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| #940341 (Received by flhurricane at: 5:03 AM 15.Sep.2018) TCDAT1 Tropical Storm Florence Discussion Number 64 NWS National Hurricane Center Miami FL AL062018 500 AM EDT Sat Sep 15 2018 Florence is slowly weakening while its center remains inland over extreme eastern South Carolina. However, WSR-88D Doppler radar still shows some intense bands of convection over the eastern portion of the circulation, and these bands have been training over the coast of North Carolina overnight. Based on current Doppler velocities of 55-60 kt at around 5500 ft, the current intensity is set at 45 kt. The system should continue to weaken as it moves farther inland today, and it is anticipated that Florence will become a tropical depression tonight. The official intensity forecast is similar to the Decay-SHIPS model guidance through around day 3. By days 4 and 5, the post-tropical cyclone is forecast to strengthen somewhat due to baroclinic processes after moving off the New England coast and passing near southern Atlantic Canada. Radar and satellite fixes indicate that Florence continues its west-southwestward motion at around 255/4 kt. A mid-level high pressure area to the northwest of Florence is forecast to shift to the north, northeast, and east of the cyclone over the next couple of days. As a result, Florence should turn northwestward and northward, and then north-northeastward through 72 hours. Late in the forecast period, the system is expected to accelerate east-northeastward in the mid-latitude westerlies. The official forecast is somewhat faster than the previous one at days 4 and 5 but is in good agreement with the latest global model runs. Although coastal storm surge flooding will gradually subside today, extremely heavy rainfall will continue to be a serious hazard associated with slow-moving Florence. More than a foot of rain has already fallen across portions of southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread inland through the weekend. Key Messages: 1. Life-threatening storm surge will continue along portions of the North Carolina coast through today, and also along the Neuse and Pamlico Rivers in western Pamlico Sound, where rainfall and freshwater flooding will also contribute to high water levels. Dangerous storm surge could also affect portions of the northeast coast of South Carolina coast today. 2. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into west-central Virginia and far eastern West Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia. 3. Tropical storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina today. 4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 33.6N 79.5W 45 KT 50 MPH 12H 15/1800Z 33.6N 80.2W 40 KT 45 MPH...INLAND 24H 16/0600Z 33.9N 81.3W 30 KT 35 MPH...INLAND 36H 16/1800Z 35.1N 82.4W 25 KT 30 MPH...INLAND 48H 17/0600Z 37.0N 83.5W 25 KT 30 MPH...INLAND 72H 18/0600Z 40.5N 80.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/0600Z 43.5N 68.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 20/0600Z 47.0N 54.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch |
