News Track: Iowa’s 2024 tornadoes break record at 125

Background

History was made in 2004 when a record 120 tornadoes touched down in Iowa. Two decades later in 2024, history was made again when a record 125 tornadoes struck.

The number of tornadoes to strike Iowa in a year varies greatly, but the average is about 50. And while twisters can strike far outside of the summertime, the typical tornado season in Iowa runs April through June.

The 2024 tornadoes not only varied from the norm in their sheer number, but also their timing.

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What’s happened since

According to the National Weather Service, there were 125 tornadoes reported in Iowa in 2024, an increase from the 72 confirmed tornadoes in 2023 — which itself was a 71 percent increase from the 42 in 2022.

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Although 2024 was a record-breaking year, majority of the twisters occurred in April and May, toward the beginning of a typical season. Out of the 125 tornadoes, 98 occurred in April and May — with 49 twisters each month.

William Gallus, a professor in the Department of the Earth, Atmosphere and Climate at Iowa State University, said 2024 was “a bit unusual” in that the majority of the tornadoes occurred in the last half of April and May.

But recently, Gallus said, there have been more tornadoes popping up in Iowa outside of the typical worst months. For example, Gallus noted, there was an outbreak on Dec. 15, 2021, that produced 61 tornadoes in Iowa, setting the record for the most in one day. He said Iowa has also seen tornadoes in early March and “a bunch” that formed in July.

“We are being reminded that tornadoes can happen any time of year,” Gallus said. “Last year was a bit more normal in the timing, although the really active period did end up a few weeks earlier than normal.”

Justin Glisan, the state climatologist with the Iowa Department of Agriculture and Land Stewardship, agreed.

“In terms of tornadic behavior, the trends that we've seen are less days in which you see one or two tornadoes … that's been decreasing since the 50s,” Glisan said of the days when tornadoes strike. “But where we have seen a trend are days in which you see 30 tornadoes or more, so more outbreak days are possible.”

What conditions make for strong tornadoes?

Multiple environmental factors must occur for a tornado to form.

Tornadoes need instability — the energy that fuels thunderstorms — that happens when hot air rises and traps warm air beneath it.

Due to abnormally persistent warm temperatures in Texas and the Gulf of Mexico during the past year, more warm air was able to make its way into Iowa’s weather patterns, Gallus said.

“We thus had the perfect ingredients come together often in Iowa with several big outbreaks of tornadoes — over 10 to 20 tornadoes in a day — as we would end up in the perfect spot relative to the weather systems,” Gallus said.

Gallus said tornadoes also need a vertical wind shear to form, which is a change in wind speed or direction.

“That allows air to have a rolling motion, like what happens if you put a pencil in your hand and roll your other hand along the top side of the pencil lying in your other hand … your hands are doing different things, which is like what is happening in the atmosphere with the winds doing different things,” Gallus said. “The storm with its rising motion can then tilt the rolling motion so it becomes a spinning motion — a rotating storm that can then make a tornado.”

The strength of tornadoes is divided into six categories, broken down on the Enhanced Fujita Scale, or the “EF scale.” They include:

Out of the 125 tornadoes in 2024, only two were confirmed as EF4 and four were EF3s. Both criteria are on the more “severe” end of the spectrum. One person died when one of those EF3 storms struck Minden on April 26. Five died when an EF4 struck Greenfield on May 21.

The vast majority of the tornadoes in 2024 scored as EF0 and EF1.

A changing climate

Going forward, Gallus said it’s difficult to predict if there will be more tornadoes each year. “Nationally, that does not appear to be happening,” he said.

Gallus said that studies have shown that Tornado Alley — which roughly runs north from Texas through Oklahoma, Kansas, Nebraska to South Dakota — will see fewer tornadoes, but that regions “near and east” of the Mississippi River will see more.

“In Iowa, that effect might mostly cancel out, with maybe a few less in Western Iowa but a few more in Eastern Iowa,” Gallus said. “The total number of tornadoes per year probably won’t change much in Iowa, but it is likely that they will continue to happen most often in the parts of the year that used to be too cold for tornadoes, like late fall, winter and early spring, and maybe become a bit more rare in summer.”

Glisan said that a warmer atmosphere with more water vapor does increase the probability of more severe weather across the board, not just for tornadoes.

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Gallus added that it would “make sense” if Iowa’s main tornado season shifts more into April and May, instead of May and June.

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: olivia.cohen@thegazette.com