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