[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 192043
TCDAT3

Tropical Storm Bret Discussion Number   2
NWS National Hurricane Center Miami FL       AL032023
500 PM AST Mon Jun 19 2023

Satellite imagery continues to show that the system is becoming
better organized. GOES 1-min data shows convective banding and a
dense central overcast, with the low-level center embedded on the
northwest side of the overcast.  Given the satellite trends and
latest Dvorak estimates from SAB and TAFB, the initial intensity is
set to 35 kt, and the depression is named Tropical Storm Bret.

Environmental conditions appear conducive for further strengthening
over the next few days, with much warmer than normal SSTs along with
plentiful mid-level moisture and light shear.  The NHC forecast
continues to show a gradual increase in wind speed, similar to the
model consensus.  However, vertical wind shear is forecast to
increase by most of the model guidance on day 3 in response to an
upper-level trough, along with more dry air nearby. Thus, the NHC
forecast shows a slow weakening after that point while Bret is
over the eastern Caribbean. There continues to be larger than usual
uncertainty, due to the wide spread between the stronger regional
hurricane models and weaker global guidance.

The initial motion estimate is 280/18 kt.  A large ridge of high
pressure over the central Atlantic Ocean is forecast to cause Bret
to move westward over the next several days. As the system nears the
Lesser Antilles late this week, the ridge should weaken, causing the
storm to move more toward the west-northwest.  The main source of
track uncertainty continues to be tied to how strong Bret becomes,
with the models farthest to the right (HWRF, HAFS) being stronger
than the consensus, while the left-leaning models (ECMWF, UKMET)
showing significant weakening at long range.  Given the large track
and intensity spread, the NHC forecast remains near the model
consensus, only a bit faster than the previous cycle. The latest
forecast remains a low confidence prediction.


KEY MESSAGES:

1. Bret is forecast to strengthen and move across the Lesser
Antilles as a hurricane on Thursday and Friday, bringing a
risk of flooding from heavy rainfall, hurricane-force winds, and
dangerous storm surge and waves.

2. Given the larger than usual uncertainty in the track forecast,
it is too early to specify the location and magnitude of where
these hazards could occur. However, everyone in the Lesser
Antilles, Puerto Rico, and the Virgin Islands should closely monitor
updates to the forecast for Bret and have their hurricane
plan in place.


FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 11.3N  42.2W   35 KT  40 MPH
 12H  20/0600Z 11.7N  44.8W   40 KT  45 MPH
 24H  20/1800Z 12.2N  47.7W   50 KT  60 MPH
 36H  21/0600Z 12.7N  50.3W   60 KT  70 MPH
 48H  21/1800Z 13.2N  52.9W   65 KT  75 MPH
 60H  22/0600Z 13.7N  55.5W   70 KT  80 MPH
 72H  22/1800Z 14.3N  58.3W   70 KT  80 MPH
 96H  23/1800Z 15.5N  63.6W   65 KT  75 MPH
120H  24/1800Z 17.0N  68.5W   60 KT  70 MPH

$$
Forecaster Blake/Kelly
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