Editing Thunderstorm (section)

==Classification==
[[File:CAPE vs SHEAR.svg|upright=1.5|thumb|Conditions favorable for thunderstorm types and complexes]]

There are four main types of thunderstorms: single-cell, multi-cell, squall line (also called multi-cell line) and supercell.<ref name="Thunderstorms and Tornadoes"/> Which type forms depends on the instability and relative wind conditions at different layers of the atmosphere ("[[wind shear]]"). Single-cell thunderstorms form in environments of low vertical wind shear and last only 20–30 minutes.

Organized thunderstorms and thunderstorm clusters/lines can have longer life cycles as they form in environments of significant vertical wind shear, normally greater than {{convert|25|kn|m/s}} in the lowest {{convert|6|km|mi}} of the [[troposphere]],<ref>Markowski, Paul and Yvette Richardson.  Mesoscale Meteorology in Midlatitudes.  John Wiley & Sons, Ltd., 2010.
pp. 209.</ref> which aids the development of stronger updrafts as well as various forms of severe weather. The supercell is the strongest of the thunderstorms,<ref name="Thunderstorms and Tornadoes"/> most commonly associated with large hail, high winds, and tornado formation.  [[Precipitable water]] values of greater than {{convert|31.8|mm|in}} favor the development of organized thunderstorm complexes.<ref>{{cite journal | author = Maddox R.A., Chappell C.F., Hoxit L.R. | year = 1979 | title = Synoptic and meso-α scale aspects of flash flood events | journal = Bull. Amer. Meteor. Soc. | volume = 60 | issue = 2| pages = 115–123 | doi = 10.1175/1520-0477-60.2.115 | bibcode = 1979BAMS...60..115M | doi-access = free }}</ref> Those with heavy rainfall normally have precipitable water values greater than {{convert|36.9|mm|in}}.<ref>Schnetzler, Amy Eliza.  Analysis of Twenty-Five Years of Heavy Rainfall Events in the Texas Hill Country.  University of Missouri-Columbia, 2008.  pp. 74.</ref> Upstream values of [[Atmospheric instability#CAPE and CIN|CAPE]] of greater than 800 J/kg are usually required for the development of organized convection.<ref>Markowski, Paul and Yvette Richardson.  Mesoscale Meteorology in Midlatitudes.  John Wiley & Sons, Ltd., 2010. pp. 215, 310.</ref>

===Single-cell===
{{Main|Air-mass thunderstorm}}
[[File:Thunderstorm over Wagga Wagga.jpg|thumb|upright|left|A single-cell thunderstorm over [[Wagga Wagga]]]]

This term technically applies to a single thunderstorm with one main updraft. Also known as [[air-mass thunderstorm]]s, these are the typical summer thunderstorms in many temperate locales. They also occur in the cool unstable air that often follows the passage of a [[weather fronts|cold front]] from the sea during winter. Within a cluster of thunderstorms, the term "cell" refers to each separate principal updraft. Thunderstorm cells occasionally form in isolation, as the occurrence of one thunderstorm can develop an outflow boundary that sets up new thunderstorm development. Such storms are rarely severe and are a result of local atmospheric instability; hence the term "air mass thunderstorm". When such storms have a brief period of severe weather associated with them, it is known as a pulse severe storm. Pulse severe storms are poorly organized and occur randomly in time and space, making them difficult to forecast. Single-cell thunderstorms normally last 20–30&nbsp;minutes.<ref name="tsbasics"/>

===Multi-cell clusters===
{{Main|Multicellular thunderstorm}}
[[File:8402 STS41B Challenger Thunderstorms over Brazil.jpg|thumb|A group of thunderstorms over Brazil photographed by the [[Space Shuttle Challenger|Space Shuttle ''Challenger'']]]]

This is the most common type of thunderstorm development. ''Mature thunderstorms'' are found near the center of the cluster, while dissipating thunderstorms exist on their downwind side. ''Multicell storms'' form as clusters of storms but may then evolve into one or more [[squall line]]s. While each cell of the cluster may only last 20&nbsp;minutes, the cluster itself may persist for hours at a time. They often arise from convective updrafts in or near mountain ranges and linear weather boundaries, such as strong cold fronts or troughs of low pressure. These type of storms are stronger than the single-cell storm, yet much weaker than the supercell storm. Hazards with the multicell cluster include moderate-sized hail, flash flooding, and weak tornadoes.<ref name="tsbasics"/>

===Multicell lines===
{{Main|Squall line}}
{{See also|List of derecho events}}

A squall line is an elongated line of [[thunderstorms#Severe thunderstorms|severe thunderstorms]] that can form along or ahead of a [[cold front]].<ref>{{cite web|url=http://amsglossary.allenpress.com/glossary/search?id=squall-line1|author=Glossary of Meteorology|title=Squall line|date=2009|access-date=14 June 2009|publisher=[[American Meteorological Society]]|url-status=dead|archive-url=https://web.archive.org/web/20081217175139/http://amsglossary.allenpress.com/glossary/search?id=squall-line1|archive-date=17 December 2008}}</ref><ref>{{cite web|url=http://amsglossary.allenpress.com/glossary/search?id=prefrontal-squall-line1|author=Glossary of Meteorology|title=Prefrontal squall line|date=2009|access-date=14 June 2009|publisher=[[American Meteorological Society]]|url-status=dead|archive-url=https://web.archive.org/web/20070817224959/http://amsglossary.allenpress.com/glossary/search?id=prefrontal-squall-line1|archive-date=17 August 2007}}</ref> In the early 20th century, the term was used as a synonym for [[cold front]].<ref name="OU">{{cite web|author=University of Oklahoma|date=2004|url=http://weather.ou.edu/~metr4424/Files/Norwegian_Cyclone_Model.pdf|title=The Norwegian Cyclone Model|access-date=17 May 2007 |archive-url = https://web.archive.org/web/20060901163934/http://weather.ou.edu/~metr4424/Files/Norwegian_Cyclone_Model.pdf |archive-date = 1 September 2006}}</ref> The squall line contains heavy [[precipitation (meteorology)|precipitation]], [[hail]], frequent [[lightning]], strong straight line winds, and possibly [[tornado]]es and [[waterspouts]].<ref>{{cite web|author=Office of the Federal Coordinator for Meteorology |date=2008 |url=http://www.ofcm.gov/slso/pdf/slsochp2.pdf |title=Chapter 2: Definitions |pages=2–1 |publisher=[[NOAA]] |access-date=3 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090506002006/http://www.ofcm.gov/slso/pdf/slsochp2.pdf |archive-date=6 May 2009 }}</ref> [[Severe weather]] in the form of strong straight-line winds can be expected in areas where the squall line itself is in the shape of a [[bow echo]], within the portion of the line that bows out the most.<ref>{{cite web|url=http://amsglossary.allenpress.com/glossary/search?p=1&query=bow+echo&submit=Search|author=Glossary of Meteorology|title=Bow echo|date=2009|access-date=14 June 2009|publisher=[[American Meteorological Society]]|url-status=dead|archive-url=https://web.archive.org/web/20110606103620/http://amsglossary.allenpress.com/glossary/search?p=1&query=bow+echo&submit=Search|archive-date=6 June 2011}}</ref> [[Tornado]]es can be found along waves within a [[line echo wave pattern]], or LEWP, where mesoscale [[low pressure area]]s are present.<ref>{{cite book|author=Glossary of Meteorology|date=2009|url=http://amsglossary.allenpress.com/glossary/search?id=line-echo-wave-pattern1|title=Line echo wave pattern|publisher=[[American Meteorological Society]]|isbn=978-1-878220-34-9|access-date=3 May 2009|url-status=dead|archive-url=https://web.archive.org/web/20080924175030/http://amsglossary.allenpress.com/glossary/search?id=line-echo-wave-pattern1|archive-date=24 September 2008}}</ref> Some bow echoes in the summer are called [[derecho]]s, and move quite fast through large sections of territory.<ref name="noaa">{{cite web| url=http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm| title=About Derechos| publisher=[[Storm Prediction Center]], NCEP, NWS, NOAA Web Site| author= Stephen F. Corfidi| author2= Jeffry S. Evans| author3= Robert H. Johns| name-list-style= amp | date=2015| access-date=17 February 2015}}</ref> On the back edge of the rain shield associated with mature squall lines, a [[wake low]] can form, which is a mesoscale low pressure area that forms behind the mesoscale high pressure system normally present under the rain canopy, which are sometimes associated with a [[heat burst]].<ref>{{cite book |author= Glossary of Meteorology |title= Heat burst |publisher= [[American Meteorological Society]] |date= 2009 |url= http://amsglossary.allenpress.com/glossary/search?id=heat-burst1 |isbn= 978-1-878220-34-9 |access-date= 14 June 2009 |url-status= dead |archive-url= https://web.archive.org/web/20110606102146/http://amsglossary.allenpress.com/glossary/search?id=heat-burst1 |archive-date= 6 June 2011 }}</ref> This kind of storm is also known as "Wind of the Stony Lake" ({{Lang-zh|s=石湖风|t=石湖風}}; shi2 hu2 feng1) in southern China.<ref>{{cite web | date = 17 June 2005 | url = http://www.hko.gov.hk/education/edu01met/wxphe/ele_squalle.htm | title = Squall lines and "Shi Hu Feng" – what you want to know about the violent squalls hitting Hong Kong on 9 May 2005 | publisher = Hong Kong Observatory | access-date = 23 August 2006 | archive-date = 25 October 2019 | archive-url = https://web.archive.org/web/20191025222307/http://www.hko.gov.hk/education/edu01met/wxphe/ele_squalle.htm | url-status = dead }}</ref>

===Supercells===
{{Main|Supercell}}
[[File:Thunderhead.anvil.jpg|thumb|The setting sun illuminates the top of a classic anvil-shaped thunderstorm cloud in eastern [[Nebraska]], United States.]]

Supercell storms are large, usually [[severe weather|severe]], quasi-steady-state storms that form in an environment where wind speed or wind direction varies with height ("[[wind shear]]"), and they have separate downdrafts and updrafts (i.e., where its associated precipitation is not falling through the updraft) with a strong, rotating updraft (a "[[mesocyclone]]"). These storms normally have such powerful updrafts that the top of the supercell storm cloud (or anvil) can break through the [[troposphere]] and reach into the lower levels of the [[stratosphere]]. Supercell storms can be {{convert|24|km|mi|0}} wide. Research has shown that at least 90&nbsp;percent of supercells cause [[severe weather]].<ref name="motion">{{cite web|url=http://www.crh.noaa.gov/images/unr/soo/scm/ZB06.pdf|title=Operational Forecasting of Supercell Motion: Review and Case Studies Using Multiple Datasets|author=Jon W. Zeitler|author2=Matthew J. Bunkers|name-list-style=amp|date=March 2005|access-date=30 August 2009|publisher=[[National Weather Service]] Forecast Office, [[Riverton, Wyoming]]}}</ref> These storms can produce destructive [[tornado]]es, extremely large [[hail]]stones ({{convert|10|cm|in|0|disp=or}} diameter), [[straight-line wind]]s in excess of {{convert|130|km/h|mph|abbr=on}}, and [[flash flood]]s. In fact, research has shown that most tornadoes occur from this type of thunderstorm.<ref>{{cite web|date=4 October 1999|url=http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/type/spr/home.rxml |title=Supercell Thunderstorms|work=Weather World 2010 Project|publisher=University of Illinois|access-date=23 August 2006}}</ref> Supercells are generally the strongest type of thunderstorm.<ref name="tsbasics"/>

===Severe thunderstorms===
In the United States, a thunderstorm is classed as severe if winds reach at least {{convert|93|km/h|mph}}, hail is {{convert|25|mm|in|0}} in diameter or larger, or if [[funnel cloud]]s or [[tornado]]es are reported.<ref>{{cite web  | title =Weather Glossary – S  | author =National Weather Service  | author-link =National Weather Service | publisher=[[National Oceanic and Atmospheric Administration]] | date =21 April 2005 | url =http://www.weather.gov/glossary/index.php?letter=s  | access-date =17 June 2007 }}</ref><ref>{{cite video  | people = Kim Runk  | title = 1" Hail  | medium = .wmv  | publisher = NOAA  | location = Silver Spring, Maryland|url= http://www.crh.noaa.gov/crh/One_Inch_Hail_Podcast.wmv  |date = 2009}}</ref><ref>{{cite web|url=http://www.wrh.noaa.gov/psr/pns/2009/April/NewHailCriteria.php?wfo=psr|author=[[National Weather Service]] Forecast Office, [[Phoenix, Arizona]]|title=New Hail Criteria|access-date=3 September 2009|date=7 April 2009}}</ref> Although a funnel cloud or tornado indicates a severe thunderstorm, a [[tornado warning]] is issued in place of a [[severe thunderstorm warning]]. A severe thunderstorm warning is issued if a thunderstorm becomes severe, or will soon turn severe. In Canada, a rainfall rate greater than {{convert|50|mm|in|0}} in one hour, or {{convert|75|mm|in|0}} in three hours, is also used to indicate severe thunderstorms.<ref>{{cite web|url=http://www.on.ec.gc.ca/severe-weather/summerwx_factsheet_e.html |title=Fact Sheet – Summer Severe Weather Warnings |author=[[Environment Canada]] Ontario Region |date=24 May 2005 |access-date=3 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090228151724/http://www.on.ec.gc.ca/severe-weather/summerwx_factsheet_e.html |archive-date=28 February 2009 }}</ref> Severe thunderstorms can occur from any type of storm cell. However, [[multicellular thunderstorm|multicell]], [[supercell]], and squall lines represent the most common forms of thunderstorms that produce severe weather.<ref name="motion"/>

===Mesoscale convective systems===
{{See also|Mesoscale convective system}}
[[File:June 2022 Midwest Mesoscale convective complex-derecho.jpg|thumb|left|MCC moving through the [[Great Lakes region]]: on 13 June 2022, at 18:45 UTC]]

A [[mesoscale convective system]] (MCS) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than [[extratropical cyclone]]s, and normally persists for several hours or more.<ref>{{cite web|url=http://amsglossary.allenpress.com/glossary/search?p=1&query=mesoscale+convective+system&submit=Search|title=Mesoscale convective system|date=2009|access-date=27 June 2009|author=Glossary of Meteorology|publisher=[[American Meteorological Society]]|url-status=dead|archive-url=https://web.archive.org/web/20110606103649/http://amsglossary.allenpress.com/glossary/search?p=1&query=mesoscale+convective+system&submit=Search|archive-date=6 June 2011}}</ref> A mesoscale convective system's overall cloud and precipitation pattern may be round or linear in shape, and include weather systems such as [[tropical cyclone]]s, [[squall line]]s, [[lake-effect snow]] events, [[polar low]]s, and [[mesoscale convective complex]]es (MCCs), and they generally form near [[weather front]]s. Most mesoscale convective systems develop overnight and continue their lifespan through the next day.<ref name="Extreme Weather" /> They tend to form when the surface temperature varies by more than {{convert|5|C-change|sigfig=1}} between day and night.<ref>{{cite journal |last1 = Haerter |first1 = Jan O. |last2 = Meyer| first2 = Bettina| last3 = Nissen| first3 = Silas Boye |title=Diurnal self-aggregation |journal=npj Climate and Atmospheric Science |date=30 July 2020 |volume=3 |issue = 1 |page = 30 |doi=10.1038/s41612-020-00132-z |arxiv= 2001.04740 |bibcode = 2020npCAS...3...30H |s2cid = 220856705 }}</ref> The type that forms during the warm season over land has been noted across North America, Europe, and Asia, with a maximum in activity noted during the late afternoon and evening hours.<ref>{{cite web|author=William R. Cotton|author2=Susan van den Heever|author3=Israel Jirak|name-list-style=amp|date=2003|url=http://rams.atmos.colostate.edu/at540/fall03/fall03Pt9.pdf|title=Conceptual Models of Mesoscale Convective Systems: Part 9|publisher=[[Colorado State University]]|access-date=23 March 2008}}</ref><ref>{{cite journal|author=C. Morel|author2=S. Senesi|name-list-style=amp|date=2002|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=13876728 |title=A climatology of mesoscale convective systems over Europe using satellite infrared imagery II: Characteristics of European mesoscale convective systems|journal=Quarterly Journal of the Royal Meteorological Society|issn=0035-9009|access-date=2 March 2008|volume=128|issue=584|page=1973|doi=10.1256/003590002320603494|bibcode = 2002QJRMS.128.1973M |s2cid=120021136 |doi-access=free}}</ref>

Forms of MCS that develop in the tropics are found in use either the [[Intertropical Convergence Zone]] or [[monsoon trough]]s, generally within the warm season between spring and fall. More intense systems form over land than over water.<ref>{{cite journal|author=Semyon A. Grodsky|author2=James A. Carton|name-list-style=amp|url=http://www.atmos.umd.edu/~carton/pdfs/grodsky&carton03.pdf|date=15 February 2003|publisher=[[University of Maryland, College Park]]|title=The Intertropical Convergence Zone in the South Atlantic and the Equatorial Cold Tongue|journal=Journal of Climate|volume=16|issue=4|pages=723|access-date=5 June 2009|bibcode=2003JCli...16..723G|doi=10.1175/1520-0442(2003)016<0723:TICZIT>2.0.CO;2|s2cid=10083024 }}</ref><ref>{{cite book|url=https://books.google.com/books?id=HiaP4yJ8wNMC&pg=PA40|title=Observations of surface to atmosphere interactions in the tropics|author=Michael Garstang|author2=David Roy Fitzjarrald|pages=40–41|date=1999|isbn=978-0-19-511270-2|publisher=Oxford University Press US}}</ref> One exception is that of [[lake-effect snow]] bands, which form due to cold air moving across relatively warm bodies of water, and occurs from fall through spring.<ref>{{cite web|author=B. Geerts|date=1998|url=http://www-das.uwyo.edu/~geerts/cwx/notes/chap10/lake_effect_snow.html|title=Lake Effect Snow|access-date=24 December 2008|publisher=[[University of Wyoming]]}}</ref> Polar lows are a second special class of MCS. They form at high latitudes during the cold season.<ref>{{cite book|author=E. A. Rasmussen|author2=J. Turner|name-list-style=amp|date=2003|title=Polar Lows: Mesoscale Weather Systems in the Polar Regions|publisher=Cambridge University Press|page=612|isbn=978-0-521-62430-5}}</ref> Once the parent MCS dies, later thunderstorm development can occur in connection with its remnant [[mesoscale convective vortex]] (MCV).<ref>{{cite web|title=3.5 The Influence of the Great Lakes on Warm Season Weather Systems During BAMEX|author=Lance F. Bosart|author2=Thomas J. Galarneau Jr.|name-list-style=amp|url=http://ams.confex.com/ams/pdfpapers/84665.pdf|publisher=6th [[American Meteorological Society]] Coastal Meteorology Conference|date=2005|access-date=15 June 2009}}</ref> Mesoscale convective systems are important to the [[United States rainfall climatology]] over the [[Great Plains]] since they bring the region about half of their annual warm season rainfall.<ref>{{cite web|author=William R. Cotton|author2=Susan van den Heever|author3=Israel Jirak|name-list-style=amp|url=http://rams.atmos.colostate.edu/at540/fall03/fall03Pt9.pdf|title=Conceptual Models of Mesoscale Convective Systems: Part 9|date=Fall 2003|access-date=23 March 2008}}</ref>