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| #1150709 (Received by flhurricane at: 10:57 PM 31.Aug.2023) TCDAT5 Post-Tropical Cyclone Idalia Discussion Number 22 NWS National Hurricane Center Miami FL AL102023 1100 PM EDT Thu Aug 31 2023 Satellite images indicate that Idalia continues to exhibit the appearance of an extratropical cyclone with a frontal boundary extending from the center northeastward. There is almost no deep convection associated with the system, but there continues to be areas of heavy rain along the front extending to near the coast of North Carolina. The initial intensity remains 55 kt. The cyclone is moving eastward at about 20 kt. A slightly slower motion to the east-southeast is expected during the next day or two as the system continues to move near the base of a mid- to upper-level trough. However, the steering currents are expected to weaken over the weekend as the storm approaches Bermuda, which should cause a significant slow down. A turn to the northeast is forecast late in the weekend when another shortwave trough approaches the system. The guidance is slower this cycle, and the NHC track forecast has been adjusted accordingly. Gradual weakening is expected through early Saturday as the system separates from the mid- to upper-level trough. However, as Idalia transitions back to a tropical cyclone near Bermuda, slow strengthening seems likely. Based on the GFS and ECMWF models, Idalia will likely transition back to an extratropical cyclone in about 5 days. The intensity forecast is similar to the previous one and fairly close to the GFS model. KEY MESSAGES: 1. Tropical storm conditions are possible in Bermuda by Saturday. Heavy rainfall will likely lead to areas of flash and urban flooding on the island. 2. Water levels are expected to subside and winds are expected to diminish along the coast of North Carolina through early Friday. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 33.1N 71.5W 55 KT 65 MPH...POST-TROPICAL 12H 01/1200Z 32.3N 69.1W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 02/0000Z 31.1N 67.2W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 02/1200Z 30.6N 65.9W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 03/0000Z 31.3N 64.5W 40 KT 45 MPH...TROPICAL CYCLONE 60H 03/1200Z 32.3N 63.0W 45 KT 50 MPH 72H 04/0000Z 34.3N 61.0W 50 KT 60 MPH 96H 05/0000Z 36.8N 59.0W 50 KT 60 MPH 120H 06/0000Z 38.7N 61.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Cangialosi |
