Tropical Storm Philippe Forecast Discussion Number 35

By | October 2, 2023

WTNT42 KNHC 020236

Tropical Storm Philippe Discussion Number  35
NWS National Hurricane Center Miami FL       AL172023
1100 PM AST Sun Oct 01 2023

Philippe's cloud pattern has not become significantly better 
organized since earlier today.  The system is still producing very 
deep convection with cloud tops to -80 deg C or colder mainly over 
the southeastern quadrant of the circulation.  There are no obvious 
curved convective banding features at this time.  Some new 
thunderstorms have developed near and over the center and this was 
noted by the Air Force Hurricane Hunters who have been investigating 
the storm this evening.  Observations from the aircraft indicate 
little change in strength, with peak SFMR-observed surface winds 
near 45 kt.

The tropical cyclone has moved rather slowly over the past several 
hours and the initial motion estimate is west-northwestward, or 
300/4 kt.  Philippe should turn northwestward to northward along 
the western periphery of a mid-level high pressure area for the 
next few days.  Then, the system should turn north-northeastward 
and move through a weakness in the ridge.  The track guidance 
through 48 hours has shifted eastward on this cycle.  In an attempt 
to maintain continuity from the previous forecasts, the NHC track 
is not shifted eastward as much as shown by the model consensus, 
and the change through 24 hours is fairly slight.  Late in the 
forecast period, there is uncertainty as to how soon the cyclone 
will move into the higher-latitude westerlies.  The new GFS model 
run suggests that the system may turn eastward and stay in the 
subtropics through 5 days.  If this turns out to be true, then 
Philippe could have a prolonged existence.

The environment for Philippe in the short term does not appear 
conducive for significant strengthening, with fairly strong 
westerly vertical wind shear likely to continue to affect the 
system through Monday.  When the system moves farther north over 
the Atlantic, it may encounter a region of reduced shear as 
indicated by some of the dynamical guidance.  The official forecast 
still shows the system becoming a hurricane in the 3- to 5-day time 
frame and this is also supported by the IVCN model intensity 


1. Tropical storm conditions are possible across portions of the
northern Leeward Islands Monday and Monday night while Philippe
passes near or just northeast of the area, and a Tropical Storm
Watch is in effect for Antigua and Barbuda.  Interests elsewhere
in the northern Leeward Islands should continue to monitor this
system as additional watches or warnings could be required later
tonight or Monday.

2. Heavy rainfall from Philippe could produce isolated to scattered
flash flooding, particularly across Barbuda and Antigua, through


INIT  02/0300Z 16.6N  59.1W   45 KT  50 MPH
 12H  02/1200Z 17.0N  59.8W   45 KT  50 MPH
 24H  03/0000Z 17.8N  60.7W   45 KT  50 MPH
 36H  03/1200Z 19.0N  61.3W   50 KT  60 MPH
 48H  04/0000Z 20.3N  61.7W   50 KT  60 MPH
 60H  04/1200Z 22.0N  61.8W   50 KT  60 MPH
 72H  05/0000Z 23.8N  61.7W   55 KT  65 MPH
 96H  06/0000Z 27.5N  60.2W   65 KT  75 MPH
120H  07/0000Z 30.1N  57.6W   75 KT  85 MPH

Forecaster Pasch

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