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Tropical Depression Sean Discussion Number   5
NWS National Hurricane Center Miami FL       AL192023
1100 PM AST Wed Oct 11 2023
 
Sean is a highly sheared tropical cyclone, with the center located 
well to the west of the associated deep convection.  Similar to what 
was observed this morning, two recent ASCAT passes showed maximum 
winds a little over 25 kt and a poorly defined surface circulation. 
Based on these data, Sean is being designated as a 30-kt tropical 
depression.

The initial motion remains west-northwestward (295 degrees) at 11 
kt.  Weak mid-level ridging to the north is expected to keep Sean on 
a west-northwestward or northwestward heading for the next several 
days, with some decrease in forward speed.  The NHC track forecast 
is very close to the previous prediction through 48 hours, but then 
deviates a little to the right on days 3 and 4.  The GFS and ECMWF 
are both on the far right side of the guidance envelope, and it's 
possible that additional rightward adjustments could be possible in 
subsequent forecasts.

Strong deep-layer shear out of the west or west-southwest is 
expected to continue for the next 36 hours or so, with some 
abatement possible after that.  By then, however, drier air will 
have infiltrated the circulation, and Sean will begin to struggle to 
maintain organized deep convection.  Due to the hostile atmosphere, 
and based on the latest intensity guidance, Sean is held as a 30-kt 
depression for the next 60 hours, with degeneration to a remnant low 
by day 3.  Dissipation to a trough is now forecast by day 5.  Some 
of the global models suggest that each of these transitions could 
occur even sooner than what is shown in the official forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/0300Z 12.0N  36.2W   30 KT  35 MPH
 12H  12/1200Z 12.4N  37.4W   30 KT  35 MPH
 24H  13/0000Z 13.1N  39.0W   30 KT  35 MPH
 36H  13/1200Z 14.0N  40.5W   30 KT  35 MPH
 48H  14/0000Z 15.0N  42.0W   30 KT  35 MPH
 60H  14/1200Z 16.1N  43.1W   30 KT  35 MPH
 72H  15/0000Z 17.2N  44.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  16/0000Z 18.5N  46.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  17/0000Z...DISSIPATED
 
$$
Forecaster Berg
 
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