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| #1150074 (Received by flhurricane at: 11:00 AM 29.Aug.2023) TCDAT5 Hurricane Idalia Discussion Number 12 NWS National Hurricane Center Miami FL AL102023 1100 AM EDT Tue Aug 29 2023 WSR-88D radar data from Key West shows that Idalia`s eye is becoming better defined at an elevation of 30,000 feet, although an eye has not yet become apparent in visible satellite imagery. A NOAA Hurricane Hunter aircraft reported a closed eye 20-25 n mi in diameter, SFMR winds as high as 70 kt, and a central pressure down to 976 mb. This pressure, and assuming some undersampling of the SFMR, supports an initial intensity of 75 kt. Idalia is moving just east of due north, or 005/12 kt, between a mid-level trough over the Gulf of Mexico and subtropical ridging over the Greater Antilles. A faster motion toward the north or north-northeast is expected while Idalia approaches the Florida coast through Wednesday morning. Confidence is increasing that Idalia will reach the coast of Florida adjacent to Apalachee Bay Wednesday morning, with all of the reliable deterministic track models honed in on that area. Track spread remains low during Idalia`s expected turn toward the northeast and east-northeast in 48-60 hours, bringing the storm`s center near or along the coast of the Carolinas. On days 3 through 5, there is significant uncertainty on whether Idalia will turn out to sea (as shown by the COAMPS-TC and HAFS models) or turn southward (as suggested by the global models). For now, the official forecast shows a slow motion at the end of the forecast period until the scenario becomes clearer. Idalia is currently over a maximum of oceanic heat content associated with the Loop Current, and water temperatures remain 30-31 degrees Celsius along the forecast path up until landfall. Vertical shear is also expected to be low for the next 18-24 hours, and these conditions are expected to foster rapid intensification before Idalia reaches the coast of Florida. The 06 UTC runs of all 4 regional hurricane models (HAFS-A, HAFS-B, HWRF, and HMON) show Idalia potentially reaching an intensity of 110-120 kt in 24 hours, and as a result, the new NHC intensity forecast indicates a peak intensity of 110 kt just before landfall. Weakening is forecast while the center of Idalia moves over land, but the system is expected to be a tropical storm while it moves near or along the coasts of Georgia and the Carolinas through Thursday. KEY MESSAGES: 1. Catastrophic impacts from storm surge inundation of 10 to 15 feet above ground level and destructive waves are expected somewhere between Aucilla River and Yankeetown, Florida. Life-threatening storm surge inundation is likely elsewhere along portions of the Florida Gulf Coast where a Storm Surge Warning is in effect. Residents in these areas should follow any advice or evacuation orders given by local officials. 2. There is the potential for destructive life-threatening winds where the core of Idalia moves onshore in the Big Bend region of Florida, with hurricane conditions expected elsewhere in portions of the Hurricane Warning area along the Florida Gulf Coast. Strong winds will also spread inland across portions of northern Florida and southern Georgia near the track of the center of Idalia where Hurricane Warnings are in effect. Residents in these areas should be prepared for long-duration power outages. 3. Areas of flash and urban flooding, some of which may be locally significant, are expected across portions of the west coast of Florida, the Florida Panhandle, and southern Georgia Tuesday into Wednesday, spreading into portions of the eastern Carolinas Wednesday into Thursday. 4. Heavy rainfall from Tropical Storm Idalia is expected across portions western Cuba and may produce areas of flash and urban flooding as well as landslides. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 24.6N 84.8W 75 KT 85 MPH 12H 30/0000Z 26.5N 84.6W 90 KT 105 MPH 24H 30/1200Z 29.3N 83.7W 110 KT 125 MPH 36H 31/0000Z 31.8N 81.7W 55 KT 65 MPH...INLAND 48H 31/1200Z 33.5N 78.8W 45 KT 50 MPH...OVER WATER 60H 01/0000Z 34.1N 75.6W 45 KT 50 MPH 72H 01/1200Z 33.8N 73.0W 45 KT 50 MPH 96H 02/1200Z 32.5N 70.2W 45 KT 50 MPH 120H 03/1200Z 32.0N 68.8W 45 KT 50 MPH $$ Forecaster Berg |
