Sweetwater/Ballinger, TX Tornadic Supercell

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Outflow Shelf and Lightning-Started
Prarie Fire Southeast of Ballinger
7:30 PM CDT, 5/31/95

Photo byThom Trimble

This storm initially formed just south of Childress. It then either (a) translated; and/or, (b) was associated with new development on the south flank so that it discretely propogated southeastward across the western portions of the Abilene area and then southeastward. We chased the storm from north of Sweetwater until sunset when it was about 100 miles southeast of San Angelo. During this life cycle, we observed one significant tornado in Sweetwater (see below and on next page) and one other possible brief tornado touchdown (unphotographed) near Ballinger.

In this picture (and one on the next page), the outflow shelf was magnificent as the storm wound down just before sunset. Lightning had started a prarie fire and the smoke from this was being ingested into the storm. We were concerned that this column might be misidentified as a tornado.

On the morning of May 31, 1995, relatively moist air ahead of a dryline extending from eastern New Mexico southward through extreme west Texas was in place across west and north-central Texas. Surface dewpoints ranged from near 60F at Midland to the mid 60's near Fort Worth. The surface chart also showed a weak low in west Texas with a quasi-stationary frontal boundary extending eastward across the southern Texas Panhandle and connecting to a cold front along the Red River Valley. Check out our subsynoptic analysis. (Dashed lines are isodrosotherms, solid contours isobars (millibars), solid arrows (subjectively-drawn streamlines).

Wallcloud Approaching Sweetwater, TX
4:25 PM CDT, 5/31/95

Photo by John Monteverdi

This view is towards the west-northwest. Sweetwater is approximately 10 km away. 4" hail, straightline winds in excess of 50 knots raked Sweetwater at this time. The cloud structure was roiled, had a large "bear cage" appearance over Sweetwater. Rain and hail wrapped around the west side of the updraft several times during this time but never completely encircled the updraft.

The hodograph was characterized pronounced veer of the wind and wind shear vectors from the surface through 3km. Surface winds were generally 10 knots or less across west and north Texas although some reports of 15 knot winds were evident. Midlevel winds were at the low end of the spectrum (30 knots at 500 mb and 20 knots at 700 mb) and supported only weak to moderate storm-relative flow. Project afternoon CAPE was in the 3500 J/kg range. The 12Z MAF sounding that a well-mixed nearly-dry adiabatic layer surmounts a 100 mb thick moist layer.

The midtropospheric flow was initially westerly over this portion of Texas but became west-northwesterly as a weak shortwave embedded in the flow progessed eastward across the Texas Panhandle. This short wave was associated with weak cold advection.

The surface cold front was likewise in the Texas Panhandle and had advanced to a Lubbock-Childress-Altus line by Noon CDT. Surface pressure falls ahead of the mid-tropospheric short wave trough axis and ahead of the surface cold front were inducing an eastward surge of the dryline, which passed Midland at around 11AM CDT. Thunderstorms had developed ahead of the dryline southwest of Childress by mid-morning. At about 1:30 PM CDT, the dryline and cold front intersection was between Lamesa and Colorado City. At this time, surface flow between Abilene and Sweetwater and backed to easterly and had increased to sustained 20 knots. The earlier thunderstorm had progessed due southward and was near this location when intersection occurred. The thunderstorm developed a backsheared anvil and mesocyclone at around this time when it was just north of Sweetwater, TX.

Click here to see more pictures of this storm as it passed through Sweetwater (N.B., images are interlaced but loading may take some time--300 kilobytes). There are two additional pages.

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