Alan Gerard and John Gagan of the National weather Service Forecast Office in Jackson, Mississippi have corroborated with John Gordon of the National Weather Service in Louisville on some interesting research.
When we think of tornado alley, we think of the area from Texas through Oklahoma into Kansas and Nebraska. And without question, more tornadoes occur there than anywhere in the world. While not questioning the existence of “tornado alley,” the intrepid trio of meteorologists have proven that there is a secondary concentration of tornado activity, and we live in the heart of it.
Mssrs. Gerard, Gagan and Gordon don’t claim credit for the term “Dixie Alley.” They credit it to Alan Pearson, who was the Director of the National Severe Storm Forecast Center. He coined the term after the terrible February 1971 tornado outbreak in the Mississippi Delta. A total of ten tornadoes killed 121 people across Mississippi and Louisiana that day. Dixie Alley covers Alabama, most of Georgia, the western two thirds of Tennessee and all of Mississippi, Louisiana and Arkansas.
The researchers used data since 1998, when Doppler radar was fully deployed. They came to the following conclusions:
1. There are 1.5 times as many strong tornadoes (F3 or greater) in Dixie Alley as compared to the traditional Tornado Alley. The total counts was 338 versus 206 during the time period they studied. So, while Tornado Alley had more tornadoes overall than Dixie Alley, the occurrence of strong to violent tornadoes is much greater in the South.
2. Killer tornadoes are more prevalent in Dixie Alley than in Tornado Alley. There were 66 versus 24. A lot of factors go into that statistic. First and foremost, the population density in Dixie Alley is greater than that of traditional Tornado Alley. Additionally, many tornadoes in Dixie Alley are obscured by terrain or wrapped in rain. This makes it harder to see them coming. Also, in the incidence of strong and violent tornadoes across the Plains drops off dramatically after sunset, while in Dixie Alley, the numbers fall much more slowly. So, many more strong tornadoes occur in the dark in the South. This makes them even deadlier.
3. Dixie Alley actually suffers from more “outbreaks” of tornadoes. During the seven year study periods, there were nine days with ten or more strong tornadoes across Dixie Alley, while there were five in Tornado Alley. In addition, the tornado threat is less seasonal in Dixie Alley, with a consistent threat from January through May and a large peak in November.
So, the excellent study is very relevant to us here in Alabama, in the middle of Dixie Alley. They stress that it is preliminary research. See their presentation at: http://www.srh.noaa.gov/jan/dixieAlley/img0.html.