[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 092031
TCDAT2

Tropical Storm Paulette Discussion Number  12
NWS National Hurricane Center Miami FL       AL172020
500 PM AST Wed Sep 09 2020

Paulette's satellite presentation has not changed since this
morning, with the center exposed just to the south of the deepest
convection.  Between this morning's ASCAT pass and the most recent
satellite classifications from TAFB and SAB, which are unchanged at
T3.0 and T3.5, respectively, the maximum wind estimate remains 50
kt.  Paulette continues to move into an area of stronger
southwesterly shear, which is now estimated to be 25-30 kt, and
this shear is likely to increase further to 30-35 kt within the
next 24 hours.  As a result, Paulette is expected to begin
weakening by Thursday, and the NHC forecast is embedded among the
tightly clustered intensity guidance during the first 2-3 days.
The shear is expected to relax gradually from 48 hours and beyond
and turn out of the southeast, which should allow for some
restrengthening on days 3 through 5 when shear magnitudes could go
as low as 10 kt.  The HWRF and COAMPS-TC models in particular take
full advantage of this environment and bring Paulette to hurricane
intensity by day 4.  The updated NHC intensity forecast is not
nearly this aggressive, but it does indicate a little more
strengthening at the end of the forecast period than has been shown
in previous forecasts, lying closest to the statistical-dynamical
guidance.  Model environmental trends will be monitored, and
additional intensity adjustments at the end of the forecast period
will be made accordingly in subsequent forecasts.

Paulette remains on a west-northwestward course (295/9 kt), located
to the south of low- to mid-level ridging which extends across the
central and western Atlantic.  The track models suggest that when
the cyclone weakens in a day or two, lower-level winds could steer
the cyclone westward for a short time.  However, a combination of
the ridge weakening and Paulette's expected re-strengthening should
cause the cyclone to turn northwestward in 2-3 days and maintain
that trajectory through the end of the forecast period.  The only
significant change from the previous forecast is that the 5-day
forecast point has been shifted westward, with the GFS, ECMWF,
HWRF, and HCCA models all lying on the left side of the guidance
envelope by that time.


FORECAST POSITIONS AND MAX WINDS

INIT  09/2100Z 20.5N  47.4W   50 KT  60 MPH
 12H  10/0600Z 20.9N  48.9W   50 KT  60 MPH
 24H  10/1800Z 21.4N  50.9W   45 KT  50 MPH
 36H  11/0600Z 21.6N  52.7W   40 KT  45 MPH
 48H  11/1800Z 22.3N  54.1W   40 KT  45 MPH
 60H  12/0600Z 23.3N  55.4W   40 KT  45 MPH
 72H  12/1800Z 24.8N  56.6W   45 KT  50 MPH
 96H  13/1800Z 28.0N  60.5W   50 KT  60 MPH
120H  14/1800Z 30.5N  64.5W   55 KT  65 MPH

$$
Forecaster Berg
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