Tuesday June 21 Severe Storms

A wave of severe thunderstorms producing damaging winds measured in excess of 75 mph in spots moved north across the area Tuesday evening.  Particularly hard hit were sections of DuPage, Northern Cook, and Lake Counties in Illinois where wind damage to trees and power lines were widespread.  The National Weather Service deployed 3 survey teams to assess and document damage, determine if any tornadoes occurred, and estimate wind speeds in the most highly damaged areas.  Findings from these surveys is at http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=lot&storyid=69963&source=0

Severe thunderstorms developed in warm moist and unstable air flowing north into northeast Illinois ahead of an area of low pressure over western Iowa Tuesday afternoon and evening.  Ground based heating which destabilized the atmosphere combined with a broad area of confluent flow of warm moist air helped fuel and drive the severe storms. 

 

Surface weather map from 11 am on June 21, showing conditions leading up to the development of severe thunderstorms across northeast Illinois.  Contours show mean sea level pressure (black), and MLCAPE (Mean Layer Convective Available Potential Energy - orange and red). 

A listing of measured wind speeds from Tuesday's storms can be found at http://www.crh.noaa.gov/product.php?site=lot&product=pns&issuedby=LOT&format=CI&version=1&glossary=0

A listing of specific damage and other reports can be found at www.crh.noaa.gov/lot/?n=lsr_summary  



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