June 4, 1995 - The La Mesa, Texas LP Supercell

I started this chase early in the morning from Amarillo, Texas. A quick review of the weather conditions at the Amarillo National Weather Service Forecast Office indicated that the optimum conditions should develop during the afternoon southwest of Amarillo, somewhere west of Plainview, Texas.

I drove south to Plainview under overcast skies with relatively cool temperatures. Visibility was poor. A severe thunderstorm warning was issued for a storm passing about 30 miles west of Plainview. I intercepted the storm which was not very impressive, but it produced hail just large enough to be considered severe. The storm, although small and in an area of cool temperatures, produced impressive mammatus (first picture below). Temperatures were still relatively chilly.

Chasers Michael Cohen and Bobby Eddins were chasing the same storm. We made contact on the 146.520 MHz national simplex "calling" frequency and met near the railroad crossing pictured below. We discussed the merits of chasing the passing storm and decided that we should move farther south in search of warmer temperatures, higher atmospheric instability and better visibility. Morning weather observations indicated clear skies near Lubbock. We all felt that the air was too cool to support the violent convection needed to produce tornadoes. Unfortunately, we didn't know that the storm we had just dismissed as being too weak would produce a spectacular multiple landspout event at Lazbuddie shortly after we gave up on it!

The high plains of the Caprock have an average elevation of around 3000 feet above sea level. Unusual and unexpected weather events often occur on the Caprock as a result of the relatively high elevation, their proximity to the Gulf of Mexico (the source of energy rich moist air), their location east of the Rocky Mountains (a source of warm dry air), and the presence of the polar and sub-tropical jet streams which frequently flow overhead during Spring. All of these factors when combined lead to some of the wildest weather anywhere on the planet.

We drove farther south to intercept another "weak" storm and met Al Moller and Chuck Doswell northwest of Lubbock. They had also started farther north and decided to move south in search of warmer temperatures (warmer temperatures equal greater potential energy at the surface for storms to consume). The group intercepted several high based storms that were following in the path of the first storm we intercepted. Although these storms had impressive updrafts with considerable upward motion evident in the storm towers, the updraft bases were elevated and undercut by outflow. For significant tornadoes to form, the storm's updraft must be connected to the boundary layer so it can ingest warm moist air from near the surface of the Earth.

We drove south to a storm developing near Reese Air Force Base. It looked better than the storms farther north and produced several funnels, one of which is included in the video record of this event. (Click here to view the video storm chase record of this chase, but you should go there after viewing the following slides.) This storm quickly became outflow dominant. We had to move farther south.

When Lubbock NWS issued a severe thunderstorm warning for a storm northwest of Lamesa, southwest of Lubbock, we immediately left to intercept it. We hoped to skirt the eastern edge of the precipitation core and set up southeast of the storm, to obtain the optimum view of the primary updraft. The storm had evolved into an HP configuration and was moving eastward too quickly. It passed across the highway ahead of us, but it left an outflow boundary behind.

A small LP storm developed on the western edge of the outflow boundary, apparently where it intersected the dry line. A "triple point" had been established by outflow from the preceding storm. (The term triple point refers to an intersection of dry, warm moist and in this case, cool moist air masses. Meso lows (small scale, less than 100 miles in diameter, low pressure systems) and supercell thunderstorms often form at these intersections, if conditions are just right.) Conditions were right and a fantastic low precipitation (LP) supercell thunderstorm quickly formed and moved slowly south along the dry line. The following images are of this LP storm. It provided some of the most spectacular storm structure images in my collection.

	Mammatus west of Plainview, Texas
	This storm produced the most unusual and spectacular spiral updraft structures I have ever seen. As I was taking this photograph, Al Moller remarked "this is perfection, this is perfection!" It was a truly awesome site.
	A long east to west inflow band developed along the old outflow boundary that was left behind by the earlier high precipitation (HP) supercell. Note the rain cascade on the right side of the image. The storm was producing its most intense precipitation core when this image was made, moving into the classic supercell category. The storm produced a deep (hail) roar, which many chasers attribute to hail. This eerie sound is more likely produced by almost continuous in-cloud lightning at the top of the updraft and in the adjacent anvil, above the precip core. Relatively few cloud to ground lightning strikes (CGs) were observed.
	Note the fantastic inflow bands. Bobby Prentice and another chase team were underneath the storm observing a weak multiple vortex tornado about the time this image was taken. I suspect the tornado was located under the storm base near the center of this image.
	The spiral updraft structure began to unwind as the storm weakened.
	As the LP storm dissipated, high base storms rolling off of the Davis Mountains became visible to the west.

Many of my photographs are now available on-line in high quality, high resolution form through WorkBookStock.com

Visit The Storm Shop - your source for excellent SKYWARN training and Storm Chase adventure videos, photographs and books.