Tornado Alley

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

Tornado Alley is a colloquial term for the area of the United States where tornadoes are most frequent. [1]

Contents

The term was first used in 1952 as the title of a research project to study severe weather in areas of Texas, Oklahoma, Kansas, South Dakota, Illinois, Iowa, Missouri, Nebraska, Colorado, North Dakota, and Minnesota. It is largely a media-driven term although tornado climatologists distinguish peaks in activity in certain areas [2] and storm chasers have long recognized the Great Plains tornado belt. [3]

Although the official boundaries of Tornado Alley are not clearly defined, the main alley extends from northern Texas, through Oklahoma, Kansas, Nebraska, Missouri, Iowa, South Dakota, and North Dakota.


States such as Minnesota, Wisconsin, Illinois, Indiana, and Ohio are sometimes included in Tornado Alley. [4] Research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian prairies. [5]

Tornado alley geographical area

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

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). [6] Thus, differences in location are the result of the different criteria used. [6] [7]

According to the National Severe Storms Laboratory (NSSL) FAQ, [6] "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. [8]

Although the official boundaries of Tornado Alley are not clearly defined, its core extends from northern Texas, Oklahoma, Kansas, Nebraska, Missouri, Iowa along with South Dakota.

Minnesota, Wisconsin, Illinois, Indiana, 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. [9]

No state is entirely free of tornadoes; however, they occur more frequently in the Central United States, between the Rocky Mountains and Appalachian Mountains. [6] Texas reports the most tornadoes of any state, but that is a function of its large size, and its location on the southern end of Tornado Alley. Kansas and Oklahoma ranked first and second respectively in the number of tornadoes per area, per data collected through 2007, however in 2013 statistics from the National Climatic Data Center show Florida ranked first.[20] Although Florida reports a high number and density of tornado occurrences, tornadoes there rarely reach the strength of those that sometimes occur in the Southern Plains. [10] Regionally, the frequency of tornadoes in the United States is closely tied with the progression of the warm season when warm and cold air masses often clash. [10]

Another criterion for the location of Tornado Alley (or Tornado Alleys) can be where the strongest tornadoes occur more frequently. [11]

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

It has also been asserted that there are numerous Tornado Alleys. [4] In addition to the Texas/Oklahoma/Kansas core, such areas include the Upper Midwest, the lower Ohio Valley, the Tennessee Valley and the lower Mississippi valley. [4] Some studies suggest that there are also smaller tornado alleys located across the United States. [2]

The tornado alleys 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 Forecasting Center (NSSFC). [12] 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 [13] . 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 super cells. [14]

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 [15] to study severe weather in parts of Texas and Oklahoma. [16]

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. [17] 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.

Frequency of tornadoes

The average tornado only stays on ground for 5 minutes. 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 tornadoes per 10,000 square miles (25,899.9 km2) per year. [18]

  1. Florida: 12.2
  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

Canadian tornadoes

After the U.S., Canada gets the most tornadoes in the world. The average number of tornadoes per 3,900 square miles or 10,000 km2 is highest in the southern parts of Alberta, Saskatchewan, and Manitoba, as well as Southern Ontario. Northern Ontario between the Manitoba border and the Lake Superior lakehead 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. [19] [20]

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 EF5 in strength have been documented in this region. [21]

Another third of Canadian tornadoes strike Southern Ontario, especially in the region halfway between the Great Lakes from Lake St. Clair to Ottawa. This happens because tornadoes in this region are triggered or augmented by lake breeze fronts from Lake Huron, Lake Erie, Lake Ontario, and Georgian Bay. Tornadoes do not often hit lake shadow regions, [19] although they are not unknown, and some, such as the 2011 Goderich, Ontario tornado, have been violent. However, most Ontario tornadoes are concentrated in a narrow corridor from Windsor and Sarnia through London, and then northeast to Barrie and Ottawa. [19] [22] Tornadoes up to EF4 in strength have been documented in this region.

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. [23]

See also

Related Research Articles

Tornadoes of 2007 Wikimedia list article

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.

Tornado climatology

Tornadoes have been recorded on all continents except Antarctica and are most common in the middle latitudes where conditions are often favorable for convective storm development. The United States has the most tornadoes of any country, as well as the strongest and most violent tornadoes. A large portion of these tornadoes form in an area of the central United States popularly known as Tornado Alley. Canada experiences the second most tornadoes. Ontario and the prairie provinces see the highest frequency, particularly with southward extent. Other areas of the world that have frequent tornadoes include significant portions of Europe, South Africa, Philippines, Bangladesh, parts of Argentina, Uruguay, and southern and southeast Brazil, northern Mexico, New Zealand, and far eastern Asia.

The tornado outbreak sequence of May 24–26, 1957, primarily affected the Western High Plains, Central Great Plains, and Central Oklahoma/Texas Plains of the United States. Forty-five 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.

Tornado outbreak of May 1–2, 2008

The Tornado outbreak of May 1–2, 2008 was a tornado outbreak that took place across the Southern and Central United States on May 1 and May 2, 2008. The outbreak was responsible for at least seven fatalities and 23 injuries in Arkansas. There were at least 29 tornado reports from Iowa to Oklahoma on May 1 and 67 more in Arkansas, Missouri, Mississippi, Tennessee, Louisiana and Texas on May 2. At least 63 tornadoes were confirmed by weather authorities.

Tornadoes in the United States

Tornadoes are more common in the United States than in any other country. 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.

Tornadoes of 2009

In 2009, tornadic activity was generally near average. Each year, tornadoes and tornado outbreaks occur worldwide primarily under conductive conditions, though a majority of tornadoes form in the United States. Tornadoes also occur to a less frequent extent in Europe, Asia, and Australia. In the U.S., there were 1,304 reports of tornadoes received by the Storm Prediction Center (SPC), and 1,159 tornadoes were confirmed to have taken place. Worldwide, 45 fatalities were caused by tornadoes; 22 in the United States, 20 in India, eight in the Philippines, four in Canada, two in Greece and one each in Serbia and Russia.

2009 North American Christmas blizzard

The 2009 North American Christmas blizzard was a powerful winter storm and severe weather event that affected the Midwestern United States, Great Plains, Southeastern United States, the Eastern Seaboard, and parts of Ontario. The storm began to develop on December 22 before intensifying to produce extreme winds and precipitation by the morning of December 24. The storm's rapid development made it difficult for forecasters to predict. The blizzard was reported to have claimed at least 21 lives, and disrupted air travel during the Christmas travel season. In the Southeastern and Central United States, there were 27 reported tornadoes on December 23–24. The storm, a Category 5 "Extreme" one on the Regional Snowfall Index, was the first winter weather event to rank as such since the Blizzard of '96.

Tornadoes of 2010

This page documents the tornadoes and tornado outbreaks of 2010. The majority of tornadoes form in the U.S., but they can occur almost anywhere under the right conditions. A lesser number occur outside the U.S., most notably in parts of neighboring southern Canada during the Northern Hemisphere's summer season, but are also known in South America, Europe, Asia, and Australia.

Tornadoes of 2011 Wikimedia list article

This page documents the tornadoes and tornado outbreaks of 2011. Extremely 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 appear regularly in neighboring southern Canada during the Northern Hemisphere's summer season, and somewhat regularly in Europe, Asia, and Australia.

2010 New Years Eve tornado outbreak

The 2010 New Year's Eve tornado outbreak was a three-day-long tornado outbreak that impacted the central and lower Mississippi Valley from December 30, 2010 to January 1, 2011. Associated with a low pressure system and a strong cold front, 37 tornadoes tracked across five states over the length of the severe event, killing nine and injuring several others. Activity was centered in the states of Missouri and later Mississippi on December 31. Seven tornadoes were rated EF3 on the Enhanced Fujita Scale; these were the strongest during the outbreak. Non-tornadic winds were recorded to have reached as high as 80 mph (130 km/h) at eight locations on December 31, while hail as large as 2.75 in (7.0 cm) was documented north-northeast of Mansfield, Missouri. Overall, damage from the outbreak totaled US$123.3 million, most of which was related to tornadoes.

Late December 2012 North American storm complex

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 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.

Tornado outbreak of May 18–21, 2013 tornado outbreak in the Midwestern and Southern United States

The tornado outbreak of May 18–21, 2013 was a significant tornado outbreak that affected parts of the Midwestern United States and lower Great Plains. This event occurred just days after a deadly outbreak struck Texas and surrounding southern states on May 15. On May 16, a slow moving trough crossed the Rockies and traversed the western Great Plains. Initially, activity was limited to scattered severe storms; however, by May 18, the threat for organized severe thunderstorms and tornadoes greatly increased. A few tornadoes touched down that day in Kansas and Nebraska, including an EF4 near Rozel, Kansas. Maintaining its slow eastward movement, the system produced another round of severe weather nearby. Activity significantly increased on May 19, with tornadoes confirmed in Oklahoma, Kansas, Iowa, Missouri, and Illinois. In Oklahoma, two strong tornadoes, one rated EF4, caused significant damage in rural areas of the eastern Oklahoma City metropolitan area; two people lost their lives near Shawnee. The most dramatic events unfolded on May 20 as a large EF5 tornado devastated parts of Moore, Oklahoma, killing 24 people. Thousands of structures were destroyed, with many being completely flattened. Several other tornadoes occurred during the day in areas further eastward, though the majority were weak and caused little damage.

Tornado outbreak of June 16–18, 2014

The tornado outbreak of June 16–18, 2014, was a tornado outbreak concentrated in the Great Plains and the Midwestern United States. Two tornadoes also occurred in Ontario. The severe weather event most significantly affected the state of Nebraska, where twin EF4 tornadoes killed two and critically injured twenty others in and around the town of Pilger on the evening of June 16. The two Pilger tornadoes were part of a violent tornado family that produced four consecutive EF4 tornadoes and was broadcast live on television. The outbreak went on to produce multiple other strong tornadoes across the northern Great Plains states throughout the next two days.

Tornado outbreak sequence of May 5–10, 2015

The tornado outbreak sequence of May 5–10, 2015 was a six-day outbreak of tornado activity that affected the Great Plains of the United States in early May 2015. On May 6, strong tornadoes impacted the Oklahoma City area, along with rural parts of Kansas, Texas, Arkansas, South Dakota, and Nebraska. The outbreak coincided with major flooding, with large amounts of rain falling in parts of Nebraska, Kansas, Oklahoma, and Texas. The National Weather Service forecast office in Norman, Oklahoma issued a "flash flood emergency" for Oklahoma City following record-breaking rainfall that occurred in the area that evening. The outbreak sequence resulted in five tornado-related deaths, along with two flood-related deaths. A total of 127 tornadoes were confirmed and rated as a result of this outbreak sequence.

2015 Texas–Oklahoma flood and tornado outbreak

Preceded by more than a week of heavy rain, a slow-moving storm system dropped tremendous precipitation across much of Texas and Oklahoma during the nights of May 24–26, 2015, triggering record-breaking floods. Additionally, many areas reported tornado activity and lightning. Particularly hard hit were areas along the Blanco River in Hays County, Texas, where entire blocks of homes were leveled. On the morning of May 26, the National Weather Service issued a flash flood emergency for southwest Harris County and northeast Fort Bend County. The system also produced deadly tornadoes in parts of Mexico, Texas, and Oklahoma.

December 2015 North American storm complex

The December 2015 North American storm complex 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 impacted areas around Dallas, Texas. Several states, especially Missouri, were affected by heavy rain and snow causing severe floods. As the system moved through the Great Lakes region, 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 in the storm system and its aftermath, which made it one of the deadliest of such systems of 2015 in the United States.

Tornado outbreak of April 8–9, 2015

The tornado outbreak of April 8–9, 2015 was a relatively small but damaging outbreak of tornadoes that occurred in parts of the Great Plains and in the Midwestern United States. 27 tornadoes were confirmed during the two days, most of them weak, however a select few of them were powerful and damaging.

Tornadoes of 2018

This page documents notable tornadoes and tornado outbreaks worldwide in 2018. Strong and destructive tornadoes form most frequently in the United States, Brazil, 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, Argentina and Australia. Tornadic events are often accompanied with other forms of severe weather, including strong thunderstorms, strong winds, and hail.

References

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    4. Results of search of Google Books for "tornado alley".
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Coordinates: 35°N88°W / 35°N 88°W / 35; -88