805 
 WTNT41 KNHC 070850
 TCDAT1
 
 Tropical Storm Florence Discussion Number  32
 NWS National Hurricane Center Miami FL       AL062018
 500 AM AST Fri Sep 07 2018
 
 Florence's structure continues to be negatively affected by strong
 southwesterly shear.  Cloud tops have generally warmed over the
 past 6 hours, and recent microwave data show that the low-level
 circulation center of Florence is displaced nearly 20 nmi to the
 southwest of the mid-level center.  Satellite intensity estimates
 have decreased since last night, and now support an initial
 intensity of 55 kt.
 
 Based on GFS and ECMWF SHIPS diagnostic output, the southwesterly
 shear is near its peak now, and should gradually decrease over the
 next 24 to 36 h.  All of the intensity guidance shows little change
 in intensity through that time. From 48 h onward, a low shear/warm
 SST environment should allow the tropical storm to re-strengthen.
 However, the extent and timing of the strengthening varies greatly
 from model to model, with the dynamical models generally showing
 more intensification, and sooner, than the statistical models.  As
 has been the case for most of Florence's existence thus far,
 confidence in the intensity forecast, especially beyond 36 h, is
 low.  The new official forecast is a little lower than the previous
 advisory for the first 48 h, but close to it after that, and lies
 between the more aggressive HCCA and less aggressive IVCN consensus
 aids.
 
 Nighttime Proxy-Vis and earlier microwave imagery indicate that
 Florence has turned westward, with an estimated initial motion of
 275/6 kt. Most of the track guidance has shifted slightly toward the
 southwest, so the NHC track forecast has also been nudged in that
 direction.  Over the next 3 days of the forecast, Florence should be
 steered generally westward, and then west-northwestward, by a
 mid-level ridge to its north.  By days 4 and 5, a developing
 mid-latitude trough could create a weakness in this ridge and allow
 Florence to move more toward the northwest, but there is still
 considerable uncertainty in the global models and their ensembles
 regarding the strength of the ridge and if the aforementioned trough
 will have any notable impact on the track of Florence.  The NHC
 forecast follows HCCA very closely, and is also near the middle of
 the large combined envelope of the GFS, UKMET, and ECMWF ensembles.
 
 Key Messages:
 
 1. Regardless of Florence's eventual track, large swells will begin
 to affect Bermuda later today and portions of the U.S. East Coast
 this weekend, resulting in life-threatening surf and rip currents.
 
 2. There is still very large uncertainty in Florence's track
 beyond day 5, and it is too soon to determine what, if any, other
 impacts Florence could have on the U.S. East Coast next week.
 
 3. Since we are near the peak of hurricane season, this is a good
 time for everyone who lives in a hurricane-prone area to ensure they
 have their hurricane plan in place.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  07/0900Z 25.1N  50.7W   55 KT  65 MPH
  12H  07/1800Z 25.1N  51.8W   55 KT  65 MPH
  24H  08/0600Z 25.0N  53.2W   55 KT  65 MPH
  36H  08/1800Z 25.0N  54.3W   60 KT  70 MPH
  48H  09/0600Z 25.1N  55.4W   70 KT  80 MPH
  72H  10/0600Z 26.2N  58.3W   95 KT 110 MPH
  96H  11/0600Z 27.5N  63.5W  110 KT 125 MPH
 120H  12/0600Z 30.0N  70.0W  110 KT 125 MPH
 
 $$
 Forecaster Zelinsky