176 WTNT41 KNHC 120254 TCDAT1 Hurricane Florence Discussion Number 51 NWS National Hurricane Center Miami FL AL062018 1100 PM AST Tue Sep 11 2018 Florence's eye became a little ragged in appearance on satellite images a couple of hours ago, but recently it has become better defined. There has also been a little cooling of the tops surrounding the eye. These features suggest that Florence is maintaining its intensity. The current intensity is kept at 120 kt, which is a little above the adjusted flight-level winds from the Air Force Hurricane Hunters and a little below the latest SATCON estimate from UW-CIMSS. Over the next couple of days, the hurricane is expected to move over a warm ocean and through an environment of low vertical shear. This would allow some additional strengthening until about 48 hours. From that time and up to landfall, the global models suggest some increase in shear which would cause some weakening. However, Florence is still likely to remain a dangerous major hurricane when its center crosses the coast. The official intensity forecast is a blend of the Decay-SHIPS and ICON intensity model consensus. The initial motion estimate is west-northwestward, or 300/15 kt. A mid-level ridge to the northeast should continue to steer Florence on a west-northwestward to northwestward heading until the hurricane nears the coast. The steering pattern from 72 hours and beyond becomes more complicated and uncertain. The latest GFS model run shows a mid-level ridge building over the east-central United States in 3-4 days. This temporarily blocks the forward progress of the hurricane and forces a southwesterly turn in the model run. Later in the period, the ridge rebuilds to the north of Florence allowing the system to move inland. The official track forecast is somewhat to the left of the previous NHC track, but to the right of the latest consensus predictions. It should be noted that, due to increased model spread, there is substantial uncertainty in the 3-5 track forecast. It is important for users to realize that significant impacts extend well away from the center of Florence, and serious hazards such as a dangerous storm surge and flooding rains will cover a large area regardless of exactly where the center moves. Key Messages: 1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests from South Carolina into the mid-Atlantic region should complete preparations and follow any advice given by local officials. 2. Life-threatening, catastrophic flash flooding and significant river flooding is likely over portions of the Carolinas and Mid-Atlantic states from late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland. 3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning has been issued for a part of this area. Damaging winds could also spread well inland into portions of the Carolinas and Virginia. 4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 12/0300Z 28.4N 68.7W 120 KT 140 MPH 12H 12/1200Z 29.6N 70.8W 125 KT 145 MPH 24H 13/0000Z 31.4N 73.4W 135 KT 155 MPH 36H 13/1200Z 32.9N 75.5W 130 KT 150 MPH 48H 14/0000Z 33.8N 76.8W 115 KT 130 MPH 72H 15/0000Z 34.3N 78.2W 95 KT 110 MPH...INLAND 96H 16/0000Z 34.3N 79.7W 45 KT 50 MPH...INLAND 120H 17/0000Z 34.9N 82.5W 25 KT 30 MPH...INLAND $$ Forecaster Pasch