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Hurricane Florence Forecast Discussion Number 41
2018-09-09 16:50:44| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sun Sep 09 2018 685 WTNT41 KNHC 091450 TCDAT1 Hurricane Florence Discussion Number 41 NWS National Hurricane Center Miami FL AL062018 1100 AM AST Sun Sep 09 2018 Satellite images indicate that Florence is strengthening. Deep convection has intensified in the central dense overcast, with hints of a ragged eye in the latest GOES-16 visible channel. The NOAA Hurricane Hunters just flew through the eye, finding 70 kt winds at flight-level and 66 kt from the SFMR. This data confirms that Florence has become a hurricane again, and the initial wind speed is set to 65 kt. The aircraft also found that the minimum pressure has decreased to 984 mb. Overnight microwave data and the Hurricane Hunter vortex message show that a mostly complete eyewall has formed with Florence. In combination with low vertical wind shear and progressively warmer waters near 29C, this structure is a blueprint for rapid intensification. Almost all of the intensity guidance is showing at least one period of rapid strengthening during the next few days, which is rather rare. The NHC wind speed forecast is raised in the first couple of days following the guidance trend, then is very similar to the previous one. All indications are that Florence will be an extremely dangerous Category 4 hurricane while it moves over the western Atlantic toward the southeastern United States. Florence continues moving slowly westward, caught between a pair of mid-level ridges over the Atlantic Ocean. A very strong ridge is forecast to build over the northwestern Atlantic during the next few days, which should steer Florence west-northwestward at a much faster forward speed. By Wednesday, the hurricane should turn northwestward, and slow down somewhat due to another ridge forming over the Ohio Valley. It is interesting to note that while the ensemble means from the ECMWF and UKMET are west of the NHC forecast, the strongest members are on the right side of their ensemble envelope. Thus, the new NHC track forecast is very similar to the previous one, and continues to lie between the corrected consensus and consensus aids. The Ohio Valley ridge is concerning because Florence could stop moving pretty quickly around day 5, potentially leading to a serious heavy rain episode and inland flood hazard. Key Messages: 1. There is an increasing risk of two life-threatening impacts from Florence: storm surge at the coast and freshwater flooding from a prolonged heavy rainfall event inland. While it is too soon to determine the exact timing, location, and magnitude of these impacts, interests at the coast and inland from South Carolina into the mid-Atlantic region should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 24.4N 56.3W 65 KT 75 MPH 12H 10/0000Z 24.5N 57.4W 80 KT 90 MPH 24H 10/1200Z 24.9N 59.3W 95 KT 110 MPH 36H 11/0000Z 25.6N 61.7W 105 KT 120 MPH 48H 11/1200Z 26.4N 64.5W 120 KT 140 MPH 72H 12/1200Z 29.0N 70.8W 125 KT 145 MPH 96H 13/1200Z 32.2N 75.8W 120 KT 140 MPH 120H 14/1200Z 35.0N 78.5W 85 KT 100 MPH...INLAND $$ Forecaster Blake
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