Official Discussion issued by the National Hurricane Center

Beta (AL222020) DATA RELEASED: 9/19/2020 10:00:00 AM UTC

Copy of official data

Tropical Storm Beta Discussion Number   8
NWS National Hurricane Center Miami FL       AL222020
1000 AM CDT Sat Sep 19 2020

Morning visible imagery indicates that Beta has become significantly 
sheared, with the low-level center mostly exposed well to the 
southwest of the main convective area.  A new convective band is 
currently forming near the center over the northwestern quadrant.  
An Air Force Reserve Hurricane Hunter aircraft reported pressures 
near 994-995 mb, along with flight-level and SFMR winds that justify 
keeping the initial intensity at 50 kt.

The storm appears to be starting its westward turn, and the initial 
motion is now 315/3.  The mid- to upper-level trough over the 
northwestern Gulf of Mexico is lifting out, with a mid-level ridge 
building to the north of Beta.  This should cause the storm to turn 
more westward during the next 6-12 h.  After that, a slow west- 
northwestward to northwestward motion should develop, with the 
center now forecast to be near or over the middle Texas coast in 
about 72 h.  Beyond 72 h, another mid-latitude trough moving 
through the central United States should cause Beta to recurve 
slowly to the northeast.  The new NHC forecast is shifted a little 
to the west and now explicitly shows landfall on the Texas coast in 
about 72 h.  This new forecast is a little to the north of the 
consensus models through 72 h and close to them after that time.

There are lots of uncertainties in the intensity forecast.  First, 
the global models suggest that the ongoing southwesterly shear may 
not subside that much even though the first trough is lifting out.  
Second, GOES-16 air mass imagery shows abundant upper-level dry air 
over the western Gulf of Mexico, including near the storm center.  
Third, surface observations show a drier low-level airmass in place 
over southeastern Texas, and some of this may get entrained into the 
storm.  The intensity guidance has trended downward to the point 
where none of the models are currently forecasting Beta to become a 
hurricane.  Based on this and the current storm structure, the 
intensity forecast has been adjusted to show little change in 
strength today, followed by slow strengthening to a hurricane by 
48-60 h.  However, this forecast is well above the guidance, and 
additional downward adjustments may be needed later today.

A Tropical Storm Warning is being issued for parts of the Texas and 
Louisiana coasts at this time.  A Hurricane Warning could still be 
issued later today or tonight depending on later intensity 

Key Messages:

1. The expected slow motion of Beta has the potential to produce a 
long duration rainfall event along the western Gulf Coast. The 
potentially prolonged period of rainfall could cause flash, urban, 
and river flooding, especially where tide levels are above normal.

2. Life-threatening storm surge and hurricane-force winds are 
possible along portions of the northwestern Gulf Coast, with 
tropical storm conditions expected by late this weekend. Storm Surge 
and Hurricane watches and Tropical Storm warnings are in effect, and 
residents in these areas should ensure they have their hurricane 
plan in place and follow advice given by local officials. 


INIT  19/1500Z 26.6N  92.6W   50 KT  60 MPH
12H  20/0000Z 26.9N  93.0W   50 KT  60 MPH
24H  20/1200Z 27.1N  93.8W   55 KT  65 MPH
36H  21/0000Z 27.5N  94.8W   60 KT  70 MPH
48H  21/1200Z 27.8N  95.5W   65 KT  75 MPH
60H  22/0000Z 28.2N  96.2W   65 KT  75 MPH
72H  22/1200Z 28.6N  96.2W   55 KT  65 MPH...INLAND
96H  23/1200Z 29.5N  95.0W   60 KT  70 MPH...INLAND
120H  24/1200Z 30.5N  93.0W   50 KT  60 MPH...INLAND

Forecaster Beven