Tropical Storm Philippe Forecast Discussion Number 9

By | September 25, 2023

WTNT42 KNHC 251442

Tropical Storm Philippe Discussion Number   9
NWS National Hurricane Center Miami FL       AL172023
1100 AM AST Mon Sep 25 2023

Visible satellite images indicate that Philippe has become less
organized this morning.  The low-level center has become fully
exposed with all of the deep convection now displaced well to the
east of the center.  The initial wind speed is held at 45 kt, in
agreement with most of the satellite intensity estimates.

Philippe is currently experiencing about 20-25 kt of
west-southwesterly vertical wind shear.  Both the GFS- and
ECMWF-based SHIPS models show the vertical wind shear increasing
even more during the next few days.  These hostile winds and dry air
entrainment should cause Philippe to continue to struggle throughout
the forecast period.  There is some spread in the guidance with a
couple of models showing slight strengthening and several of the
models showing slight weakening.  Based on the guidance and expected
continued shear, the new forecast is lower than the previous one and
shows no change in strength during the next several days.

Geostationary and microwave satellite images indicate that Philippe
has jogged to the left this morning.  Smoothing through this wobble
yields an initial motion of 280/11 kt.  A turn back to the
west-northwest is expected by tonight, followed by a northwestward
motion in a couple of days as Philippe moves toward a weakness in
the subtropical ridge.  There is a vast amount of spread in the
track models this morning with the GFS and its ensemble mean on the
far right side of the guidance envelope and the ECMWF on the left
side.  An examination of the GFS model fields suggests that the
model is showing a vortex that is likely too vertically aligned, and
not representative of the environmental conditions.  Therefore,
that model is considered an outlier for the time being.  The new
NHC track forecast is adjusted to the left toward the various
consensus models.


INIT  25/1500Z 17.3N  45.5W   45 KT  50 MPH
 12H  26/0000Z 17.6N  47.2W   45 KT  50 MPH
 24H  26/1200Z 18.1N  49.2W   45 KT  50 MPH
 36H  27/0000Z 18.9N  51.2W   45 KT  50 MPH
 48H  27/1200Z 19.9N  52.9W   45 KT  50 MPH
 60H  28/0000Z 21.1N  54.2W   45 KT  50 MPH
 72H  28/1200Z 22.1N  55.4W   45 KT  50 MPH
 96H  29/1200Z 23.7N  56.9W   45 KT  50 MPH
120H  30/1200Z 24.6N  57.9W   45 KT  50 MPH

Forecaster Cangialosi/Konarik

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