[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 120834
TCDAT4

Tropical Depression Sean Discussion Number   6
NWS National Hurricane Center Miami FL       AL192023
500 AM AST Thu Oct 12 2023

Sean remains a sheared, poorly organized tropical cyclone. Recent
AMSR2 passive microwave images show the surface circulation lies
well to the west of the associated deep convection. The lackluster
satellite presentation of Sean has resulted in decreasing subjective
Dvorak data-T numbers from TAFB and SAB, which supports keeping the
system a tropical depression. The initial intensity is held at 30
kt, consistent with the ASCAT data from yesterday evening.

The depression is moving west-northwestward at 300/10 kt. A weak
low- to mid-level ridge to the north and northeast of Sean should
steer the cyclone to the west-northwest and northwest through early
next week. A slight rightward adjustment was made to the NHC track
forecast to reflect the latest multi-model consensus trends. But
otherwise, the updated forecast is similar to the previous
prediction.

Moderate to strong westerly shear is expected to persist over the
depression for the next day or two. By the time the shear relents,
simulated satellite images from the GFS and ECMWF models suggest
that Sean could struggle to sustain organized convection near its
center within a drier and more convergent upper-level environment.
While small intensity fluctuations cannot be ruled out during the
next couple of days, the NHC intensity forecast follows the HCCA and
IVCN aids and keeps Sean a depression through 60 h. Sean is forecast
to degenerate to a post-tropical remnant low soon thereafter and
dissipate to a trough by day 4, although this could occur even
sooner if the cyclone remains poorly organized.


FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 12.5N  36.7W   30 KT  35 MPH
 12H  12/1800Z 13.0N  38.0W   30 KT  35 MPH
 24H  13/0600Z 13.8N  39.6W   30 KT  35 MPH
 36H  13/1800Z 14.8N  41.2W   30 KT  35 MPH
 48H  14/0600Z 16.0N  42.6W   30 KT  35 MPH
 60H  14/1800Z 17.3N  43.9W   25 KT  30 MPH
 72H  15/0600Z 18.2N  45.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  16/0600Z...DISSIPATED

$$
Forecaster Reinhart
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