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| #1199763 (Received by flhurricane at: 10:42 PM 23.Sep.2024) TCDAT4 Potential Tropical Cyclone Nine Discussion Number 3 NWS National Hurricane Center Miami FL AL092024 1100 PM EDT Mon Sep 23 2024 Satellite imagery indicates that there has been little change in the organization of the system since earlier today. Most of the deep convection is over the eastern part of the broad circulation. Animation of proxy-vis GOES images, and radar observations from Grand Cayman Weather Service suggest that the disturbance still does not have a well-defined center of circulation, so the system is kept as a potential tropical cyclone for the time being. The advisory intensity is held at 30 kt which is in agreement with a Dvorak estimate from TAFB. An Air Force reconnaissance aircraft is scheduled to investigate the area in a few hours to provide a better description of the system's structure along with an updated intensity estimate. The initial motion estimate is a rather uncertain 330/5 kt. During the next day or so, the disturbance is expected to turn northwestward along the southern and southwestern side of a mid-level high pressure area. Then, the high is expected to shift eastward while a mid-level trough drops into the central United States. This evolution of the steering pattern should cause the system to accelerate northward to north-northeastward over the eastern Gulf of Mexico and toward the northeastern Gulf Coast through Thursday. There is good agreement in the track guidance, and the official forecast is close to the corrected dynamical consensus model, HCCA, prediction. This is also very similar to the previous NHC forecast. An upper-level low over the northeastern Yucatan Peninsula has been imparting some southwesterly vertical wind shear over the disturbance. This has probably caused a temporary disruption in development. Dynamical guidance shows this low weakening with time, resulting in a reduction of shear in an environment that is otherwise very conducive for intensification. The system is projected to move over waters of very high ocean heat content, which should lead to considerable strengthening during the forecast period. The official intensity forecast is similar to the previous one and lies between the statistical-dynamical model guidance and the purely dynamical model predictions. It should be noted that the 72-hour forecast allows for a little weakening after moving inland, so the cyclone is still expected to be at major hurricane strength at landfall. It should also be noted that the cyclone is expected to grow in size while it traverses the Gulf. Thus, the storm surge, wind, and rainfall impacts will extend well away from the center, particularly to the east of the system. In addition, the fast forward speed while it crosses the coast will likely result in farther inland penetration of strong winds over parts of the southeastern United States after landfall. KEY MESSAGES: 1. The disturbance is forecast to intensify and be near hurricane strength when it reaches the far northwestern Caribbean Sea Tuesday night. Tropical storm conditions are expected over portions of western Cuba and the northeastern coast of the Yucatan Peninsula with hurricane conditions possible. 2. The system is expected to intensify into a major hurricane before it approaches the northeastern Gulf Coast on Thursday. While it is too soon to pinpoint the exact location and magnitude of impacts, the potential for life-threatening storm surge and damaging hurricane-force winds along the coast of the Florida Panhandle and the Florida west coast is increasing. Hurricane Watches and additional Storm Surge watches will likely be issued for a portion of that area Tuesday morning, and residents should ensure they have their hurricane plan in place. 3. Potential Tropical Cyclone Nine will bring heavy rain to portions of the western Caribbean, which will cause considerable flooding and mudslides across western Cuba. Heavy rainfall will likely result in locally considerable flash and urban flooding across portions of Florida, with isolated flash and urban flooding possible across the Southeast, Southern Appalachians, and the Tennessee Valley Wednesday through Friday. Minor to isolated moderate river flooding will be possible. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 18.4N 82.4W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 24/1200Z 19.1N 83.5W 35 KT 40 MPH...TROPICAL CYCLONE 24H 25/0000Z 20.2N 84.6W 45 KT 50 MPH 36H 25/1200Z 21.6N 85.6W 60 KT 70 MPH 48H 26/0000Z 23.4N 85.8W 75 KT 85 MPH 60H 26/1200Z 26.2N 84.9W 90 KT 105 MPH 72H 27/0000Z 30.4N 83.9W 95 KT 110 MPH...INLAND 96H 28/0000Z 37.0N 85.0W 15 KT 15 MPH...POST-TROPICAL 120H 29/0000Z...DISSIPATED $$ Forecaster Pasch |
