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WTNT42 KNHC 241442

TCDAT2

 

Tropical Storm Philippe Discussion Number   5

NWS National Hurricane Center Miami FL       AL172023

1100 AM AST Sun Sep 24 2023



Philippe is a challenging tropical cyclone to analyze this morning. 

On one hand, the overall satellite presentation has improved since 

yesterday, and a 0907Z SSMIS microwave pass shows a possible 

mid-level eye.  Yet the 1-min GOES16 imagery reveals a weak 

low-level swirl southwest of the main convective blob, and ASCAT-B 

near 12Z showed a disorganized inner core with less wind than one 

might expect (albeit very contaminated with rain).  Overall, 

intensity estimates have risen since the last advisory, so the 

initial wind speed is set to 45 kt, similar to the TAFB/SAB values, 

but this should be considered fairly uncertain.



Little change in intensity is forecast with the storm during the 

next couple of days as increasing shear is forecast to otherwise 

counteract a conducive environment.  There are a variety of 

solutions after that point, with some models showing a stronger 

Philippe after finding a lower-shear environment, while others 

suggesting that the storm succumbs to the shear from an 

upper-level trough.  There are no easy answers here with moderate 

shear cases in high SST/moisture conditions well known to have 

higher errors due to an inherent lack of predictability.  The new 

forecast splits the difference in the model guidance, lying near 

the consensus and the previous forecast, and we will just have to 

see if a trend emerges for the eventual intensity of Philippe.



The long-term motion of the storm is westward or 280/10 kt. The 

subtropical ridge to the north of Philippe is forecast to gradually 

weaken and slide eastward in a day or two, allowing the tropical 

storm to move more west-northwestward and northwestward by the 

middle of the week.  Uncertainty grows after that point, with the 

track seemingly dependent on the intensity.  A stronger system 

would probably turn northward, like the GFS/HWRF/HMON models, while 

a weaker one, like the UKMET/ECMWF solutions, would take a left 

turn under the low-level subtropical ridge.  For now, little change 

was made to the long-range forecast given all of the uncertainty.



 

FORECAST POSITIONS AND MAX WINDS

 

INIT  24/1500Z 16.2N  41.7W   45 KT  50 MPH

 12H  25/0000Z 16.5N  43.3W   45 KT  50 MPH

 24H  25/1200Z 16.9N  45.6W   45 KT  50 MPH

 36H  26/0000Z 17.4N  47.8W   45 KT  50 MPH

 48H  26/1200Z 18.0N  49.7W   45 KT  50 MPH

 60H  27/0000Z 18.9N  51.0W   50 KT  60 MPH

 72H  27/1200Z 20.0N  52.5W   50 KT  60 MPH

 96H  28/1200Z 22.5N  54.5W   55 KT  65 MPH

120H  29/1200Z 24.0N  55.5W   55 KT  65 MPH

 

$$

Forecaster Blake