By NATHAN GREGORY
According to a recent study conducted by tornado researchers at The Weather Channel, data compiled from 1990-2010 by the National Weather indicates Mississippi ranks fifth on a list of states with the most tornadoes per 10,000 square miles within that time.
Mississippi State University professor of meteorology and climatology Charles Wax said the study carries weight because it takes into account each state’s size in determining the density of activity in the areas. He said though other states receive more tornadoes than Mississippi, the fact that the state is approximately 47,000 square miles while other states are larger is indicative of the volume the state receives each year.
“Texas gets three or four times more tornadoes than we do, but they’re three to four times larger than we are,” he said. If you normalize it by area it’s about the same per square mile.”
He said in statistics compiled from 1950-2006, there were 13 confirmed tornado touchdowns in Oktibbeha County and 1,541 statewide. What makes Mississippi unique is when it receives tornado activity. He said the state receives 29 tornadoes per year on average and is in the heart of what is unofficially termed Dixie Alley. Due to its proximity to the Gulf of Mexico, he said, there are two distinct seasons when tornadoes are most likely to occur.
“Normally in a season when the winter is retreating and ... warm air masses are coming up from the Gulf, that’s when we experience our highest rate of activity,” Wax said. “We have a secondary maximum here. Late February into April (is the primary window where the most activity takes place). November is a secondary occurrence period when we’re getting into winter and the cold air begins to intrude with the warm air that is already in place and is trying to push it out. It’s just the opposite of what we see in the spring.”
MSU assistant professor of climatology and meteorology Grady Dixon said another variable that adds to the danger of the storms when they occur in the state. There are many tornadoes that happen at night, he said.
“If you look at the real physical variables, why they happen at night is we get tornadoes from November through May ... when days are short. (Also) our storms tend to move a lot faster because they happen in cooler seasons, and that’s when we have those big low pressure centers,” Dixon said. “They also move much faster here. (If) a single tornado touches down in western Kansas it may be down for 10 minutes and only travel two miles; one can be on the ground for 10 minutes here and travel 10 miles. If it happens at night, it makes it that much more dangerous.”
In a recent study published in the April 2011 issue of the Bulletin of the American Meteorological Society, Dixon said despite the identification of a few isolated locations in the Southeast with unusually high tornado densities (including Smith County in Mississippi, which the study named the most tornado-prone area in the country), Dixie Alley is not necessarily its own distinct region separate from Tornado Alley, which comprises much of the Midwest.
“Statistical analysis shows that regions with similar tornado-day densities are located throughout the Great Plains, the Corn Belt and the Deep South without areas of statistically significant differences separating them. There are a few discontinuous patches of significantly reduced tornado-day density stretching from northeastern Missouri down through western Arkansas and southeastern Oklahoma. The result is merely a somewhat circular region of elevated risk with maxima located in places such as Mississippi, Arkansas, Oklahoma, Nebraska and Illinois,” Dixon said in the article. “This circular pattern is most likely due to the relative lack of events over the relatively complex, elevated terrain of the Ozark and Ouachita Mountains. It is possible that this line of relatively little tornado activity is partially responsible for the emergence of Dixie Alley as a separate region. Hence, if there were no mountains in Missouri, Arkansas and southeastern Oklahoma, it is likely that Tornado Alley would be a continuous region of increased tornado frequency stretching from the Great Plains through the Corn Belt and Deep South.”