in the presence of a strong upper -level jet stream, [[tornado]] formation is possible.<ref name="Tornadoes"> {{cite web

|title | title = Tornadoes: Nature's Most Violent Storms

|publisher | publisher = [http://www.nssl.noaa.gov/ National Severe Storms Laboratory (NOAA)]

|date | date = [[2002-03-13]]

|url | url = http://www.nssl.noaa.gov/NWSTornado/

|access-date = 2006-10-21

| accessdate = 2006-10-21 }}</ref> While tornadoes can form anywhere on Earth, the greatest number occur in the Great Plains in the [[United States]], as downsloped winds off the north-south oriented Rocky Mountains, also known as a dryline, aids their development from as weak as [[Fujita scale|F0]] to as powerful as [[Fujita scale|F5]].

|archive-url = https://web.archive.org/web/20061026065708/http://www.nssl.noaa.gov/NWSTornado/

|archive-date = 2006-10-26

}}</ref> Although tornadoes can form anywhere on Earth, the greatest number occur in the [[Great Plains]] in the United States, because downsloped winds off the north–south oriented [[Rocky Mountains]], which can form a dry line, aid their development at any [[Fujita scale|strength]].{{Citation needed|date=January 2021}}

Explosive development of extratropical cyclones can be sudden. The bombstorm known in theGreat Britain and UKIreland as the "[[Great Storm of 1987]]" deepened to {{convert|953&nbsp;[[|mbar]]|inHg|2}} with a highest recorded wind of 119&nbsp;[[knots]] (61&nbsp;[[m{{convert|220|km/s]])h|mph|abbr=on}}, resulting in the loss of 19 lives', 15 &nbsp;million trees, widespread damage to homes and an estimated economic cost of [[pound sterling|£]]1.2&nbsp;billion ([[United States dollar|US$]]2.3&nbsp;billion).<ref name="MetoGreatStorm87"> {{cite web

| title = The Great Storm of 1987

| publisher = [http://www.metoffice.gov.uk [Met Office]]

| url = http://www.metometoffice.gov.uk/education/secondary/students/1987.html

| access-date = 2006-10-30 |archive-url=https://web.archive.org/web/20070402210526/http://www.metoffice.gov.uk/education/secondary/students/1987.html |archive-date=2007-04-02}}</ref>

| accessdate = 2006-10-30 }}</ref><ref name="C4GreatStorm87"> {{cite web

| title = What we should fear in 2006

| author = Bill McGuire

| publisher = [http://www.channel4.com/news/ Channel 4 News]

| date = [[2005-12-22]]

| url = http://www.channel4.com/news/special-reports/special-reports-storypage.jsp?id=1409&parasStartAt=2

| accessdate = 2006-10-30 }}</ref>

WhileAlthough most tropical cyclones that become extratropical quickly dissipate or are absorbed by another weather system, they can still retain winds of hurricane or gale force. In 1954, [[Hurricane Hazel]] became extratropical over [[North Carolina]] whileas a strong Category &nbsp;3 storm. The [[Columbus Day Storm of 1962]], which evolved from the remains of Typhoon Freda, caused heavy damage well north in [[Oregon]] and [[Washington (U.S. state)|Washington]] states, with widespread damage equivalent to at least a Category &nbsp;3 or higher hurricane. MoreIn recently2005, [[Hurricane Wilma]] in 2005 began to lose tropical characteristics while still sporting Category &nbsp;3-force winds (and became fully extratropical while stillas a Category &nbsp;1 storm).<ref name="Wilma">{{cite web

| title = Tropical Cyclone Report&nbsp;— Hurricane Wilma

<ref name="Wilma">{{cite web

|author1= Richard J. Pasch |author2=Eric S. Blake |author3= Hugh D. Cobb III |author4=David P Roberts

| title = Tropical Cyclone Report - Hurricane Wilma

|name-list-style=amp| publisher = National Hurricane Center (NOAA)

| author = Richard J. Pasch; Eric S. Blake;, Hugh D. Cobb III; and David P Roberts

| date = 2006-01-12

| publisher = [http://www.nhc.noaa.gov National Hurricane Center (NOAA)]

| url = {{NHC TCR url|id=AL252005_Wilma}}

| date = [[2006-01-12]]

| access-date = 2006-10-11 |format=PDF}}</ref>

| url = http://www.nhc.noaa.gov/pdf/TCR-AL252005_Wilma.pdf

| accessdate = 2006-10-11 }}</ref>

In summer, extratropical cyclones are generally weak, but some of the systems can cause significant [[flood]]s overland because of torrential rainfall. The [[July 2016 North China cyclone]] never brought [[gale]]-force sustained winds, but it caused devastating floods in [[mainland China]], resulting in at least 184 deaths and [[Renminbi|¥]]33.19&nbsp;billion ([[United States dollar|US$]]4.96&nbsp;billion) of damage.<ref name="mca_north">{{cite web|title=华北东北黄淮强降雨致289人死亡失踪|url=http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001291.shtml|publisher=Ministry of Civil Affairs|access-date=July 25, 2016|archive-url=https://web.archive.org/web/20160725134133/http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001291.shtml|archive-date=July 25, 2016|language=zh|date=July 25, 2016}}</ref><ref name="mca_southwest">{{cite web|title=西南部分地区洪涝灾害致80余万人受灾|url=http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001289.shtml|publisher=Ministry of Civil Affairs|access-date=July 25, 2016|archive-url=https://web.archive.org/web/20160725134427/http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001289.shtml|archive-date=July 25, 2016|language=zh|date=July 25, 2016}}</ref>

== See also ==

{{tcportal}}

{{Cyclones}}

* [[Surface weather analysis]]

* [[Cyclogenesis]]

* [[Tropical cyclones]]

* [[Tropical cyclogenesis]]

* [[Nor'easter]]

* [[European windstorm]]

An emerging topic is the co-occurrence of wind and precipitation extremes, so-called compound extreme events, induced by extratropical cyclones. Such compound events account for 3–5% of the total number of cyclones.<ref name=":0" />

== References ==

<div class="references-small">

===Climate and general circulation===

<references/>

In the classic analysis by [[Edward Lorenz]] (the [[Lorenz energy cycle]]),<ref>Holton, James R. 1992 An introduction to dynamic meteorology / James R. Holton Academic Press, San Diego : https://www.loc.gov/catdir/toc/els032/91040568.html</ref> extratropical cyclones (so-called atmospheric transients) acts as a mechanism in converting potential energy that is created by pole to equator temperature gradients to eddy kinetic energy. In the process, the pole-equator temperature gradient is reduced (i.e. energy is transported poleward to warm up the higher latitudes).{{Citation needed|date=January 2021}}

</div>

The existence of such transients are also closely related to the formation of the Icelandic and Aleutian Low&nbsp;— the two most prominent general circulation features in the mid- to sub-polar northern latitudes.<ref>Linear Stationary Wave Simulations of the Time-Mean Climatological Flow, Paul J. Valdes, [[Brian Hoskins|Brian J. Hoskins]], Journal of the Atmospheric Sciences 1989 46:16, 2509–2527</ref> The two lows are formed by both the transport of kinetic energy and the latent heating (the energy released when water phase changed from vapor to liquid during precipitation) from the mid- latitude cyclones.{{Citation needed|date=January 2021}}

==Historic storms==

[[File:Antarctic Low 2022-10-16 2200Z.jpg|thumb|The [[October 2022 Southern Ocean cyclone]], the most intense extratropical cyclone on record]]

The most intense extratropical cyclone on record was [[October 2022 Southern Ocean cyclone|a cyclone]] in the [[Southern Ocean]] in October 2022. An analysis by the [[European Centre for Medium-Range Weather Forecasts]] estimated a pressure of {{cvt|900.7|mbar|inHg}} and a subsequent analysis published in ''[[Geophysical Research Letters]]'' estimated a pressure of {{cvt|899.91|mbar|inHg}}.<ref>{{cite web |last1=Hewson |first1=Tim |last2=Day |first2=Jonathan |last3=Hersbach |first3=Hans |title=The deepest extratropical cyclone of modern times? |url=https://www.ecmwf.int/en/newsletter/174/news/deepest-extratropical-cyclone-modern-times |website=Newsletter |publisher=European Centre for Medium-Range Weather Forecasts |access-date=8 November 2023 |date=January 2023}}</ref><ref name="GRL">{{cite journal |last1=Lin |first1=Peiyi |last2=Zhong |first2=Rui |last3=Yang |first3=Qinghua |last4=Clem |first4=Kyle R. |last5=Chen |first5=Dake |title=A Record-Breaking Cyclone Over the Southern Ocean in 2022 |journal=Geophysical Research Letters |date=28 July 2023 |volume=50 |issue=14 |doi=10.1029/2023GL104012|bibcode=2023GeoRL..5004012L |doi-access=free}}</ref> The same ''Geophysical Research Letters'' article notes at least five other extratropical cyclones in the Southern Ocean with a pressure under {{cvt|915|mbar|inHg}}.<ref name="GRL" />

In the North Atlantic Ocean, the most intense extratropical cyclone was the [[Braer Storm]], which reached a pressure of {{cvt|914|mbar|inHg}} in early January 1993.<ref>{{cite journal|last1=Odell|first1=Luke|last2=Knippertz|first2=Peter|last3=Pickering|first3=Steven|last4=Parkes|first4=Ben|last5=Roberts|first5=Alexander|title=The Braer storm revisited|journal=Weather|date=April 2013|volume=68|issue=4|pages=105–111|doi=10.1002/wea.2097|bibcode=2013Wthr...68..105O|s2cid=120025537|url=http://eprints.whiterose.ac.uk/76587/7/s1-ln138778891716616411-1939656818Hwf-1327875997IdV-53057588613877889PDF_HI0001%281%29_with_coversheet.pdf |access-date=8 November 2023}}</ref> Before the Braer Storm, an extratropical cyclone near [[Greenland]] in December 1986 reached a minimum pressure of at least {{cvt|916|mbar|inHg}}. The [[Deutscher Wetterdienst|West German Meteorological Service]] marked a pressure of {{cvt|915|mbar|inHg}}, with the possibility of a pressure between {{cvt|912-913|mbar|inHg}}, lower than the Braer Storm.<ref>{{cite journal|last1=Burt|first1=S. D.|title=A New North Atlantic Low Pressure Record|journal=Weather|date=February 1987|volume=42|issue=2|pages=53–56|doi=10.1002/j.1477-8696.1987.tb06919.x|url=http://shpud.com/atlantic-storm-1986.pdf|access-date=16 August 2015|bibcode=1987Wthr...42...53B}}</ref>

The most intense extratropical cyclone across the North Pacific Ocean occurred in November 2014, when [[November 2014 Bering Sea cyclone|a cyclone]] partially related to [[Typhoon Nuri (2014)|Typhoon Nuri]] reached a record low pressure of {{cvt|920|mbar|inHg}}.<ref>{{cite web |title=Marine Weather Warning for GMDSS Metarea XI 2014-11-08T06:00:00Z |url=https://www.wis-jma.go.jp/cms/warning/2014/11/08/marine-weather-warning-for-gmdss-metarea-xi-2014-11-08t060000z/ |publisher=Japan Meteorological Agency |access-date=12 November 2023 |archive-url=https://web.archive.org/web/20141108103401/https://www.wis-jma.go.jp/cms/warning/2014/11/08/marine-weather-warning-for-gmdss-metarea-xi-2014-11-08t060000z/ |archive-date=8 November 2014 |date=8 November 2014 |url-status=dead}}</ref><ref>{{cite news |last1=Wiltgen |first1=Nick |last2=Erdman |first2=Jonatha |title=Bering Sea Superstorm Among the Strongest Extratropical Cyclones on Record |url=https://weather.com/storms/hurricane/news/bering-sea-superstorm-alaska-aleutians-20141105 |access-date=12 November 2023 |publisher=The Weather Channel |date=9 November 2014}}</ref> In October 2021, the [[October 2021 Northeast Pacific bomb cyclone|most intense]] [[Pacific Northwest windstorm]] occurred off the coast of [[Oregon]], peaking with a pressure of {{cvt|942|mbar|inHg}}.<ref>{{cite news |last1=Zaffino |first1=Matt |title=Bomb cyclone: What it is, where the term came from and why it's not a hurricane |url=https://www.kgw.com/article/weather/why-bomb-cyclone-is-not-a-hurricane/283-c58389c6-b135-4871-9bd2-0384bf80ab96 |access-date=12 November 2023 |publisher=KGW |date=27 October 2021}}</ref> One of the strongest [[nor'easter]]s occurred in [[January 2018 North American blizzard|January 2018]], in which a cyclone reached a pressure of {{cvt|950|mbar|inHg}}.<ref>{{cite web |last1=Kong |title=STORM SUMMARY NUMBER 5 FOR EASTERN U.S. WINTER STORM |url=https://www.wpc.ncep.noaa.gov/winter_storm_summaries/storm23/stormsum_5.html |publisher=Wea |access-date=19 November 2023 |archive-url=https://web.archive.org/web/20180105070213/https://www.wpc.ncep.noaa.gov/winter_storm_summaries/storm23/stormsum_5.html |archive-date=5 January 2018 |date=4 January 2018 |url-status=dead}}</ref>

Extratropical cyclones have been responsible for some of the most damaging floods in European history. The [[Great storm of 1703]] killed over 8,000 people and the [[North Sea flood of 1953]] killed over 2,500 and destroyed 3,000 houses.<ref>{{Cite web |title=Freak storm dissipates over England |date=13 November 2009 |url=https://www.history.com/this-day-in-history/freak-storm-dissipates-over-england |access-date=6 December 2023 |publisher=HISTORY}}</ref><ref>{{cite web |title=The flood of 1953 - Rescue and consequences |url=http://www.deltawerken.com/Rescue-and-consequences/309.html |publisher=Deltawerken |access-date=6 December 2023 |archive-url=https://web.archive.org/web/20190506151002/http://www.deltawerken.com/Rescue-and-consequences/309.html |archive-date=6 May 2019}}</ref> In 2002, [[2002 European floods|floods in Europe]] caused by two [[genoa low]]s caused $27.115 billion in damages and 232 fatalities, the most damaging flood in European since at least 1985.<ref>{{cite web |title=System Explanation of Floods in Central Europe |url=http://nadine.helmholtz-eos.de/risks/flood/info/fl_system_en.html |publisher=Natural Disaster Networking Platform |access-date=6 December 2023 |archive-url=https://web.archive.org/web/20080304064019/http://nadine.helmholtz-eos.de/risks/flood/info/fl_system_en.html |archive-date=4 March 2008 |url-status=dead}}</ref><ref>{{cite journal |last1=Kundzewicz |first1=Zbigniew W. |last2=Pińskwar |first2=Iwona |last3=Brakenridge |first3=G. Robert |title=Large floods in Europe, 1985–2009 |url=https://floodobservatory.colorado.edu/Publications/Europefloods.pdf |journal=Hydrological Sciences Journal |access-date=6 December 2023 |___location=Hydrological Sciences Journal |pages=1–7 |doi=10.1080/02626667.2012.745082 |date=January 2013|volume=58 |issue=1 |bibcode=2013HydSJ..58....1K }}</ref> In late December 1999, Cyclones [[Cyclone Lothar|Lothar]] and [[Cyclone Martin (1999)|Martin]] caused 140 deaths combined and over $23 billion in damages in Central Europe, the costliest European windstorms in history.<ref>{{cite news |last1=Tatge |first1=Yörn |title=Looking Back, Looking Forward: Anatol, Lothar and Martin Ten Years Later |url=https://www.air-worldwide.com/publications/air-currents/looking-back-looking-forward-anatol-lothar-and-martin-ten-years-later/ |access-date=6 December 2023 |publisher=Verisk |date=9 December 2009}}</ref><ref>{{cite news |title=Christmas 20 years ago: Storms Lothar and Martin wreak havoc across Europe |url=https://www.swissre.com/risk-knowledge/mitigating-climate-risk/winter-storms-in-europe/storms-lothar-martin-wreak-havoc-across-europe.html |access-date=6 December 2023 |publisher=Swiss Re}}</ref>

[[File:Apr 27 2011 tornado outbreak Southern USA.jpg|thumb|The extratropical cyclone responsible for the [[2011 Super Outbreak]]]]

In October 2012, [[Hurricane Sandy]] transitioned into an extratropical cyclone off the coast of the [[Northeastern United States]]. The storm killed over 100 people and caused $65 billion in damages, the second [[List of the costliest tropical cyclones|costliest tropical cyclone]] at the time.<ref>{{cite report |url={{NHC TCR url|id=AL182012_Sandy}} |title=Hurricane Sandy: October 22&nbsp;– 29, 2012 |author=Blake, Eric S |author2=Kimberlain, Todd B |date=12 February 2013 |author3=Berg, Robert J |author4=Cangialosi, John P |author5=Beven II, John L |publisher=National Hurricane Center |access-date=21 December 2023 }}</ref><ref>{{cite report|title=Costliest U.S. tropical cyclones tables updated|url=https://www.nhc.noaa.gov/news/UpdatedCostliest.pdf|publisher=National Hurricane Center|date=26 January 2018|access-date=21 December 2023}}</ref> Other extratropical cyclones have been related to major [[tornado outbreaks]]. The tornado outbreaks of [[1965 Palm Sunday tornado outbreak|April 1965]], [[1974 Super Outbreak|April 1974]] and [[2011 Super Outbreak|April 2011]] were all large, violent, and deadly tornado outbreaks related to extratropical cyclones.<ref>{{cite web |title=Storm Events Database |url=https://www.ncdc.noaa.gov/stormevents/ |publisher=National Centers for Environmental Information |access-date=5 January 2024}}</ref><ref>{{cite web|url=http://www.wpc.ncep.noaa.gov/winter_storm_summaries/2011/storm11/stormsum_11.html|title=Storm Summary Number 11 For Central U.S. Heavy Rain Event|author=Mike Soltow|publisher=[[Weather Prediction Center]]|date=25 April 2011|access-date=5 January 2024}}</ref><ref>{{cite web |last1=Corfidi |first1=Stephen F. |last2=Levit |first2=Jason J. |last3=Weiss |first3=Steven J. |title=The Super Outbreak: Outbreak of the Century |url=https://www.spc.noaa.gov/publications/corfidi/3apr74.pdf |publisher=Storm Prediction Center |access-date=5 January 2024}}</ref><ref>{{cite web |title=April 11th 1965 Palm Sunday Tornado Outbreak |url=https://www.weather.gov/iwx/1965_palmsunday_50 |publisher=National Weather Service |access-date=5 January 2024}}</ref> Similarly, [[winter storms]] in [[Great Blizzard of 1888|March 1888]], [[Great Appalachian Storm of 1950|November 1950]] and [[1993 Storm of the Century|March 1993]] were responsible for over 300 deaths each.<ref>{{cite web |title=On Mar 12 in weather history... |url=http://www.crh.noaa.gov/iwx/program_areas/wxhisttdy/index.php?url=Mar12 |publisher=National Weather Service |access-date=20 January 2024 |archive-url=https://web.archive.org/web/20140201165648/http://www.crh.noaa.gov/iwx/program_areas/wxhisttdy/index.php?url=Mar12 |archive-date=1 February 2014 |url-status=dead}}</ref><ref>{{cite web |archive-date=15 August 2000 |title=NOAA's Top U.S. Weather, Water and Climate Events of the 20th Century |url=http://www.noaanews.noaa.gov/stories/s334c.htm |publisher=National Ocean and Atmospheric Administration |access-date=20 January 2024 |archive-url=https://web.archive.org/web/20000815070452/http://www.noaanews.noaa.gov/stories/s334c.htm}}</ref><ref>{{cite web |title=Superstorm of 1993 "Storm of the Century" |url=https://www.weather.gov/ilm/Superstorm93 |publisher=National Weather Service |access-date=20 January 2024}}</ref>

In [[December 1960 nor'easter|December 1960]] a nor'easter caused at least 286 deaths in the Northeastern United States, one of the deadliest nor'easters on record.<ref>{{cite news |title=East Thaws Out From Freeze; 286 Left Dead |url=https://www.newspapers.com/article/pasadena-independent/2282541/ |access-date=23 January 2024 |agency=Pasadena Independent |publisher=Newspapers.com |date=15 December 1960}}</ref> 62 years later in [[December 2022 North American winter storm|2022]], a winter storm caused $8.5 billion in damages and 106 deaths across the United States and Canada.<ref>{{cite web |title=Billion-Dollar Weather and Climate Disasters |url=https://www.ncei.noaa.gov/access/billions/events |publisher=National Centers for Environmental Information. |access-date=23 January 2024}}</ref>

In September 1954, the extratropical remnants of [[Typhoon Marie (1954)|Typhoon Marie]] caused the ''[[Tōya Maru]]'' to [[run aground]] and [[capsize]] in the [[Tsugaru Strait]]. 1,159 out of the 1,309 on board were killed, making it one of the deadliest typhoons in [[Japanese history]].<ref>{{Cite web|last=|first=|date=|title=洞爺丸台風 昭和29年（1954年） ９月24日～９月27日|url=https://www.data.jma.go.jp/obd/stats/data/bosai/report/1954/19540924/19540924.html|access-date=23 January 2024 |website=www.data.jma.go.jp|language=ja}}</ref><ref>{{Cite web|last=((第２版,日本大百科全書(ニッポニカ) ))|first=((百科事典マイペディア,デジタル大辞泉プラス,世界大百科事典 ))|date=|title=洞爺丸台風(とうやまるたいふう)とは|url=https://kotobank.jp/word/%E6%B4%9E%E7%88%BA%E4%B8%B8%E5%8F%B0%E9%A2%A8-855386|access-date=23 January 2024|website=コトバンク|language=ja}}</ref> In July 2016, [[July 2016 North China cyclone|a cyclone]] in Northern China left 184 dead, 130 missing, and caused over $4.96 billion in damages.<ref>{{cite web|title=华北东北黄淮强降雨致289人死亡失踪|url=http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001291.shtml|publisher=Ministry of Civil Affairs|accessdate=23 January 2024|archiveurl=https://web.archive.org/web/20160725134133/http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001291.shtml|archivedate=25 July 2016|language=Chinese|date=23 July 2016}}</ref><ref>{{cite web|title=西南部分地区洪涝灾害致80余万人受灾|url=http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001289.shtml|publisher=Ministry of Civil Affairs|accessdate=23 January 2024|archiveurl=https://web.archive.org/web/20160725134427/http://www.mca.gov.cn/article/yw/jzjz/zqkb/zqhz/201607/20160700001289.shtml|archivedate=25 July 2016|language=Chinese|date=25 July 2016}}</ref>

For older extratropical storms occurring before the 20th century, new [[Paleotempestology|paleotempestological]] methods can be used to assess their intensity. Cross-referencing environmental and historical records in Western Europe has highlighted the intense storms of 1351-1352, 1469, 1645, 1711 and 1751, which caused severe damage and long-lasting flooding along much of Europe's coastline.<ref>{{Cite journal |last1=Pouzet |first1=Pierre |last2=Maanan |first2=Mohamed |date=2020-07-21 |title=Climatological influences on major storm events during the last millennium along the Atlantic coast of France |journal=Scientific Reports |language=en |volume=10 |issue=1 |pages=12059 |doi=10.1038/s41598-020-69069-w |issn=2045-2322 |pmc=7374694 |pmid=32694711|bibcode=2020NatSR..1012059P }}</ref>

==See also==

{{portal|Weather}}

*[[Nor'easter]]

*[[Sudestada]]

*[[Cyclogenesis]]

*[[Explosive cyclogenesis]]

*[[Cyclolysis]]

==References==

{{reflist}}

==External links==

*{{commons category-inline}}

{{Cyclones}}

{{DEFAULTSORT:Extratropical Cyclone}}

[[Category:Midlatitude weather]]

[[Category:TropicalExtratropical cyclonecyclones| meteorology]]

[[Category:TypesArticles ofcontaining cyclonevideo clips]]