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| #1149911 (Received by flhurricane at: 5:02 PM 28.Aug.2023) TCDAT5 Tropical Storm Idalia Discussion Number 9 NWS National Hurricane Center Miami FL AL102023 400 PM CDT Mon Aug 28 2023 The satellite presentation of Idalia has continued to improve this afternoon. The center of the storm is embedded within an area of deep convection with cloud tops colder than -75C. Although the early reconnaissance aircraft and radar data from Cuba have not yet indicated the presence of an eyewall, the aircraft data did indicate that the pressure had fallen to around 987 mb on the final pass through the center earlier this afternoon. Believable SFMR winds of 60 kt were reported to the east of the center, and Idalia`s intensity was raised to that value on the 1800 UTC intermediate advisory and it remains at that value for this advisory. NOAA and Air Force Reserve Hurricane Hunter aircraft are scheduled to be in the storm environment again this evening and should provide additional information on the structure and intensity of the tropical cyclone. Another NOAA G-IV synoptic surveillance mission is underway and that data should be assimilated into the dynamical model runs this evening. Idalia is moving northward or 360/7 kt. The storm should continue to be steered northward between a mid-level trough over the central Gulf of Mexico and a ridge near the Greater Antilles through tonight. On Tuesday, a faster north-northeastward motion should begin as a trough moves into the east-central United States. This motion should bring the center of Idalia to the Gulf coast of Florida on Wednesday. The dynamical models continue to have some spread after 36 hours, with the GFS and HAFS guidance along the western side of the envelope and the ECMWF along the eastern side. The consensus aids were slightly west of the previous cycle, and the NHC forecast has been nudged in that direction. The NHC track forecast is in best agreement with the HFIP corrected consensus model. It is still worth stressing that only a small deviation in the track could cause a significant change in Idalia`s landfall location in Florida due to the paralleling track to the west coast of the state. When Idalia nears the Atlantic coast of the southeastern United States the guidance suggests the cyclone will turn more eastward as the aforementioned trough passes to the north of the storm. The upper-level wind pattern is forecast to become more conducive for significant strengthening when Idalia moves over the southeastern Gulf of Mexico tonight and Tuesday. At the same time, the storm is forecast to move over an area of high ocean heat content. These conditions are likely to allow for a period of rapid strengthening which is explicitly shown in the official forecast through 36 hours. Idalia is likely to become a hurricane this evening, and is predicted to become major hurricane over the eastern Gulf within 36 hours. The NHC intensity forecast is just a little above the latest HFIP corrected consensus guidance. Idalia is forecast to move into an area very susceptible to storm surge, and regardless of the cyclone`s landfall intensity, there is increasing confidence of a significant storm surge event. KEY MESSAGES: 1. There is a danger of life-threatening storm surge inundation along portions of the Florida Gulf Coast where a Storm Surge Warning is in effect, including Tampa Bay and the Big Bend region of Florida. Inundation of 8 to 12 feet above ground level is expected somewhere between Chassahowitzka and Aucilla River. Residents in these areas should follow any advice given by local officials. 2. Hurricane conditions are expected within portions of the Hurricane Warning area along the Florida Gulf Coast, with the potential for destructive winds where the core of Idalia moves onshore. Strong winds will also spread inland across portions of northern Florida near the track of the center of Idalia. 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. Hurricane-force winds are expected across portions of far western Cuba tonight. Heavy rainfall is also expected across portions of western Cuba and may produce areas of flash and urban flooding as well as landslides. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 21.4N 85.1W 60 KT 70 MPH 12H 29/0600Z 22.7N 85.2W 75 KT 85 MPH 24H 29/1800Z 24.9N 85.0W 90 KT 105 MPH 36H 30/0600Z 27.6N 84.4W 105 KT 120 MPH 48H 30/1800Z 30.4N 82.9W 80 KT 90 MPH...INLAND 60H 31/0600Z 32.7N 80.4W 50 KT 60 MPH...INLAND 72H 31/1800Z 34.0N 76.8W 50 KT 60 MPH...OVER WATER 96H 01/1800Z 34.1N 71.4W 45 KT 50 MPH 120H 02/1800Z 34.0N 69.0W 45 KT 50 MPH $$ Forecaster Brown |
