Tropical Storm Philippe Forecast Discussion Number 20

By | September 28, 2023

WTNT42 KNHC 280900

Tropical Storm Philippe Discussion Number  20
NWS National Hurricane Center Miami FL       AL172023
500 AM AST Thu Sep 28 2023

Philippe remains a disorganized, sheared storm.  Deep convection 
has continued through the night to the southeast of the estimated 
low-level center. Imagery from a 0525 UTC satellite microwave pass 
showed a decent curved band associated with this convection in the 
89 GHz channel.  Unfortunately, ASCAT missed the storm entirely. 
The initial intensity is held at 45 kt for this advisory, closest 
to the TAFB Dvorak estimate.  

There is still low confidence in Philippe's track forecast.  As 
stated in previous advisories, the future location of the storm is 
closely linked to its structure and intensity.  Should Philippe 
remain a weaker, shallower cyclone, it is more likely to follow the 
low-level westerly to southwesterly flow.  This advisory favors that 
scenario and shows the storm slowly drifting generally westward to 
southwestward through day 4.  By day 5, global models are suggesting 
a trough to the north will lift Philippe or its remnants 
northwestward.  A complicating factor to this track forecast is the 
proximity of an area of disturbed weather to the east of the 
cyclone.  Some models are still showing a binary interaction between 
the two systems, which will largely depend on the strength of each.  
Significant changes have been made to the most recent track 
forecast, that are largely related to a slower westward progression 
of Philippe.  Still, this forecast is a blend of the previous 
advisory and the latest model guidance.  Further adjustments may be 
required in subsequent advisories. 

Philippe is in an environment with moderate southwesterly vertical 
wind shear and lower, upshear, mid-level relative humidities.  These 
conditions are likely to inhibit intensification in the near-term 
time frame.  In about 48 h, global models predict the vertical wind 
shear to increase and likely cause Philippe to gradually weaken 
through the forecast period. However, there remains 
higher-than-average uncertainty in the intensity forecast.  The 
latest NHC forecast still calls for Philippe to become a remnant low 
by day 4.


INIT  28/0900Z 18.8N  54.6W   45 KT  50 MPH
 12H  28/1800Z 19.1N  55.4W   45 KT  50 MPH
 24H  29/0600Z 19.3N  56.0W   45 KT  50 MPH
 36H  29/1800Z 19.2N  56.5W   40 KT  45 MPH
 48H  30/0600Z 18.9N  57.1W   40 KT  45 MPH
 60H  30/1800Z 18.5N  57.6W   35 KT  40 MPH
 72H  01/0600Z 18.0N  58.3W   35 KT  40 MPH
 96H  02/0600Z 18.2N  59.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  03/0600Z 19.0N  60.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

Forecaster Bucci

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