Disasters and Emergencies
According to the National Weather Service, a derecho (pronounced similar to “deh-REY-cho”) is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to the strength of tornadoes, the damage typically is directed in one direction along a relatively straight swath. As a result, the term “straight-line wind damage” sometimes is used to describe derecho damage. By definition, if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho.
In Iowa, derechos occur every year or two on average. Winds above 85 mph like that of the August 10, 2020, derecho are quite unusual.
While meteorologists can forecast potential severe weather outbreaks a few days in advance, predicting a derecho can be difficult. Meteorologists can look at a radar to better identify a derecho-type event, but this may only provide a few hours notice.
Whenever there is a threat for severe weather in the area, it’s best to stay alert and prepared —whether it’s a derecho or a severe thunderstorm capable of producing damaging wind gusts.
Know what to do before, during, and after a derecho.
Iowa disaster history
2020 August Derecho
A derecho swept across the states of South Dakota, Nebraska, Iowa, Wisconsin, Illinois, Indiana, Michigan, and Ohio on Monday, August 10, 2020, leaving behind widespread and shockingly devastating damage in its wake, hitting central and eastern Iowa the hardest. Millions across the Midwest were affected by wide-scale utility disruptions, residential and commercial property damage, and severe damage to corn and soybean crops. Cedar Rapids was the most severely damaged, suffering a near-complete blackout that lasted for weeks in some areas, widespread and severe property damage, and an estimated loss of at least half of the city’s tree canopy. The derecho caused an estimated $11 billion in damages and spawned a years-long cleanup effort. As of October 2020, it is the most costly thunderstorm in US history.
Video credit: Nick Stewart, Meteorologist and storm chaser for CBS2/Fox 28 news in Cedar Rapids