Mesoscale Discussion 0065
NWS Storm Prediction Center Norman OK
0543 AM CST Sun Feb 11 2018
Areas affected...Portions of the central Gulf Coast
Concerning...Severe potential...Watch unlikely
Valid 111143Z - 111415Z
Probability of Watch Issuance...20 percent
SUMMARY...A gradual uptick in thunderstorm activity this morning may
yield a potential for isolated strong gusts and perhaps a brief
tornado. Watch issuance is not expected.
DISCUSSION...Convective activity has slowly increased near the
Louisiana coastline early this morning, likely aided by a minor
increase in a south/southwesterly low-level jet, and this trend
should continue across the central Gulf Coast this morning. As of
1130Z, a marine air mass, characterized by surface dew points in the
upper 60s to near 70, is making slow northward progress across
southeastern Louisiana. Near/south of this boundary, modified
forecast soundings and mesoanalysis data suggest around 500-800 J/kg
of MLCAPE is present -- adequate for a few stronger updrafts.
Meanwhile, southwesterly mid-level flow around 50 kt is encouraging
modest organization/rotation within the strongest cores.
Despite a relatively convoluted pattern of surface winds, somewhat
backed flow exists near the marine/outflow boundary, stretching from
far southeastern Louisiana eastward to points just offshore the
Mississippi/Alabama coast. The related subtle enhancement of
low-level shear may yield a few embedded supercell structures and
bowing segments, with an attendant threat for stronger gusts and
perhaps a brief tornado from southeastern Louisiana to far southern
Mississippi/Alabama this morning, assuming a richer maritime air
mass can move ashore here. To account for this threat, the 13Z
outlook will expand MRGL probabilities to the southwest.
Nonetheless, poor lapse rates and the predominance of veered flow
above the surface will limit the overall severe threat, precluding
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 29079042 29179072 29379072 29789029 30428918 30578865
30588765 30448731 30258754 29758837 29338875 29108934