Tropical Storm Nigel Discussion Number   7
NWS National Hurricane Center Miami FL       AL152023
1100 PM AST Sat Sep 16 2023

The satellite presentation of the cyclone has improved this evening 
as there has been an increase in convective banding over the 
northern portion of the circulation.  The center appears to be 
located near the southern portion of the convective mass.  Dvorak 
Data T-numbers from both SAB and TAFB were T2.5 (35 kt) at 0000 UTC 
and objective satellite estimates from UW/CIMSS are in the 35 to 40 
kt range.  Based on these data, the initial intensity has been 
raised to 35 kt.  Nigel becomes the 10th named storm to form in 
the Atlantic basin since August 20th. 

Nigel is moving northwestward at about 14 kt.  A mid-level ridge 
to the northeast of the cyclone should steer the storm 
northwestward during the next few days.  After that time, Nigel is 
expected to turn northward around the western side of the ridge. By 
the middle of next week, the global model guidance indicates that 
the storm should turn northeast ahead of a broad mid-latitude 
trough over the western Atlantic.  There is fairly good agreement 
in the global model guidance on the overall scenario, but there are 
some timing or forward speed difference later in the period.  The 
NHC forecast track is near the HFIP corrected consensus which is 
close to a blend of the latest GFS and ECMWF models. 

Environmental conditions are expected to be conducive for steady 
intensification during the next few days, with low vertical wind 
shear and warm sea surface temperatures along the forecast track.  
A period of rapid intensification is is certainly possible within 
the next two to three days.  Although the SHIP RI probabilities are 
not very high at the moment, DTOPS gives a 50 percent chance of a 65 
kt increase in intensity during the next 72 hours. The NHC forecast 
is close to that, showing a 60 kt increase in strength during the 
time.  After 72 hours, increasing southwesterly shear is likely to 
cause gradual weakening.  The NHC wind speed forecast is closest to 
the HFIP corrected consensus. 


FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 22.0N  48.0W   35 KT  40 MPH
12H  17/1200Z 23.6N  49.2W   45 KT  50 MPH
24H  18/0000Z 25.3N  50.6W   55 KT  65 MPH
36H  18/1200Z 26.7N  52.2W   65 KT  75 MPH
48H  19/0000Z 27.8N  54.0W   75 KT  85 MPH
60H  19/1200Z 29.4N  55.7W   85 KT 100 MPH
72H  20/0000Z 31.3N  56.7W   95 KT 110 MPH
96H  21/0000Z 36.0N  55.6W   85 KT 100 MPH
120H  22/0000Z 41.9N  47.3W   80 KT  90 MPH

$$
Forecaster Brown