Monthly Archives: March, 2011

Another Doppler Event: 22 March 2011 in Iowa

The two images in this post are from a recent severe weather outbreak in the central plains.

Doppler Couplet near Winterset, IA on 22 March 2011

The first image shows a closeup of the rotating mesocyclone at 2324 UTC with a beam tilt of 0.5. As you can see, the rotation is centered in the yellow circle with the arrows showing the direction of the cyclonic rotation. The high reflectivity green colors are indicating strong winds flowing towards the radar. Adjacent to those are bright red which show strong winds flowing away from the Des Moines NWS radar site. The hexagon outlined in purple is the area under the current tornado warning.

In the second image, we have a wider view of the supercell and the area under the tornado warning. As you can see, the green and red colors in the couplet are even brighter than in the first image which indicates the rotational velocity has increased to approximately 84 knots, over 90 m.p.h. Within the purple hexagon is the Des Moines, IA metro. Any time a couplet of this intensity is present the risk of tornado development is very high. Some supercells can rotate very strongly in the mid to upper levels but if the low level rotation is undercut by the RFD or the storm transitions to an HP outflow dominant status, a tornado may not form. Nevertheless, this is an amazing display of the usefulness of doppler radar and it’s invaluable use as a tool in storm observation.

Doppler Image Of The Month

This image is a SRV image of a tornadic supercell from 8 March 2011. The storm was east of Paris, TX near the town of Clarksville.

As you can see by the arrows, the green indicated winds blowing towards the radar while red shows winds blowing away. The area within the circle is the approximate location of the mesocyclone.

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