美国国家公共电台 NPR--Derechos, or fierce windstorms, are becoming regulars in the Midwest

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Derechos, or fierce windstorms, are becoming regulars in the Midwest

Transcript¹

Severe storms and tornadoes² are common in the Midwest and Great Plains, and now Derechos are becoming well-known too. (Story first aired on All Things Considered on Dec. 20, 2022.)

WEATHER

'Derechos,' or fierce windstorms, are becoming regulars in the Midwest

STEVE INSKEEP, HOST:

The winter storm of recent days was worse than usual in many places. But, of course, severe cold and severe weather are common in the Midwest and on the Plains. One year ago this month, the fierce winds of a derecho were part of storms that hit Iowa and nearby states, killing³ at least five people and leaving devasted neighborhoods. Now scientists are working to figure out what future derechos might look like. Iowa Public Radio's Katie Peikes reports.

KATIE PEIKES, BYLINE⁴: December 15, 2021, was an unseasonably warm day - record highs in the 70s in some parts of Iowa - when a derecho blew through. The widespread, long-lived windstorm hit Matt Thompson's seed-and-fertilizer-application business more than 70 miles northwest of Des Moines.

MATT THOMPSON: There was a building there. You can see the pad still sitting there, the gravel⁵. That's where one of the buildings was.

PEIKES: Lost Grove⁶ Ag Services lost five of its six buildings. Thompson recalls getting to the business early the next morning to survey the damage.

THOMPSON: And when the sun came up, it was - we didn't know what we were going to do. It was pretty devastating⁷ to see. It was unbelievable. I'll never forget that.

PEIKES: This derecho was unique, the first recorded in December anywhere in the U.S. Wind gusts⁸ exceeded 80 miles per hour. The straight-line winds and tornadoes that accompanied left nearly $2 billion in damage stretching from Kansas to Michigan. Iowa, in particular, has been caught in the crosshairs of derechos over the last couple of years. Bill Gallus is a meteorology professor at Iowa State University. He says derechos thrive on warm, humid air in the atmosphere's lower levels, creating thunderstorms, something the Midwest often has.

BILL GALLUS: Those thunderstorms are able to tap into very strong winds happening higher up in the atmosphere, even up toward the jet stream, so that they can bring those strong winds down to the ground. That is what happened in the recent December 2021 derecho in the Midwest.

PEIKES: There isn't a lot of research on derechos, so scientists say it's hard to know how they'll fare in a warming earth. Gallus says there's more energy in the atmosphere as it warms, and that could pave the way for more powerful and more frequent derechos. But scientists can't say for sure. And some attribute the uncertainty⁹ to the fact that there's no official database for derechos like there is for hurricanes or tornadoes where they can look for historic trends. That's something the National Weather Service is working on. Meteorologist Matthew Elliott says derechos have no formal definition.

MATTHEW ELLIOTT: When you hear the word derecho, it's got to trigger something. It's got to trigger that this is the worst windstorm that I'm going to see.

PEIKES: Once they have a label and better data, Elliott says it'll make forecasting derechos easier and will give people more warning to get to safety. The National Weather Service has improved the alert system. That's after a highly destructive derecho hit the Midwest back in August 2020, killing four people. Now when a severe thunderstorm warning is issued with strong winds of at least 80 miles per hour, people get an alert on their phones. But Walker Ashley, a disaster geographer¹⁰ at Northern Illinois University, says more should be done with urban planning and building codes.

WALKER ASHLEY: We build at the bare minimum standards in this country. And that has all sorts of consequences from heating costs to damage within extreme damaging wind events.

PEIKES: After all, Ashley says as cities grow and sprawl¹¹ out, they're putting more people in harm's way of extreme weather like derechos. For NPR News, I'm Katie Peikes in Ames, Iowa.

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