More tornadoes in Conn. possible, experts say
Tornadoes, even small ones like those that hit Connecticut this weekend, are difficult to predict, but experts believe that as human-induced climate change continues, the conditions that tornadoes need will become more common.
“There isn't a clear answer on whether there will be more frequent tornadoes,” said Anji Seth, a professor at the University of Connecticut’s Department
of Geography and chair of the university’s atmospheric sciences group. “But there is definitely already a sense that when the conditions exist, the outbreaks are becoming bigger and there is a greater likelihood of tornadoes.”
Tornadoes are not so rare in Connecticut, but a tornado in November was previously never recorded.
“They’re so extremely rare that these four were the first on record,” said Gary Lessor, of Western Connecticut State University’s
weather center. “The latest we’ve ever seen a tornado since 1950 was on Oct. 29 of 2018 in Stonington.”
The reason is temperature. Tornadoes require three things, as Seth and Lessor explained, and a warmer ground temperature with moist air is key among them.
“They need very warm, moist conditions near the surface,” Seth said. “They need drier, colder conditions up above. and they need winds to strengthen as you go from the surface to higher in the atmosphere. That's what they call ‘wind shear.’”
So, as climate change proceeds and the Northeast region continues to get incrementally warmer, those conditions are more likely to occur, experts said.
“There is research that shows that as the climate warms, this very warm moist air near the surface will occur more frequently,” Seth said.
One problem with projecting an increase in the number and strength of tornadoes is that they take place over a short period of time, in small, localized area.
“These are very smallscale
events, in short timescale and small spatial scales,” Seth said. “So the models really can't simulate a tornado, they can simulate the environment for tornadoes, and there's research that has shown that those environments might be increasing.”
That being said, climate shifts in one part of the world can affect the weather in other parts of the world, and there is evidence, according to Seth, that the general circulation
of weather is shifting in a northeasterly direction.
“There's research about the way warming affects the larger, global circulation. We know that as Earth's surface warms, we have a pretty good understanding of the general circulation of the atmosphere,” Seth said. “Eastward, and poleward is the expansion of the general circulation.”
That might suggest that “there could be a shift eastward in the tornado tracking,” she said.
But warm, moist air at the surface is only one condition typically needed for tornadoes to form. Even if you have high winds, a tornado needs vertical wind gust.
“Whether you get more wind shear, the vertical change in speed, is still a question,” Seth said.
Though tornadoes typically need warmer, wetter conditions on the ground, Lessor said Saturday’s tornadoes were more a result of “upper level dynamics.”
“Conditions really weren't all that warm or humid this time,” he said.
In this case, Lessor said there was cold air higher up, with “a southeast flow ahead of the front, so the air was rising very rapidly,” creating the necessary wind shear. There also was a “jet max in the area,” which means there was very forceful winds both higher in the atmosphere and closer to the ground.
The conditions, Lessor said, were perfect.
“The alignment of everything has to be perfect in November for something to happen,” he said. “This was an overachiever. The conditions were prime.”