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Tropical Storm Florence Forecast Discussion Number 8
2018-09-01 10:56:36| National Hurricane Center (Atlantic)
Issued at 500 AM AST Sat Sep 01 2018 081 WTNT41 KNHC 010856 TCDAT1 Tropical Storm Florence Discussion Number 8 NWS National Hurricane Center Miami FL AL062018 500 AM AST Sat Sep 01 2018 A recent SSMIS microwave pass has revealed that the cyclone has become much better organized with more pronounced convective banding. Satellite intensity estimates are wide ranging, spanning from T1.5/25 kt from SAB to T3.4/53 kt from the UW-CIMSS ADT. Since the numbers overall have increased, and the structure has improved, the initial intensity is raised to 35 kt, in closest agreement to the TAFB estimate, but this could be conservative. This makes the depression Tropical Storm Florence, the sixth named storm of the season. Florence is moving west-northwestward, or 285/12 kt, and should maintain this motion for the next 48 hours while traveling along the southern periphery of the subtropical ridge. After 48 hours, the storm is expected to reach a break in the ridge, causing it to slow down and turn northwestward by day 5. The biggest change noted among the track models on this cycle was a westward shift in the overall guidance envelope. The European model, in particular, swung significantly to the left, showing a weaker Florence not feeling the break in the ridge quite as much. I'd like to see this trend continue before making a significant change to the forecast, so for now the updated NHC track prediction is only nudged westward. That said, the models appear to be trending away from a definitive recurvature scenario. The environment is mixed with positives and negatives for Florence's strengthening. For the first 3 days, vertical shear over Florence should be quite low, but the cyclone will also be moving through a less-than-ideal thermodynamic environment with marginal sea surface temperatures and decreasing mid-level moisture. After 3 days, the thermodynamic environment should begin to improve, but then the shear is forecast to strengthen. These conflicting signals point to only gradual strengthening, and the suite of intensity models aren't too far off from one another, nor from the previous NHC forecast. For that reason, no significant changes were made in this forecast package. FORECAST POSITIONS AND MAX WINDS INIT 01/0900Z 14.5N 26.7W 35 KT 40 MPH 12H 01/1800Z 15.0N 28.7W 40 KT 45 MPH 24H 02/0600Z 15.7N 31.2W 45 KT 50 MPH 36H 02/1800Z 16.4N 33.7W 50 KT 60 MPH 48H 03/0600Z 17.1N 36.3W 55 KT 65 MPH 72H 04/0600Z 18.7N 41.4W 60 KT 70 MPH 96H 05/0600Z 21.0N 45.5W 60 KT 70 MPH 120H 06/0600Z 23.5N 48.5W 55 KT 65 MPH $$ Forecaster Berg
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