Monday, July 11, 2011

Severe Wind Storm Blasts the Windy City This Morning...

A severe bow echo (also known as a "Derecho") produced widespread wind gusts of 70-85 mph across the Chicago area earlier this morning. The map below (click to enlarge) shows severe wind gust reports and damage reports that were mainly received between 7:30 and 8:30 central time this morning:

On the text portion of the image (roughly the left half), the far right hand column shows any measured gusts that correspond with a given report.  As you can see, gusts of 70-80 mph were common.  Most of the damage reports so far consist of tree limbs and power lines being downed, with some of the downed tree limbs reportedly as large as 4-6 inches in diameter.  Power outages are widespread and major disruptions can be expected in all forms of transportion, both ground and air, across the region for the foreseeable future.

This system continues to race to the East and is traversing much of far southern Michigan, northern Indiana and taking aim on northwest Ohio at this time.  A 9:25 AM CDT radar image is below:

The left half of the above image is the radar in reflectivity mode (showing rain, any hail, etc.), while the right half of the image shows the radar in velocity (wind speed & direction) mode.  The brighter green shaded areas on the velocity image at the head of the bow echo along the Michigan / Indiana border indicate 70-80 mph wind gusts are continuing at this time.

A new Severe Thunderstorm Watch has just been issued farther to the East, into much of Northern Ohio.  This band of damaging winds will likely continue to threaten the region through midday and into this afternoon:

If you live in the area ahead of this line of storms, remain alert this morning into the afternoon.  Listen for warnings pertaining to your area and seek shelter immediately if threatening weather approaches.

**Update, 6pm CDT:
There were reportedly over 800,000 people without power in the Chicago area as a result of this storm.  This is the largest single day power outage for the area in at least a decade - if not longer.  

The image below was captured by a staff member at the NWS office in Grand Rapids, Michigan, as the northern end of the bow echo approached the office there:

The tower in the lower right corner of the image is the WSR-88D radar at the NWS office.  You can see the bowing shape of the cloud deck approaching the office, which signifies strong, gusty winds blowing out of the front of the thunderstorm line.

This line of severe storms originated in western Nebraska on Sunday evening, and over 12 hours later is currently advancing Southeast into the Mid-Atlantic region - that's over 1200 miles!

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1 comment:

Anthill_Goddess said...

Roughly 20 miles north of the DSM metro area, one of the local stations had their doppler "ball" and "dish" removed from the top of the tower by the winds! The survey team has said, as of right now, winds ranged from 65 to 110 in northern/eastern Iowa!