A Couple of Supercells in far SW Texas
3 June 2007

 

All images and text
© copyright Gene Moore

   
 

If you were on a desolate highway south of Midland, Texas and saw this cloud off in the distance.....would you give it much thought? Actually there is quite a big going on here that's not obvious at first glance. We already knew this storm had earlier produced a tornado, so it was a feature to be watched. At the time of this photograph there were dirt circulations under the base of the wall cloud and a strong inflow tail coming into it from the north. Maybe another tornado we thought, but something very different happened. I've got a bunch of tornado pictures over the years, but nothing like this. Even my chase partner from Switzerland that came to see tornadoes was impressed with this storm and the show it put on for us. What I'm posting today is the digital set, I'll have the color slides done in coming weeks.

 

   
 

The closer it came the greener it got. We leaned up against a barb wire fence watching it get nearer, not so smart with lighting starting to pop over our heads. I began to hunker down a bit, hoping that might make a difference to the next bolt.

 

   
 

Now we've got some colors! These are wide angle shots because this scene stretched across the sky. We could hear a steady rumble, maybe thunder but probably hail knocking heads up in the top of that cloud.

 

   
 

My chase partner thought it looked like a allegator. He's can be rather strange sometimes, but I had to admit at this time it even had that lump for the eyes. The sun was burning through the bottom of the cloud, it does that sometimes with hailstorms, a not so nice trick of nature.

 


   
 

The next storm to move southeast toward us had also produced a tornado in the county northwest. That phase of the storm didn't last long. Now it was "gusting out" as the main updraft collapsed. A shelf cloud was forming on the leading edge from cold outflow winds. This is a pretty classic example of one we call a arcus gust front. When you see a cloud like this expect strong colder winds from the direction of the storm.

 


   
 

As the gust front widened and neared our position the daylight lightning bolts became more frequent. I was able to capture a few shooting a slow stopped down aperture off a tripod before the storm got too close and we had to move back. In order to cover the width of this storm across the horizon I stitched two images together horizontally using Canon software. It's not as accurate as Photoshop in my opinion, but it is faster provided the two images have like features.

 


 
 

Our arcus gust from from the panorama shots changed drastically in these next images. We are looking at the south side of the outflow and the gust front is breaking up into individual convective towers. The one on the south end is strong enough to pull up and condense moisture in the clear air like a wall cloud.

 

In this shot a steady stream of inflow has established from near ground level to the base of the new convective element. Meanwhile, look at the change in the second tower. In only about a minute it has grown to the top of the old cloud base and punched through.

 

   
 

At this stage the updraft on the south end of the storm has a strong inflow path to the cloud base. Since it's passing over rain and hail cooled ground from the previous storm the air reaches saturation quickly when combined and lifted with the cooler outflow. Meanwhile, the new towers along the leading edge of the storm have reached maturity and are raining out. This is called gust front propagation and it keeps the storm reintensifying as long as it moves into unstable air. In some cases a structure like this cold be mistaken for a tornado, especially from a long distance.

 

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