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Overview

A powerful line of severe thunderstorms known as a "Derecho" tracked across eastern Iowa and northwest Illinois on the afternoon of Monday, August 10th producing widespread straight line wind damage. A swath of damage from Benton County, through portions of Linn, Jones, Cedar, and Clinton Counties, is consistent with intermittent straight line winds in the 100-130 mph range. Maximum estimated winds were around 140 mph, which caused extensive damage to an apartment complex in southwest Cedar Rapids, IA. Straight line winds of this magnitude are equivalent to an EF3 tornado. The maximum measured unofficial wind gust was 126 mph at Atkins, Iowa in Benton County.

A derecho of this intensity is a roughly once-in-a-decade occurrence in this region. Other notable derechos occurred in 1998 and 2011. What is unique about this event, making it even more extreme, is the long duration of the high winds. Many locations experienced sustained high winds and damaging gusts for 30 to 45 minuties. One storm-related fatality has been reported so far in the NWS Quad Cities area of responsibility. The Linn County Sheriff's Department reports a bicyclist died after being struck by a falling tree. There were numerous injuries reported, especially in the Cedar Rapids area.

Storms initially developed in northern Nebraska and southeast South Dakota early in the morning, and quickly intensified as they moved eastward into Iowa. Storms quickly became severe in western Iowa, and produced damaging winds near and around the Des Moines metro. At this point, storms began to tap into an extremely unstable environment, and began producing more widespread wind damage as they tracked through eastern Iowa. The most extreme winds, estimated at 110-140 mph, destroyed or damaged numerous outbuildings, barns, grain bins, homes, mobile homes, apartment buildings, trees, and power poles in parts of Benton, Linn, Jones, Cedar, and Clinton Counties. The Cedar Rapids area was particularly hard hit. Several homes, apartment complexes, and businesses sustained damage consistent with 130-140 mph winds. Radio transmission towers in Marion and Clinton, IA collapsed due to winds estimated around 130 mph. Winds gusts of 80-100 mph were common as the line of storms moved through the Quad Cities area and then through northwest Illinois. A small pocket of winds estimated at 100-110 mph impacted Princeton, IL in Bureau County, where a 150 foot communications tower collapsed and numerous power poles were snapped. In addition to the damage, numerous long-duration power outages occurred across the region. Numerous semi trucks were also blown off of major highways.

NOTE: This information is preliminary. Additional information on this historic storm will continue to be added to this page in the coming weeks. The National Weather Service thanks Emergency Management and media partners, as well as the public, for assistance with remote surveys.

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Radar Animation From the Advanced Weather Interactive Processing System (AWIPS) display inside KDVN. Severe Thunderstorm Warnings are lined in yellow, with Tornado Warnings in red.

Graphic showing preliminary peak winds
KMZ file

Timeline of Watch/Warnings/Reports During Event

     


Video from northern Cedar Rapids near intersection of Blairs Ferry Rd and C Ave. Courtesy: Evan Hindman

 

 

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