Hurricane Nigel Discussion Number  15
NWS National Hurricane Center Miami FL       AL152023
1100 PM AST Mon Sep 18 2023

Nigel has become a little better organized this evening, with a 
ragged eye becoming more apparent in infrared satellite imagery. An 
earlier SSMIS microwave overpass revealed a fairly well-defined 
low-level inner-core structure, but the eye was open to the 
northwest. Subjective Dvorak intensity estimates from TAFB and SAB 
were a consensus T4.5 (77 kt), and the various objective estimates 
were in the 70-80 kt range at 0000 UTC.  Based on a blend of these 
intensity estimates, the initial wind speed is set at 75 kt for 
this advisory. 

Although Nigel's strengthening appears to have been disrupted by 
dry air entrainment today, the hurricane has about another 24-36
hours within low shear conditions and over warm SSTs in which 
to strengthen. The NHC intensity forecast calls for additional 
strengthening during that time, but the peak intensity has been 
lowered slightly.  After 36-48 hours, increasing southwesterly 
vertical wind shear and cooler SSTS along the track of Nigel are 
expected to cause gradual weakening.  The NHC wind speed forecast 
is in best agreement with the HFIP corrected-consensus aid, which 
is at the higher end of the guidance in the short term.  The global 
models indicate that extratropical transition is likely to begin by 
72 hours, and that process should be complete by day 4.  

Nigel continues to move northwestward (310 degrees) at about 10 kt. 
The hurricane should continue on that general heading and speed 
through midday Tuesday, but as it nears the western extent of the 
ridge, Nigel is predicted to turn northwestward and northward 
shortly thereafter.  By 48 hours, an approaching mid- to upper-level 
trough is forecast to cause Nigel to accelerate northeastward over 
the central and northeastern Atlantic through the remainder of the 
forecast period.  The track guidance remains tightly clustered, with 
the primary differences being how much Nigel accelerates 
northeastward later in the period.  The NHC track forecast is a 
blend of the typically reliable GFS and ECMWF models, nd is close 
to the various consensus aids. 


FORECAST POSITIONS AND MAX WINDS

INIT  19/0300Z 28.6N  52.7W   75 KT  85 MPH
12H  19/1200Z 29.9N  53.8W   85 KT 100 MPH
24H  20/0000Z 32.1N  54.5W   90 KT 105 MPH
36H  20/1200Z 34.7N  54.1W   90 KT 105 MPH
48H  21/0000Z 37.6N  51.6W   85 KT 100 MPH
60H  21/1200Z 40.5N  46.6W   80 KT  90 MPH
72H  22/0000Z 43.4N  39.5W   70 KT  80 MPH
96H  23/0000Z 50.0N  24.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  24/0000Z 57.0N  17.4W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown