United States Experiencing the devastation caused by tornado gusts. At least five people were killed Wednesday as a tornado hit southeastern Missouri. Six people died in New Jersey and one in Delaware, the widest range of deaths in the state on record. Last weekend, a series of tornadoes in the South and Midwest killed more than 30 people. And he had 168 preliminary tornado reports in January, almost five times the average for the month from 1990 to 2010.
The start of tornado season is busy and deadly, with twisters hitting areas that would normally be spared. These two factors are driving the formation of tornadoes. But experts warn that it’s too early to tie a single major event or season to climate change. What they are seeing is changes in when and where tornadoes strike, potentially putting more people at risk.
Jana Houser, professor of meteorology at Ohio State University, said: Meteorologists can observe increases in humidity and warming, along with changes in the jet stream, and see how those affect storms that cause tornadoes. But Hauser said, “We can’t pinpoint exactly what we expect in terms of when and where tornadoes will occur.”
Most tornadoes arise from rare supercell thunderstorms. A tornado needs warm, moist air near the ground to form. But you also need strong vertical wind shear caused by the changing wind direction and speed between ground and high altitude. The air begins to rotate horizontally in a cylinder-like shape. As it lifts and gains speed, it narrows and forms a terrifying funnel recognized as a tornado.
To understand how tornado patterns change, meteorologists are looking at trends in parent-supercell storms. As the heat in the atmosphere increases, it becomes more humid and unstable. But wind shear, another component of tornadoes, may actually decrease over time with climate change. As the temperature difference between the Arctic and mid-latitude air decreases, the jet stream weakens and can affect wind shear. The ultimate result of these changes mixing into the atmosphere is not clear.
“We’re still experimenting,” says Walker Ashley, a professor of meteorology at Northern Illinois University who wrote a recent paper on changes in tornado patterns. “We are changing when we look at the fundamental factors that create violent storms. It is a question of how much and how big.”
Supercell storms are likely to hit the United States more frequently in late winter and early spring, and less frequently in late summer and fall, experts say. Also, the tornado area is changing. Tornado Alley, which spans parts of Texas, Louisiana, Oklahoma, Kansas, South Dakota, Iowa and Nebraska, has long been a hotbed of twisters. But the drought has reduced the number of storms, says Robert He Trapp, a professor and director of the Department of Atmospheric Sciences at the University of Illinois at Urbana.
