2010-12-31 DISC: AR, IL, LA, MO, MS

Mike Smith

I wanted to post a couple of images from Friday's St. Louis-area tornadoes. The first is the STL TDWR at approximately 11:50 am. The -88D "hiccuped" and there was missing velocity on the azimuth of Fenton-Sunset Hills tornado. Fortunately, the TDWR showed it and the smaller Balwin tornado (farther north) very well.


The second image is of the same storm when it was farther southwest and producing the damaging tornado near Robertson, MO. Those of you who have read Warnings may recall my description of a November tornado echo that looked like a "candy cane." Here is a similar echo:



Given the lack of conventional hooks, it would have been very difficult to warn of these tornadoes in the pre-Doppler era. There is no doubt the warnings saved many lives Friday and we in the meteorological profession should be very proud of our contribution.
 

Mike Smith

KMOX Radio Tonight to Talk About the Storms

I have been invited to be on the "John Carney Show" on 1120 KMOX (www.kmox.com for streaming) at 10:30 CST tonight. We'll be talking about the tornado swarm that hit the St. Louis area and about Warnings: The True Story of How Science Tamed the Weather.
 
Apr 10, 2008
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Quincy, IL
www.wiu.edu
Based on a previous Case Study done by Jon Davies, I went back through to some RUC soundings and found some interesting features from the NYE Outbreak.



An indicator that tornadoes and significant tornadoes may be likely in a high shear/low cape environment is the location of the CAPE. The lower in the sounding the highest CAPE is located, the better for tornadic supercell development. (In an otherwise favorably sheared environment of course.) Several of the soundings from Dec 31 exhibited that feature.

You can read more here on the soundings and a wrap up of the full event here: http://convectiveaddiction.com/2011/01/03/suprise-new-years-eve-tornado-outbreak-case-study/
 
Jul 2, 2004
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Hastings, Michigan
www.stormhorn.com
Ryan, that's a great observation and I totally agree with you. I don't know the location for that sounding, but when this event was pending I noticed a couple different NAM reads for 3 km MLCAPE of 75 J/kg in Missouri. One run placed a sort of bullseye northwest of St. Louis, and a later run depicted a narrow strip extending through central MO out of Arkansas. (I ran a RAOB sounding that I wish I had saved, which showed a nice, fat low-level CAPE profile.) I believe there was an even higher value down in LA or AR. The two central MO storms, including the Rolla EF3, coincided with that strip, which presumably moved east and provided the necessary low-level energy.

I think 3 km MLCAPE is a valuable tool for winter and cold core setups; I believe that's something I got out of Davies' article when I read it (it's been a while), and NYE certainly bears it out. I've also been paying attention to normalized CAPE as an overall indicator of parcel acceleration, and suppose that by its definition it would apply to low-topped storms as well as to typical, higher-topped convection.

All that being said, some of the storms the other day went tornadic in environments that had some pretty skinny, stretched-out CAPE. But maybe there was something I missed; I just remember being surprised when I looked at some soundings.
 
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Apr 10, 2008
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Decatur IL
www.pawleewurx.com
This past week I put together a short presentation for ILX with regard to the Petersburg IL event of this day and something I observed that I believe may have contributed to the intensity of it. They concur with the possibility so I figured I'd share it with you. I had been watching convection through the overnight including a cell to come into the area around sunrise that I knew would have an elongated arcus cloud trailing with it. I took off from Decatur towards Lincoln IL to view this cloud after work and though no photos for traveling with the inability to stop, it was as I expected, pretty cool looking and especially for the golden light filtering down through. Besides that, I also noted backing at the surface as well as considerable rising motion on the leading edge. This boundary would slow down to the point of stalling as it drifted SE. I would travel E with it on State RT 10 for a little while, outrunning it before US 51 and head home only to go back out again for the big show a short while later. Hindsight being what it is, I wish I would have gotten more images and video of the activity I witnessed because it draped from Logan county SW into Menard county. Cells training up from the SW would earn warning but only one went nuts. Radar review in correlation to where I understood this boundary to be visually put most of the cells on the cold side with the Petersburg cell bisecting at ground zero. The area of most significant damage was of course very limited and it would seem to me that a supercell crossing a surface boundary in that area is to blame as evident by the path length. Referencing IEM radar saves superimposed with a line where I believe this boundary hung, I would be curious anyone's thoughts regarding the animation found below. My meteorology has never been very good (sorry) but identifying surface boundaries is an aspect to capture my interest for some time now and this was a great opportunity for doing so.

WMV 11.7MB
http://pawleewurx.com/123110.wmv
 
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