Issued at 500 AM EDT Thu Sep 29 2022
000 WTNT44 KNHC 290859 TCDAT4 Tropical Storm Ian Discussion Number 27 NWS National Hurricane Center Miami FL AL092022 500 AM EDT Thu Sep 29 2022 Ian's center continues to move northeastward across central Florida, and nearly all of the heavy rains are located to the north over northeastern Florida. NWS WSR-88D Doppler velocities from the Melbourne and Tampa radars have decreased significantly since last evening, and based on that data, Ian is now a tropical storm with maximum sustained winds of 55 kt. This intensity is also supported by wind observations across Florida, with the highest recent sustained wind being 52 kt at New Smyrna Beach. Ian's current motion is northeastward, or 040/7 kt. The tail end of a deep-layer trough is expected to detach from the main trough axis over the southeastern United States during the next 24 to 48 hours, and Ian is forecast to move around the eastern periphery of this feature, turning north-northeastward later today and then north-northwestward by Friday night. In this scenario, Ian should move off the east coast of Florida later today, and then swing northward toward the South Carolina coast during the next 36 hours or so. Although there is some cross-track spread in the guidance, they all agree on this general scenario, and the NHC track forecast lies where most of the models are packed. No significant changes were made to the previous prediction. Little change in intensity is forecast during the next 24 hours or so, mainly due to strong southwesterly shear. After 24 hours, global models are suggesting that Ian could have some favorable interaction with the eastern U.S. trough, all while it's moving over the warm 28-29 degree Celsius waters of the Gulf Stream. As a result, some slight strengthening is indicated in the official forecast by 36 hours, and Ian could be near hurricane intensity as it's approaching the coast of South Carolina. This possibility is accounted for by the Hurricane Watch that is effect for the area. After moving inland, Ian is expected to weaken quickly, and global models indicate it should dissipate or become absorbed by another broader area of low pressure over the Carolinas by day 3. Key Messages: 1. Coastal water levels continue to subside along the west coast of Florida. There is a danger of life-threatening storm surge today through Friday along the coasts of northeast Florida, Georgia, and South Carolina. Residents in these areas should follow any advice given by local officials. 2. Tropical-storm-force winds are expected to spread northward across northeastern Florida, Georgia, and the Carolina coasts through Friday. Hurricane conditions are possible through Friday along the coasts of northeastern Florida, Georgia and South Carolina where a Hurricane Watch in effect. 3. Widespread, life-threatening catastrophic flooding, with major to record river flooding, will continue today across portions of central Florida with considerable flooding in northern Florida, southeastern Georgia and eastern South Carolina expected today through the end of the week. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 28.0N 80.9W 55 KT 65 MPH...INLAND 12H 29/1800Z 28.9N 80.4W 55 KT 65 MPH...OVER WATER 24H 30/0600Z 30.2N 80.0W 55 KT 65 MPH...OVER WATER 36H 30/1800Z 32.2N 80.1W 60 KT 70 MPH...OVER WATER 48H 01/0600Z 34.3N 80.8W 35 KT 40 MPH...INLAND 60H 01/1800Z 35.8N 81.7W 25 KT 30 MPH...INLAND 72H 02/0600Z...DISSIPATED $$ Forecaster Berg
