The “Flat Corn” Derecho

Posted: Aug 10, 2020 / 02:00 PM EDT Updated: Aug 10, 2020 / 08:59 PM EDT

In Michigan: Gust to 67 mph at Benton Harbor. 1.5 ft. storm surge at Benton Harbor. South Haven had gusts to +40 mph. A viewer send us a picture of a trampoline folded in half by the winds in the Dorr area. Numerous power outages along and south of I-94. Here’s Grand Rapids radar:

Click for latest Base Reflectivity radar loop from the Grand Rapids/Muskegon, MI radar and current weather warnings
Severe Thunderstorm Watch until midnight

A derecho with winds over 100 mph caused significant damage from E. Nebraska thru Central Iowa, Northern Illinois, far Southern Wisconsin and finally into SW Michigan and Indiana. Peak gusts: 112 mph Midway IA, 106 mph Le Grand IA, 100 mph Hiawatha IA, 99 mph Albion IA, 95 mph Marshalltown IA. Significant building damage has occurred in Iowa and Illinois. Watch this roof blow off in Chicago. Besides the structural damage, vehicles were flipped on highways, including I-80 and US 30 in Iowa. The storm caused semis to roll over on Highways 17 and 169. Some of those drivers have been taken to the hospital for minor injuries. Gusts hit 92 mph at Dixon, Illinois, where winds blew at 50 mph for more than 20 minutes. Other peak gusts: 86 mph Moline IL, 72 mph Midway Airport and at the water intake in Chicago, 62 mph at O’Hare. Roof damage was reported in Lake Co. IL. Winds hit 53 mph at Racine WI, with wind damage near Kenosha and Lake Geneva WI. Report that a barn and grain bins “completely gone” in Wakarusa, Indiana. Wind gusts were under generally 45 mph or less north of I-94.


A seiche or meteotsunami occurred on Lake Michigan this evening. The water level rose 1.5 FEET at Benton Harbor. Here’s an example of a seiche/meteotsunami. The strong winds from a line of thunderstorms push the water toward the Michigan shore. The water level rises at a fairly rapid rate. You can get caught out on the piers and breakwaters. As the storm passes, the water sloshes back toward the Illinois and Wisconsin shore. As it does, strong currents are possible, moving from the shore to the west and out toward open water. On July 4, 2003, seven people drowned when caught in currents following a severe thunderstorm in St. Joseph Michigan.

Seiche in Chicago in 1954
Seiche drawing Lake Michigan_1523671404520.gif.jpg
Here’s a graphic on the seiche of 1954

Millions of acres of corn has been blown down. There are 470,000 customers without power in Iowa and another 215,000 in N. Illinois. Tornado warnings were issued for a large portion of the Chicago area.

The Severe Thunderstorm Watch is for Muskegon, Kent and Montcalm Counties to the south until midnight. Severe Thunderstorm Warnings for Berrien and Cass Counties.

WW0427 Radar

Storm reports:

Here’s storm reports:

today Reports Graphic

Roof partially off the Buccaneers Arena at Urbandale IA. There were counties in Iowa where +95% of the county is without power. Millions of acres of corn has been blown down!