Tornadoes can be extremely deadly and destructive, but few weather words strike fear into the hearts of Iowans like derecho, and Iowa forecasters say conditions are developing to make one of those massive storms possible tonight.
Meteorologist Donna Dubberke, at the National Weather Service, says it’s an “evolving situation” and she’s warning everyone across the region to keep a very close ear on the forecast and an eye on the sky.
“We do expect storms to develop in South Dakota into Minnesota late this afternoon into early evening and then start to track to the east or southeast,” Dubberke says. “The questions are where exactly that’s going to track, and then the other question is, how strong is it going to be?”
Iowa took the brunt of a powerful derecho in August of 2020 that packed winds which, based on the damage, may’ve hit 140 miles an hour. That’s the equivalent to a Category 4 hurricane, in fact, some refer to derechos as “land hurricanes.” It was one of the most destructive storms ever to hit the Midwest, with damage in multiple states estimated at over $11-billion.
Dubberke says it does -not- appear tonight’s events will be anywhere near as severe.
“There is potential for it to be strong enough to be a derecho, but at this point we don’t expect it to be the same as what we had, for example, in 2020, which is the one that so many people remember because it was a high-end, extreme case, even for a derecho,” Dubberke says. “We are worried about severe thunderstorms with damaging winds being the main threat.”
A derecho is a widespread, long-lived, straight-line wind storm that’s associated with a fast-moving group of severe thunderstorms, and Dubberke says they’re rare, and they can be exceptional devastating.
“Once you get it moving, it just keeps going and so it makes the storm very strong,” she says. “And the thing with a derecho is you get an enhanced wind threat, so damaging wind that lasts for a long time, covers a long area, and is stronger than your average thunderstorm, so we’re talking winds of 75 to 80 miles an hour or stronger.”
The winds that hit Iowa in 2020 were much stronger, flattening crops, ripping roofs off houses, and destroying more than half of the tree canopy in Cedar Rapids. Cleanup took a full year. Dubberke says a derecho is a gargantuan storm.
“That’s what makes them unusually impactful, is they affect a large area,” she says. “It’s not just an isolated downburst, it’s something that affects many people over multiple counties — or an entire state. They’re an extreme type of storm.”
Dubberke is also especially concerned about toppling trees as Iowa has had so much rain lately, a powerful wind storm could knock over trees with compromised or shallow root systems in the moist soil.