ONE YEAR AGO: Winds up to 140 mph from derecho slam eastern Iowa

This is the one year anniversary of a powerful storm system creating a derecho that swept through parts of Iowa with wind gusts of up to 140 miles an hour.

At the height of the storm, more than 400,000 customers across Iowa were without power. The number had dropped by half by mid-afternoon. Muscatine Power and Water had all but about 150 customers back on by 3 p.m.

A derecho is a widespread, long-lived wind storm associated with bands of rapidly moving showers or thunderstorms variously known as bow echoes, squall lines, or quasi-linear convective systems, according to the National Weather Service.

Although a derecho can produce destruction similar to that of a tornado, the damage typically occurs in one direction along a relatively straight path.

The storm toppled trees and tossed trampolines in Muscatine. Shannon Ballenger shared video of tree limbs being snapped at Greenwood Cemetery.

In Des Moines, the roof of the Buccaneers Ice Hockey Arena was damaged. Hockey lessons were underway inside the building at the time, but no kids were hurt, Radio Iowa reported.

Willow Street off of Park Ave. By Dina Danielson

Roads across the eastern part of the state were impassable due to storm damage, which also impacted communications to digital message boards, so incoming traffic may not be alerted to the closures as they normally would be.

Rich Kinney is the warning coordination meteorologist at the National Weather Service in the Quad Cities and he inspected the devastation himself in communities across eastern Iowa.

“The maximum estimated winds at this point are around 140 miles-an-hour,” Kinney says, “and that’s associated with structural damage in the Cedar Rapids area.” Wind speeds for a major, Category Four hurricane range from 130 to 156 miles-an-hour — lending credence to those who’ve called this powerful storm a “prairie hurricane.”

Kinney, who’s been with the weather service 23 years, says he’s never seen this type of destruction before, especially in Iowa. Cedar Rapids got the worst of it, he says. “Some apartment complexes where the entire roof was lifted off,” Kinney says. “Most of the exterior walls on the top floor were gone and a few of the interior walls as well.”

The highest estimated winds in this storm were gusts of 126 miles-an-hour, recorded at a home weather station of an emergency manager in the Benton County town of Atkins. The estimated winds of 140 miles-an-hour that were based on the structural damage could be an all-time Iowa record for straight-line winds.

A radio antenna near Van Horne that was rated to be able to withstand 125 miles-an-hour winds was snapped off in the storm. Another radio tower in Clinton, carrying the signal of Radio Iowa affiliate KROS, was flattened in winds Kinney estimates at 130 miles-an-hour.

NOAA estimates damage left by the decrecho at $11 billion, and it’s considered the most costly thunderstorm in U.S. history.