Tornado Alley

File:Tornado Alley.svg

Over the years, the location(s) of Tornado Alley have not been clearly defined. No definition of tornado alley has ever been officially designated by the National Weather Service (NWS). Thus, differences in location are the result of the different criteria used.{{cite web |title = Tornado FAQ |work = Storm Prediction Center |publisher = NOAA |date = January 29, 2007 |url = http://www.spc.noaa.gov/faq/tornado#alley1 |access-date = September 29, 2013 |url-status = live |archive-url = https://web.archive.org/web/20120302230203/http://www.spc.noaa.gov/faq/tornado/#alley1 |archive-date = March 2, 2012 }}

According to the National Severe Storms Laboratory (NSSL) FAQ, "Tornado Alley" is a term used by the media as a reference to areas that have higher numbers of tornadoes. A study of 1921–1995 tornadoes concluded almost one-fourth of all significant tornadoes occur in this area.{{cite web |title = Climatology Risk of Strong and Violent Tornadoes In the United States |publisher = Northern Illinois University & NOAA/ERL/National Severe Storms Laboratory |date = January 29, 2007 |url = http://www.nssl.noaa.gov/users/brooks/public_html/concannon |access-date = April 26, 2007 |url-status = live |archive-url = https://web.archive.org/web/20070503091216/http://www.nssl.noaa.gov/users/brooks/public_html/concannon/ |archive-date = May 3, 2007 }}

Illinois, Wisconsin, Minnesota, Indiana, Michigan, and western Ohio are sometimes included in Tornado Alley. Some research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian Prairies.{{cite web|url=https://www.usask.ca/water/news-and-events/news/news43.php |title=The new tornado alley |last=Ferguson |first=Mark |date=2012-10-09 |publisher=University of Saskatchewan |access-date=2014-01-16 |url-status=dead |archive-url=https://web.archive.org/web/20140118195234/http://www.usask.ca/water/news-and-events/news/news43.php |archive-date=2014-01-18 }}

No place on earth is entirely free of tornadoes, however, they occur much more frequently in the United States, particularly in the Central states, between the Rocky Mountains to the west and Appalachian Mountains to the east.{{cite web |title = Severe Weather 101: Tornado FAQ |work = National Severe Storms Laboratory |publisher = NOAA |date = January 29, 2007 |url = http://www.nssl.noaa.gov/education/svrwx101/tornadoes/faq |access-date = September 29, 2013 |url-status = live |archive-url = https://web.archive.org/web/20131030104520/http://www.nssl.noaa.gov/education/svrwx101/tornadoes/faq/ |archive-date = October 30, 2013 }} Texas has the most overall number of tornadoes of any state. Per data collected through 2007, Kansas and Oklahoma ranked first and second respectively in the number of tornadoes per area. However, in 2013 statistics from the National Climatic Data Center reported Florida ranked first in tornadoes per area, although Florida is not a part of Tornado Alley.{{cite web |title = Tornado Climatology |publisher = National Climatic Data Center |date = January 29, 2007 |url = http://www.ncdc.noaa.gov/oa/climate/severeweather/tornadoes.html |access-date = April 26, 2007 |url-status = live |archive-url = https://web.archive.org/web/20110629012820/http://www.ncdc.noaa.gov/oa/climate/severeweather/tornadoes.html |archive-date = June 29, 2011 }} Florida's high ranking on the tornado list also has to do with the fact that the state sees a high number of waterspouts, small tornadoes that form over water. Although strong land-tornadoes have hit Florida and reports show Florida has a very high number of overall tornadoes, the tornadoes in the state seldom reach the velocity of those that may occur in the Southern Plains. In the United States, tornadoes typically occur in late spring and early summer during the changing season patterns as a warm air mass typically collides with a cold air mass resulting in tornadoes.

Another criterion for the location of Tornado Alley can be where the strongest tornadoes occur more frequently.{{cite tech report |title=Taking Shelter from the Storm: Building a Safe Room for Your Home or Small Business |number=P-320 |institution=FEMA |date=December 2014 |url=http://www.fema.gov/media-library-data/1418837471752-920f09bb8187ee15436712a3e82ce709/FEMA_P-320_2014_508.pdf |access-date=July 18, 2015 |edition=4th |url-status=live |archive-url=https://web.archive.org/web/20150721201637/http://www.fema.gov/media-library-data/1418837471752-920f09bb8187ee15436712a3e82ce709/FEMA_P-320_2014_508.pdf |archive-date=July 21, 2015 }}

Tornado Alley can also be defined as an area reaching from central Texas to the Canadian Prairies and from eastern Colorado to western Ohio.

File:May 20, 2013 Moore, Oklahoma tornado.JPG

Some researchers argue that there are several Tornado Alleys. In addition to the Texas/Oklahoma/Kansas core, such other areas include the Upper Midwest, the lower Ohio Valley, the Tennessee Valley, and the lower Mississippi valley, which may have respective distinguishing characteristics. A coherent conception considers that there is a single Tornado Alley in the United States and Canada, and that this can simply be subdivided into smaller areas based on regional attributes.{{cite conference |first=Chris |last=Broyles |author2=C. Crosbie |title=Evidence of Smaller Tornado Alleys Across the United States Based on a Long Track F3-F5 Tornado Climatology Study from 1880-2003 |book-title=22nd Conference on Severe Local Storms |publisher=American Meteorological Society |date=October 2004 |location=Hyannis, MA |url=https://ams.confex.com/ams/11aram22sls/techprogram/paper_81872.htm |url-status=live |archive-url=https://web.archive.org/web/20131002101420/https://ams.confex.com/ams/11aram22sls/techprogram/paper_81872.htm |archive-date=2013-10-02 }}

The extension of the North American tornadically active in the southeastern U.S., notably the lower Mississippi Valley and the upper Tennessee Valley, are sometimes called by the nickname "Dixie Alley", coined in 1971 by Allen Pearson, former director of the National Severe Storms Forecast Center (NSSFC).{{cite journal |last1=Gagan |first1=John P. |last2=Gerard |first2=Alan |last3=Gordon |first3=John |title=A historical and statistical comparison of 'Tornado Alley' to 'Dixie Alley' |journal=National Weather Digest |volume=34 |issue=2 |date=2010 |pages=145–155 |url=http://nwafiles.nwas.org/digest/papers/2010/Vol34No2/Pg145-Gagan-etal.pdf }} A 2018 study found in the U.S., over the study period 1979–2017, an overall eastward shift of tornado frequency and impacts - toward Dixie Alley.{{cite web |last1=Rice |first1=Doyle |title=USA's infamous 'Tornado Alley' may be shifting east |url=https://www.usatoday.com/story/weather/2018/10/17/tornado-alley-shifting-east/1660803002/ |publisher=USA Today |date=17 October 2018}} The study found, since 1979, relatively-lower tornado frequency and impacts in parts of the traditional Tornado Alley, especially areas from north-central Texas toward the Houston, TX area, and relatively-higher tornado frequency and impacts in parts of the Mid-South, especially eastern Arkansas, the greater Memphis, TN area and northern Mississippi - all areas near the heart of Dixie Alley - see especially Figure 4.

In Tornado Alley, warm, humid air from the equator meets cool to cold, dry air from Canada and the Rocky Mountains. This creates an ideal environment for tornadoes to form within developed thunderstorms and supercell.{{Cite web|url=http://www.worldatlas.com/articles/what-is-tornado-alley-where-are-tornadoes-most-likely-to-occur-where-is-the-tornado-belt.html|title=Tornado Alley: The Most Tornado Prone Region In The World|date=September 16, 2016|website=www.worldatlas.com|access-date=October 15, 2016|url-status=live|archive-url=https://web.archive.org/web/20161025153639/http://www.worldatlas.com/articles/what-is-tornado-alley-where-are-tornadoes-most-likely-to-occur-where-is-the-tornado-belt.html|archive-date=October 25, 2016}}

The term "tornado alley" was first used in 1952 by U.S. Air Force meteorologists Major Ernest J. Fawbush (1915–1982) and Captain Robert C. Miller (1920–1998), as the title of a research project{{cite web|title=Essay Tornado|url=http://essaytornado.com|work=Major Ernest J. Fawbush and Captain Robert C. Miller|access-date=November 25, 2015|url-status=live|archive-url=https://web.archive.org/web/20161103074031/http://essaytornado.com/|archive-date=November 3, 2016}} to study severe weather in parts of Texas and Oklahoma.{{cite news |last1=Singer-Vine |first1=Jeremy |title=How Did 'Tornado Alley' Get Its Name? |url=https://slate.com/news-and-politics/2013/05/oklahoma-tornado-how-and-when-did-tornado-alley-get-its-name.html |work=Slate |date=21 May 2013 }}{{cite news | url = http://www.nssl.noaa.gov/goldenanniversary/awards.html | archive-url = https://web.archive.org/web/20010504111215/http://www.nssl.noaa.gov/goldenanniversary/awards.html | title = Weather officers commended | newspaper = Take-Off | publisher = Tinker Air Force Base | location = Midwest City, Oklahoma | date = January 16, 1953 | archive-date = 4 May 2001}}

File:Henryville tornado damage 12.jpg

Despite the elevated frequency of destructive tornadoes, building codes, such as requiring strengthened roofs and more secure connections between the building and its foundation, are not necessarily stricter compared to other areas of the United States and are markedly weaker than some hurricane prone areas, such as south Florida. One particular tornado-afflicted town, Moore, Oklahoma, managed to increase its building requirements in 2014.{{cite news |last1=Simmons |first1=Kevin M. |title=Opinion {{!}} An Oklahoma Suburb, Tornado-Ready |url=https://www.nytimes.com/2015/05/14/opinion/an-oklahoma-suburb-tornado-ready.html |work=The New York Times |date=14 May 2015 }} Other common precautionary measures include the construction of storm cellars and the installation of tornado sirens. Tornado awareness, preparedness, and media weather coverage are also high.

The southeastern United States is particularly prone to violent, long track tornadoes. Much of the housing in this region is less robust compared to other areas in the United States, and many people live in mobile homes. As a result, tornado-related casualties in the southern United States are higher. Significant tornadoes occur less frequently than in the traditionally recognized tornado alley; however, very severe and expansive outbreaks occur every few years.{{cn|date=April 2024}}

These figures, reported by the National Climatic Data Center for the period between 1991 and 2010, show the seventeen U.S. states with the highest average number of EF0-EF5 tornadoes per {{convert|10000|sqmi|km2|abbr=out|1}} per year.{{cite web|title=Average Annual Number of EF0-EF5 Tornadoes per 10,000 square miles during 1991 - 2010|url=http://www1.ncdc.noaa.gov/pub/data/cmb/images/tornado/clim/avg-ef0-ef5-torn1991-2010.gif|work=National Climatic Data Center|publisher=NOAA.gov|access-date=October 26, 2013|archive-url=https://web.archive.org/web/20131029191409/http://www1.ncdc.noaa.gov/pub/data/cmb/images/tornado/clim/avg-ef0-ef5-torn1991-2010.gif|archive-date=October 29, 2013|location=U.S. Tornado Climatology|format=gif|url-status=live}}

{{div col|colwidth=12em}}

1. Florida: 12.3
2. Kansas: 11.7
3. Maryland: 9.9
4. Illinois: 9.7
5. Mississippi: 9.2
6. Iowa: 9.1
7. Oklahoma: 9
8. South Carolina: 9
9. Alabama: 8.6
10. Louisiana: 8.5
11. Arkansas: 7.5
12. Nebraska: 7.4
13. Missouri: 6.5
14. North Carolina: 6.4
15. Tennessee: 6.2
16. Indiana: 6.1
17. Texas: 5.9

{{div col end}}

Canada records the second most tornadoes in the world after the United States.{{Citation needed|date=March 2023}} The average number of tornadoes per equal area of land is highest in the southern parts of Alberta, Saskatchewan, Manitoba, and Ontario.

File:Canadian Tornado Alleys.png

Roughly half of all Canadian tornadoes strike the Canadian Prairies and Northern Ontario as far east as Lake Superior. Together, these regions make up the northernmost border of the U.S. Tornado Alley. Tornadoes up to F5 in strength have been documented in this region.{{cite web |title=Spring and Summer Weather Hazards |date = 9 June 2010|url=http://ec.gc.ca/meteo-weather/default.asp?lang=En&n=6C5D4990-1#tornadoes |publisher=Government of Canada |archive-url=https://web.archive.org/web/20160802230612/http://ec.gc.ca/meteo-weather/default.asp?lang=En&n=6C5D4990-1 |archive-date=2 August 2016}}

Another third of Canadian tornadoes strike Southern Ontario and Quebec, especially in the region between the Great Lakes and the nation's capital city, Ottawa. Tornadoes do not often hit lake shadow regions, although they are not unknown, and some, such as the 2011 Goderich tornado, have been violent. However, most Ontario tornadoes are concentrated in a narrow corridor from Windsor to Ottawa{{cite web |url=http://www.yorku.ca/pat/research/dsills/papers/GLOMW2012/Sills_GLOMW2012.pdf |title=A Fresh Spin on Tornado Occurrence and Intensity in Ontario |last=Sills |first=David |publisher=Environment Canada |access-date=2014-01-17 |url-status=live |archive-url=https://web.archive.org/web/20140118175543/http://www.yorku.ca/pat/research/dsills/papers/GLOMW2012/Sills_GLOMW2012.pdf |archive-date=2014-01-18 }}{{cite web |last1=Meiklejohn |first1=Scott |title=The current 'Tornado Alley' |url=http://mobile.theweathernetwork.com/news/storm_watch_stories3&stormfile=Should__Tornado_Alley__be_expanded__11_04_2012?ref=ccbox_news_topstories |publisher=The Weather Network |archive-url=https://web.archive.org/web/20140121025510/http://mobile.theweathernetwork.com/news/storm_watch_stories3%26stormfile%3DShould__Tornado_Alley__be_expanded__11_04_2012?ref=ccbox_news_topstories |archive-date=21 January 2014 |date=11 April 2012}} as well as through portions of Central Quebec.{{Cite web|last=Salazar|first=Antoinette|date=2021-12-13|title=Where is the Tornado Alley in Canada?|url=https://cubetoronto.com/canada/where-is-the-tornado-alley-in-canada/|access-date=2022-01-18|website=About Canada|language=en-CA}}{{Cite web|title=Northern Tornadoes Project|url=https://www.uwo.ca/ntp/|access-date=2022-01-18|website=Northern Tornadoes Project|language=en}} Tornadoes up to F4 in strength have been documented in this region.

In more recent years, an emerging trend has suggested that the Ottawa Valley is seeing an increasing number of frequent and violent tornadoes. The 2018 National Capital Region Outbreak spawned a high-end EF3+ and high-end EF2 which caused catastrophic damage to areas in both Ottawa and Gatineau. 2023 saw 5 tornadoes of varying intensities strike the region, including two EF1 tornadoes which touched down in the Barrhaven suburb within minutes of one another. This phenomenon, while still in the preliminary stages of study, has led some to name this hotspot "Tornado Valley".{{cn|date=April 2024}}

Southwestern Ontario weather is strongly influenced by its peninsular position between the Great Lakes. As a result, increases in temperature in this region are likely to increase the amount of precipitation in storms due to lake evaporation. Increased temperature contrasts may also increase the violence and possibly the number of tornadoes.{{cite web |url=http://www.sciences360.com/index.php/weather-predictions-made-by-the-global-warming-model-3254/ |title=Weather Predictions Made by the Global Warming Model |last=Scott |first=Cameron |publisher=Sciences 360 |date=2012-04-11 |access-date=2014-01-17 |url-status=live |archive-url=https://web.archive.org/web/20140201185344/http://www.sciences360.com/index.php/weather-predictions-made-by-the-global-warming-model-3254/ |archive-date=2014-02-01 }}

Northern Ontario between the Manitoba border and Lake Superior is also prone to severe tornadoes, but tornadoes in this area are believed to be underestimated due to the extremely low population in this region.{{cite web |url=http://www.accuweather.com/en/weather-blogs/anderson/when-is-peak-tornado-season-in-canada/31509 |title=When is Peak Tornado Season in Canada? |publisher=AccuWeather |date=2010-05-14 |access-date=2014-01-16 |url-status=live |archive-url=https://web.archive.org/web/20140118051928/http://www.accuweather.com/en/weather-blogs/anderson/when-is-peak-tornado-season-in-canada/31509 |archive-date=2014-01-18 }}

{{portal|Tornadoes}}

• Hailstorm Alley
• Lists of tornadoes and tornado outbreaks
• Tornado climatology

{{reflist|2}}

• [http://www.nssl.noaa.gov/users/brooks/public_html/tornado/ NSSL Tornado Climatology]
• {{cite journal |last1=Brooks |first1=Harold E. |last2=Doswell |first2=Charles A. |last3=Kay |first3=Michael P. |title=Climatological Estimates of Local Daily Tornado Probability for the United States |journal=Weather and Forecasting |date=August 2003 |volume=18 |issue=4 |pages=626–640 |doi=10.1175/1520-0434(2003)018<0626:CEOLDT>2.0.CO;2 |bibcode=2003WtFor..18..626B }}
• [https://web.archive.org/web/20081029181406/http://www.cas.sc.edu/geog/hrl/Hazard_Pubs/2003_TornadoHazardsUSA.pdf Tornado hazards in the United States]
• {{cite journal |last1=Dotzek |first1=Nikolai |last2=Grieser |first2=Jürgen |last3=Brooks |first3=Harold E. |title=Statistical modeling of tornado intensity distributions |journal=Atmospheric Research |date=July 2003 |volume=67-68 |pages=163–187 |doi=10.1016/S0169-8095(03)00050-4 |bibcode=2003AtmRe..67..163D }}

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{{U.S. Belt regions}}

Category:Tornado

Category:Regions of the United States