Tornado Alley

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A diagram of tornado alley based on 1 tornado or more per decade. Rough location (red), and its contributing weather systems Tornado Alley Diagram.svg
A diagram of tornado alley based on 1 tornado or more per decade. Rough location (red), and its contributing weather systems

Tornado Alley is a loosely defined location of the central United States and Canada where tornadoes are most frequent. [1] The term was first used in 1952 as the title of a research project to study severe weather in areas of Texas, Louisiana, Oklahoma, Kansas, South Dakota, Iowa and Nebraska. Tornado climatologists distinguish peaks in activity in certain areas [2] and storm chasers have long recognized the Great Plains tornado belt. [3]

Contents

As a colloquial term there are no definitively set boundaries of Tornado Alley, but the area common to most definitions extends from Texas, through Oklahoma, Kansas, Nebraska, South Dakota, Iowa, Minnesota, Wisconsin, Illinois, Indiana, Missouri, Arkansas, North Dakota, Montana, Ohio, and eastern portions of Colorado and Wyoming. [4] Research suggests that the main alley may be shifting eastward away from the Great Plains, [5] [6] and that tornadoes are also becoming more frequent in the northern and eastern parts of Tornado Alley where it reaches the Canadian Prairies, Ohio, Michigan, and Southern Ontario. [7] [8]

Geographical area

Tornado activity in the United States. Tornado Alley.svg
Tornado activity in the United States.

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). [9] Thus, differences in location are the result of the different criteria used. [9] [10]

According to the National Severe Storms Laboratory (NSSL) FAQ, [9] "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. [11]

Illinois, Wisconsin, Minnesota, Indiana, Michigan, and western Ohio are sometimes included in Tornado Alley. [4] Some research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian Prairies. [7]

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. [9] 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. [12] 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. [12] 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. [12]

Another criterion for the location of Tornado Alley can be where the strongest tornadoes occur more frequently. [13]

Tornado Alley can also be defined as an area reaching from central Texas to the Canadian Prairies and from eastern Colorado to western Ohio. [4]

Some researchers argue that there are several Tornado Alleys. [4] 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. [4] 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. [2]

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). [14] 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. [15] 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. [16]

Origin of the term

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 [17] to study severe weather in parts of Texas and Oklahoma. [18] [19] [20]

Impact

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. [21] 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.[ citation needed ]

Frequency of tornadoes

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 10,000 square miles (25,899.9 km2) per year. [22]

  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

Tornadoes in Canada

Canada records the second most tornadoes in the world after the United States.[ citation needed ] The average number of tornadoes per equal area of land is highest in the southern parts of Alberta, Saskatchewan, Manitoba, and Ontario.

Canadian Tornado Alley Canadian Tornado Alleys.png
Canadian Tornado Alley

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. [23]

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, [24] 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 [24] [25] as well as through portions of Central Quebec. [26] [27] 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".[ citation needed ]

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. [28]

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. [24] [29]

See also

Related Research Articles

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A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 180 kilometers per hour, are about 80 meters across, and travel several kilometers before dissipating. The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), are more than 3 kilometers (2 mi) in diameter, and stay on the ground for more than 100 km (62 mi).

<span class="mw-page-title-main">Supercell</span> Thunderstorm that is characterized by the presence of a mesocyclone

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<span class="mw-page-title-main">Tornadoes of 2006</span> List of notable worldwide tornadoes that occurred in 2006

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<span class="mw-page-title-main">Climate of Minneapolis–Saint Paul</span>

The climate of Minneapolis–Saint Paul is the long term weather trends and historical events of the Minneapolis–Saint Paul metropolitan area in east central Minnesota. Minneapolis and St. Paul, together known as the Twin Cities, are the core of the 15th largest metropolitan area in the United States. With a population of 3.6 million people, the region contains approximately 60% of the population of Minnesota. Due to its location in the northern and central portion of the U.S., the Twin Cities has the coldest average temperature of any major metropolitan area in the nation. Winters are very cold, summer is warm and humid, snowfall is common in the winter and thunderstorms with heavy rainfall occur during the spring, summer and autumn. Though winter can be cold, the area receives more sunlight hours in mid-winter than many other warmer parts of the country, including all of the Great Lakes states, the Pacific Northwest, parts of the South, and almost all of the Northeast. Unless otherwise indicated, all normals data presented below are based on data at Minneapolis/St. Paul International Airport, the official Twin Cities climatology station, from the 1981−2010 normals period.

<span class="mw-page-title-main">Tornadoes of 2007</span> List of notable worldwide tornadoes that occurred in 2007

This page documents the tornadoes and tornado outbreaks that occurred in 2007, primarily in the United States. Most tornadoes form in the U.S., although some events may take place internationally, particularly in parts of neighboring southern Canada during the summer season. Some tornadoes also take place in Europe, e. g. in the United Kingdom or in Germany.

<span class="mw-page-title-main">Tornado climatology</span> Climate factors contributing to the formation of tornadoes

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<span class="mw-page-title-main">Tornadoes of 2001</span>

This page documents notable tornadoes and tornado outbreaks worldwide in 2001. Strong and destructive tornadoes form most frequently in the United States, Bangladesh, and Eastern India, but they can occur almost anywhere under the right conditions. Tornadoes also develop occasionally in southern Canada during the Northern Hemisphere's summer and somewhat regularly at other times of the year across Europe, Asia, and Australia. Tornadic events are often accompanied with other forms of severe weather, including strong thunderstorms, strong winds, and hail.

"Dixie Alley" is a colloquial term sometimes used for areas of the southern United States which are particularly vulnerable to strong to violent tornadoes. Some argue this is distinct from the better known "Tornado Alley" and that it has a high frequency of strong, long-track tornadoes that move at higher speeds. The term was coined by National Severe Storms Forecast Center (NSSFC) Director Allen Pearson after witnessing a tornado outbreak which included more than 9 long-track, violent tornadoes that killed 121 on February 21–22, 1971. The specific characteristics of the Southeast led to VORTEX-SE, a field project studying tornadogenesis, diagnosis and forecasting, in addition to social science implications, and examines both supercellular tornadoes and those resulting from quasi-linear convective system (QLCS) thunderstorm structures. This was followed a few years later by another major field project, PERiLS, focusing on QLCS tornadoes.

On May 24–25, 1957, a tornado outbreak primarily affected the Western High Plains, Central Great Plains, and Central Oklahoma/Texas Plains of the United States. 45 tornadoes touched down over the area, most of which took place across northern and western Texas, in addition to southern Oklahoma. Overall activity initiated over eastern New Mexico and spread northeastward as far as southwestern Wisconsin. The strongest tornado, which occurred in southern Oklahoma on May 24, was assigned a rating of F4 near Lawton. Anomalously, some tornadoes touched down during the early morning hours, rather than late afternoon or early evening, when daytime heating typically peaks.

<span class="mw-page-title-main">Climate of the United States</span> Varies due to changes in latitude, and a range of geographic features

The climate of the United States varies due to changes in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.

On March 21–22, 1952, a severe tornado outbreak generated eight violent tornadoes across the Southern United States, causing 209 fatalities—50 of which occurred in a single tornado in Arkansas. In addition, this tornado outbreak is the deadliest on record to ever affect the state of Tennessee, with 66 of the fatalities associated with this outbreak occurring in the state; this surpasses the 60 fatalities from a tornado outbreak in 1909, and in terms of fatalities is well ahead of both the 1974 Super Outbreak and the Super Tuesday tornado outbreak, each of which generated 45 and 31 fatalities, respectively. The severe weather event also resulted in the fourth-largest number of tornado fatalities within a 24-hour period since 1950. To date this was considered the most destructive tornado outbreak in Arkansas on record.

<span class="mw-page-title-main">Tornadoes of 1999</span>

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<span class="mw-page-title-main">Tornadoes in the United States</span>

Tornadoes are more common in the United States than in any other country or state. The United States receives more than 1,200 tornadoes annually—four times the amount seen in Europe. Violent tornadoes—those rated EF4 or EF5 on the Enhanced Fujita Scale—occur more often in the United States than in any other country.

<span class="mw-page-title-main">Climate of Alabama</span> Overview of the climate of the U.S. state of Alabama

The state of Alabama is classified as humid subtropical (Cfa) under the Köppen climate classification. The state's average annual temperature is 64 °F (18 °C). Temperatures tend to be warmer in the state's southern portion with its proximity to the Gulf of Mexico, while its northern portions, especially in the Appalachian Mountains in the northeast, tend to be slightly cooler. Alabama generally has hot, humid summers and mild winters with copious precipitation throughout the year. The state receives an average of 56 inches (1,400 mm) of rainfall each year and experiences a lengthy growing season of up to 300 days in its southern portion. Hailstorms occur occasionally during the spring and summer here, but they are seldom destructive. Heavy fogs are rare, and they are confined chiefly to the coast. Thunderstorms also occur year-around. They are most common in the summer, but they are most commonly severe during the spring and late autumn. That is when destructive winds and tornadoes occur frequently, especially in the northern and central parts of the state. Central and northern Alabama are squarely within Dixie Alley, the primary area in the U.S. outside the Southern Plains with relatively high tornado risk. Alabama is ranked second in the U.S for the deadliest tornadoes. Hurricanes are quite common in the state, especially in the southern part. Major hurricanes occasionally strike the coast, such as Hurricane Frederic in September 1979 and Hurricane Ivan in September 2004; both storms resulted in significant to devastating damage in the Mobile area.

<span class="mw-page-title-main">Tornadoes of 1983</span>

This page documents the tornadoes and tornado outbreaks of 1983, in the United States. Most tornadoes form in the U.S., although some events may take place internationally. Tornado statistics for older years like this often appear significantly lower than modern years due to fewer reports or confirmed tornadoes.

On December 18–20, 1957, a significant tornado outbreak sequence affected the southern Midwest and the South of the contiguous United States. The outbreak sequence began on the afternoon of December 18, when a low-pressure area approached the southern portions of Missouri and Illinois. Supercells developed and proceeded eastward at horizontal speeds of 40 to 45 miles per hour, yielding what was considered the most severe tornado outbreak in Illinois on record so late in the calendar year. Total losses in the state were estimated to fall within the range of $8–$10 million.

<span class="mw-page-title-main">Late December 2012 North American storm complex</span> 2012 storm in North America

Near the end of 2012, a massive storm complex developed that produced both a tornado outbreak and a blizzard across the southern and eastern United States. On Christmas Day 2012, a tornado outbreak occurred across the Southern United States. This severe weather/tornado event affected the United States Gulf Coast and southern East Coast over a two-day span. It occurred in conjunction with a much larger winter storm event that brought blizzard conditions to much of the interior United States. In total, 31 tornadoes were confirmed by the National Weather Service in five states from Texas to North Carolina. All but one of the tornadoes that occurred during the outbreak touched down on December 25, with the other occurring the following day in North Carolina. Two of the tornadoes were destructive enough to be rated EF3 on the Enhanced Fujita Scale. At least 16 people died as a result of the related blizzard, and thousands were without power.

<span class="mw-page-title-main">Tornadoes of 2015</span>

This page documents notable tornadoes and tornado outbreaks worldwide in 2015. Strong and destructive tornadoes form most frequently in the United States, Bangladesh, Brazil and Eastern India, but they can occur almost anywhere under the right conditions. Tornadoes also develop occasionally in southern Canada during the Northern Hemisphere's summer and somewhat regularly at other times of the year across Europe, Asia, and Australia. Tornadic events are often accompanied with other forms of severe weather including strong thunderstorms, winds and hail.

<span class="mw-page-title-main">December 2015 North American storm complex</span> 2015 massive storm system that affected North America

The December 2015 North American storm complex, also known as Winter Storm Goliath, was a major storm complex that produced a tornado outbreak, a winter storm, a blizzard and an ice storm in areas ranging from the Southwestern United States to New England. Tornadoes struck the Dallas–Fort Worth metroplex in Texas while several other states, especially Missouri, were affected by heavy rain and snow causing severe floods. As the system moved through the Great Lakes, heavy rain, ice pellets and heavy snow fell in the entire region. Wintry mix moved through southern Ontario and Quebec had significant snowfall on December 29. Almost 60 people were killed during the storm system's progression and aftermath, making it one of the deadliest such systems of 2015 in the United States.

<span class="mw-page-title-main">Tornado outbreak sequence of December 1–6, 1953</span> Weather event affecting Southeastern United States

The first six days of December 1953 produced a destructive and deadly tornado outbreak sequence across the Southern United States. There were 19 confirmed tornadoes, including a violent F4 tornado that hit the northwest side of Alexandria, Louisiana and even more violent F5 tornado that hit Vicksburg, Mississippi. In all, the tornadoes killed 49 people, injured 404 others, and caused $45,709 million in damage. The death toll made this deadliest December tornado outbreak ever recorded and it would not be surpassed until 2021. This was also the last of the series of deadly and catastrophic tornado outbreaks to strike the US in 1953.

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