Tropical Disturbance 91L Is Strengthening

Subsurface Equatorial Pacific Is Cooling…Supports La Nina Onset Q4/2021
09/06/2021, 3:32 pm EDT
T.S. Mindy Weakens Inland. Heavy Rains Ahead for Texas/Louisiana.
09/09/2021, 5:39 am EDT
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NOAA/NESDIS/STAR GOES ABI BAND 13 OR_ABI-L1b-RadC-M6C13_G16_s20212511801190_e20212511803575_c20212511804030.nc

Highlight: Tropical Disturbance 91L is strengthening. Not quite enough time to reach T.S. strength before making landfall. ECM has their version of a Texas rainstorm days 6-10.

Fig. 1: The Gulf of Mexico weather satellite view of Tropical Disturbance 91L.

Fig. 2: ECM rainfall forecast for the Gulf of Mexico through 7AM CDT Friday.

Discussion: Despite the shear pattern to the north of the center of Tropical Disturbance 91L and lingering cold core in the upper atmosphere southwest of the core (Fig. 1), this system is gaining strength heading toward the western Florida Panhandle. Weather satellite confirms a squall line east of the center of 91L due to move northeastward and brings squalls/thunderstorms/gully-washer rains to the Florida Panhandle and possibly farther east and northeast overnight (Fig. 2). A low-pressure center forms just prior to moving inland the Florida Panhandle overnight therefore a last-second tropical cyclone is possible but not forecast. The system weakens considerably once inland. However, re-emergence off the Southeast U.S. Coast leaves the chance of regeneration in the forecast. Note the thunderstorm activity southwest of 91L in the central Gulf of Mexico. This activity is likely to linger well offshore and then shift westward (slowly) and gain strength while over Texas in the 6-10-day period producing extreme rainfall but not a tropical cyclone (Fig. 3).

Fig. 3: ECM rainfall forecast for the Gulf of Mexico for days 6-10.