Thursday, April 21, 2011

First Rotation from Bono to Paragould

A tornado warning was issued shortly before 9:00 pm on Tuesday Night for some rotation near Bono. I am going back through some radar data to see what was happening in the atmosphere during this event. The above radar image is from 9:06. It's  the "Reflectivity" data or the "where it is raining" mode. While this is great, the "what are the winds doing" mode is more important at this point. This is known as velocity mode. Here is the velocity data at the same time as the above image:
I have circled the area that prompted the warning. While this was seen on radar, we had a corresponding report of a funnel cloud from a storm spotter, Let's go over a few things that will be needed for this blog and for the next blog post. When we show this to you on air, we talk about seeing "reds and greens" close together, but it much more than that. Sure, the greens show the winds "TOWARD" the radar site and the reds show winds "AWAY" from the radar site. But there are some things to watch out for! For example, in the above image, that bright shade of red in that circle is not wind going away from the radar. That is a velocity aliasing problem. It should be bright green, but the wind speeds are exceeding the given scale for the program, so when you see bright colors in the middle of the opposite colors, just assume it is also bright green. This is something we constantly need to watch for when covering severe storms. The rotation is just NE of that bright red.... or upper-right hand corner of that circle. This is the rotation when it was around the Lorado/Finch area. We had some tree damage in this region.
At 9:11, we see that rotation coming into SW Paragould. Notice, we do not have an aliasing problem in this radar image (click to enlarge). While radar showed some rotation, the damage that occurred at GCT was from straight-line winds. It was extensive, but it was caused from a downdraft in this storm. If you notice, the rotation went south of GCT. I surveyed the damage and so did the NWS and we both concluded it was straight line wind damage.

Later today, I'm going to blog about the storm that caused damage in Craighead and Mississippi County.The winds were FIERCE in that storm! I'll show the radar images in my next blog post.

I'm going shopping and out to lunch with my wife. Have a great day!


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