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| #1153618 (Received by flhurricane at: 4:50 AM 20.Sep.2023) 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 |
