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Hurricane FLORENCE


Hurricane Florence Discussion Number  24
NWS National Hurricane Center Miami FL       AL062018
500 AM AST Wed Sep 05 2018

Conventional satellite enhanced BD-curve infrared imagery and a
0511 UTC GMI color composite microwave pass reveal improved inner
core structure with impressive outer banding over the eastern
semicircle.  Dvorak intensity estimates have again increased, and
the initial intensity is once more increased to 90 kt, which also
agrees with the latest SATCON analysis.

This intensity forecast is still a bit murky.  The deterministic
models show increasing southwesterly vertical shear and a less than
favorable mid-tropospheric thermodynamic environment affecting the
tropical cyclone over the next 48 hours.  This less-than-conducive
environment should induce weakening during this time frame.
Thereafter, and through the remaining forecast, most of the
models show a mid- to upper-level low developing to the south of
Florence in the base of the mid- Atlantic deep-layer trough, which
should promote a somewhat more favorable diffluent upper wind
pattern.  This more conducive upper wind pattern, and increasing sea
surface temperatures, is expected to cause Florence to restrengthen.
The NHC forecast is a little bit higher than the previous one
between the 48 and 96 hr periods to agree more with the IVCN and
NOAA-HCCA consensus forecasts.

Florence is estimated to be moving northwestward, or 305/11 kt,
which appears to be a temporary trochoidal eyewall wobble.  A turn
back toward the west-northwest is expected later today, and this
general motion is expected to continue through day 4 while the
hurricane is steered by the southwestern periphery of the
subtropical ridge.  By the end of the forecast period, Florence is
expected to turn northwestward and slow down as it enters a break in
the ridge.  The ECMWF model track forecast has shifted significantly
toward the left this evening, closer to the other global models and
their ensemble means, indicating less steering influence from the
predicted growing weakness in the subtropical ridge.  Subsequently,
an adjustment to the left of of the previous advisory, beyond 48
hours, was made in order to nudge closer to the guidance suite and
the consensus models.


INIT  05/0900Z 21.4N  44.8W   90 KT 105 MPH
 12H  05/1800Z 22.2N  46.3W   90 KT 105 MPH
 24H  06/0600Z 23.2N  48.2W   80 KT  90 MPH
 36H  06/1800Z 24.2N  50.0W   70 KT  80 MPH
 48H  07/0600Z 24.9N  51.5W   70 KT  80 MPH
 72H  08/0600Z 25.6N  54.1W   75 KT  85 MPH
 96H  09/0600Z 26.8N  56.3W   80 KT  90 MPH
120H  10/0600Z 28.7N  58.2W   85 KT 100 MPH

Forecaster Roberts