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Inside the derecho that pummeled the Midwest

On August 10, a weather complex known as a “derecho” sent intense winds and thunderstorms over a 700-mile stretch from Nebraska to Indiana. Now, Iowa works to recover from its damage.

BySukee BennettNOVA NextNOVA Next

Members of the Iowa Air National Guard remove trees limbs near downed power lines in Cedar Rapids, Iowa on August 18, 2020, eight days after a powerful derecho hit the Midwest. Image credit: Senior Master Sgt. Vincent De Groo, U.S. Air National Guard

A global pandemic. Forest fires in the West. And now a derecho.

On the evening of Monday, August 10, a weather complex known as a “derecho” sent intense winds and thunderstorms over a 700-mile stretch from Nebraska to Indiana. In Iowa, the hardest-hit state, three deaths have been reported so far and hundreds of thousands of people went without power for days. More than 40% of the state’s corn and soybean crop, the core of Iowa’s economy, was severely damaged by the storm, whose winds reached 110-140 mph, equivalent to those of a Category 3 or 4 hurricane. Patrick Marsh, science support chief at the National Weather Service’s Storm Prediction Center in Norman, Oklahoma compared it to the devastating “Super Derecho” of 2009, which extended from Kansas to Tennessee.

Destruction to Iowa’s homes, farms, businesses, livestock, and crops translates to a $4 billion hit, Donnelle Eller reports for the Des Moines Register.

Cedar Rapids was one of the hardest hit cities in the state. More than 800 buildings suffered partial collapse of the roof, walls, ceiling, or floors, and more than 20 schools sustained damage, Cedar Rapids Fire Chief Greg Smith tells CNN.

“Nearly every home has damage. Most big trees in the city fell. Most local businesses are closed. Every business is damaged. Most roads are impassable,” writes Cedar Rapids resident Ben Kaplan on Medium.

“Our city of Cedar Rapids has been destroyed by a Derecho, a term for a type of storm I’ve never heard of and never want to hear of again,” one Iowa resident tweeted.

Though derechos are often referred to as “inland hurricanes” because of their extreme rainfall and winds that can exceed the hurricane threshold of 74 mph, “that is where the similarities end,” Marshall Shepherd, director of University of Georgia’s Atmospheric Sciences Program writes for Forbes.

The National Oceanic and Atmospheric Association defines a derecho as a widespread, long-lived wind storm associated with a band of rapidly moving showers or thunderstorms. Though the damage they can create can be similar to damage inflicted by tornadoes, there’s a key difference: Unlike the spiraling winds and winding paths of twisters, derechos tend to move in one direction along a relatively straight line. Thus their path of destruction is also relatively linear.

“Meteorologists like me will often refer to this hazard as ‘straight-line wind damage,’” Shepherd writes. Much like blizzards, he adds, derechos are defined by very specific criteria. For a storm to be considered one, it must have wind gusts at or greater than 58 mph, pockets of 75 mph or greater gusts, and cause a band of wind damage that is greater than 250 miles long.

In the Eastern half of the United States, one derecho is expected to occur between every .75 and 4 years, depending on the location. Researchers aren’t yet sure whether climate change is affecting derechos or the frequency at which they occur. Warming global temperatures may actually inhibit the cooler temperature gradients that derecho-producing thunderstorms need to grow. What’s more certain, NOAA states, is that climate change is causing the jetstream to move toward the pole. So it’s likely that derechos will shift poleward in a warming world, too.


Derecho frequency for the lower 48 United States. Derechos in North America form predominantly from April to August, peaking in frequency from May into July. Image credit: Wikimedia commons

The storms associated with derechos can be arranged in a line and be accompanied by squalls of high wind and heavy rain (a “squall line”) or like the curve of a boomerang (a “bow echo”), Shepherd writes. Collectively, squall lines, bow echoes, and other types of thunderstorms that act as a single system are called “mesoscale convective systems.”

On August 10 in Iowa, swaths of 90 to 100 mph winds may have been between 30 and 50 miles wide at times, radar signatures indicate. In Marshalltown, a community of 27,000 people northeast of Des Moines, a personal weather station measured a 106-mph gust of wind, Matthew Cappucci reports for the Washington Post; in Midway, a town just north of Cedar Rapids, winds clocked in at an alarming 112 mph.

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Thousands of Iowans remained without power and dozens were in shelters as of Thursday, August 20. And then there’s the damage to Iowa’s agriculture, which approximately 90% of the state’s land is dedicated to. Iowa has been the number-one corn producer in the United States for the past 26 years, and experts can’t yet tell the extent of the derecho’s destruction to this year’s crop. “A lot of the corn is in the later development stages,” Keely Coppess, communications director for the Iowa Agriculture Department, tells the Washington Post. “Some is at a 45-degree angle, but it may attempt to stand back up. But it’s really too soon to tell.”

Now, volunteers are now traveling from out of town to assist with cleanup efforts in Cedar Rapids. Among the volunteers are Dave and Diane Lobermeier from Amherst, Wisconsin, about 300 miles away.

“We’re retired so we decided we’ll take some time and pack up and come,” Diane tells Cedar Rapids’ local news station KCRG, adding that it’s “the right thing to do.” She and her husband Dave came armed with donations and a chainsaw.

“They found Pete Martin, from North Liberty, wanting to help, too,” Aaron Scheinblum reports for KCRG. “‘I feel like we all have a part to make a difference and help recover from this, so this is what I’m going to do,’ Martin said.”

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