MD 0181 CONCERNING TORNADO WATCH 33… FOR PORTIONS OF WESTERN/SOUTHERN LA AND FAR EAST TX
Mesoscale Discussion 0181 NWS Storm Prediction Center Norman OK 1115 AM CST Tue Feb 14 2017 Areas affected...Portions of western/southern LA and far east TX Concerning...Tornado Watch 33... Valid 141715Z - 141845Z The severe weather threat for Tornado Watch 33 continues. SUMMARY...The risk for damaging wind gusts and perhaps a couple of tornadoes continues across Watch 33, though the severe potential presently appears to be becoming increasingly isolated/conditional. DISCUSSION...The latest mosaic radar imagery indicates a broken squall line advancing eastward across portions of the lower Sabine Valley vicinity, and this activity will continue to spread eastward during the next few hours. Cloud tops accompanying the broader convective system have been warming based on infrared satellite imagery, implying an overall weakening convective trend. Furthermore, surface pressure tendencies ahead of this activity are small in magnitude. This is likely a reflection of the deeper ascent accompanying a deamplifying midlevel cyclonic perturbation lagging well to the northwest of richer Gulf moisture serving as inflow to the convective system. Nevertheless, the latest visible satellite imagery and surface observations suggest that a more substantially modified Gulf air mass continues advancing inland ahead of the aforementioned activity. This air mass is preceded by a marine boundary extending around 30-60 miles north of the southern LA coast. Diurnal surface heating east of the ongoing convection -- especially where mid/high-level cloud canopies are thinning -- may support sufficient destabilization amidst this moisture for a conditional severe risk persisting into the afternoon. The LCH VAD wind profile indicates around 45-50 kt of 0-6-km bulk shear with sufficient low-level directional shear for around 200 m2/s2 of 0-1-km SRH. As such, damaging winds and perhaps some tornado potential could conditionally accompany deeper convective elements embedded within the squall line -- especially if more vigorous updrafts were to become separated within the line. ..Cohen.. 02/14/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LCH...SHV... LAT...LON 29549223 29869397 30849412 31429386 31589350 31429295 30429235 29549223
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