Most everyone has heard of Tornado Alley, stretching from Texas, through Oklahoma and into Nebraska and Iowa. It’s an area that we typically associate with numerous tornadoes through severe weather season, but just recently some research shows an eastward trend in tornadoes.
Victor Gensini, Ph.D., a meteorology professor at Northern Illinois University, decided to investigate tornado frequency after storm chasing trips yielded lower results over the past several years.
“The major message here is not that Kansas, Oklahoma and Texas do not get tornadoes anymore, that’s not true. They obviously still get lots of tornadoes every year, it’s just that places further east are seeing more in terms of their trend every year,” says Gensini.
By combining tornado report data and weather model parameters that show where tornadoes would be most likely on a given day. The resulting research showed a pattern of tornadoes becoming more numerous further to the east.
Gensini explains, “There has been a downward trend in places like Texas Oklahoma, and Kansas in terms of the number of tornadoes that they experience every year, and an increasing trend further to the east in places like Illinois, Indiana, Mississippi and Tennessee. Some portions of the Midwest and Mid-South.”
Perhaps one of the most important things isn’t that the trends are simply increasing, but WHERE they are increasing. Once you move east of the Mississippi the population density rises, as do the number of mobile home users.
“These are the sort of events that happen east of the Mississippi that are more likely to kill and injure people,” adds Gensini, “ So, if we are seeing an increasing trend in those areas, we really need to start thinking about exposure, mitigation, vulnerability and how best to protect people that are living at the surface in these mobile homes.”
After hearing about this research, Sam Lashley from the National Weather service in Northern Indiana, investigated our regional trends and found something interesting.
“We are seeing an increase in our lower end tornadoes, EF-0 to EF-1 tornadoes but we are seeing a decrease in the stronger and more violent tornadoes in our area. So, while we are seeing an increase on average every year in tornadoes. The strength of them are actually on the weaker side. We’ve gone from averaging around 8 tornadoes per year in our region. To about 10 tornadoes per year now, and that’s kind of changed over the last 20-30 years”, describes Lashley.
The reason for this eastward shift is still being investigated but the initial thinking is that it is related to a drying out of the plains, meaning less moisture for storms, making them form further east.
Gensini explains, “It’s certainly very consistent with a drying out of the southern great plains and central great plains, that is projected by our climate models, as we go forward over the next 50-100 years. So, it’s kind of easy to jump to that climate change conclusion right now. But it’s hard to say, you know in 30 years maybe the trends will reverse, and they go back towards the great plains. So maybe this is more of natural variability. We are still not sure; we are not able to answer that question definitively right now.”
Gensini concludes that this is research that will continue as more tornado events happen. “Every time a tornado event occurs it leaves behind a fingerprint, not only on the ground where you have damage but also in the atmosphere. So, if we could better use artificial intelligence and data mining to be able to extract out a better representation of the environment that is present when these tornadoes occur. It will allow us to create a stronger relationship between the environment and the report, and then we will be able to say with much greater certainty whether or not these trends are real and allow us to better forecast what maybe might happen 30-40 years from now.”