[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 220853
TCDAT3

Tropical Storm Bret Discussion Number  12
NWS National Hurricane Center Miami FL       AL032023
500 AM AST Thu Jun 22 2023

Bret threw some interesting data at us during the couple of hours
after the release of the previous advisory.  On the last pass of the
Air Force Reserve Hurricane Hunter aircraft through Bret's center,
the plane measured SFMR winds as high as 69 kt and a dropsonde
surface pressure of 996 mb with 31 kt of wind.  Significant
mid-level westerly shear is still affecting the system, and a 0539
UTC AMSR2 microwave pass revealed a well-defined mid-level eye
feature displaced about a degree to the east of Bret's low-level
center.  It appears that the strong SFMR winds were measured beneath
the strong convection in the western mid-level eyewall feature, so
it's possible that they were transient and convectively driven.
That said, Bret's initial intensity was raised to 60 kt on the 2 am
intermediate advisory out of an abundance of caution, and that
remains the current estimate.  Another reconnaissance aircraft is
scheduled to investigate Bret in a few hours and will hopefully
confirm whether or not the storm is still producing winds that
strong.

Vertical shear is expected to gradually increase over the next
couple of days as Bret approaches an upper-level trough located over
the eastern Caribbean Sea.  The storm could maintain its intensity
or fluctuate in intensity through much of today, but it is expected
to begin weakening by tonight once it crosses the Lesser Antilles
and moves over the eastern Caribbean Sea.  Global model fields
indicate that Bret should degenerate into a trough over the central
Caribbean Sea by day 3, which is shown in the official forecast.

There are no changes in the track forecast reasoning.  Bret is
moving toward the west, or 280/13 kt, steered by a low- to mid-level
ridge to its north.  An accelerated westward motion is expected
during the next few days as Bret weakens, and the NHC track forecast
is a little faster than the consensus aids, hedging toward the
faster GFS and ECMWF solutions.  Users are reminded that NHC's track
forecasts have average errors of about 40 n mi at 24 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 today and then
move across those islands this evening and tonight as a strong
tropical storm.

2. A Hurricane Watch and a Tropical Storm Warning are in effect
for St. Lucia, and a Tropical Storm Warning is in effect for
Martinique and Dominica.  There is a risk of flooding from heavy
rainfall, strong winds, and dangerous waves along the coast within
the warning area.  A Tropical Storm Watch remains in effect for
Barbados and St. Vincent and the Grenadines.  Additional watches or
warnings are possible for some islands in the Lesser Antilles later
today.


FORECAST POSITIONS AND MAX WINDS

INIT  22/0900Z 13.7N  56.6W   60 KT  70 MPH
 12H  22/1800Z 13.9N  58.8W   60 KT  70 MPH
 24H  23/0600Z 14.1N  61.8W   55 KT  65 MPH
 36H  23/1800Z 14.3N  65.2W   50 KT  60 MPH
 48H  24/0600Z 14.4N  68.7W   45 KT  50 MPH
 60H  24/1800Z 14.6N  72.2W   40 KT  45 MPH
 72H  25/0600Z...DISSIPATED

$$
Forecaster Berg
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