Tropical Storm Nigel Discussion Number   9
NWS National Hurricane Center Miami FL       AL152023
1100 AM AST Sun Sep 17 2023

Based on satellite imagery, Nigel appears to be steadily 
strengthening. A prominent curved band of deep convection wraps 
around the northern half of the tropical storm, with additional 
convective activity recently observed very near its center. 
Satellite intensity estimates range from around 45 to 55 kt, so the 
initial intensity is set at a near-consensus value of 50 kt.

Nigel is in an environment that should support strengthening, and in 
fact the SHIPS-RII and DTOPS rapid intensification models indicate 
it has a near 50/50 chance of strengthening 25 kt in the next 24 h 
and/or 55 kt in the next 48 h. Recent SSMIS imagery at 0911 UTC 
indicated that the inner core of Nigel is probably not yet 
well-enough developed to support immediate rapid intensification, 
but that could happen at some point later today. Most of the 
intensity models indicate that Nigel's intensity will peak in about 
60 h, before increasing wind shear and cooler waters begin to affect 
it. Extratropical transition should then begin in about 4 days, and 
that process will likely be near complete at the end of the forecast 
period. Only very small adjustments were made to the NHC intensity 
forecast, which is very near the IVCN intensity consensus.

Likewise, nearly no changes were made to the official track 
forecast. For the next 4-5 days, Nigel should generally move between 
a ridge centered between Nigel and Margot, and a mid-latitude trough 
that is forecast to move off the eastern coasts of the U.S. and 
Canada early this week. These features will likely steer Nigel 
generally northwestward for the next 2 days, and cause it to 
accelerate northeastward after that. The NHC track forecast 
continues to be based primarily on the HCCA and TVCN models.


FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 24.0N  49.1W   50 KT  60 MPH
12H  18/0000Z 25.3N  50.2W   60 KT  70 MPH
24H  18/1200Z 26.8N  51.7W   75 KT  85 MPH
36H  19/0000Z 28.2N  53.1W   85 KT 100 MPH
48H  19/1200Z 29.8N  54.6W   95 KT 110 MPH
60H  20/0000Z 31.8N  55.4W  100 KT 115 MPH
72H  20/1200Z 34.2N  54.9W   95 KT 110 MPH
96H  21/1200Z 39.6N  49.0W   85 KT 100 MPH
120H  22/1200Z 46.5N  35.5W   65 KT  75 MPH

$$
Forecaster D. Zelinsky