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| #1150338 (Received by flhurricane at: 11:03 AM 30.Aug.2023) TCDAT3 Hurricane Franklin Discussion Number 40 NWS National Hurricane Center Miami FL AL082023 1100 AM AST Wed Aug 30 2023 The large eye of Franklin has become a bit ragged in recent satellite images. Upper-level outflow from Hurricane Idalia continues to impinge on the western side of Franklin`s circulation, and recent SSMIS microwave data show a thinner ring of inner core convection on the western side of the eye, though the eyewall remains closed. The overall satellite presentation has degraded some since yesterday, and this is reflected in the latest objective and subjective satellite estimates. The initial intensity is lowered slightly to 90 kt, based on consensus T5.0/90 kt Dvorak estimates from SAB and TAFB and UW-CIMSS ADT and AiDT estimates around 85-90 kt. Radar data from Bermuda reveal an outer band of the hurricane is passing near the island, and tropical storm conditions are expected to spread over the area within the next few hours. The flow between a deep-layer trough over the eastern United States and Canada and a high pressure ridge over the central Atlantic is steering Franklin northeastward (50/11 kt). The aforementioned trough is forecast to move eastward during the next couple of days, and the flow ahead of this feature should cause Franklin to move slightly faster toward the east-northeast. Little change was made to this portion of the forecast. It is still unclear whether or not Franklin will become completely captured by the trough, which introduces greater uncertainty in the days 3-5 track forecast. The GFS favors a faster northeastward motion with greater trough interaction, while the ECMWF and UKMET keep Franklin on a slower eastward track before it is steered deeper into the mid-latitudes. The updated NHC forecast follows the consensus trends and is again slower than the previous prediction beyond 72 h. Franklin is forecast to become extratropical by 96 h, although this timing largely depends on the extent of trough interaction. Increasing northwesterly shear is expected over Franklin during the next couple of days. This should induce at least gradual weakening in the near term, though the tropical-storm-force wind field is likely to expand as the system accelerates and gains latitude. The updated track forecast brings Franklin over sub-26C waters in about 72 h, with extratropical transition forecast to occur by 96 h. Note that this timing largely depends on the extent of trough interaction that occurs in the coming days, so future adjustments could be necessary. KEY MESSAGES: 1. Tropical storm conditions are expected on Bermuda today while Franklin makes its closest approach to the island. 2. Life-threatening surf and rip currents are occurring along the east coast of the United States. These conditions are expected to continue during the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 33.6N 67.1W 90 KT 105 MPH 12H 31/0000Z 34.4N 65.2W 85 KT 100 MPH 24H 31/1200Z 35.2N 62.2W 80 KT 90 MPH 36H 01/0000Z 36.1N 58.9W 75 KT 85 MPH 48H 01/1200Z 37.2N 55.3W 70 KT 80 MPH 60H 02/0000Z 38.4N 52.0W 65 KT 75 MPH 72H 02/1200Z 40.1N 49.0W 60 KT 70 MPH 96H 03/1200Z 44.5N 44.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 04/1200Z 49.1N 40.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Reinhart |
