Dixie Alley

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"Dixie Alley" is a colloquial term sometimes used for areas of the southern United States which are particularly vulnerable to strong to violent tornadoes. [1] 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.[ citation needed ] 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. [2] 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. [3] [4] This was followed a few years later by another major field project, PERiLS, focusing on QLCS tornadoes. [5] [6]

Contents

Geography

The Dixie Alley region indicated by red shaded area. DixieAlleymap.png
The Dixie Alley region indicated by red shaded area.

Dixie Alley includes much of the area of the lower Mississippi Valley. [7] It stretches from eastern Texas and Arkansas across Louisiana, Mississippi, Tennessee, Alabama, Georgia, and mid to western Kentucky to upstate South Carolina and western North Carolina; the area reaches as far north as southeast Missouri. [8] Another source places all of Arkansas within Dixie Alley. [9]

Although tornadoes are less frequent in these states than they are in the southern Plains[ citation needed ], the southeastern states have had more tornado-related deaths than any of the Plains states (excluding Texas). This is partly due to the fact that there are relatively high numbers of strong/violent long tracked tornadoes and higher population density of this region, as well as the Southern United States having the highest percentage of manufactured homes in the US, where 63% of the overall tornado-related fatalities occur. [10] According to the National Climatic Data Center (NCDC), for the period January 1, 1950 – October 31, 2006, Alabama and Kansas received the largest amount of F5 tornadoes. Complicating matters is that tornadoes are rarely visible in this area, as they are more likely to be rain-wrapped, embedded in shafts of heavy rain, and that the hilly topography and heavily forested landscape makes them difficult to see. [10]

Prevalent tornado characteristics

Tornado in Mississippi, located in Dixie Alley, obscured by trees and featuring a notably low, rugged base. Tornado in Mississippi on December 23, 2015.jpg
Tornado in Mississippi, located in Dixie Alley, obscured by trees and featuring a notably low, rugged base.

Dixie Alley is part of a region of enhanced tornadic activity extending between the Appalachian and Rocky Mountains, [11] but tornadoes and outbreaks in the Dixie Alley region exhibit some statistically distinguishable characteristics from the more well known Tornado Alley. [12] Tornadic storms in Dixie Alley are most often high precipitation supercells due to an increase of moisture from proximity to the nearby Gulf of Mexico. The Dixie Alley tornadoes accompanying the HP supercells are often partially or fully wrapped in rain, impairing the visibility of the tornadoes to storm spotters and chasers, law enforcement, and the public. [10] [13] Increases of warmth and instability in conjunction with strong wind shear in the Dixie Alley region impacts the times when tornadoes form. In the traditional Tornado Alley, tornadoes most often form from the mid afternoon to early evening. Dixie Alley's instability can be maintained long after sunset due to being adjacent to the Gulf, increasing the frequency of intense nighttime and early morning tornadoes. [10] There is also a less focused tornado season which tends to be most active in early spring and late autumn but can continue throughout the winter and into late spring, which can lead to complacency among residents of the region. The region often is subject to tornadoes much earlier than the general national peak from May and June, usually from February to Mid-April, [14] and several notorious outbreaks have struck during the late winter and early spring and also in late fall. [10] The complacency situation was noted after the 2008 Super Tuesday tornado outbreak in February 2008 that hit the Dixie Alley killing 57 people, many people indicated that they had underestimated the threat of severe weather on that day since it was well before the peak of tornado season. [10]

A 2018 study found in the U.S. an overall eastward shift of tornado frequency and impacts – toward Dixie Alley. [15] The study found relatively-lower tornado frequency and impacts in parts of the traditional Tornado Alley, especially areas from north-central Texas toward the Houston, Texas area, and relatively-higher tornado frequency and impacts in parts of the Mid-South, especially eastern Arkansas, the greater Memphis, Tennessee area and northern Mississippi – all areas near the heart of Dixie Alley (see especially Figure 4). [16]

Variations in climate patterns and teleconnections, such as the El Niño–Southern Oscillation (ENSO) can also have significant impacts on tornadic activity in the region from year to year. Climate change is also expected to affect tornado activity in the region. [17] [18]

Notable outbreaks

Dixie Alley has been subject to numerous tornado outbreaks throughout history, including very intense outbreaks and those of very large spatial and temporal extent. Notorious outbreaks affecting the region include: the Great Natchez Tornado, the 1884 Enigma tornado outbreak, the April 1924 tornado outbreak, the 1932 Deep South tornado outbreak, the 1936 Tupelo–Gainesville tornado outbreak, the April 1957 Southeastern tornado outbreak, the 1984 Carolinas tornado outbreak, and the November 1992 tornado outbreak. The 1974 Super Outbreak also hit the area very hard, producing multiple F5 tornadoes in Alabama, and F4 tornadoes in North Georgia and the Appalachian southwest of North Carolina. More recently the region was hit by the 2008 Super Tuesday tornado outbreak followed by the tornado outbreak of April 14–16, 2011, the deadliest since the 2008 outbreak. [10] Two weeks after the April 14–16 event, Dixie Alley was the epicenter of the 2011 Super Outbreak, which was the largest tornado outbreak ever recorded, as well as the fourth-deadliest outbreak in United States history, with over 300 people dead. [19] The Easter 2020 Tornado Outbreak also happened in Dixie Alley. It spawned over 100 tornadoes and has a spot in the top most tornadoes in 24 hours in an outbreak.

See also

Related Research Articles

<span class="mw-page-title-main">Tornado</span> Violently rotating column of air in contact with both the Earths surface and a cumulonimbus cloud

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

A supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours.

<span class="mw-page-title-main">Mesocyclone</span> Region of rotation within a powerful thunderstorm

A mesocyclone is a meso-gamma mesoscale region of rotation (vortex), typically around 2 to 6 mi in diameter, most often noticed on radar within thunderstorms. In the northern hemisphere it is usually located in the right rear flank of a supercell, or often on the eastern, or leading, flank of a high-precipitation variety of supercell. The area overlaid by a mesocyclone’s circulation may be several miles (km) wide, but substantially larger than any tornado that may develop within it, and it is within mesocyclones that intense tornadoes form.

<span class="mw-page-title-main">1974 Super Outbreak</span> Tornado outbreaks in the U.S. and Canada

The 1974 Super Outbreak was the second-largest tornado outbreak on record for a single 24-hour period, just behind the 2011 Super Outbreak. It was also the most violent tornado outbreak ever recorded, with 30 F4/F5 tornadoes confirmed. From April 3–4, 1974, there were 148 tornadoes confirmed in 13 U.S. states and the Canadian province of Ontario. In the United States, tornadoes struck Illinois, Indiana, Michigan, Ohio, Kentucky, Tennessee, Alabama, Mississippi, Georgia, North Carolina, Virginia, West Virginia, and New York. The outbreak caused roughly $843 million USD in damage, with more than $600 million occurring in the United States. The outbreak extensively damaged approximately 900 sq mi (2,331 km2) along a total combined path length of 2,600 mi (4,184 km). At one point, as many as 15 separate tornadoes were occurring simultaneously.

<span class="mw-page-title-main">1999 Oklahoma tornado outbreak</span> Tornado outbreak in May 1999

The 1999 Oklahoma tornado outbreak was a significant tornado outbreak that affected much of the Central and parts of the Eastern United States, with the highest record-breaking wind speeds of 301 ± 20 mph (484 ± 32 km/h). During this week-long event, 154 tornadoes touched down. More than half of them were on May 3 and 4 when activity reached its peak over Oklahoma, Kansas, Nebraska, Texas, and Arkansas.

<span class="mw-page-title-main">Waterspout</span> Tornado occurring over a body of water

A waterspout is an intense columnar vortex that occurs over a body of water. Some are connected to a cumulus congestus cloud, some to a cumuliform cloud and some to a cumulonimbus cloud. In the common form, a waterspout is a non-supercell tornado over water having a five-part life cycle: formation of a dark spot on the water surface; spiral pattern on the water surface; formation of a spray ring; development of a visible condensation funnel; and ultimately, decay.

<span class="mw-page-title-main">Wall cloud</span> Cloud formation occurring at the base of a thunderstorm

A wall cloud is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typically beneath the rain-free base (RFB) portion of a thunderstorm, and indicates the area of the strongest updraft within a storm. Rotating wall clouds are an indication of a mesocyclone in a thunderstorm; most strong tornadoes form from these. Many wall clouds do rotate; however, some do not.

<span class="mw-page-title-main">Tornado Alley</span> Geographical place in the United States where tornadoes commonly occur

Tornado Alley is a loosely defined location of the central United States and Canada where tornadoes are most frequent. 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 and storm chasers have long recognized the Great Plains tornado belt.

<span class="mw-page-title-main">Funnel cloud</span> Funnel-shaped cloud extending from a cloud base but doesnt touch the ground

A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud base. Funnel clouds form most frequently in association with supercell thunderstorms, and are often, but not always, a visual precursor to tornadoes. Funnel clouds are visual phenomena, but these are not the vortex of wind itself.

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

This page documents notable tornadoes and tornado outbreaks worldwide in 2006. 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, Argentina, Brazil and Australia. Tornadic events are often accompanied with other forms of severe weather, including strong thunderstorms, strong winds, and hail.

<span class="mw-page-title-main">Tornadogenesis</span> Process by which a tornado forms

Tornadogenesis is the process by which a tornado forms. There are many types of tornadoes and these vary in methods of formation. Despite ongoing scientific study and high-profile research projects such as VORTEX, tornadogenesis is a volatile process and the intricacies of many of the mechanisms of tornado formation are still poorly understood.

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

Tornadoes have been recorded on all continents except Antarctica. They 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. 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 southeastern Brazil, northern Mexico, eastern and western Australia, New Zealand, and far eastern Asia.

<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">Tornadoes of 2011</span>

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.

<span class="mw-page-title-main">Tornado outbreak of April 14–16, 2011</span> Tornado outbreak in the United States

From April 14–16, 2011, a tornado outbreak, among the largest recorded tornado outbreaks in U.S. history, produced 178 confirmed tornadoes across 16 states, resulting in severe destruction on all three days of the outbreak. A total of 38 people were killed from tornadoes and an additional five people were killed as a result of straight-line winds associated with the storm system. The outbreak of severe weather and tornadoes led to 43 deaths in the Southern United States. This was the largest number of fatalities in an outbreak in the United States since the 2008 Super Tuesday tornado outbreak. It is locally referred to as the "Forgotten Outbreak" in Alabama as it was vastly overshadowed by the 2011 Super Outbreak less than two weeks later.

<span class="mw-page-title-main">2011 Super Outbreak</span> Largest, costliest tornado outbreak in United States history

The 2011 Super Outbreak was the largest, costliest, and one of the deadliest tornado outbreaks ever recorded, taking place in the Southern, Midwestern, and Northeastern United States from April 25 to 28, 2011, leaving catastrophic destruction in its wake. Over 175 tornadoes struck Alabama, Mississippi, and Tennessee, which were the most severely damaged states. Other destructive tornadoes occurred in Arkansas, Georgia, Kentucky, Louisiana, New York, and Virginia, with storms also affecting other states in the Southern and Eastern United States. In total, 360 tornadoes were confirmed by NOAA's National Weather Service (NWS) and Government of Canada's Environment Canada in 21 states from Texas to New York to southern Canada. Widespread and destructive tornadoes occurred on each day of the outbreak. April 27 was the most active day, with a record 216 tornadoes touching down that day from midnight to midnight CDT. Four of the tornadoes were rated EF5, which is the highest ranking on the Enhanced Fujita scale; typically these tornadoes are recorded no more than once a year.

<span class="mw-page-title-main">Tornado outbreak sequence of May 21–26, 2011</span> United States meteorological event

From May 21 to May 26, 2011, one of the largest tornado outbreaks on record affected the Midwestern and Southern regions of the United States. A six-day tornado outbreak sequence, most of the tornadoes developed in a corridor from Lake Superior southwest to central Texas, while isolated tornadoes occurred in other areas. An especially destructive EF5 tornado destroyed one-third of Joplin, Missouri, resulting in 158 deaths and over 1,000 injuries. The Joplin tornado was the deadliest in the United States since April 9, 1947, when an intense tornado killed 181 in the Woodward, Oklahoma, area. Tornado-related deaths also occurred in Arkansas, Kansas, Minnesota, and Oklahoma. Overall, the tornado outbreak resulted in 186 deaths, 8 of those non-tornadic, making it second only to the 2011 Super Outbreak as the deadliest since 1974. It was the second costliest tornado outbreak in United States history behind that same April 2011 outbreak, with insured damage estimated at $4–7 billion.

The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.

<span class="mw-page-title-main">2011 Smithville tornado</span> 2011 EF5 tornado in Mississippi and Alabama

The 2011 Smithville, Mississippi tornado was an extremely powerful EF5 wedge tornado that devastated areas of rural Mississippi and Alabama, including the town of Smithville, Mississippi during the afternoon of April 27, 2011, resulting in catastrophic damage and numerous fatalities. This tornado was a part of the 2011 Super Outbreak, the largest tornado outbreak in United States history. The tornado reached an estimated maximum width of 3⁄4 of a mile with estimated wind speeds up to 205 mph (330 km/h).

<span class="mw-page-title-main">2010–11 North American winter</span>

The 2010–11 North American winter was influenced by an ongoing La Niña, seeing winter storms and very cold temperatures affect a large portion of the Continental United States, even as far south as the Texas Panhandle. Notable events included a major blizzard that struck the Northeastern United States in late December with up to 2 feet (24 in) of snowfall and a significant tornado outbreak on New Year's Eve in the Southern United States. By far the most notable event was a historic blizzard that impacted areas from Oklahoma to Michigan in early February. The blizzard broke numerous snowfall records, and was one of the few winter storms to rank as a Category 5 on the Regional Snowfall Index. In addition, Oklahoma set a statewide low temperature record in February.

References

  1. ↑ Cox, John D. (April 27, 2010). "Redefining Tornado Alleys". Discovery Channel . Retrieved March 1, 2012.
  2. ↑ Rice, Doyle (April 26, 2011). "Dixie Alley may see more tornado action than even Tornado Alley". USA Today . Retrieved March 1, 2012.
  3. ↑ VORTEX Southeast
  4. ↑ "VORTEX-SE". Earth Observing Laboratory. National Center for Atmospheric Research. Retrieved 2022-05-19.
  5. ↑ Pirtle, Keli (February 22, 2022). "Experts to preview major study on tornadoes in southeast United States" (Press release). Norman, OK: NOAA. NSSL. Retrieved 2022-05-19.
  6. ↑ "PERiLS". Earth Observing Laboratory. National Center for Atmospheric Research. Retrieved 2022-05-19.
  7. ↑ Douglas, Paul (April 28, 2010). "Deadlier than Tornado Alley: "Dixie Alley"". Star Tribune . Retrieved March 1, 2012.
  8. ↑ "New study puts metro Atlanta in 'Dixie Alley' for tornadoes". Atlanta Journal-Constitution. April 28, 2010. Retrieved March 1, 2012.
  9. ↑ Wind Design (Technical report). FM Global. October 2016. p. 97. Data Sheet 1-28.
  10. 1 2 3 4 5 6 7 Hayes, John L. (March 2009). "Service Assessment on the Super Tuesday Tornado Outbreak of February 5-6, 2008" (PDF). NOAA . Retrieved March 1, 2012.
  11. ↑ Dixon, P. Grady; A. E. Mercer; J. Choi; J. S. Allen (2011). "Tornado Risk Analysis: Is Dixie Alley an Extension of Tornado Alley?". Bull. Amer. Meteor. Soc. 92 (4): 433–441. Bibcode:2011BAMS...92..433D. doi: 10.1175/2010BAMS3102.1 .
  12. ↑ Gagan, John P.; A. Gerard; J. Gordon (2010). "A Historical and Statistical Comparison of "Tornado Alley" to "Dixie Alley"" (PDF). NWA Digest. 13 (2): 145–155.
  13. ↑ "Safety Helmets: A Practical, Inexpensive Solution for Reducing the Risk of Head Injuries Resulting from Tornadoes". University of Alabama Birmingham. Retrieved February 23, 2012.
  14. ↑ Saslow, Rachel (April 28, 2011). "Tornado season is at its height in 'Dixie Alley'". The Washington Post. Retrieved March 1, 2012.
  15. ↑ "USA's infamous 'Tornado Alley' may be shifting east". USA Today .
  16. ↑ Gensini, Vittorio A.; Brooks, Harold E. (17 October 2018). "Spatial trends in United States tornado frequency". npj Climate and Atmospheric Science. 1 (1): 1–5. doi: 10.1038/s41612-018-0048-2 .
  17. ↑ Strader, Stephen M.; W. S. Ashley; T. J. Pingel; A. J. Krmenec (2017). "Projected 21st century changes in tornado exposure, risk, and disaster potential". Climatic Change. 141 (2): 301–313. doi:10.1007/s10584-017-1905-4. S2CID   45309590.
  18. ↑ Strader, Stephen M.; W. S. Ashley; T. J. Pingel; A. J. Krmenec (2017). "Observed and Projected Changes in United States Tornado Exposure". Wea. Climate Soc. 9 (2): 109–123. Bibcode:2017WCS.....9..109S. doi: 10.1175/WCAS-D-16-0041.1 .
  19. ↑ "April 2011 tornado information". NOAA . USA.gov. May 9, 2011. Retrieved May 16, 2011.
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