Official Discussion issued by the National Hurricane Center

Philippe (AL172023) DATA RELEASED: 9/28/2023 9:00:00 PM UTC

Copy of official data

Tropical Storm Philippe Discussion Number  22
NWS National Hurricane Center Miami FL       AL172023
500 PM AST Thu Sep 28 2023

Philippe remains poorly organized.  Visible satellite images
indicate that the circulation is elongated from east to west and
appears to have multiple centers along a trough axis.  The center
position listed in the advisory seems to be the main center and
there is some deep convection on its east and southeast sides.
Philippe barely meets the criteria needed for a tropical cyclone as
it has lost some organization today.  The initial intensity is
lowered to 40 kt, which is near the high end of the latest satellite
intensity estimates.

The initial motion is highly uncertain since the storm is elongated
and confidence in the initial position remains low.  The track
forecast is challenging, in part due to Philippe's close proximity
to Tropical Storm Rina.  During the next few days, Philippe will 
likely move slowly southwestward as it rotates around Rina 
currently to its east.  By late in the weekend, however, a sharp 
northward turn is expected when a mid-level ridge becomes 
established over the central subtropical Atlantic.  There remains a 
very large east-west spread in the models, and disagreements on 
where Philippe makes its northward turn.  The GFS is the right-most 
model while the ECMWF remains the model farthest west.  The NHC 
track forecast is little changed from the previous one and remains 
closest to the ECMWF model, which has been performing best so far 
for this storm.

The observed weakening of the system today appears to be related to 
its interaction with Rina and some environmental dry air.  Since 
these factors are expected to persist, some additional weakening is 
forecast during the next day or so, and it is possible that Philippe 
dissipates sometime during the next couple of days.  However, if the 
storm does survive, environmental conditions are expected to become 
a little more favorable when Philippe and Rina become more 
separated later in the forecast period.  There is a huge spread in 
the intensity models with HWRF, HMON, and the GFS showing Philippe 
becoming a significant hurricane while the HAFS-A and HAFS-B models 
show gradual weakening.  The NHC intensity forecast is a little 
lower than the previous one in the short term, but is otherwise 
unchanged and closer to the low end of the model guidance.


INIT  28/2100Z 18.9N  55.1W   40 KT  45 MPH
12H  29/0600Z 18.9N  55.5W   35 KT  40 MPH
24H  29/1800Z 18.7N  55.9W   35 KT  40 MPH
36H  30/0600Z 18.3N  56.2W   40 KT  45 MPH
48H  30/1800Z 17.9N  56.4W   45 KT  50 MPH
60H  01/0600Z 17.5N  57.0W   45 KT  50 MPH
72H  01/1800Z 17.0N  57.6W   45 KT  50 MPH
96H  02/1800Z 18.6N  58.6W   45 KT  50 MPH
120H  03/1800Z 20.6N  59.1W   40 KT  45 MPH

Forecaster Cangialosi