[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 290838
TCDAT2

Tropical Storm Philippe Discussion Number  24
NWS National Hurricane Center Miami FL       AL172023
500 AM AST Fri Sep 29 2023

A 0546 UTC GMI microwave pass showed that Philippe continues to
have a broad circulation, with the low-level center located
somewhere near the northwestern edge of a large area of deep
convection.  There is a large range in the subjective Dvorak
estimates (30-55 kt), but the various objective numbers from
UW-CIMSS are in closer agreement (35-45 kt).  Using a blend of
these values, as well as ASCAT data from last evening, Philippe's
intensity is held at 40 kt.

While there is a bit of uncertainty in the exact location of the
center, the storm does appear to be drifting toward the southwest
(235 degrees) at about 2 kt.  Philippe's movement during the next
3-4 days is likely to be dictated by binary interaction with
Tropical Storm Rina to the east.  The bulk of the track guidance
indicates that Philippe will dip farther toward the southwest during
the next 48 hours due to Rina's influence, but then turn toward the
northwest and north on days 3 through 5 as a mid-tropospheric high
builds over the central Atlantic.  The new NHC track forecast is
not much different from the previous prediction and is close to the
TVCA and HCCA consensus aids.  The HAFS regional hurricane models
show little to no interaction between Philippe and Rina during the
next few days.  However, with the two storms located only 500 n mi
apart from each other, some degree of interaction is likely, and
therefore the western solutions shown by those models (near or over
the northern Leeward Islands) appear to be outliers at this time.
That said, there continues to be larger-than-normal uncertainty in
Philippe's future track.

A combination of shear, dry air, and Philippe's proximity to Rina
are likely to cause little change in intensity for the next day or
so.  However, the global models have trended toward Philippe not
only surviving the next few days, but also deepening in an
environment of increasing upper-level divergence (and still over
very warm waters of 29-30 degrees Celsius).  The NHC intensity
forecast has been nudged upward from 36 hours onward, although it
still sits well below most of the intensity models, including the
consensus aids, during the latter part of the forecast period.
Until it becomes more clear how Philippe will evolve over the next
couple of days, the official intensity forecast will remain on the
conservative side, but future adjustments to the forecast are
becoming more likely.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 18.5N  55.2W   40 KT  45 MPH
 12H  29/1800Z 18.3N  55.4W   40 KT  45 MPH
 24H  30/0600Z 17.9N  55.7W   40 KT  45 MPH
 36H  30/1800Z 17.4N  56.0W   45 KT  50 MPH
 48H  01/0600Z 17.1N  56.4W   50 KT  60 MPH
 60H  01/1800Z 17.1N  56.8W   50 KT  60 MPH
 72H  02/0600Z 17.6N  57.2W   55 KT  65 MPH
 96H  03/0600Z 20.0N  57.9W   55 KT  65 MPH
120H  04/0600Z 23.1N  58.1W   55 KT  65 MPH

$$
Forecaster Berg
This weather bulletin was brought to you by:
www.nashvilleweather.net