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Hurricane FLORENCE


Hurricane Florence Discussion Number  22
NWS National Hurricane Center Miami FL       AL062018
500 PM AST Tue Sep 04 2018

Despite being over marginally warm water and in an environment of
moderate west-southwesterly shear, Florence's intensity has
increased during the day.  The hurricane has a cloud-filled eye in
visible imagery, and the central dense overcast is becoming more
symmetric.  Based on Dvorak estimates of T4.5 from TAFB and SAB,
and a SATCON estimate of 77 kt, the initial intensity is now,
somewhat surprisingly, 75 kt.  Since the current intensification
trend may not be over, the official forecast calls for Florence to
strengthen just a little more during the next 6-12 hours.  Even
though the hurricane will be moving over progressively warmer
waters, increasing vertical shear and dry air in the middle levels
of the atmosphere should induce some weakening in the 24-72 hour
time frame.  Lower shear after 72 hours will likely allow Florence
to regain hurricane strength by the end of the forecast period.
The NHC intensity forecast is primarily adjusted to account for the
recent strengthening trend, and is closest to the Florida State
Superensemble and HCCA guidance.

Florence remains on a west-northwestward course at 300/10 kt.  This
trajectory is expected to continue through 36 hours while the
hurricane remains near the southwestern edge of the subtropical
ridge.  After 36 hours, Florence is expected to turn northwestward
and slow down as it enters a break in the ridge.  The track models
are in good agreement and show little spread through 48 hours.  On
days 3-5, the biggest outlier is the UKMET, which lies to the south
of the guidance suite. In fact, the bulk of the models, including
the deterministic GFS and ECMWF, are all now showing a more
definitive poleward motion by day 5.  While the official NHC track
forecast reflects this thinking, there is still considerable spread
among the associated global model ensembles, and the longer-term
forecast should be considered low confidence.


INIT  04/2100Z 20.3N  43.2W   75 KT  85 MPH
 12H  05/0600Z 21.0N  44.8W   80 KT  90 MPH
 24H  05/1800Z 22.1N  46.8W   75 KT  85 MPH
 36H  06/0600Z 23.2N  48.7W   65 KT  75 MPH
 48H  06/1800Z 24.3N  50.4W   60 KT  70 MPH
 72H  07/1800Z 26.0N  53.0W   55 KT  65 MPH
 96H  08/1800Z 27.5N  55.0W   60 KT  70 MPH
120H  09/1800Z 29.5N  56.5W   70 KT  80 MPH

Forecaster Berg