Tornado season is here again, with twisters striking in Indiana, Pennsylvania, and Florida over the past few weeks. While severe storms in spring are nothing new, subtle changes in tornado patterns in recent years portend a more dangerous future for communities across the country.
According to a preliminary count from the National Centers for Environmental Information, 547 tornadoes were documented from January through April 2024.
That figure is higher than the year-to-date average — 338 — the organization calculated between 1991 and 2020 but in line with the number observed in 2022 and 2023 in the same time frame.
And even as the number of tornadoes has stayed relatively consistent in the last few years, experts say there have been key changes in their behavior over time that could have major consequences.
More tornadoes are now concentrated in fewer days, meaning they are less spread out and there’s a higher number occurring on the same day, according to a 2019 study published in Theoretical and Applied Climatology.
A growing number of tornadoes are also occurring in the southeastern part of the US in addition to the Great Plains, where they have been historically most common.
Experts still don’t know why both these trends are occurring, and it’s not clear if climate change is playing a role. What is more certain is that these shifts mean people will have to prepare for these natural disasters in new ways, with some communities enduring more severe storms in rapid succession and others being forced to build infrastructure for tornadoes they had rarely experienced before.
Scientists have some information about why there are more concentrated tornadoes, or clustering, and why the locations of tornadoes have shifted slightly.
Clustering is tied to the presence of atmospheric and wind conditions that fuel dozens of tornadoes at once. Changes in geography are related to parts of the country drying out while other areas are seeing more rain.
Tyler Fricker, author of the 2019 study on the subject, says the increase in tornado clustering has been observed since the 1980s and continues into the present day.
According to that study, while 11 percent of tornadoes occurred on days when there were 20 or more tornadoes from 1950 to 1970, now 29 percent of them do.
The prevalence of low-pressure systems, warm moist environments, and high wind shear (changes in speed and direction of wind combined with height) all fuel these clusters. (CONTINUE)
