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Monday, April 21, 2008

Severe Weather Season Is Here....

Due to the storms yesterday and what is expected today- I will not be posting about the Chesapeake Health and Earth Day as expected. Sorry....
Yesterday's Tornado Warning was issue by NWS due to Doppler Indicated Tornado. There was none spotted at the time on the ground, but here are the Doppler Images showing what we look for.
Note: This image on the left is your standard return of rain intensity measure in DDZ you might see on TV or online. This was the image from Baltimore County around 6:20pm Sunday. The rainfall rates were over 1 inch per hour with small pea size hail in Parkton (account from a co worker). I've highlighted the central point of the storm and wind field, however the possible 'hook' on the south side in the rain free zone is a signature of rotation in a storm. Most tornadoes are in the rain free section on the south or southeast side of a storm.

This image is a different level showing the wind profile. The whole premise for Doppler Radar is measuring a frequency change as wind/rain, etc move towards or away from the radar site. Much like the sound Danica Patrick's car winning in Japan's Indy race. That change in movement is measure and shown here with wind away from the radar in red, and towards the radar in green. When they are stacked side by side, that indicates rotation and potential spin of a funnel cloud. You'll notice I did not say tornado yet since this is all at cloud level. There is no guarantee that it will reach the ground, and as of this posting (6am), I did not see any confirmation of touchdown.

I am working on placing the lighting tracker with Radars and Stuff, but until then I will continue to post a live image here:
In terms of rain, how about those giant drops? This type of environment will produce what appears to be larger drops as small hail generated in these storms will melt on the way down from the clouds. The wind turbulence will help to break up these drops, but some can hold together. There is a lot of moisture available, so rain amounts under these storms may exceed a few inches.
Our severe weather is all thanks to a cold upper level trough with this pocket of warm moist air underneath. That allows the freedom for this air to rise and quickly dump rain. The spin from the upper low (check it out on Water Vapor Loop)

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