[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 032042
TCDAT2

Tropical Storm Philippe Discussion Number  42
NWS National Hurricane Center Miami FL       AL172023
500 PM AST Tue Oct 03 2023

Philippe has continued to lose organization for much of the day.
Satellite images and aircraft fixes from this morning indicate that
the circulation has become elongated, and the remaining deep
convection has relatively little, if any, organization relative to
the center, which is now located just north of the Virgin Islands.
The initial intensity remains 40 kt based on the earlier SFMR data,
but this could be generous given the overall loss of convective
organization.

The current motion is northwestward, or 310/10 kt.  Over the next
couple of days, Philippe is expected to turn northward between a
strong mid-level high over the subtropical Atlantic and a developing
cut-off low east of Florida, with its forward speed increasing in
2-3 days when it becomes positioned between these two features.  The
northward motion is expected to continue through the end of the
forecast period as another deep-layer trough moves eastward across
eastern North America.  The most notable change in this NHC forecast
is that the guidance has again shifted westward, both due to an
adjustment caused by Philippe's recent motion and a general westward
trend in the track guidance.   The official forecast is close to the
TVCA consensus aid, but it's not as far to the west as the latest
ECMWF and HCCA solutions.  The risk continues to increase for some
form of Philippe, likely as a post-tropical cyclone, to reach
Atlantic Canada or eastern New England in about 5 days.

The deep-layer trough located near the east coast of the United
States is likely to keep moderate-to-strong westerly or
southwesterly shear over Philippe for much of the forecast period.
As a result, little change in strength is forecast during the next
2-3 days.  The GFS and ECMWF are now in good agreement that a
separate baroclinic/non-tropical low will develop just to the west
of Philippe in about 3 days.  These two systems are likely to
interact, with Philippe becoming attached to the warm front, and
therefore becoming extratropical, by day 4.  It's possible that
Philippe could strengthen slightly due to this baroclinic
interaction, and that scenario is shown in the official forecast.


KEY MESSAGES:

1. Heavy rainfall from Philippe is expected to produce scattered
flash flooding across portions of the northern Leeward Islands and
the British Virgin Islands into early Wednesday.

2. Gusty winds are likely to continue across portions of the
northern Leeward Islands and the Virgin Islands through Wednesday.

3. The risk is increasing for tropical storm conditions to occur on
Bermuda later this week.  Interests on Bermuda should monitor the
progress of Philippe.


FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 19.6N  64.9W   40 KT  45 MPH
 12H  04/0600Z 20.4N  65.4W   40 KT  45 MPH
 24H  04/1800Z 22.0N  66.1W   40 KT  45 MPH
 36H  05/0600Z 23.8N  66.6W   40 KT  45 MPH
 48H  05/1800Z 26.2N  66.6W   40 KT  45 MPH
 60H  06/0600Z 29.2N  66.0W   45 KT  50 MPH
 72H  06/1800Z 32.2N  65.7W   45 KT  50 MPH
 96H  07/1800Z 38.1N  66.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  08/1800Z 45.8N  66.9W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg
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