[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 270240
TCDAT2

Tropical Storm Philippe Discussion Number  15
NWS National Hurricane Center Miami FL       AL172023
1100 PM AST Tue Sep 26 2023

After the previous advisory, there was a convective burst with cloud
tops as cold as -80C that formed near the circulation center. More
recently, this burst has been waning in intensity, and it would not
be surprising to see the vortex become exposed again shortly as
20-30 kt southwesterly vertical wind shear continues. While
subjective and objective intensity estimates continue to suggest a
weaker storm, a helpful 0015 UTC ASCAT-B pass still showed a large
region of 35-40 kt winds in the northeastern side of the
circulation, in fact requiring an expansion of the tropical storm
force winds in that quadrant. Based primarily on the scatterometer
data, Philippe's intensity remains 40 kt for this advisory.

The intensity forecast appears rather straightforward. The current
vertical wind shear over Philippe is expected to continue through
most of the forecast period, helping to import drier air into the
circulation, that should prevent additional convective bursts from
organizing the system. By 72 hours, both the GFS and ECMWF are in
agreement that Philippe should no longer have organized deep
convection, which is when the forecast shows the system becoming a
post-tropical remnant low. As mentioned previously, this could
happen sooner than forecasted given the unfavorable environment.

After moving south of due west earlier today, Philippe appears to
have resumed a north of due west heading, estimated at 280/10 kt.
The track guidance is in good agreement on this motion continuing
with a bend westward in 36-48 hours as the cyclone becomes
primarily steered by the low-level flow. The latest NHC track
forecast remains along or just south of the model guidance consensus
aids, and is between the GFS and ECMWF solutions.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 17.4N  52.0W   40 KT  45 MPH
 12H  27/1200Z 17.9N  53.4W   40 KT  45 MPH
 24H  28/0000Z 18.8N  55.2W   35 KT  40 MPH
 36H  28/1200Z 19.4N  56.8W   35 KT  40 MPH
 48H  29/0000Z 19.8N  58.3W   35 KT  40 MPH
 60H  29/1200Z 20.0N  59.8W   30 KT  35 MPH
 72H  30/0000Z 20.0N  61.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  01/0000Z 20.1N  64.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  02/0000Z 20.2N  67.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Papin
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