Thunderstorm Stage(s) With Associated Wet Microburst As Viewed From Midland, Looking ENE, June 7, 2009

Attached is series of a maturing convective tower, during, 1)late stage growth , 2)collapsing downdraft, and 3)dissipation stage. During the collapsing stage a wet microburst was noted. The images were taken from Midland looking toward the east/northeast during late afternoon, Sunday. The first image depicts the late stage growth of a vertically (little associated upper level tilt) oriented updraft tower with crisp edges and indication of some mid level rotation due to helix configuration. Note the convex protruding dome centered above "helix" tower.

The next image illustrates the wet microburst, during collapsing downdraft stage as noted by inverted V shaped rain and core descending beneath prior updaft region. The image has been color enhanced in order to provide resolution to outflow processes which include Virga to the left of the microburst at contact stage. Note the convex dome has collapsed and suspended rain and hail descended.

The final image denotes the dissipation stage, after microburst event, whereby the cloud structures are less crisp and the once helix shaped tower, flattened.

Small Wet Microburst(s) Associated With High Based MultiCelled Convection, East Central Midland County, Texas, June 6th, 2009

The early evening of June 6, between approximately 2330Z through 0130Z, produced multi celled clusters in Eastern Midland and Glasscock Counties. Very steep lapse rates at low and mid levels combined with surface dew points in the low 50's coupled with strong surface heating provided lifted indices below -5 at timing of initial convection. The forced lifting was suspected to be along a sharpened dry line which trended NE-SW very near MAF. Comparing MAF 00Z sounding with earlier 1200Z there was an increase of mid to upper level winds from southwestern advancing embedded shortwave. Developed Cells were high based and produced noted downburst from visual observations, at a distant, as well as personal observation of wet microburst as encountered. The first image is of an evolving downburst (pre contact stage) taken around 2345Z from Midland, looking distant approximately 15 miles, toward the south/southeast.

The next image is inferred to be at contact stage of a wet microburst, taken shortly thereafter, but not able to see ground from vantage point to see outward spread.


At this time it was decided to drive southeast along SH 158 toward Spraberry. In transit and along Florida Avenue nearing the Interstate 20 intersection, very strong straight line winds from combined outflow of suspected distant multiple small wet microbursts were encountered and judged to be in excess of 45 mph by witnessing fully extended whipping flags. In addition blowing dust had reduced visibility dramatically. While driving along SH 158 approximately 10 miles from Midland one east bound lane was obstructed by wind transported debris ( road construction materials). The strongest winds were encountered approximately 5 miles south of the SH 158 and 137 intersection accompanied by very heavy mixture of hail and rain which reduced visibility to less than 100 feet. Wind speeds were estimated to have exceeded 60 mph. It was assumed that such occurrence was right beneath a small wet microburst at the contact stage. The next image, on SH 137, was taken after visibility cleared enough in order to photograph during the outburst stage and presumed to have been directly earlier beneath the contact stage. The next two images were taken a short time later with clearing skies from the north which highlighted the rainbow, first, and second image of heavy runoff of rain and melted hail alongside road.

The final image was taken of another small wet microburst during the cushion stage as the moving multicelled complex continued to produce downbursts as it entered central Glasscock County County. Note the upward curling of rain/hail during this cycle of the small microburst on the left central side of image above ground level.

Unique "Centralized" Supercell,West Central Dawson County, Texas, May 14, 2009

The author witnessed a very strange phenomena during the early evening of May 14th , 0100Z to 0300Z, with respect to observing a stationary SuperCell, no directional movement for over 2 hours, centered in west central Dawson County. The long time duration storm became supercellular after several discrete convecting storms converged becoming an amalgamated composite which NEXRAD radar revealed, through progressive time loops, to spin counter-clockwise for over 90 minutes.

Mesoscale synoptics were favorable for thunderstorm development due to moderately steep mid and lower lapse rates and abundant low and mid level moisture advecting from the south and southeast providing for high lifted indices producing MLCAPE above 2500 J/kg east of a pronounced dry line which was moving beyond the Central Permian Basin by mid afternoon due to strong surface heating in far western Texas. Directional shear was favorable due to the previously mentioned southeast surface and low level WAA coupled with western flow aloft at mid and upper levels of the troposphere. However the speed shear was not impressive as only 25-30 knots were noted at the 500-300 mb levels from the 0000Z sounding at MAF. The SPC listed the Permian Basin in a Slight Risk category but initiation of convection was a concern in order to overcome a weak Cap due to a lack of upper level forcing. Low level convergence would have to provide the needed lift, noting that in the afternoon a cyclonic surface low had developed, centered near MAF, which might aid in convective initiation.

It was noted around 00Z from NEXRAD radar that a boundary was evident and moving northwest, north of Midland, in an arcuate fashion (may have been increasing moisture return, retreating demarcation of the dryline; MAF sounding at 00Z revealed surface dewpoints lowered to 46 with respect to higher values, above 60, further east). Convection initiated along this apparent observed boundary in southwestern, central and east central Dawson County. The author left Midland, traveling north on SH 349, once it became apparent that storm towers were growing. While driving and monitoring MAF radar via Mobile Threat Net, it became apparent that the convection was congealing into a central updraft foci. The first image was captured from central Martin County looking north into southwestern Dawson County at back building convection towers along a developing rear flanking line of a centralized updraft central core, noted beneath and to the west (right of image).

The next image, below, after crossing the intersection of SH 176 and proceeding north, revealing lowering of the updraft rain free base, followed by another closer image capturing a small tail inflow extending from a developing Wall Cloud .




Screen capture of the radar presentation, as the author neared the Martin/Dawson County line, illustrating the developing SuperCell with noted V-notching signature, indicative of venting (diffluence) aloft. Another image is captured after driving nearer to the circulation along
RR 829 north of Patricia close to 0145Z. The next image, from same location as previous, illustrates strong inflow surface wind directed toward updraft base as noted by sand blowing across road.

At this time the author continued to drive north along RR 829 until reaching the intersection of FM 2052 near a church in southwestern Dawson County and pulled off the road for the remainder of the duration of filmed documentation. It was near 0200Z and had become to dark to photograph with the digital camera so the next series of images are from video stills which were enhanced to help discern silhouette(s). It became apparent that the lowered updraft base had taken the appearance of a oval disc and that a pronounced Wall Cloud was descending. The images were aided in lighting from the RFD clear slot which helped illuminate the observed features beneath the updraft base. The first video still demonstrates the oval disc shaped updraft base. The next several video stills reveal a descending Wall Cloud and attached funnel.


The next image and possibly the proceeding define a funnel which may have reached the ground as tornado due to the dust swirl beneath.











The above images were generally taken after 0200Z and before 0230Z. In all this was a very strange event with respect to a developed SuperCell in an environment of high lifted indices but with very weak speed shear. The long duration over a central position without any appreciable movement was also unique and undoubtedly produced torrential rain and large hail over a confined limited area. The canopy spread from this lone Supercell, eventually collapsing around 0330Z, covered six counties along a west to east transect from the updraft.

Spreading Anvil at Sunset, Scurry and Kent Counties, Texas, May 12, 2009

The Eastern Permian Basin was included in a Slight Risk Category by the SPC on May 12th due to forecasted and observed steep mid level lapse rates, rich surface moisture, and strong surface heating west of a sharpening north south trending dry line for late afternoon and early evening. A Severe Thunderstorm Watch was eventually issued as convection initiated, overcoming a weakening capping inversion. SBCAPE values were rather impressive, exceeding 2500 J/kg, but mid to upper level speed shear, although increasing from earlier 1200Z sounding with respect to 0000Z soundings at MAF, were 40-50 knots of zonal west to east flow. Several images were taken of multi-cellular thunderstorms near the townsite of Ira in Scurry County at 0130Z looking from west to the east and northeast (northeast Mitchell, southeast Scurry counties extending into Kent County) at spreading anvils of mature/dissipating stages highlighted from setting sun. The first image is sun highlighted spreading anvil of mature/dissipating storm near Scurry/ Mitchell county line. The second image is looking further northeast into Kent County at spreading anvil underside with large Mammatus

Retreating Dryline Is Focus For Severe Outbreak, April 16th, 2009

The author returned to the Permian Basin before noon on April 16th after a short trip to San Antonio. It was noted that driving west of Kerrville to Sonora, mid morning, low LCL's produced Stratus clouds, indicating a nocturnal resurgence of low level moisture return northwestward from the Gulf. At Ozona, broken Altostratus prevailed before eventually clearing skies when arriving in Midland at noon, indicating the central Permian Basin was on the western periphery of the LLJ. An approaching Upper Level Closed Low over the Four Corners of the southwestern US was proceeding eastward which promised accelerating the LLJ and expanding it further west and north to include the Permian Basin. Colder air aloft, rounding the base of the Closed Low, was contributing to steep lapse rates and a strong 300 mb jet of over 100 knots was creating divergence aloft. The stage was set for a severe outbreak and the Permian Basin was included in a Slight Risk category by the SPC. Both speed and directional wind shear, compliments of the Closed Low aloft(from southwest) and LLJ (from southeast) respectively, would provide rotation and the threat of Tornadoes if Supercells developed.

During mid afternoon, the dryline pushed further east from strong surface heating in southwestern Texas and southeast New Mexico, impinging on the northwestward advance of the LLJ. Surface dewpoints at MAF had droped to the low 40's and were in the teen's in far west Texas as compared with the low 60's as near as the Concho Valley. Lapse rates had steepened but low level moisture was waning in the central Permian Basin. The author traveled to south of Spraberry around 2100Z to photograph a small convective tower which was developing in central Midland county which was updraft dominate and struggling with low moisture inflow (see the first two digital images). It was decided to drive to the northeast where radar returns indicated better convection and closer to more abundant surface moisture.

The next image is taken southwest of Lenorah in Martin county of a stronger cell with a lower storm base and expanding anvil. The next two images are taken a little further north near Ackerly in extreme southeastern Dawson County of a double-barrelled storm updraft composite with noted shear tilted storm towers.

The next several images denote an inflow dominate struggling LP south of Lenorah at approximately 2345Z. The updraft base was very low indicating that surface dewpoints were on the rise (Dryline retreating back to the west, providing lift). This was the beginning of a very severe outbreak, notably in Martin and Howard Counties for later in the evening.

The next image was captured looking north beyond Ackerly at a larger storm base and a well developed mid level inflow band and sheared tilt of storm tower.


The final images were captured around 0045Z looking south from the intersection of SH 176 and SH 349 in central Martin county toward the Midland County line at the southern end (tail-end Charlie) of a N-S trending multi-celled complex at a lowering of the storm base updraft which was the precursor to the eventual Tornadic Supercell which was confirmed by storm spotters as a 1/4 mile wide tornado near Knott and Fairview in south central Howard C.













Below, I am posting a perspective of the lowered Wall Cloud as viewed from the south in downtown Midland, looking north, from a good friend of mine, a geologist, who captured the following magnificent image (not to be reproduced). The image defines the lowering of the updraft base into a descended oval disc which rotated "clockwise". The Clear Slot, notched from an intensifying RFD, can be seen to the immediate left on the image.