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| #1149711 (Received by flhurricane at: 5:03 PM 27.Aug.2023) TCDAT5 Tropical Storm Idalia Discussion Number 5 NWS National Hurricane Center Miami FL AL102023 400 PM CDT Sun Aug 27 2023 Idalia`s cloud pattern is gradually becoming a little better organized, with a curved convective band forming over the southern semicircle of the circulation. Upper-level outflow is currently restricted over the northern portion of the system, however. The advisory intensity is held at 35 kt based on a subjective Dvorak estimate from TAFB. Another aircraft reconnaissance mission into the storm is scheduled for tonight. The tropical cyclone continues to move rather slowly, and the initial motion estimate is 040/3 kt. Idalia should remain in a weak steering pattern through tonight so slow and possibly erratic motion is likely for the next 12 hours. On Monday, a mid-level ridge begins to build to the northeast of the tropical cyclone. This should result in a slightly east of northward motion during the next day or two. When the system moves into the northeast Gulf of Mexico, a mid-level trough developing over the eastern United states will likely cause Idalia to turn northeastward with an increase in forward speed. The new official forecast is again shifted slightly eastward, and is somewhat faster than the previous one. This is a blend of the latest ECMWF and GFS solutions and is also between the simple and corrected dynamical consensus tracks. The intensity forecast is somewhat challenging. Idalia will be traversing eastern Gulf of Mexico waters of high oceanic heat content, and the environmental air mass should remain fairly moist. The flow to the east of an upper-level trough could impart some vertical wind shear over the system, but this shear could also be compensated by the conducive effect of upper-level diffluence. There is considerable spread in the model intensity guidance, ranging from minimal to major hurricane status before landfall on the northeast Gulf coast. The official intensity forecast is a little higher than the previous one, and remains near the higher end of the guidance. Given the uncertainties, users should monitor future NHC forecasts for possible changes in the predicted strength of Idalia, and prepare for possible significant impacts within the hurricane and storm surge watch areas. KEY MESSAGES: 1. Idalia is forecast to become a hurricane over the eastern Gulf of Mexico, and there is an increasing risk of life-threatening storm surge and hurricane-force winds along portions of the west coast of Florida and the Florida Panhandle beginning as early as Tuesday. Although it is too soon to specify the exact location and magnitude of these impacts, residents in these areas should monitor updates to the forecast and follow any advice given by local officials. Storm surge and hurricane watches have been issued 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. Scattered flash and urban flooding can be expected across portions of the west coast of Florida, the Florida Panhandle and portions of the Southeast U.S. by Tuesday into Thursday. Flooding from heavy rainfall is likely over portions of the southeast U.S. by mid to late week. 3. Heavy rainfall from Tropical Storm Idalia is expected across portions of the eastern Yucatan and western Cuba and may produce areas of flash and urban flooding as well as landslides across western Cuba. 4. Tropical storm conditions are expected over portions of the Yucatan Peninsula and extreme western Cuba with tropical storm conditions possible on the Isle of Youth. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 20.1N 85.5W 35 KT 40 MPH 12H 28/0600Z 20.5N 85.3W 45 KT 50 MPH 24H 28/1800Z 21.7N 85.0W 55 KT 65 MPH 36H 29/0600Z 23.4N 84.9W 65 KT 75 MPH 48H 29/1800Z 25.6N 84.5W 75 KT 85 MPH 60H 30/0600Z 28.7N 83.7W 85 KT 100 MPH 72H 30/1800Z 31.3N 81.9W 50 KT 60 MPH...INLAND 96H 31/1800Z 34.5N 76.0W 50 KT 60 MPH...OVER WATER 120H 01/1800Z 35.0N 71.0W 55 KT 65 MPH $$ Forecaster Pasch |
