Heavy Iowa windstorm met criteria to be considered a derecho, NWS says

Wednesday evening’s unprecedented December storm killed one person after gusts toppled a semi, left thousands across the state waking up without power and met the criteria to be classified as a derecho — although not as severe as the infamous one in 2020 from which Eastern Iowa still is recovering.

The storm — hitting Iowa on a rare warm December day near 70 degrees — caused damage across the state but mostly in Western and north-Central Iowa, damaging homes and taking down power lines. Heavy wind gusts that continued Thursday also carried the smell of smoke from wildfires in Kansas and caused poor air quality, with people in Des Moines and Cedar Rapids reporting they could smell the smoke.

“After the derecho of August 2020 ... folks may assume every derecho is that bad. But in terms of climate, we actually get one or two in our area every year, but they are rarely as extreme as the one in August 2020,.”

Storm leaves one dead near Walford

The strong gusts rolled a semi truck and its trailer on its side near Walford, on the border of Linn and Benton counties, killing the driver, according to the Iowa State Patrol.

The driver was heading south Wednesday night on Highway 151 just west of Walford as the storm was moving through the area. The driver was not wearing a seat belt, according to patrol.

The death near Walford was the only reported fatality across the Midwest due to the major storm. The driver’s name has not yet been released.

Storm qualifies as derecho

Rich Kinney, warning coordination meteorologist for the National Weather Service in the Quad Cities, said Wednesday night’s storm met the requirements to be called a derecho.

“We certainly did reach the criteria yesterday, so the line of storms did qualify as a derecho,” Kinney told The Gazette. But he noted that just like regular thunderstorms and tornadoes, derechos vary in their strength and impact.

“After the derecho of August 2020, which was such an extreme event, folks may assume every derecho is that bad. But in terms of climate, we actually get one or two in our area every year, but they are rarely as extreme as the one in August 2020,” he said. “Just like there are relatively weak tornadoes and there are violent ones, there are varieties of derechos as well.”

The Aug. 10, 2020, derecho left three people in Iowa dead, and a fourth in Indiana.

Other than having extreme winds, which doesn’t include a specific number for speeds but typically is having gusts over 60 to 70 mph, the length qualifier for a derecho is 240 miles.

“At its basic definition, it’s a widespread, straight-line windstorm,” Kinney said. “Damage must also incur continuously or intermittently over a swath of at least 400 miles and a width of 60 miles.”

Though multiple tornadoes were reported in Western and Central Iowa, none were reported in Eastern Iowa, Kinney said. “We don’t have any plans today to send out survey crews or anything like that,” Kinney said.

Wind speeds Wednesday night did not match the August 2020 derecho, but the weather service said Winnebago reported peak winds of 86 mph. The Eastern Iowa Airport reported winds at 66 mph and the Iowa City Airport reported gusts of 70 mph.

A wind gust of 74 mph was reported at the Des Moines International Airport, its highest non-convective gust since 1970.

Over half a million in Midwest without power

As the major storm traveled across the Great Plains region, heading north, it left behind over half a million homes and businesses still without electricity Thursday morning in Iowa, Colorado, Kansas, Nebraska, Minnesota, Wisconsin, Illinois and Michigan, according to poweroutage.us.

As of 11 a.m., 507,932 people were without power across those eight states, with over 37,000 of those in Iowa.

In Iowa, the majority of power outages at 11 a.m. followed a diagonal line across where the most powerful winds traveled from the southwest corner to the northeast corner of the state.

In Linn County 171 Alliant Energy customers were without power as of 11 a.m. Linn County Rural Electric Cooperative reported just 17 outages in Linn County.

In Johnson County, the combined number of outages between Alliant and MidAmerican Energy was 23.

Reynolds issues disaster proclamations

On Thursday, Gov. Kim Reynolds issued a disaster proclamation for 43 counties affected by the severe weather.

A proclamation from the governor allows state resources to be used to respond and recover from severe weather, and activates the Iowa Individual Assistance Grant program for qualifying residents.

The following counties were including in the proclamation: Allamakee, Appanoose, Audubon, Bremer, Buena Vista, Butler, Calhoun, Cass, Cerro Gordo, Cherokee, Chickasaw, Davis, Emmet, Fayette, Floyd, Franklin, Greene, Guthrie, Hamilton, Hancock, Hardin, Harrison, Howard, Humboldt, Ida, Kossuth, Lucas, Madison, Marshall, Mills, Mitchell, Monroe, Montgomery, O’Brien, Page, Palo Alto, Pocahontas, Pottawattamie, Ringgold, Sac, Shelby, Union, Washington, Webster, Winnebago, Winneshiek, Woodbury, Worth and Wright.

The grant application and instructions are available at dhs.iowa.gov/disaster-assistance-programs. Applicants have 45 days from the proclamation to submit a claim.

Comments: (319) 398-8255; gage.miskimen@thegazette.com