[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 210236
TCDAT3

Tropical Storm Bret Discussion Number   7
NWS National Hurricane Center Miami FL       AL032023
1100 PM AST Tue Jun 20 2023

Bret has become a little better organized this evening, with
increased convection near and north of the center and some outer
bands developing in the eastern semicircle.  This development has
lead to satellite intensity estimates from TAFB and SAB increasing
to 45 kt, and that will be the initial intensity for this advisory.
Unfortunately, the ASCAT overpasses this evening again managed to
miss Bret.

Satellite imagery continues to suggest some vertical wind shear is
undercutting Bret's otherwise favorable looking outflow pattern and
slowing the rate of intensification.  This shear is expected to
continue for the next 36 h or so, and the storm is forecast to
continue to slowly strengthen during this time. The new intensity
forecast calls for Bret to have a 55-kt intensity when it passes
near or over the Lesser Antilles around the 48-h point.   After
that, stronger shear associated with an upper-level trough over the
eastern Caribbean should stop intensification and cause Bret to
weaken.  Indeed, the global models continue to forecast the system
to degenerate to a tropical wave by 96 h.  The new intensity
forecast will continue to have a 96 h point followed by dissipation
before 120 h.  However, it will show a faster weakening from 72-96 h
than the previous forecast.

The initial motion is westward or 280/15 kt.  There is again little
change to either the track forecast guidance or the track forecast
since the last advisory, with low- to mid-level ridging north of
Bret expected to steer the cyclone westward through dissipation.
Users are reminded that NHC's track forecasts have average errors
of about 60 n mi at 48 hours, and it is too soon to know exactly
where Bret's center will move across the Lesser Antilles chain.


KEY MESSAGES:

1. Bret is forecast to approach the Lesser Antilles through
Thursday morning and then move across the islands Thursday
afternoon and Thursday night as a tropical storm, bringing a risk of
flooding from heavy rainfall, strong winds, and dangerous waves
along the coast.

2. Given the uncertainty in the track and intensity forecasts, it
is too early to specify the location and magnitude of where Bret's
associated hazards could occur.  A Tropical Storm Watch has been
issued for Barbados, Dominica, Martinique, and St. Lucia, and
additional watches and warnings are likely for these and other
islands in the Lesser Antilles on Wednesday.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 12.5N  50.2W   45 KT  50 MPH
 12H  21/1200Z 12.9N  52.3W   50 KT  60 MPH
 24H  22/0000Z 13.3N  54.7W   55 KT  65 MPH
 36H  22/1200Z 13.7N  57.5W   55 KT  65 MPH
 48H  23/0000Z 14.0N  60.6W   55 KT  65 MPH
 60H  23/1200Z 14.3N  63.9W   50 KT  60 MPH
 72H  24/0000Z 14.6N  67.6W   45 KT  50 MPH
 96H  25/0000Z 15.0N  75.0W   30 KT  35 MPH
120H  26/0000Z...DISSIPATED

$$
Forecaster Beven
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