000 WTNT45 KNHC 290258 TCDAT5 Tropical Storm Idalia Discussion Number 10 NWS National Hurricane Center Miami FL AL102023 1000 PM CDT Mon Aug 28 2023 Idalia is producing intense bursts of convection near the center, with an overall comma-shaped cloud pattern along with a dry slot over the western part of the circulation. Upper-level outflow is restricted over the northwestern quadrant. Radar images from the Meteorological Service of Cuba show a partial eyewall forming. Flight-level and dropwindsonde data from NOAA and Air Force aircraft indicate that Idalia is very near hurricane strength. The maximum winds are set again to 60 kt for this advisory. The system has moved a bit slower than earlier today with an initial motion estimate of just slightly east of due north at around 7 kt. Idalia should be steered northward along the western side of a mid-level ridge and then turn north-northeastward due to a trough to its northwest. This track will take the center across the northeastern Gulf coast on Wednesday morning, and over northern Florida and southeastern Georgia thereafter. In 2 to 3 days, a mid-tropospheric trough moving off the eastern U.S. coast will likely cause the tropical cyclone to turn northeastward to eastward off the coast of the Carolinas. The official track forecast for this advisory is essentially the same as the previous one. This is near the middle of the track guidance, which are fairly tightly clustered, with the GFS on the left side and the ECMWF on the right side. Although Idalia is currently experiencing some moderate northwesterly vertical wind shear, the dynamical guidance indicates that the shear will lessen while the system is over the eastern Gulf of Mexico. This, along with a conducive thermodynamic atmospheric environment and high oceanic heat content, should cause Idalia to strengthen rapidly in the 12- to 36-hour time frame. The official intensity forecast, like the previous one, shows the system becoming a major hurricane before landfall along the Florida Gulf coast. This is in general agreement with the regional hurricane hurricane models, HAFS and HWRF, but above much of the other intensity guidance. Idalia is forecast to move into an area that is highly susceptible to storm surge, and regardless of the cyclone's specific landfall intensity, there is increasing confidence that a significant storm surge event will occur. 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. Heavy rainfall from Tropical Storm Idalia is expected across portions of western Cuba and may produce areas of flash and urban flooding as well as landslides. 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. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 22.0N 85.0W 60 KT 70 MPH 12H 29/1200Z 23.7N 85.0W 75 KT 85 MPH 24H 30/0000Z 26.2N 84.6W 90 KT 105 MPH 36H 30/1200Z 29.0N 83.7W 105 KT 120 MPH 48H 31/0000Z 31.5N 81.6W 50 KT 60 MPH...INLAND 60H 31/1200Z 33.2N 78.8W 50 KT 60 MPH...OVER WATER 72H 01/0000Z 34.0N 76.0W 50 KT 60 MPH 96H 02/0000Z 33.5N 72.0W 45 KT 50 MPH 120H 03/0000Z 33.0N 70.0W 45 KT 50 MPH $$ Forecaster Pasch