(Radio Iowa) – The tree-planting program called Re-Leaf is holding a ceremony in Cedar Rapids this (Thursday) morning, marking the devastating derecho that swept across Iowa three years ago today. Winds peaked at 140 miles an hour and it was the most costly storm in U-S history. Cedar Rapids was especially hard hit, losing two-thirds of its canopy — or some 670-thousand trees. In this interview from August of 2020, state climatologist Justin Glisan said the storm started in southern South Dakota.

“The derecho itself held together for 770 miles over 14 hours before losing strength as it entered western Ohio,” Glisan says. Many Iowans had never even heard the term “derecho” before the powerful storm blasted across the state’s midsection, wiping out trees, power lines and crops. Three Iowans were killed, many were hurt. To be designated as a derecho, a storm must have a width of at least 60 miles and travel at least 400 miles. In this file interview, Dennis Todey, director of the U-S-D-A’s Midwest Climate Hub in Ames, said derechos are hard to predict.

“Unfortunately, we can’t forecast these things too well in advance,” Todey says, “but once it set up and it was starting to look consistent, the Weather Service was right on top of it then and was doing warnings well ahead of it, letting people know this was a pretty nasty situation and had the potential for doing severe damage, which it did.” More than a half-million Iowa homes and businesses lost power during the storm, easily among the worst weather disasters for the state’s electric utilities. The governor declared 20 counties disaster areas. Todey says a derecho is very atypical to the storms Iowans are used to seeing during the summer months.

NWS photo near Shellsburg, August 10, 2020

“Unlike some thunderstorms which build up, rain out and then the cold air that spreads out from that shuts down the instability around a storm, this one is able to feed on itself,” Todey says. “The wind coming out ahead of it is able to lift warmer, moister air ahead of it and that keeps feeding back on that storm and maintain its strength all the way through.”

Derecho is a Spanish word that can be translated as direct or straight ahead. It was first coined by Dr. Gustavus Hinrichs at the University of Iowa in the late 1800s. Hinrichs, who started the first state weather service, is also among the researchers credited with the discovery of the atom and the Periodic Table of Elements.