Tropical Storm Nigel Discussion Number  10
NWS National Hurricane Center Miami FL       AL152023
500 PM AST Sun Sep 17 2023

Nigel's organization continues to increase, with several convective
bands noted over the northern portion of the circulation.
Although microwave imagery shows that an eyewall structure has not
yet formed, it seems likely that an inner core will develop fairly
soon.  The current intensity is set at 55 kt based on a subjective
Dvorak satellite intensity estimate from TAFB although objective
estimates are a little lower.

Nigel continues northwestward with an estimated motion of 325/11 kt.
The system should continue on a generally northwestward track over
the next couple of days while a mid-level high builds to its
east-northeast.  By Wednesday, Nigel should turn northward and move
along the western side of the high.  Later in the forecast period,
the system is expected to accelerate northeastward in the flow on
the southeast side of a strong mid-latitude trough.  The NHC
forecast is roughly in the middle of the track guidance envelope and
lies between the simple and corrected dynamical model consensus
solutions.

The system's environment appears to be very conducive for
strengthening.  The vertical wind shear is quite weak and there is
well-defined upper-level anticyclonic outflow over the area.  The
various rapid intensification (RI) indices are in agreement on a
significantly higher-than-normal likelihood of RI.  This is also
reflected in the official intensity forecast, which shows Nigel
becoming a major hurricane within the next couple of days.  By the
end of the forecast period, the system will likely become embedded
within a frontal zone and transition into a strong extratropical
cyclone.


FORECAST POSITIONS AND MAX WINDS

INIT  17/2100Z 25.1N  49.5W   55 KT  65 MPH
12H  18/0600Z 26.3N  50.6W   70 KT  80 MPH
24H  18/1800Z 27.8N  52.1W   85 KT 100 MPH
36H  19/0600Z 29.2N  53.6W  100 KT 115 MPH
48H  19/1800Z 31.0N  55.0W  100 KT 115 MPH
60H  20/0600Z 33.1N  55.4W  100 KT 115 MPH
72H  20/1800Z 35.7N  54.2W   90 KT 105 MPH
96H  21/1800Z 41.3N  45.9W   75 KT  85 MPH
120H  22/1800Z 47.8N  31.7W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch