Hurricane Nigel Discussion Number  22
NWS National Hurricane Center Miami FL       AL152023
500 PM AST Wed Sep 20 2023

Nigel has changed little in organization on satellite images since 
earlier today.  The ragged-looking eye remains quite large, reported 
to be 60 n mi in diameter by the NOAA Hurricane Hunter aircraft.  
There are still bands of deep convection with cloud tops to near -70 
deg C, primarily over the northwestern and western portions of the 
circulation, and the overall cloud pattern continues to have a 
symmetrical appearance.  The central pressure measured by the 
aircraft has not changed much since earlier today and wind data from 
the plane suggest that the intensity remains near 80 kt.

Center fixes from the Hurricane Hunters and satellite images show 
that the hurricane's motion is beginning to bend to the right and is 
now north-northeastward, or around 030/16 kt.  Nigel should move 
along the northwestern periphery of a subtropical high pressure cell 
tonight.  In 12 to about 60 hours,  the flow on the southeastern 
side of a strong mid-latitude 500 mb trough should carry the system 
northeastward at a fast pace toward, and over, the northern 
Atlantic.  According to the global models, in 72 to 96 hours, Nigel 
should undergo a binary interaction with a large extratropical low 
over the North Atlantic.  By 120 hours or sooner, the system is 
forecast to merge with this low.

Over the next few days, Nigel will be moving over progressively 
cooler ocean waters and into an environment of stronger 
southwesterly vertical wind shear.  Gradual weakening is forecast, 
and the system is expected to become embedded in a baroclinic zone 
on Friday.  Therefore, extratropical transition is indicated in the 
48 hour forecast.   Since Nigel is expected to merge with the 
aforementioned North Atlantic low in about 5 days, dissipation is 
shown at the end of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 37.4N  53.0W   80 KT  90 MPH
12H  21/0600Z 39.8N  49.6W   80 KT  90 MPH
24H  21/1800Z 42.8N  43.2W   75 KT  85 MPH
36H  22/0600Z 45.7N  35.2W   60 KT  70 MPH
48H  22/1800Z 49.0N  27.6W   55 KT  65 MPH...POST-TROP/EXTRATROP
60H  23/0600Z 53.0N  23.4W   50 KT  60 MPH...POST-TROP/EXTRATROP
72H  23/1800Z 56.0N  23.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
96H  24/1800Z 57.0N  23.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  25/1800Z...DISSIPATED

$$
Forecaster Pasch