Sunday, April 27, 2008

LP (Updraft dominate) High Based Cells Northeastern Permian Basin, April 26, 2008














A return of Low Level Moisture proceeding the arrival of Upper Level dynamic Forcing, east of the dry-line, allowed for severe weather potential and the Central and Eastern Permian Basin were included in a slight category by the SPC. A developing Theta-E Ridge trending southeast to northwest due to warm moist air advecting from the Gulf was established by 1800Z. During the next several hours drier air was filtering into the Central Permian Basin where dew points had dropped into the high 30's to low 40's. A decision was made to target the Eastern Permian Basin as Cumulus development was beginning to occur by 2230Z in Sterling County, where low level moisture was still potent. The 500MB winds were generally trending west to east and the 300MB winds a little north of west to east. Steep lower and mid layer lapse rates were noted and Lifted Indices were greater than -5 (SB CAPE between 1500-2000 J/kG) which suggested rapid storm tower convection once initiated. The first image is of a developing Storm Tower(s) complex as viewed from west looking east on SH 158, 3 miles east of intersection SH 137 at 2330Z in Glasscock County (Towers are in Sterling County). A decision was made after arriving in Garden City to take FM 33 north to Big Spring and target the quickly convecting Storm Towers and developing LP Supercell occurring in eastern Howard County as shown from the next image approximately 8 miles north of Garden City looking north-northeast at 0000Z. The next image was taken at the intersection of FM 461 and SH 87, near Forsan in southeast Howard County at 0010Z, looking northnorth-east. The next image is while driving north on FM 821 in eastern Howard County, looking NNE, noting the crispness, scalloped grooves, of southern tower as it convects upward toward the Equilibrium Level. The next image is a zoom of the previous. The author continued north on FM 821 until intersecting Interstate 20 and then proceeded east capturing the next image, at 0030Z, of the updraft intake area (slightly lowered Wall Cloud), center, an attached small "Beavers Tail" inflow band attached to Shelf Cloud, right, and an associated hail shaft, left, that had begun to fall from this LP cell. Storm movement is slightly south of parallel to Interstate, away from camera. The complex appeared to be back-building with newer convection occurring west of previous. The next image is a closer viewed portion of the updraft region and RFD notching. The next photograph is taken from Interstate 20 near the Howard and Mitchell County boundary, looking southeast, beneath Rain Free Base of current chased storm toward a distant spreading Anvil from earlier convection in Coke and Sterling counties,background, and new convecting storm towers, foreground. Hail, generally nickel size but some quarter size was encounter-ed near Westbrook, Mitchell County, at 0100Z. The authored traveled to Colorado City, remaining in hail, and turned south on SH 208 to "punch the core" of a another backbuilding complex which was moving southeast. Approximately 6-8 miles south of said State Highway intense hail was encountered, generally nickel size but some larger but falling very densely. The next image(s), approximately at 0110Z to 0130Z, is of hailstone covered State Highway south of Colorado City in Mitchell County.


The first image from a video still, below, is of accumulation of nickel and quarter size hail forming levees between channelized rushing water runoff on SH 208. The next image also from a video still is looking south while driving on lithified hailstone ice. The last image is at 0130Z looking at hail accumulation on SH 208 and adjoining farm furrowed fields approximately 10 miles south-southeast of Colorado City, Mitchell County.

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