[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 020839
TCDAT2

Tropical Storm Philippe Discussion Number  36
NWS National Hurricane Center Miami FL       AL172023
500 AM AST Mon Oct 02 2023

The overall structure of Philippe has changed very little during the
past day or so.  Deep convection remains confined to the
southeastern portion of the circulation due to moderate to strong
northwesterly vertical wind shear.  There is no significant banding
features, but the cloud tops within the main convective mass are
quite cold.  Radar imagery from Barbados shows very heavy rainfall
is occurring just east of the Lesser Antilles.  The initial
intensity is held at 45 kt in deference to the earlier aircraft
data, and the latest subjective Dvorak intensity estimates which are
unchanged from before.  The next Air Force Reserve reconnaissance
aircraft mission is scheduled to investigate Philippe later this
morning.

Center fixes during the past 6-12 hours indicate that Philippe has
turned northwestward (315 degrees) and is moving a little faster,
around 6 kt.  Philippe is forecast to move around the southwestern
portion of a mid-level ridge over the subtropical Atlantic during
the next couple of days.  After that time, Philippe should turn
northward between the aforementioned ridge and a mid- to upper-level
trough over the southwestern Atlantic.  Around day 5, there is
increasing uncertainty as to whether Philippe will turn
east-northeastward or continue on a more northerly trajectory ahead
of a large trough moving into the eastern United States. Little
change was made to the previous forecast through 72 hours, but after
that time the track was adjusted northwestward closer to the GFS
ensemble mean.  The new track is not as far west as the latest ECMWF
or the multi-model consensus aids.

Strong westerly vertical wind shear is expected to prevent
significant strengthening for about another 12-24 hours.  After that
time, Philippe is expected to encounter a more favorable upper-level
wind pattern as it moves northward over the Atlantic. This should
allow for steady strengthening, and much of the guidance predicts
that Philippe will become a hurricane in 3 to 4 days.  The NHC
intensity forecast follows suit, and is a blend of the HFIP
corrected consensus model and the multi-model (ICVN) intensity aid.


KEY MESSAGES:

1. Tropical storm conditions are possible across portions of the
northern Leeward Islands through tonight 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.

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


FORECAST POSITIONS AND MAX WINDS

INIT  02/0900Z 17.1N  60.0W   45 KT  50 MPH
 12H  02/1800Z 17.7N  60.7W   45 KT  50 MPH
 24H  03/0600Z 18.6N  61.4W   45 KT  50 MPH
 36H  03/1800Z 19.8N  61.8W   50 KT  60 MPH
 48H  04/0600Z 21.2N  62.2W   50 KT  60 MPH
 60H  04/1800Z 22.7N  62.3W   55 KT  65 MPH
 72H  05/0600Z 24.6N  62.2W   60 KT  70 MPH
 96H  06/0600Z 28.3N  60.8W   70 KT  80 MPH
120H  07/0600Z 31.7N  58.9W   75 KT  85 MPH

$$
Forecaster Brown
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