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, Western Kentucky, 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> Rotating air column connecting the Earth’s 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), can be more than 3 kilometers (2 mi) in diameter, and can 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">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 violent 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 $600 million USD in damage. 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

From May 2 to 8, 1999, a large tornado outbreak took place across much of the Central and parts of the Eastern United States, as well as southern Canada. During this week-long event, 152 tornadoes touched down in these areas. The most dramatic events unfolded during the afternoon of May 3 through the early morning hours of May 4 when more than half of these storms occurred. Oklahoma experienced its largest tornado outbreak on record, with 70 confirmed. The most notable of these was the F5 Bridge Creek–Moore tornado which devastated Oklahoma City and suburban communities. The tornado killed 36 people and injured 583 others; losses amounted to $1 billion, making it the first billion-dollar tornado in history. Overall, 50 people lost their lives during the outbreak and damage amounted to $1.4 billion. For these reasons, the outbreak is known in Oklahoma as the May 3rd outbreak or the Oklahoma tornado outbreak of 1999.

<span class="mw-page-title-main">Tornado records</span> List of world records related to tornadoes

This article lists various tornado records. The most "extreme" tornado in recorded history was the Tri-State tornado, which spread through parts of Missouri, Illinois, and Indiana on March 18, 1925. It is considered an F5 on the Fujita Scale, holds records for longest path length at 219 miles (352 km) and longest duration at about 3+1⁄2 hours. The 1974 Guin tornado had the highest forward speed ever recorded in a violent tornado, at 75 mph (121 km/h). The deadliest tornado in world history was the Daulatpur–Saturia tornado in Bangladesh on April 26, 1989, which killed approximately 1,300 people. In the history of Bangladesh, at least 19 tornadoes killed more than 100 people each, almost half of the total for the world. The most extensive tornado outbreak on record was the 2011 Super Outbreak, which resulted in 367 tornadoes and 324 tornadic fatalities, whereas the 1974 Super Outbreak was the most intense tornado outbreak on tornado expert Thomas P. Grazulis's outbreak intensity score with 578, as opposed to the 2011 outbreak's 378.

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

A waterspout is a rotating column of air that occurs over a body of water, usually appearing as a funnel-shaped cloud in contact with the water and a cumuliform cloud. There are two types of waterspout, each formed by distinct mechanisms. The most common type is a weak vortex known as a "fair weather" or "non-tornadic" waterspout. The other less common type is simply a classic tornado occurring over water rather than land, known as a "tornadic", "supercellular", or "mesocyclonic" waterspout, and accurately a "tornado over water". A fair weather waterspout has 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. Most waterspouts do not suck up water.

<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, also known as Tornado Valley, 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 not touching 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">Tornado outbreak</span> Multiple tornadoes spawned from the same weather system

A tornado outbreak is the occurrence of multiple tornadoes spawned by the same synoptic scale weather system. The number of tornadoes required to qualify as an outbreak typically are at least six to ten, with at least two rotational locations or at least two supercells producing multiple tornadoes.

<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, varying 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">Convective storm detection</span> Meteorological observation

Convective storm detection is the meteorological observation, and short-term prediction, of deep moist convection (DMC). DMC describes atmospheric conditions producing single or clusters of large vertical extension clouds ranging from cumulus congestus to cumulonimbus, the latter producing thunderstorms associated with lightning and thunder. Those two types of clouds can produce severe weather at the surface and aloft.

<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">2011 Hackleburg–Phil Campbell tornado</span> 2011 natural disaster in the United States

The 2011 Hackleburg–Phil Campbell tornado was a large, long-lived, and devastating EF5 tornado that impacted several towns in rural northern Alabama before tearing through the northern suburbs of Huntsville on the afternoon and early evening of April 27, 2011. It was the deadliest tornado of the 2011 Super Outbreak, the largest tornado outbreak in United States history. The second of four EF5 tornadoes to touch down on April 27, the tornado reached a maximum width of 1.25 miles (2.01 km) and was estimated to have had peak winds of 210 mph (340 km/h).

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 a fast-moving and extremely violent 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 23 fatalities. This tornado was a part of the 2011 Super Outbreak, the largest tornado outbreak in United States history, and the third of four EF5 tornadoes to touch down on April 27, 2011, during the outbreak's most prolific day for tornadoes. The tornado reached an estimated maximum width of 3⁄4 of a mile with estimated wind speeds over 205 mph (330 km/h).

<span class="mw-page-title-main">Tornado outbreak of November 29–30, 2022</span> Late-season tornado outbreak in the Southern United States

A late-season tornado outbreak in the Southern United States affected the states of Louisiana, Mississippi, Alabama, and Georgia, from the afternoon of November 29 into the morning of November 30, 2022. The outbreak was the result of an intense upper-level trough that materialized over the aforementioned states where increased moisture, atmospheric instability, and elevated wind shear were present, creating conditions highly conducive to supercell thunderstorms. Multiple tornadic storms developed in the risk area, producing numerous tornadoes. Several of these tornadoes were strong and destructive, prompting the issuance of multiple PDS tornado warnings. Two low-end EF3 tornadoes caused severe damage near Clarks, Louisiana and Tibbie, Alabama respectively while the Flatwood and Willow Springs communities north of Montgomery, Alabama was struck by an EF2 tornado, which caused two fatalities. Numerous weaker tornadoes also touched down, including a high-end EF1 tornado that caused considerable damage in Eutaw, Alabama. In all, 27 tornadoes were confirmed.

<span class="mw-page-title-main">History of tornado research</span>

The history of tornado research spans back centuries, with the earliest documented tornado occurring in 200 and academic studies on them starting in the 18th century. This is a timeline of government or academic research into tornadoes.

References

  1. ↑ Cox, John D. (April 27, 2010). "Redefining Tornado Alleys". Discovery Channel. Archived from the original on March 1, 2012. 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. Archived from the original on February 25, 2012. 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): 38. Bibcode:2018npCAS...1...38G. 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. Bibcode:2017ClCh..141..301S. 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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