An intense line of thunderstorms moving at a speed of 75 mph. A wind speed of 112 mph. Cars fly on the freeways in Iowa. Embedded tornado warnings. This is what parts of the Midwest held out Monday as a derecho leap across multiple states.
A derecho is a widespread, intense and prolonged windstorm. According to NOAA’s Storm Prediction Center, by strict definition, the swath of wind damage should extend beyond 250 miles and include wind gusts of at least 58 mph along most of its length. A derecho should also contain several, well-separated 75 mph or larger. It can produce destruction similar to a tornado, only the damage typically occurs in one direction along a relatively straight path.
“Derecho” is a Spanish word meaning “straight”, “direct” or “straight ahead.” They typically occur in the summer and can vary in intensity. Monday’s derecho was in the top echelon of intensity.
The derecho started early Monday morning as a small unsettled cluster near the border of Nebraska and Iowa, but as derechos typically do, it grew in size, picked up speed and gained intensity as it headed east.
By 4 p.m., the derecho reached the Chicago area, causing wind gusts of 60-90 mph, along with the risk of embedded tornadoes.
At 3:40 a.m., the National Water Service in Chicago warned of imminent danger: “Very high winds were likely to turn toward downtown #Chicago with gusts of 80 to 90 mph likely based on radar estimates! Stay away from windows and head straight in as you walk at tall buildings. “
The lusts caused serious damage to homes and buildings in Iowa and Illinois, some caused by downed trees and streamlines. More than 250,000 Mid-American customers were affected by power outages in the state of Iowa, NBO affiliate WHO reported.
By the time it passed through Iowa and Illinois, here were some of the strongest winds:
- Midway, Iowa: 112 mph
- Le Grand, Iowa: 106 mph
- Hiawatha, Iowa: 100 mph
- Albion, Iowa: 99 mph
- Marshalltown, Iowa: 95 mph
- Dixon, Illinois: 92 mph
- Urbandale, Iowa: 85 mph
- Des Moines: 80 mph
- Chicago (Midway Airport): 72.5 mph
- Chicago (O’Hare): 62 mph
At times, 60+ mph winds stayed 20-30 minutes straight.
The derecho was expected to continue to bring destructive winds to parts of the Midwest and Great Lakes as it heads east, where severe warnings for thunderstorms that precede the line of storms are in operation until midnight. The National Water Service even issued a warning for the eastern edge of Lake Michigan, warning of the strong winds associated with the derecho large and deadly waves can produce for anyone on the beach.
Doha Madani contributed.
