Climatologist says time will tell future severity of storms

State Climatologist Justin Glisan acknowledges that with the Greenfield tornado as the centerpiece as the third-strongest observed tornado on record and only the third with wind speeds of over 300 mph, Iowa’s severe weather season has been much stronger than usual in 2024. The state has seen 129 tornadoes, which is much higher than the 44-48 it usually sees annually.

While there may be signals on the horizon of how future years will go, he cautions that time will truly tell the story of how severe next year’s storm season will be.

“We are still sifting through atmospheric signals for clues as to why this season has been anomalous. There was a shift from a strong El Nino that gave us the second warmest winter in 152 years to ENSO-neutral; near-normal Pacific) conditions through spring and early summer,” Glisan said. “In years where we’ve seen this transition, springs are typically warmer and wetter, and seeing a warmer and wetter atmosphere means more thunderstorms. Combine that with a slightly more northerly-oriented jet stream and various heat domes and Iowa happened to be in a prime position for substantial severe weather events.”

Precipitation has followed with storm chances this year as the state snapped a streak of 2024 consecutive weeks for moderate or worse drought, which was the longest drought since the 1950s.

“What we saw set up in early 2024 was a drought buster,” Glisan said. Through July, southwest Iowa has had its 36th wettest start to the year since 1895, while statewide, the sixth wettest.

Glisan thinks that a warming environment means more water vapor will be available, which means added ingredients needed for severe weather in the future.

“While tornadic activity has shifted farther south and east, we are seeing more tornado outbreaks with 30 or more tornadoes per event,” Glisan said. “We shouldn’t expect seasons such as we are having now, but we need to be weather aware and cognizant of what the trends are showing us.”