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Tropical Storm Beta Discussion Number  14
NWS National Hurricane Center Miami FL       AL222020
1000 PM CDT Sun Sep 20 2020
 
Satellite and radar imagery shows that the deep convection
associated with Beta has decreased considerably since this
afternoon.  This appears to be the result of dry air entrainment 
and vertical wind shear.  Despite the recent decrease in convective 
organization, an Air Force Reserve Hurricane Hunter aircraft has 
found SFMR winds of around 45 kt, and there have been a couple of 
ship observations this evening of winds of 45-50 kt. Therefore, the 
initial intensity of 50 kt has been maintained.  Data from the most 
recent center dropwindsonde indicate that the pressure is around 
995 mb.
 
Beta is forecast to remain within an area of moderate vertical wind
shear, and that along with intrusions of dry air are likely to
prevent Beta from strengthening before it nears the Texas coast.
As a result, the NHC intensity forecast shows little change in
strength before landfall in about 24 hours.  Gradual weakening
should occur after the center moves over land, but the weakening
rate may be slower-than-normal as a portion of the circulation
will remain offshore. In 2-3 days, the system is expected to weaken 
to a tropical depression, and it should become a remnant low by 96 h
as it move farther inland over the lower Mississippi Valley.  The
NHC intensity forecast is near the upper-end of the intensity
guidance through 24 hours, and is in best agreement with the SHIPS
statistical model.
 
Beta has jogged westward this evening, but the longer-term motion
estimate is 290/5 kt.  There is once again no change the previous
track forecast philosophy.  The tropical storm is located between a
mid-level ridge over Florida and another ridge over the Southern
Plains. Beta should move slowly west-northwestward toward the coast
of Texas during the next 12 to 24 hours.  After that time, the ridge
over the Plains should weaken allowing the ridge to the east to 
steer Beta northward, and then northeastward near the Upper-Texas 
coast by mid-week.  With the recent westward jog, the new track 
forecast has been nudged slightly south of the previous track 
through 24 hours, but is slightly east of the previous advisory 
thereafter to be closer to the various consensus aids.
 
 
Key Messages:
 
1. The expected slow motion of Beta will produce a long duration 
rainfall event from the middle Texas coast to southern Louisiana. 
Flash, urban, and river flooding is likely. Rainfall will also  
spread northward into the ArkLaTex region and east into the Lower 
Mississippi Valley where flash, urban, and river flooding is 
possible.
 
2. There is the danger of life-threatening storm surge near times of
high tide through Tuesday along portions of the Texas and Louisiana
coasts within the storm surge warning areas. Residents in these
areas should follow advice given by local officials.
 
3. Tropical-storm-force winds are occurring along portions of the
northwestern Gulf Coast within the tropical storm warning area in
Louisiana.  These winds will spread westward to the Texas coast 
overnight and Monday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0300Z 27.6N  94.5W   50 KT  60 MPH
 12H  21/1200Z 28.0N  95.4W   50 KT  60 MPH
 24H  22/0000Z 28.5N  96.4W   45 KT  50 MPH
 36H  22/1200Z 28.8N  96.7W   35 KT  40 MPH...INLAND
 48H  23/0000Z 29.1N  96.2W   30 KT  35 MPH...INLAND
 60H  23/1200Z 29.5N  95.2W   30 KT  35 MPH...INLAND
 72H  24/0000Z 30.1N  94.0W   30 KT  35 MPH...INLAND
 96H  25/0000Z 31.9N  91.6W   20 KT  25 MPH...POST-TROP/INLAND
120H  26/0000Z...DISSIPATED
 
$$
Forecaster Brown
 
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