####018003562####
WTNT42 KNHC 302043

TCDAT2

 

Tropical Storm Philippe Discussion Number  30

NWS National Hurricane Center Miami FL       AL172023

500 PM AST Sat Sep 30 2023

 

Philippe remains a sheared tropical cyclone. Its low-level center

has become increasingly separated from the deep convection today.

Visible satellite images and and fixes from the Air Force Hurricane

Hunters indicate the center is farther south and slightly east of

our previous estimates. In terms of Philippe's current intensity,

there were mixed signals in the aircraft data. The peak 850-mb

flight-level winds were only 49 kt, and a center dropsonde indicated

no change of the minimum pressure (999 mb) since the previous

flight. On the other hand, the SFMR retrievals showed winds of 45-50

kt outside of convection that were visually supported by the flight

crew, but a coincident dropsonde reported much lower near-surface

wind speeds. Given the conflicting data and less impressive

satellite presentation, the initial intensity is held at 45 kt.

 

The tropical storm has continued to move southwestward today, with

an initial motion of 215/4 kt. In the near term, the models suggest

Philippe will not move very much and could drift erratically through

early Sunday while Tropical Storm Rina passes to its north. Then,

there is general agreement that the storm will turn toward the

west-northwest and northwest around the western extent of a low- to

mid-level ridge over the central Atlantic. While there is still a

large spread in the track guidance during the 24-72 h time frame, it

is noteworthy that the 12z ECMWF has trended eastward this cycle and

shows Philippe passing farther east of the northern Leeward Islands.

The latest NHC track forecast is slightly farther south and west

early in the forecast due to the center relocation. However, the

updated prediction ends up near or slightly east of the previous

forecast at 36-72 h, in best agreement with the TVCA simple

consensus. By days 4-5, Philippe is forecast to accelerate northward

and northeastward between a central Atlantic ridge and a deep-layer

trough over the western Atlantic.

 

Only modest strengthening is forecast during the next 24-36 h while 

Philippe contends with moderate to strong northwesterly shear. The 

upper-level winds are forecast to become more conducive for 

intensification in a couple of days or so, which should allow the 

cyclone to become more vertically aligned and establish an inner 

core. Thus, more strengthening is forecast at days 2-4 while 

Philippe moves over the very warm SSTs of the central Atlantic, 

which is supported by almost all of the intensity guidance. The NHC 

forecast calls for Philippe to become a hurricane by 60 h with 

continued strengthening thereafter. The peak intensity was raised to 

bring the NHC forecast slightly closer to the latest HCCA and IVCN 

aids at days 4-5, but it is noted that the regional hurricane models 

are even stronger than the current NHC forecast.

 

 

FORECAST POSITIONS AND MAX WINDS

 

INIT  30/2100Z 16.3N  56.5W   45 KT  50 MPH

 12H  01/0600Z 16.2N  56.7W   50 KT  60 MPH

 24H  01/1800Z 16.6N  57.4W   55 KT  65 MPH

 36H  02/0600Z 17.4N  58.1W   55 KT  65 MPH

 48H  02/1800Z 18.5N  58.9W   60 KT  70 MPH

 60H  03/0600Z 19.9N  59.5W   65 KT  75 MPH

 72H  03/1800Z 21.6N  59.7W   70 KT  80 MPH

 96H  04/1800Z 25.7N  59.0W   80 KT  90 MPH

120H  05/1800Z 29.5N  56.0W   80 KT  90 MPH

 

$$

Forecaster Reinhart