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| #938106 (Received by flhurricane at: 5:06 AM 02.Sep.2018) TCDAT1 Tropical Storm Florence Discussion Number 12 NWS National Hurricane Center Miami FL AL062018 500 AM AST Sun Sep 02 2018 Florence continues to gradually strengthen. Microwave imagery from a recent AMSR overpass indicates that a majority of the deep convection is located in the northern semicircle of the tropical storm, but its center is still well embedded within the central dense overcast. A blend of satellite intensity estimates from SAB and TAFB supports increasing the intensity to 50 kt. Some additional slight strengthening is still expected over the next day or so while Florence remains in a light shear environment and over marginal SSTs. Beginning in about 3 days, slow weakening is forecast due to an expected increase in wind shear associated with an extensive mid- to upper-level trough over the central Atlantic. The intensity guidance is in generally good agreement through 120 h, and the official forecast remains near the intensity consensus. The initial motion is now 290/13. The track guidance is fairly tightly packed for the first 48 h or so, with the spread increasing more quickly beyond that time. For the next couple of days, the subtropical ridge should keep Florence moving westward to west-northwestward at a similar forward speed. By day 3, a west-northwest to northwest motion is forecast to begin, as the aforementioned mid- to upper-level trough influences the track of the tropical storm. While all of the global models show this general scenario, the extent to which Florence will gain latitude is less certain. A stronger Florence will likely turn more toward the northwest, while a weaker, shallower system should continue on a more westward to west-northwestward track. For now, the NHC forecast remains near the middle of the guidance envelope, close to all of the consensus models. This track is also generally in line with the official intensity forecast, which shows a somewhat weaker system than the GFS (on the north side of the guidance), but a stronger one than the ECMWF (on the south side). FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 16.5N 31.4W 50 KT 60 MPH 12H 02/1800Z 17.0N 33.5W 55 KT 65 MPH 24H 03/0600Z 17.5N 36.3W 55 KT 65 MPH 36H 03/1800Z 18.0N 39.0W 55 KT 65 MPH 48H 04/0600Z 18.5N 41.4W 55 KT 65 MPH 72H 05/0600Z 20.1N 45.5W 55 KT 65 MPH 96H 06/0600Z 22.0N 49.5W 50 KT 60 MPH 120H 07/0600Z 24.0N 53.0W 45 KT 50 MPH $$ Forecaster Zelinsky |
