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| #1153647 (Received by flhurricane at: 10:45 AM 20.Sep.2023) TCDAT5 Hurricane Nigel Discussion Number 21 NWS National Hurricane Center Miami FL AL152023 1100 AM AST Wed Sep 20 2023 Nigel is maintaining a ragged-appearing eye on visible and infrared satellite imagery. Bands of deep convection with tops to around -70C continue to rotate around the center, and the system`s cloud pattern remains fairly symmetrical. Although microwave imagery from around 0900 UTC showed a closed eyewall, recent geostationary images suggest breaks in the eyewall over the eastern portion of the circulation. Dvorak CI numbers from TAFB and SAB are 4.5, corresponding to a 77-kt intensity, and an objective ADT estimate from UW-CIMSS was 79 kt. Based on these values, the advisory intensity estimate was reduced only slightly, to 80 kt. NOAA Hurricane Hunter aircraft are scheduled to investigate Nigel soon. The hurricane is moving northward, or perhaps slightly east of north, with an initial motion of 010/16 kt. The system has been moving around the western periphery of a mid-level high pressure area. A mid-latitude trough to the northwest of Nigel should cause the cyclone to turn toward the northeast and the cyclone should continue to move northeastward at a faster forward speed over the next couple of days. In 48 to 72 hours, Nigel is expected to rotate counter-clockwise around the eastern side of a large extratropical cyclone over the north Atlantic. Although the official forecast shows track points at 4 and 5 days, there is a good chance that Nigel will merge with, or become absorbed by, the other cyclone around that time. The official forecast is very similar to the previous NHC track prediction. Nigel has only about 12 hours remaining before moving over cooler waters, and southwesterly vertical shear is forecast to increase tonight. Gradual weakening is expected over the next 2-3 days, in general agreement with the consensus intensity forecast guidance. The intensity forecast in the latter part of the forecast period is uncertain, given the distinct possibility that Nigel could merge with the other extratropical cyclone. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 36.1N 54.4W 80 KT 90 MPH 12H 21/0000Z 38.4N 51.8W 80 KT 90 MPH 24H 21/1200Z 41.6N 46.4W 75 KT 85 MPH 36H 22/0000Z 44.6N 39.0W 65 KT 75 MPH 48H 22/1200Z 47.6N 31.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 60H 23/0000Z 51.3N 24.8W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 23/1200Z 55.0N 23.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 24/1200Z 57.0N 24.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 25/1200Z 58.0N 23.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch |
