Sunday, October 5, 2008

Rogue Mesocyclone Develops near Pecos River, West of Grandfalls, and Traverses Ward, Crane, Upton and Midland Counties, October 5, 2008

















A rogue mesocyclone with impressive mid level updraft rotation and descending Wall Cloud(s) was observed as it developed near the Pecos River in extreme northeastern Reeves County and eventually tracked through central Crane, northern Upton and southern Midland counties from 2030Z until 2250Z, October 5th, 2008. A second mesocyclone "sister", forming southwest of the previous, following a similar trajectory, was also captured beginning at 2250Z. Both SuperCells would be tornado warned during a portion of their life-cycle(s) by MAF/NWS.


The author left Midland around 1900Z deciding upon a target area in south-central Permian Basin were solar insolation was believed to be more abundant during the day through a broken stratus deck and improve instability . The Permian Basin was listed in a slight risk category by the SPC due to being in a favorable shear environment due to a rather strong LLJ contributing to warm air advection (Theta e ridge) beneath a strong mid level (500MB0) southwesterly flow aloft and a very intense Upper Jet (250MB) with 90K winds rounding the base of an amplified Upper Trough. The mid and upper level strong winds would provide ascent forcing due to divergence aloft. The MLCAPE was not real impressive from the 1200Z soundings due to abundant mid level warm moisture present, lessening lapse rates. Surface dew-points were near 60 degrees. The strong directional and speed shear as "progged" was believed to allow for rotation of any storm towers which developed. Cumulus development was noted when leaving Midland and some convection had already initiated in the northern Permian Basin, southeastern New Mexico and the South Plains. The SPC issued a Severe Thunderstom Watch around 1910Z and its configuration along with radar reflectivity is shown in the first image (the author would travel toward the southwest from Midland). The second image was captured along RR 1233, approximately 2 miles west of the intersection with SH 385, in eastern Crane county at 2030Z looking toward the southwest at developing storm tower's southern end. A radar capture is also included which shows the location of the storm tower near the Pecos River in extreme north-eastern Reeves county and the location of the author's truck. The author proceeded west on RR 1233 crossing the intersection of FM 1601 and stopped 4 miles west of the Waddell Compressor Station and captured the next image of lowered condensation into the improving storm's Rain Free Base at 2100Z. Included is a zoomed image moments later. The next image is a radar capture taken at approxi-mately 2105Z which also notes an improving V-notching to the northeast of updraft region demonstrating good outflow and venting of emerging mesocyclone. At this time it became apparent that this storm was a rogue and isolated from a linear multi-celled complex to the north. It would not have to compete with other cells for inflowing moisture and upon reaching mid and upper level height, directional and speed shear, should begin to allow for rotation from it's base. The author retreated back to the east along RR 1233 since the storm's direction had begun to take more of a "right turn" and in order to get a better look at the evolving mesocyclone. The next image, captured at 2130Z, reveals the impressive mesocyclone's striated updraft base and tower which had begun to visually rotate counter-clockwise.














The NWS in Midland tornado warned this mesocyclone at 2140Z. The next image is taken, a short time later, of the updraft base, rotating, and a descending wall cloud, centered over the road background, in sepia format in order to enhance the resolution. The next two images are of the engorged Wall Cloud with Inflow Tail and Fractus scud to left, the last of the two a zoomed image. The next image, taken at approxi-mately 2200Z shows the Wall Cloud becoming less robust and the tail cloud becoming detached. The author continued to back tract to the east and captured the next image around 2205Z at more inflowing bands into the updraft circulation east of the Waddell Compressor Station.







At approxi-mately 2210Z another Wall Cloud lowering was noted south of RR1230 after the author continued to drive east, as the circulation center was tracking a little south of due east. Driving back to SH 385 and turning north it was noted that there was a second updraft base seen to the southwest of the currently chased mesocyclone. The next image is of lowered condensation infow into this second evolving mesocyclone and it was taken approximately at 2250Z. A radar capture is also included for reference to the "chased supercell" and with respect to the author's truck. The next image was taken a short time later after traveling back south along SH 385 and capturing a zoomed image looking toward the southwest. It was beginning to become dark not only because of nearing dusk but because an advancing multicelled squall line approaching from the west. The next image is a radar capture of the aforementioned linear squall line playing "catch up" to the two rogue mesocyclones (image is blurred... my apologies). It is noted that the second mesocyclone was tornado warned by MAF/NWS as it enters Upton County, center of the concentric rings. While driving back toward Midland on FM 1788 in southern Midland county the advancing shelf cloud and accompany-ing gust front edge of the advancing squall line was captured. The next two images are, first, radar capture (clearer than previous) showing location of truck with respect to advancing gust front and second, a picture of the advancing shelf cloud. While traveling north on FM 1788 in central Midland county straight line winds estimated to be near 60 mph were encountered, blowing from west to east.

The author never observed a tornado from the primary chased mesocyclone (#1) and did not have an opportunity to witness mesocyclone(#2) for a long enough duration before encountering dark or obstruction of viewing angle to provide ground truth.