Mesoscale Discussion 1339
NWS Storm Prediction Center Norman OK
0723 PM CDT Sat Jul 25 2020
Areas affected...the lower Texas Coastal Plain vicinity
Concerning...Severe potential...Watch possible
Valid 260023Z - 260530Z
Probability of Watch Issuance...40 percent
SUMMARY...Transient, weak rotation has been noted in cells
associated with outer bands of Hurricane Hanna this evening. This
activity will likely continue into the overnight hours.
DISCUSSION...Over the last hour or so, transient rotating cells have
been noted in an intense outer band of Hurricane Hanna. As of 00z,
this band was located about 30 miles offshore the barrier islands of
the Lower TX Coast, and generally shifting toward the coast at
around 8-10 kt. 0-1 km SRH will increase this evening into the
overnight hours as the center of Hanna shifts west/southwest toward
the lower Rio Grande River, resulting in backing low level wind
profiles. This could support a few transient rotating cells capable
of a brief tornado or two over the lower coastal plain.
Additional cells further north closer to Corpus Christi have also
shown some weak and transient rotation recently. Low level winds are
still from the east/northeast, but will continue to become more
east/southeasterly with time. Most recent velocity data from KCRP
shows rotation is fairly shallow. Nevertheless, a brief spin-up
cannot be ruled out given strong low level shear and enhanced SRH.
At this time, it does not appear a tornado watch is needed
imminently, but convective trends will be monitored closely and a
watch may be possible this evening or during the overnight hours.
..Leitman/Guyer.. 07/26/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CRP...BRO...
LAT...LON 26969714 27419711 27629707 27759711 27869725 27859760
27749782 27589798 27269799 26649793 26149783 25939772
25859747 25809719 25909707 26149699 26799714 26969714
Read morefrom SPC Forecast Products http://www.spc.noaa.gov/products/md/md1339.html
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