[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 211455
TCDAT3

Tropical Storm Bret Discussion Number   9
NWS National Hurricane Center Miami FL       AL032023
1100 AM AST Wed Jun 21 2023

Bret's cloud pattern remains ragged, and cloud top temperatures have
warmed a bit compared to earlier this morning.  Since there has not
been an appreciable increase in organization, the initial intensity
remains 50 kt, which is a blend between the latest subjective
numbers from TAFB and SAB, and objective final-T numbers (which
have been decreasing).  An Air Force Reserve Hurricane Hunter
aircraft is scheduled to investigate Bret in a few hours and should
provide a better estimate of the storm's intensity and wind field
size.

The storm still appears to be under the influence of moderate
westerly shear below the cirrus level, with the bulk of the deep
convection displaced to the east of the center.  Bret still has an
opportunity to strengthen slightly over the next day or so, and the
NHC intensity forecast is close to the SHIPS, LGEM, and HCCA
solutions through 36 hours.  Stronger deep-layer shear is expected
to cause weakening in about 36 to 48 hours after Bret moves into the
eastern Caribbean Sea, and global model fields indicate that the
circulation could open up into a trough by Saturday.  As a result,
dissipation is now shown in the official forecast by day 4, although
it could occur sooner than that.

Low- to mid-level ridging continues to push Bret westward at 280/12
kt.  The steering flow is expected to strengthen some in the next
couple of days, and Bret is therefore forecast to accelerate toward
the west on Thursday and Friday as it's approaching and passing
across the Lesser Antilles.  There have been no significant shifts
in the track guidance on this cycle, and the new NHC track forecast
is therefore unchanged from the 5 am forecast.  Users are reminded
that NHC's track forecasts have average errors of about 45-50 n mi
at 36 hours, and there is risk of strong winds and heavy rainfall
for several islands within the Lesser Antilles regardless of
exactly where the center crosses the island chain.


KEY MESSAGES:

1. Bret is forecast to approach the Lesser Antilles through
Thursday and then move across those islands late Thursday and
Thursday night as a strong 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 still too early to specify the exact location and magnitude of
where Bret's associated hazards could occur.  A Tropical Storm
Warning is now in effect for St. Lucia, and a Tropical Storm Watch
remains in effect for Barbados, Dominica, and Martinique.
Additional warnings are likely for some islands in the Lesser
Antilles later today.


FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 13.0N  52.5W   50 KT  60 MPH
 12H  22/0000Z 13.2N  54.4W   55 KT  65 MPH
 24H  22/1200Z 13.5N  57.1W   55 KT  65 MPH
 36H  23/0000Z 13.9N  60.1W   55 KT  65 MPH
 48H  23/1200Z 14.3N  63.5W   50 KT  60 MPH
 60H  24/0000Z 14.6N  67.1W   45 KT  50 MPH
 72H  24/1200Z 14.7N  70.7W   40 KT  45 MPH
 96H  25/1200Z...DISSIPATED

$$
Forecaster Berg
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