MD 0635 CONCERNING SEVERE POTENTIAL…TORNADO WATCH LIKELY FOR SOUTHEAST TX AND SOUTHERN LA
Mesoscale Discussion 0635
NWS Storm Prediction Center Norman OK
0704 AM CDT Wed May 03 2017
Areas affected...Southeast TX and southern LA
Concerning...Severe potential...Tornado Watch likely
Valid 031204Z - 031330Z
Probability of Watch Issuance...80 percent
SUMMARY...WW issuance is likely within the hour. Storms will
continue to increase in intensity (as observed with ongoing activity
north of HOU and across southwest LA at 12Z) and coverage this
morning.
DISCUSSION...A couple of storms have developed and intensified
across southeast TX (near and north of the Houston metro), and
moving onshore the southwest LA coastal region from the northwest
Gulf of Mexico per trends in mosaic radar imagery. Although overall
storm coverage is limited at this time, observational data indicated
the storms that have formed have developed strong updrafts (some
with weak low- to mid-level rotation and rapidly cooling cloud tops
to 50,000+ ft.).
Early morning surface analyses showed a warm front advancing north
across southeast TX and approaching the LA coast with storms thus
far developing near this front. Rich low-level moisture was located
across the warm sector (dew points into the lower 70s). This
combined with the presence of steep midlevel lapse rates (exceeding
8 C/km) per objective analyses and 12Z soundings will continue to
contribute to a destabilizing air mass from south to north and
MLCAPE ranging from 1500-2500 J/kg this morning.
Meanwhile, water-vapor imagery showed an eastward-moving midlevel
shortwave trough in south-central to southeast TX as 700-mb winds
have veered to westerly at SJT/DRT and EWX with the passage of this
trough. Forcing for ascent with this trough and within the exit
region of an accompanying 50-55 kt westerly 500-mb jet will support
further thunderstorm development this morning across southeast TX
into southwest LA. The favorable thermodynamics and strong
low-level (increasing SRH values) and deep-layer shear (vertically
veering winds) will favor organized storms, with hail as the initial
threat. However, the ongoing reduction of inhibition will allow for
storms to become surface based this morning with additional
severe-weather hazards (including damaging winds and a tornado
threat).
..Peters/Guyer.. 05/03/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LIX...LCH...SHV...HGX...FWD...
LAT...LON 29029347 29489489 30619583 31169595 31739462 31749221
31189183 30759151 29689152 29109176 29029347
from SPC Mesoscale Discussions http://bit.ly/2pXBwNk
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