[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 090251
TCDAT2

Tropical Storm Paulette Discussion Number   9
NWS National Hurricane Center Miami FL       AL172020
1100 PM AST Tue Sep 08 2020

Microwave and satellite data suggest that vertical shear is
weakening Paulette.  The center is near the southern side of a large
thunderstorm cluster, with the bulk of deep convection in the
northeastern quadrant of the cyclone.  A recent ASCAT-B pass showed
maximum winds of 45-50 kt, a little lower than the other satellite
estimates, and 50 kt is chosen as the initial wind speed.

With Paulette already on a weakening trend, it seems that the window
for significant strengthening has closed.  More likely, a gradual
decay of the storm is anticipated due to moderate or strong shear
during the next few days.  This shear could abate by the end of the
forecast period due to Paulette moving around the northeastern side
of a large mid-to-upper level low, which is a common position for
the re-intensification of a tropical cyclone after encountering the
mid-oceanic trough.  The new forecast is lowered from the previous
one for the first few days and then raised slightly at the longer
ranges. This is consistent with a blend of the intensity model
consensus, leaning toward the NOAA corrected-consensus guidance at
the end.

The storm is moving northwestward at about 8 kt.  There has been
some convergence of the model guidance during the next few days as
Paulette should move west-northwestward tomorrow and westward on
Thursday around a mid-level ridge.  Thus, little change has been
made from the previous forecast during the first 48-72h. Afterwards,
the forecast is shifted to the north by 45-60 n mi under the
assumption that Paulette stays coherent as a tropical cyclone and
takes a turn to the northwest this weekend on the eastern flank of
the aforementioned mid-to-upper level low.  The new track forecast
is northeast of the model consensus and places less emphasis on
models, like the 12Z ECMWF, which show Paulette staying weaker and
missing the full influence of the low.


FORECAST POSITIONS AND MAX WINDS

INIT  09/0300Z 19.2N  45.0W   50 KT  60 MPH
 12H  09/1200Z 19.8N  46.2W   50 KT  60 MPH
 24H  10/0000Z 20.2N  48.1W   50 KT  60 MPH
 36H  10/1200Z 20.6N  50.0W   45 KT  50 MPH
 48H  11/0000Z 20.8N  51.7W   45 KT  50 MPH
 60H  11/1200Z 21.1N  52.9W   40 KT  45 MPH
 72H  12/0000Z 21.9N  53.8W   40 KT  45 MPH
 96H  13/0000Z 24.4N  55.7W   45 KT  50 MPH
120H  14/0000Z 27.5N  59.0W   55 KT  65 MPH

$$
Forecaster Blake
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