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| #1153322 (Received by flhurricane at: 10:42 PM 17.Sep.2023) TCDAT5 Tropical Storm Nigel Discussion Number 11 NWS National Hurricane Center Miami FL AL152023 1100 PM AST Sun Sep 17 2023 Proxy-vis and infrared satellite imagery show that Nigel is becoming better organized and continues to strengthen this evening. Deep convection continues to burst near the center, with cold cloud tops to -80 degrees Celsius. An earlier SSMI/S microwave pass depicts that an inner core has developed and it is vertically aligned with the low-level center. Subjective Dvorak estimates from TAFB and SAB were T4.0/T3.5, respectively. Given a blend of these estimates, the initial intensity is increased to 60 kt for this advisory. Nigel is moving north-northwestward with an estimated motion of 330/10 kt. This general north-northwestward heading should continue for the next couple of days as a mid-level ridge builds to the northeast of the system. In about 2 to 3 days, Nigel should begin to round the western edge of the ridge and move more northward. By the end of the forecast period, a strong trough will pick up the system, and Nigel should accelerate towards the northeast. The NHC track forecast is similar to the previous advisory, and lies near the simple and corrected consensus aids. The environment around Nigel is conducive for steady to rapid intensification. Vertical wind shear is fairly low, with warm sea surface temperatures, and outflow aloft continues to become more pronounced. The SHIPS and DTOPS rapid intensification (RI) indices continue to show above climatological normal chances of RI. Given the improving structure and the favorable environment, the NHC intensity forecast reflects this and forecasts rapid intensification over the next 24-36 hrs, with Nigel expected to become a hurricane overnight, and a major hurricane on Tuesday. Towards the end of the period, Nigel will likely become a strong extratropical cyclone as the aforementioned trough picks up the system, and it becomes embedded within a frontal zone. The NHC intensity forecast lies near the upper-end of the guidance envelope, closest to the HCCA and IVCN intensity consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 25.8N 50.2W 60 KT 70 MPH 12H 18/1200Z 27.0N 51.3W 75 KT 85 MPH 24H 19/0000Z 28.5N 52.8W 90 KT 105 MPH 36H 19/1200Z 30.1N 54.2W 100 KT 115 MPH 48H 20/0000Z 32.1N 55.2W 100 KT 115 MPH 60H 20/1200Z 34.4N 54.8W 95 KT 110 MPH 72H 21/0000Z 37.4N 52.5W 90 KT 105 MPH 96H 22/0000Z 43.1N 42.1W 75 KT 85 MPH 120H 23/0000Z 50.8N 28.0W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Kelly |
