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| #1153456 (Received by flhurricane at: 10:48 PM 18.Sep.2023) TCDAT5 Hurricane Nigel Discussion Number 15 NWS National Hurricane Center Miami FL AL152023 1100 PM AST Mon Sep 18 2023 Nigel has become a little better organized this evening, with a ragged eye becoming more apparent in infrared satellite imagery. An earlier SSMIS microwave overpass revealed a fairly well-defined low-level inner-core structure, but the eye was open to the northwest. Subjective Dvorak intensity estimates from TAFB and SAB were a consensus T4.5 (77 kt), and the various objective estimates were in the 70-80 kt range at 0000 UTC. Based on a blend of these intensity estimates, the initial wind speed is set at 75 kt for this advisory. Although Nigel`s strengthening appears to have been disrupted by dry air entrainment today, the hurricane has about another 24-36 hours within low shear conditions and over warm SSTs in which to strengthen. The NHC intensity forecast calls for additional strengthening during that time, but the peak intensity has been lowered slightly. After 36-48 hours, increasing southwesterly vertical wind shear and cooler SSTS along the track of Nigel are expected to cause gradual weakening. The NHC wind speed forecast is in best agreement with the HFIP corrected-consensus aid, which is at the higher end of the guidance in the short term. The global models indicate that extratropical transition is likely to begin by 72 hours, and that process should be complete by day 4. Nigel continues to move northwestward (310 degrees) at about 10 kt. The hurricane should continue on that general heading and speed through midday Tuesday, but as it nears the western extent of the ridge, Nigel is predicted to turn northwestward and northward shortly thereafter. By 48 hours, an approaching mid- to upper-level trough is forecast to cause Nigel to accelerate northeastward over the central and northeastern Atlantic through the remainder of the forecast period. The track guidance remains tightly clustered, with the primary differences being how much Nigel accelerates northeastward later in the period. The NHC track forecast is a blend of the typically reliable GFS and ECMWF models, nd is close to the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 28.6N 52.7W 75 KT 85 MPH 12H 19/1200Z 29.9N 53.8W 85 KT 100 MPH 24H 20/0000Z 32.1N 54.5W 90 KT 105 MPH 36H 20/1200Z 34.7N 54.1W 90 KT 105 MPH 48H 21/0000Z 37.6N 51.6W 85 KT 100 MPH 60H 21/1200Z 40.5N 46.6W 80 KT 90 MPH 72H 22/0000Z 43.4N 39.5W 70 KT 80 MPH 96H 23/0000Z 50.0N 24.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 24/0000Z 57.0N 17.4W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown |
