[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 271453
TCDAT2

Tropical Storm Philippe Discussion Number  17
NWS National Hurricane Center Miami FL       AL172023
1100 AM AST Wed Sep 27 2023

Visible, infrared and microwave imagery depicts that Philippe is a
slightly better organized system this morning. A burst of deep
convection continues near and east of the center. In addition,
earlier AMSR and SSMI/S microwave passes show that a convective
band has been developing on the eastern side of the circulation.
However, visible satellite images within the past hour depict that
the low-level center is becoming partially exposed on the western
edge of the convection. Subjective and objective satellite
intensity estimates have increased this cycle, with a TAFB Dvorak
data-T number of 3.0, 45 kt. Given the developing banding feature
and satellite intensity estimates, the initial intensity is raised
to 45 kt for this advisory.  This is also in agreement with a
recent ASCAT-B pass.

Philippe is expected to remain in a sheared environment
over the next few days. However, the GFS SHIPS vertical wind shear
forecast shows a slight decrease, which may allow  to the storm to
withhold convection near the low-level center a little longer than
what was previously anticipated. Philippe is forecast to move into a
slightly drier mid-level airmass in a few days, which may also
inhibit the overall convective pattern. Some slight fluctuations in
intensity may occur due to the pulsing convective nature of the
system during the next few days, with an overall slow weakening
trend later this weekend. The NHC intensity forecast was raised
slightly given the initial higher intensity. There remains
uncertainty in the intensity forecast and it is possible Philippe
maintains its tropical cyclone status as it reaches the northern
Leeward Islands.

The storm has not gained much latitude this morning and continues to
move mainly westward at around 280/8 kt.  Philippe is currently
being steered by the flow around a weak mid-level ridge and is
expected to move west-northwestward over the next couple of days.
In the latter part of the forecast period, the weakening and shallow
system should turn toward the west-southwest. The track forecast is
highly dependent on the intensity forecast, however.  The official
track forecast has again been shifted southward in 3-5 days, but
not as far south as the consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 17.5N  53.7W   45 KT  50 MPH
 12H  28/0000Z 18.0N  54.7W   45 KT  50 MPH
 24H  28/1200Z 18.6N  56.1W   45 KT  50 MPH
 36H  29/0000Z 19.0N  57.8W   40 KT  45 MPH
 48H  29/1200Z 19.0N  59.5W   40 KT  45 MPH
 60H  30/0000Z 18.9N  60.8W   35 KT  40 MPH
 72H  30/1200Z 18.7N  62.2W   35 KT  40 MPH
 96H  01/1200Z 18.4N  64.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  02/1200Z 18.1N  66.9W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Kelly
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