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| Date(s) | August 10-11, 2020 |
|---|---|
| Duration | 20+ hours (ongoing) |
| Peak wind gust (measured) | 112 mph (180 km/h; 50.1 m/s) (Midway, Iowa) |
| Damage costs | Widespread |
| Areas affected | South Dakota (SE), Iowa, Nebraska (NE), Wisconsin, Missouri, Illinois, Indiana (N), Michigan, Kentucky, Ohio |
The August 2020 Midwest derecho, a high-wind type of storm, is a weather event which took place beginning on August 10, 2020 across the Midwestern United States. Moderate to severe damage occurred across the affected area, with the greatest damage occurring in Iowa and northern Illinois. Wind speeds of 70 miles per hour (115 km/h) were prevalent across much of the affected area, with maximum recorded wind gusts over 110 miles per hour (175 km/h). The impact subjected hundreds of thousands to utility disruptions.
Storm Overview
Beginning in the early morning, the event storm system developed in southeastern South Dakota and pushed its way east into Iowa, followed by the southern Great Lakes region.
Official NWS Storm Warnings
Starting in the early morning of August 10, the National Weather Service tracked and published a series of warning bulletins for the event storm system. This tracking continued as the storm did throughout the day and into August 11.
| Bulletin # | Issued (CDT) | Type | Covered Areas | Storm Location | Storm Heading | Warning Details | |
|---|---|---|---|---|---|---|---|
| 424 | 6:05am (until 11:00am) | STW | South Dakota (SE), Nebraska (NE), Iowa (NW) | South Dakota-Nebraska border area | East (into eastern Iowa) | High Winds (75mph+) and Hail | |
| 425 | 8:55am (until 2:00am) | STW | Iowa (most of state) | Iowa-Nebraska-South Dakota border area | East (into central Iowa) | High Winds (80mph+) and Large Hail | |
| 426 | 11:25am (until 7pm) | STW | Iowa (E), Illinois (N), Wisconsin (S) | Iowa (central) | East (toward Lake Michigan) | Extreme Winds (100mph+) and Large Hail | |
| 427 | 1pm (until 7pm) | STW | Wisconsin (E), Michigan (Upper Peninsula) | Iowa-Illinois border area | East (spreading north toward Lake Michigan) | High Winds (70mph+) and Large Hail | |
| 428 | 4:25pm (until 12am) | STW | Michigan (S), Indiana (N) | Illinois (N) | East (toward Indiana) | High Winds (70mph+) and Large Hail | |
| 429 | 2:55pm (until 10pm) | STW | Illinois, Missouri (E) | Iowa-Illinois border area, East Illinois | East (spreading south toward southern Illinois) | High Winds (80mph+) and Large Hail | |
| 430 | 6:30pm (until 12am) | STW | Illinois (S), Indiana (S), Kentucky (NW) | Illinois (central), Indiana (central), Missouri (E) | Southeast (spreading toward Kentucky) | High Winds (70mph+) and Significant Hail | |
| 431 | 7:05pm (until 12am) | STW | Ohio (E) | Indiana, Michigan, Illinois (S) | East (Ohio) | High Winds (70mph+) and Significant Hail |
Highest Recorded Winds
| Recording Location | Peak Wind Gust Speed | |
|---|---|---|
| Midway, Iowa | 112 mph (180 km/h) | |
| La Grand, Iowa | 106 mph (170 km/h) | |
| Hiawatha, Iowa | 100 mph (160 km/h) | |
| Marshalltown Municipal Airport | 99 mph (159 km/h) | |
| Albion, Iowa | 99 mph (159 km/h) | |
| Marshalltown, Iowa | 95 mph (152 km/h) | |
| Marshalltown, Iowa | 91 mph (146 km/h) | |
| Atkins, Iowa | 90 mph (144 km/h) | |
| Blairstown, Iowa | 90 mph (144 km/h) | |
| Davenport, Iowa | 86 mph (138 km/h) | |
| Moline, Illinois | 85 mph (136 km/h) | |
| Ankeny Airport | 78 mph (125 km/h) | |
| Des Moines International Airport | 75 mph (120 km/h) | |
| Midway International Airport | 72 mph (116 km/h) |
Impact
The complex of storms has knocked out power and caused tree damage from around Omaha, Nebraska, to central Iowa. More than 1 million people were without power in the wake of the storms from eastern Nebraska to northern Illinois as the storms raced eastward into southern Michigan and Indiana. A personal weather station in Des Moines clocked a surface gust of 85 miles per hour (135 km/h), while several locations clocked gusts exceeding 100 miles per hour (160 km/h). The storm’s intensity marginally waned as it headed east, but Chicago’s Midway Airport clocked a gust to 73 miles per hour (115 km/h). Chicago experienced its most severe winds around 20:00 UTC when, in addition to the 73 mph gust at Midway, O’Hare International Airport saw a 62-mile-per-hour (100 km/h) gust. The National Weather Service tweeted that “much of northern Illinois has pockets of damage with downed trees, debris, and power lines blocking roadways” after the worst had passed.
The severe thunderstorm warning for the Chicago and areas east to the Indiana State Line, issued at 18:54 UTC by the Weather Service, affected 7.8 million people. Several tornado warnings were issued in northern Illinois from near Rockford, Illinois, to Chicago’s north and west suburbs, including Evanston, as the Weather Service observed areas of enhanced winds on the leading edge of the line. One tornado probably did touch down near Lisbon, about 60 miles southwest of Chicago. Winds gusted to 62 mph in Aurora, Illinois, west of downtown Chicago, as the storms barreled through. Numerous reports of significant winds, and at times extreme winds, have been received from across the Corn Belt:
In Cedar Rapids, Iowa, an eyewitness on social media described “utter destruction.” The Iowa Department of Transportation reported that Interstate 35 and other roads were blocked due to overturned vehicles and storm damage between Cedar Rapids and Iowa City.
References
- "Storm Prediction Center Severe Thunderstorm Watch 424". www.spc.noaa.gov. Retrieved 2020-08-11.
- "Storm Prediction Center Severe Thunderstorm Watch 425". www.spc.noaa.gov. Retrieved 2020-08-11.
- "Storm Prediction Center PDS Severe Thunderstorm Watch 426". www.spc.noaa.gov. Retrieved 2020-08-10.
- "Storm Prediction Center Severe Thunderstorm Watch 427". www.spc.noaa.gov. Retrieved 2020-08-11.
- "Storm Prediction Center Severe Thunderstorm Watch 428". www.spc.noaa.gov. Retrieved 2020-08-11.
- "Storm Prediction Center Severe Thunderstorm Watch 429". www.spc.noaa.gov. Retrieved 2020-08-11.
- "Storm Prediction Center Severe Thunderstorm Watch 430". www.spc.noaa.gov. Retrieved 2020-08-11.
- "Storm Prediction Center Severe Thunderstorm Watch 431". www.spc.noaa.gov. Retrieved 2020-08-11.
- "Midwest Derecho Has Raced Eastward Bringing Widespread Damaging Winds". The Weather Channel. Retrieved 2020-08-11.
- Cappucci, Matthew; CappucciMeteorologist, closeMatthew; GangEmailEmailBioBioFollowFollow, Capital Weather; Freedman, rew; close; weather, rew FreedmanEditor focusing on extreme; Change, Climate; science; SamenowEditor, the environment EmailEmailBioBioFollowFollowJason SamenowcloseJason. "Destructive derecho blasts Chicago with winds over 70 mph; more than 1 million lose power in Upper Midwest". Washington Post. Retrieved 2020-08-10.