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WTNT45 KNHC 200841

TCDAT5

 

Hurricane Nigel Discussion Number  20

NWS National Hurricane Center Miami FL       AL152023

500 AM AST Wed Sep 20 2023

 

Nigel's overall satellite appearance has not changed much from the 

previous advisory. Deep convection remains on the southern portion 

of a thick band around the center of the system. Infrared imagery 

shows that the eyewall has been opened on the northern side, but has 

tried to fill in recently. There have been no microwave passes over 

the system overnight to get a better idea of the overall structure 

of Nigel. Subjective intensity estimates have remained fairly 

steady, with a CI of 4.5/5.0 from TAFB and SAB, respectively. Given 

these estimates and similar satellite appearance, the initial 

intensity is held at 85 kt.

 

Nigel has about 18-24 hours before it is expected to move over 

cooler sea surface temperatures and into significantly stronger 

vertical wind shear. As a result, the latest NHC intensity forecast 

shows Nigel remaining steady to slightly weakening in the short 

term, followed by steady weakening through the remainder of the 

forecast period. Although weakening is forecast, Nigel is expected 

to be a strong extratropical cyclone in about 48 hours.

 

The system is moving toward the north at 14 kt, as Nigel rounds the 

edge of a mid-level ridge over the central subtropical Atlantic.  

Later today, the system is expected to turn northeastward and 

accelerate in the flow of a deep-layer trough located over Atlantic 

Canada. The track guidance remains in fairly good agreement in the 

short term with only slight along-track speed differences. The NHC 

track forecast is slightly faster than the previous one, and lies 

near the consensus aids, but still not as fast as HCCA. As Nigel 

reaches high latitudes, the extratropical low is forecast to 

interact with a broader cyclonic circulation over the north 

Atlantic, and it is possible that Nigel gets absorbed by this 

broader circulation towards the end of the period. There is higher 

track uncertainty towards the end of the forecast period due to this 

interaction.

 

 

FORECAST POSITIONS AND MAX WINDS

 

INIT  20/0900Z 34.4N  54.9W   85 KT 100 MPH

 12H  20/1800Z 36.7N  53.5W   85 KT 100 MPH

 24H  21/0600Z 39.8N  49.5W   80 KT  90 MPH

 36H  21/1800Z 42.8N  43.0W   70 KT  80 MPH

 48H  22/0600Z 45.7N  35.5W   60 KT  70 MPH...POST-TROP/EXTRATROP

 60H  22/1800Z 49.2N  28.4W   50 KT  60 MPH...POST-TROP/EXTRATROP

 72H  23/0600Z 52.4N  24.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

 96H  24/0600Z 57.1N  23.7W   45 KT  50 MPH...POST-TROP/EXTRATROP

120H  25/0600Z 59.1N  20.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

 

$$

Forecaster Kelly