Tropical Storm Sean Forecast Discussion Number 2

By | October 11, 2023

WTNT44 KNHC 110836

Tropical Storm Sean Discussion Number   2
NWS National Hurricane Center Miami FL       AL192023
500 AM AST Wed Oct 11 2023

Satellite images indicate that deep convection has increased near 
the center of the cyclone, with some curved banding features 
located both north and south of the center.  Subjective and 
objective Dvorak estimates from TAFB/SAB/UW-CIMSS range from 30-47 
kt, and a conservative blend of this data gives an initial wind 
speed of 35 kt for this advisory.  Thus Tropical Storm Sean has 
formed, the 19th named storm in this busy 2023 Atlantic season.  

Sean could intensify a bit more during the next day or so before 
increasing southerly shear affects the core of the cyclone.  Some 
hints of this shear can already be seen in cirrus cloud motions from 
convective activity northwest of the tropical cyclone. Thereafter, 
moderate-to-strong shear is expected to generally cancel out the 
enhancing effects of a relatively moist and unstable environment, 
leading to little net change for a few days.  By the end of the 
week, while the shear could weaken, global models are generally 
showing an influx of drier mid-level air along with upper-level 
convergence, which would typically weaken any associated deep 
convection.  Many of the regional hurricane models, however, 
actually show some strengthening at long range, but they have been 
inconsistent at that time frame.  The NHC forecast leans more on 
the global models for now, similar to the previous forecast and the 
model consensus, and continues to show Sean becoming a remnant low 
on day 5.

The storm is moving west-northwestward at about 11 kt.   A mid-level 
ridge located to the northeast of the cyclone should steer Sean 
west-northwestward to northwestward through Friday. Very late in the 
forecast period, a bend back toward the west-northwest is 
anticipated as the cyclone weakens and is steered by the low-level 
trade wind flow.  The new NHC track forecast is adjusted a bit west 
of the last one at longer range, between the model-consensus and 
corrected-consensus aids, which favors the weaker track aids on the 
left side of the guidance envelope.


INIT  11/0900Z 10.3N  33.1W   35 KT  40 MPH
 12H  11/1800Z 10.7N  34.8W   40 KT  45 MPH
 24H  12/0600Z 11.2N  36.5W   40 KT  45 MPH
 36H  12/1800Z 11.8N  38.0W   40 KT  45 MPH
 48H  13/0600Z 12.6N  39.5W   40 KT  45 MPH
 60H  13/1800Z 13.5N  40.8W   40 KT  45 MPH
 72H  14/0600Z 14.5N  42.0W   35 KT  40 MPH
 96H  15/0600Z 16.7N  44.6W   35 KT  40 MPH
120H  16/0600Z 18.0N  47.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

Forecaster Blake

Leave a Reply