[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 252038
TCDAT2

Tropical Storm Philippe Discussion Number  10
NWS National Hurricane Center Miami FL       AL172023
500 PM AST Mon Sep 25 2023

Visible satellite images continue to show Philippe with a fully
exposed center far removed to the west of all of the deep
convection. The continued disorganized appearance suggests at least
some weakening has occurred, and satellite intensity estimates
concur. Thus, the wind speed has been lowered to 40 kt.

Philippe continues to be impacted by 20-25 kt of deep-layer
west-southwesterly vertical wind shear. This wind shear is forecast
by both GFS- and ECMWF-based SHIPS models to persist or even
increase further during the next few days. This unfavorable shear
combined with dry air entrainment will hinder strengthening through
the forecast period. A few models suggest some slight increase in
intensity in the 48- to 72-hour time frame due to warmer sea-surface
temperatures, but other environmental factors will remain negative.
The new forecast indicates no change in strength over the next
several days, with some weakening toward the end of the forecast
period.

The exposed low-level center of Philippe has been moving west today
with a slight increase in forward motion this afternoon. The system
should veer toward the west-northwest tonight then turn northwest by
mid-week as Philippe moves toward a weakness in the subtropical
ridge.  By late week, this weakness becomes less pronounced and the
overall steering flow diminishes. The forecast track at the end of
the period therefore slows and curves back toward the
west-northwest. There remains considerable spread in the track
models this afternoon, with the GFS and its ensemble members
representing far rightward outliers. With the ongoing motion to the
west and a leftward shift of the overall guidance output, the NHC
forecast track has been adjusted slightly west, especially beyond 72
hours due to the aforementioned steering flow changes.


FORECAST POSITIONS AND MAX WINDS

INIT  25/2100Z 17.3N  46.7W   40 KT  45 MPH
 12H  26/0600Z 17.7N  48.5W   40 KT  45 MPH
 24H  26/1800Z 18.4N  50.4W   40 KT  45 MPH
 36H  27/0600Z 19.3N  52.3W   40 KT  45 MPH
 48H  27/1800Z 20.4N  54.0W   40 KT  45 MPH
 60H  28/0600Z 21.6N  55.4W   40 KT  45 MPH
 72H  28/1800Z 22.2N  56.3W   40 KT  45 MPH
 96H  29/1800Z 22.9N  57.7W   40 KT  45 MPH
120H  30/1800Z 23.4N  59.5W   35 KT  40 MPH

$$
Forecaster Konarik/Cangialosi
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