|Mesoscale Discussion 84|
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Mesoscale Discussion 0084
NWS Storm Prediction Center Norman OK
0141 AM CST Sat Jan 21 2017
Areas affected...southwest...south-central and central Louisiana
Concerning...Tornado Watch 9...
Valid 210741Z - 210845Z
The severe weather threat for Tornado Watch 9 continues.
SUMMARY...The greatest threat for additional severe storms across WW
9 is expected across eastern portions of this watch in south-central
and east-central Louisiana. The portion of WW 9 in south-central
Louisiana may need to be extended temporally beyond the expiration
of 08Z as discrete storms continue to develop over that region and
also move inland from the Gulf of Mexico.
Meanwhile, storms tracking to the east-northeast from southeast
Texas into Louisiana should continue to diminish in intensity
allowing the rest of WW 9 to expire at 08Z.
DISCUSSION...Trends in early overnight water-vapor imagery indicated
two midlevel shortwave troughs aiding in focused thunderstorm
coverage across the northwest Gulf Coast region from southeast TX
through LA to southwest MS.
The lead impulse and associated thunderstorms from south-central LA
to southwest MS are expected to remain the primary severe-weather
threat, as this activity advances to the east-northeast into a
strongly sheared and moistening environment. Backed (southerly)
low-level winds beneath southwesterly midlevel winds will sustain
bulk shear for organized storms. LIX holograph also indicated 0-1
km SRH values around 200 m2/s2 favorable for low-level storm
rotation and a continued tornado threat for storms across
LAT...LON 29769362 30869254 31119226 31219175 30529168 29709114
29429131 28989133 29099194 29419362 29769362
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