Official Discussion issued by the National Hurricane Center

Philippe (AL172023) DATA RELEASED: 10/2/2023 9:00:00 PM UTC

Copy of official data

Tropical Storm Philippe Discussion Number  38
NWS National Hurricane Center Miami FL       AL172023
500 PM AST Mon Oct 02 2023

The center of Philippe remains exposed this afternoon with
some convection firing closer to the center over the last few
hours. Heavy rainfall and thunderstorms remain displaced to the 
south and southeast of the center as high northwesterly vertical 
wind shear persists. The initial intensity is again held steady at 
45 kt for this advisory, consistent with SFMR data from the Air 
Force Reserve reconnaissance aircraft mission showing a large area 
of 40-45 surface winds mostly on the east and southeast side of the 
system earlier this afternoon. Another Air Force Reserve mission is
scheduled for this evening.

The storm continues to move to the northwest (305 degrees) at 6 kt 
this afternoon.  Philippe refuses to gain much vertical depth as a 
tropical cyclone and has been steered more by the lower-level 
ridge.  Thus, the track forecast is again adjusted westward to 
match recent satellite trends and in line with the weaker model 
guidance.  The cyclone is forecast to pass near Barbuda tonight 
before turning north-northwest north of the Leeward Islands.  
Around mid-week, Philippe should turn northward due to flow between 
a mid-level trough in the southwest Atlantic and the subtropical 
ridge.  Uncertainty greatly increases after that point, with huge 
differences showing up between the GFS- and ECMWF-based guidance.  
The differences in model track forecasts are related to whether this 
trough captures Philippe's circulation, causing Philippe to move 
more to the north-northwest, or whether it is shunted more to the 
northeast ahead of the trough.  Consistent with model guidance, the 
track forecast has shifted farther west from the previous advisory 
and is in line with the consensus aids and mean ensemble track 
guidance. Further adjustments to the west may be necessary.

Strong northwesterly vertical wind shear is expected to
prevent significant strengthening in the short term. Shear is 
forecast to decrease a bit for a short period of time in the next 2 
to 3 days and could allow for some strengthening.  However, almost 
all of the guidance is showing a less conducive environment, and 
the NHC forecast reflects this trend, lying on the high end of 
model guidance but in line with HCCA.  The uncertainty is extremely 
large at the end of the forecast period as some models are now 
showing an extratropical transition due to the mid-latitude trough, 
but a lot depends on how strong Philippe eventually becomes, which 
has clearly not been very predictable during this storm's lifetime.


1. Tropical storm conditions are expected across Barbuda and
Antigua beginning this evening while Philippe passes near and 
north of the area.  Interests elsewhere in the northern Leeward 
Islands should continue to monitor this system.

2. Heavy rainfall from Philippe could produce isolated to scattered
flash flooding over the northern Leeward Islands, particularly
across Barbuda and Antigua, through Tuesday.


INIT  02/2100Z 17.6N  61.5W   45 KT  50 MPH
12H  03/0600Z 18.2N  62.2W   45 KT  50 MPH
24H  03/1800Z 19.1N  62.6W   45 KT  50 MPH
36H  04/0600Z 20.6N  63.0W   45 KT  50 MPH
48H  04/1800Z 22.2N  63.4W   45 KT  50 MPH
60H  05/0600Z 23.9N  63.8W   50 KT  60 MPH
72H  05/1800Z 26.0N  63.8W   55 KT  65 MPH
96H  06/1800Z 30.6N  62.2W   60 KT  70 MPH
120H  07/1800Z 35.0N  60.0W   65 KT  75 MPH

Forecaster Blake/Stevenson