For more than 70 years, a stripe through the middle of the United States extending from Texas north to Nebraska was known as Tornado Alley.
But meteorologists say that in the last 20 years, the alley has shifted away from the northern Great Plains and toward the Southeast, meaning fewer tornadoes are happening in Nebraska.
“Historically, Nebraska is a unique point,” Ross Dixon, an assistant professor of Earth and atmospheric science at the University of Nebraska-Lincoln, said. “Where we are in Nebraska, maybe there will be less severe storms, especially in the North and West, which can be problematic because we get a lot of precipitation from these storms.”
In a 2023 experiment published by The American Meteorological Society, atmospheric scientists were able to create future simulations on how various climate factors could play a role in the shift of supercell storms, which give birth to tornadoes. By creating calculated changes to wind shear and an increase in greenhouse gas concentrations, these simulations showed a move Southeast.
“Generally, this macroscale analysis of ingredients suggests there will be a reduced number of future environments supportive of supercells in portions of the Great Plains,” Walker Ashley, an atmospheric scientist at Northern Illinois University and one of the authors of the study, said. Ashley said that the likelihood is for more impactful tornadoes to occur in the Ozarks, mid-South and Tennessee Valley.
“Of particular concern for future impacts is the growing likelihood of supercells to contain stronger and more intense mesocyclones, which correlates with the production of significant tornadoes and hail,” Ashley said.
What is causing the shift? Scientists theorize it’s climate change. When air temperature and wind conditions change, so does tornado density.
“It seems that the climate factors or changes in radiation absorption, almost on a global scale, will change storm environments enough to produce that kind of shift,” said Matthew Van Den Broeke, an associate Professor of Earth and atmospheric science at UNL. “When there is an increase in radiation absorption, the sea level temperature increases which in turn affects the wind conditions and thus increases the likelihood of tornadoes occurring in more humid areas such as the Southeastern United States” Van Den Broeke said..
According to maps published as part of the study, the shift shows more supercell thunderstorm development in eastern Oklahoma, Arkansas, southern Missouri and western Tennessee.
“An increase in supercells would drive tornado distribution down toward the southeast,” Michael Shambaugh-Miller, a lecturer in the school of Global Integrative Studies at UNL, said. “If you look at how dense are the storms that produce tornadoes, we see a shift away from the Great Plains, especially the Northern Great Plains and the High Plains, all the way down to West Texas and Western Oklahoma, and that does shift down toward the Southeast.”
As Tornado Alley moves away from the Great Plains, an area that is accustomed to severe weather events, residents could expect a change in weather patterns.
With less precipitation, Nebraskans could face drought conditions or other contingent issues. However, Dixon said there have been extreme droughts in the Great Plains, before, and that there have been studies showing a generally drying out of the Great Plains.
“There are cycles of moist and dry conditions in the Great Plains, which last about 20 to 40 years,” Dixon said.