Dixie Alley is a nickname sometimes given to areas of the southern United States which are particularly vulnerable to strong or violent tornadoes. This is distinct from the better known Tornado Alley and has a high frequency of strong, long-track tornadoes that move at higher speeds. The term was coined by NSSFC Director Allen Pearson after witnessing a tornado outbreak which included more than 9 long-track, violent tornadoes that killed 121 on February 21, 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 thunderstorm structures.
Geography
Dixie Alley includes much of the area of the lower Mississippi Valley. It stretches from eastern Texas and Arkansas across Louisiana, Mississippi, Tennessee, Alabama, Georgia, and far western Kentucky to upstate South Carolina and western North Carolina; the area reaches as far north as southeast Missouri. Another source places all of Arkansas within Dixie Alley. Although tornadoes are less frequent in these states than they are in the southern Plains, the southeastern states have had more tornado-related deaths than any of the Plains states. This is partly due to the fact that there are relatively high number 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. According to the National Climatic Data Center, 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.
Dixie Alley is part of a region of enhanced tornadic activity extending between the Appalachian and Rocky Mountains, but tornadoes and outbreaks in the Dixie Alley region exhibit some statistically distinguishable characteristics than the more well known Tornado Alley. 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 visually impairing the tornadoes to storm spotters and chasers, law enforcement, and the public. 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. 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, and several notorious outbreaks have struck during the late winter and early spring and also in late fall. 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. A 2018 study found in the U.S. an overall eastward shift of tornado frequency and impacts - toward Dixie Alley. 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. Variations in climate patterns and teleconnections, such as the El Niño–Southern Oscillation 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.
