Squall Line Tornado in Eastern Kansas

All images and text © copyright Gene Moore
unless otherwise indicated
.

  severe storm southwest

On September 5th, 1992 severe storms formed across northeastern Kansas. During the late evening and after dark these storms developed into southern Kansas producing tornadoes. The storm and tornado illustrated here was part of what I believe was an LEWP, or on radar, a line-echo-wave-pattern. That's a mouthful huh? It means the squall line developed a wave of low pressure on it and in this situation, the thunderstorm associated with that wave became tornadic. I have seen many of these storms, but until this day captured the associated tornado on film. The reason these situations are so difficult is the circulation producing the tornado, the mesocyclone, is generally buried in a notch that wraps into the storm; therefore, it is generally obscured by rain. This time I got lucky and found a storm that developed a mesocyclone (wall cloud) in a visible location. Additionally, this set of images may not convince some that a tornado occurred. LEWP tornadoes are usually controversial, but these images are provided to draw your own conclusions.


  wall cloud zoom

This day started with a good forecast and intercept on an isolated supercell in northeast Kansas. I had been with this storm for hours before the tornado came down. I made a navigation error that cost me the tornado. It was getting late in the day so instead of trying to chase back to the north and put the day back together, I decided to drop south for a new storm. The cells that developed to my south quickly "lined out", or formed a squall line. This usually means the tornado potential is very low except on the south end of the line. One storm in the line appeared to be dominant and I decided to target that cell. The gust front was wrapping back into a wall cloud and updraft area.

The updraft region in advance of this storm was extensive and the storm to the north was currently weak, only a thin area of rain was directly north of the wall cloud. This is usually a favorable configuration for tornado formation from a gust front storm. The cold outflow air from the proceeding storm would be less likely to impede the further development of the strong storm containing the wall cloud. The simple position of a storm with relation to an adjacent cell may not sound important, but many times it can make or break the tornado formation. During these observations rotation was apparent within the wall cloud and and small funnels were spinning up and dissipating. I decided to change positions to set up a tripod. The twilight from the setting sun was all I had to shoot this scene.

 

In this shot the area of strong up motion and rotation is located to the right of the grain elevator. It has become separated from the original lowering associated with the gust front. The leading edge of the cold outflow, the gust front, is the lowering to the left and in back of the grain elevator. It contained turbulent clouds and strong up motion, but no rotation.

The system was progressing northeast faster and I needed to move again, but if I did it could cost me the storm. If anything was going to happen it would have to be in these last few minutes of daylight. The storm begin to form and lift large chunks of condensation into the wall cloud. Give or take a few hundred meters the photography position I had now was the one I was stuck with for end of daylight on this storm.

  strong rotation beginning


Experienced chasers know when storm reaches tornadic potential the spin up can happen fast. That's what happened in this situation. I was forced to change my filming position just a little further north to get a better vantage point of the rotation. At that time the tornado formed. Since clouds were condensing close to the ground already it was only a moment for the funnel to lower. It was a wide condensation funnel, ragged on the front and smooth on the back side.

During this time I noticed the gust front was making a dramatic surge to the northeast. Were the two occurrences related? I would bet they were, but in this case the gust front would destroy the tornado. In the image the gust front with its strong southwest wind is the lowering on the left. It is moving from left to right. Daylight separates the gust front from the tornado in this shot. On the left there is a block lowering with rotation and strong up motion on the north (right) side.
tornado northwest

  tornado

One might ask; is this attached deep into the storm or is it a surface based feature driven by the gust front? I can't answer that question, all I know is it was rotating at tornadic speed. Also the leading edge of the gust front was to the west of it when it spun up, therefore below cloud base it was not gust front "driven". Part of the clouds that extends to ground is in the foreground and not attached to the storm base, but from my vantage point the back of the cloud mass under the circulation was connected to the storm. The enlargement the tornado shows the laminar flow on the left side of the funnel.

One more image was taken before the strong surge of cold air over ran the tornado, obscuring it from view and I assume, destroying the circulation. I estimate the total life of the circulation was about 2 minutes. A good case of being in the right place at the right time, and most of all being lucky. After all, I had just had a dose of bad luck earlier today when I had done everything right; this only seemed fair. The remainder of the night was filled with continuous lightning and severe thunderstorm warnings. I shot lightning pictures during the trip south to Tulsa.

 

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