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Tropical Depression Beta Discussion Number  20
NWS National Hurricane Center Miami FL       AL222020
1000 AM CDT Tue Sep 22 2020
 
High-resolution visible satellite imagery, surface observations, and 
NOAA Doppler weather radar data from San Antonio, Corpus Christi, 
and Houston, Texas, indicate that Beta has moved a little farther 
inland and has weakened to a tropical depression. The same data 
also show that Beta has started a slow drift toward the northeast. 
Deep convection has waned considerably since the previous 
advisory, especially during the past few hours, with cloud tops now 
warmer than -30 deg C, which no longer meets the Dvorak satellite 
classification criterion. The initial intensity is 30 kt is based 
on average Doppler velocities of 35-40 kt between 1500-2500 ft ASL 
just to the southeast and south of Galveston.
 
The initial motion estimate is now 045/02 kt.  Steering currents 
around Beta remain weak. However, water vapor imagery indicates that 
a broad mid- to upper-level trough over western Texas is moving 
slowly eastward, and that feature should gradually force Beta 
east-northeastward later today and tonight, followed by a faster 
motion toward the northeast on Wednesday and Thursday across 
Louisiana and Mississippi before dissipating in about 4 days. The 
new NHC forecast track is similar to the previous advisory track, 
which keeps Beta just inland from the Gulf coast, and lies near a 
blend of the simple consensus models TVCA and GFEX, and the NOAA 
corrected-consensus model HCCA.
 
Since Beta's center is forecast to remain just inland for the next 
36-48 hours, chances of the cyclone regaining tropical storm status 
are becoming less likely. As a result, the new official intensity 
forecast shows Beta remaining a 25-30 kt depression during that 
time, followed by weakening to a remnant low by 48 hours, and 
dissipation over Mississippi or Alabama by 96 hours. This is 
consistent with the various simple and corrected-consensus models.

Although Beta is now an inland tropical depression, the National 
Hurricane Center will continue to issue advisories on the cyclone 
due to its proximity to the Gulf of Mexico and until it becomes 
clear that re-strengthening into a tropical storm is unlikely.

Key Messages:
 
1. Significant flash and urban flooding is occurring and will 
continue for the middle and upper Texas coast today. The slow motion 
of Beta will continue to produce a long duration rainfall event from 
the middle Texas coast to southern Louisiana. Flash, urban, and 
minor to isolated moderate river flooding is likely. Periods of 
rainfall will spread east into the Lower Mississippi Valley and 
portions of the Southeast through the end of the week. Flash, urban, 
and isolated minor river flooding is possible on smaller rivers.
 
2. Persistent onshore flow will continue to result in above normal 
high tides, and coastal flooding over the next few days will be slow 
to recede. For information on the ongoing coastal flooding, please 
refer to coastal flood products issued by local National Weather 
Service offices.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/1500Z 28.9N  96.7W   30 KT  35 MPH...INLAND
 12H  23/0000Z 29.0N  96.3W   30 KT  35 MPH...INLAND
 24H  23/1200Z 29.6N  95.1W   30 KT  35 MPH...INLAND
 36H  24/0000Z 30.4N  93.7W   25 KT  30 MPH...INLAND
 48H  24/1200Z 31.7N  92.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  25/0000Z 33.1N  90.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  25/1200Z 34.4N  88.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  26/1200Z...DISSIPATED INLAND
 
$$
Forecaster Stewart
 
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