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| #1149795 (Received by flhurricane at: 5:05 AM 28.Aug.2023) TCDAT5 Tropical Storm Idalia Discussion Number 7 NWS National Hurricane Center Miami FL AL102023 400 AM CDT Mon Aug 28 2023 Idalia has intensified overnight. Data from an Air Force Reserve Hurricane Hunter aircraft showed believable surface winds of 50-55 kt and a central pressure falling to around 989 mb. The wind data is also confirmed by NOAA buoy 42056, located just southeast of the center, which has reported maximum 1-minute adjusted sustained winds above 50 kt within the past hour or two. These data support raising the initial wind speed to 55 kt. It seems like Idalia is finally on the move, with aircraft fixes indicating a northward motion of about 6 kt. This motion should continue through Tuesday as Idalia moves between a mid-level trough over the central Gulf of Mexico and a strengthening ridge over the Greater Antilles. The storm is likely to move faster to the north-northeast and northeast by early Wednesday due to a deeper trough that is expected to swing across the mid-western United States. The new NHC track forecast is quite close to the last one with little significant changes to the track guidance. It should be emphasized that only a small deviation in the track could cause a big change in Idalia`s landfall location in Florida due to the paralleling track to the west coast of the state. The center of Idalia is on the northern edge of the deep convective mass, a refection of moderate northwesterly shear, and the last aircraft pass showed a vortex tilted southward with height. This shear and structure should persist for about the next 24 hours, helping to keep the intensity of the storm from increasing too quickly despite the extremely warm waters it will be traversing. The NHC short-term forecast will continue to indicate Idalia as a hurricane near western Cuba, similar to the guidance. Over the Gulf of Mexico, the environment is forecast to become conducive for significant strengthening of Idalia due to a new trough dropping south over the western Gulf of Mexico as a upper-level ridge builds near the cyclone. Additionally, Idalia will be moving over waters near 31C, and some of the guidance is even indicating favorable jet dynamics on Wednesday with Idalia in the right-rear quadrant of the jet over the southeastern United States. The bottom line is that rapid intensification is becoming increasingly likely before landfall, and the NHC forecast now explicitly indicates it between 24-48 h in the forecast. This is consistent with almost all of the regional hurricane models and the SHIPS rapid intensification indices, which are 5-10 times the climatological mean. The new prediction shows a 100-kt hurricane over the eastern Gulf of Mexico at 48 hours, but Idalia should keep strengthening up to landfall along the Gulf coast of Florida. Interests within the storm surge and hurricane watch areas are urged to prepare for possible significant impacts and monitor future updates to the forecast for this increasingly dangerous situation. KEY MESSAGES: 1. Idalia is now forecast to become a major hurricane before it reaches the Gulf coast of Florida. The risk continues to increase for life-threatening storm surge and dangerous hurricane-force winds along portions of the west coast of Florida and the Florida Panhandle beginning as early as late Tuesday. Storm surge and hurricane watches are in effect for portions of the west coast of Florida and the coast of the Florida Panhandle, and residents in these areas should monitor updates to the forecast and follow any advice given by local officials. 2. 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. 3. Hurricane-force winds are expected across portions of far western Cuba later today. Heavy rainfall is also expected across portions of western Cuba and may produce areas of flash and urban flooding as well as landslides across western Cuba. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 20.1N 85.2W 55 KT 65 MPH 12H 28/1800Z 21.1N 85.1W 65 KT 75 MPH 24H 29/0600Z 22.6N 85.1W 70 KT 80 MPH 36H 29/1800Z 24.8N 84.8W 85 KT 100 MPH 48H 30/0600Z 27.7N 84.0W 100 KT 115 MPH 60H 30/1800Z 30.7N 82.1W 65 KT 75 MPH...INLAND 72H 31/0600Z 32.8N 79.0W 55 KT 65 MPH...OVER WATER 96H 01/0600Z 34.5N 72.0W 50 KT 60 MPH 120H 02/0600Z 34.5N 67.0W 50 KT 60 MPH $$ Forecaster Blake |
