[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 051454
TCDAT2

Tropical Storm Philippe Discussion Number  49
NWS National Hurricane Center Miami FL       AL172023
1100 AM AST Thu Oct 05 2023

Philippe's low-level circulation remains broad this morning with
most of the associated deep convection located within the eastern
semicircle.  Despite the continued disorganized structure, an Air
Force Reserve Hurricane Hunter mission this morning measured peak
850-mb flight-level winds of 56 kt and SFMR surface winds of 40-45
kt.  Based on these data, Philippe's initial intensity is raised to
45 kt.

The latest fixes suggest that Philippe is moving just west of due
north (355 degrees) at 10 kt.  This northward motion, with an
increase in forward speed, is expected to continue through Saturday
while Philippe moves over the western Atlantic between a deep-layer
trough east of Florida and a mid-level high over the central
Atlantic.  A north-northwestward turn is likely to occur as the
cyclone is approaching Atlantic Canada or eastern New England, due
to a larger trough approaching from the west.  Since Philippe may
interact with a baroclinic zone and a developing non-tropical low
to its west in another day or two, the nuances of the track
forecast still need to be worked out, but nearly all of the track
guidance agrees on the forecast scenario described above.  The NHC
forecast is close to the HCCA consensus aid and brings the center
to the coast of Nova Scotia, New Brunswick, or eastern Maine
between 60 and 72 hours.  The center should then be absorbed by a
broad area of low pressure to its west over Quebec some time on
Sunday.

Little change in intensity is expected during the next day or two,
particularly since model guidance suggests that the shear over
Philippe could strengthen further.  Despite the shear, some
additional strengthening is possible in about 48 hours when
Philippe could receive an injection of baroclinic energy from the
trough located east of Florida.  That process should also
kick-start extratropical transition, and the NHC forecast shows the
transition complete by 60 hours (late Saturday) when Philippe is
located offshore of Nova Scotia.  Weakening is forecast once
Philippe moves inland, and it's likely that the strongest winds from
the system will continue to occur on the eastern side of the
circulation, primarily over parts of Atlantic Canada.


KEY MESSAGES:

1. Tropical storm conditions are expected on Bermuda beginning
early Friday morning, and a Tropical Storm Warning remains in
effect.  Heavy rainfall will also begin to affect the island today,
which could produce flash-flooding.

2. Philippe is expected to move over portions of Atlantic Canada and
eastern New England as a post-tropical cyclone this weekend.
Regardless of Philippe's intensity or structure, interests in those
areas should be prepared for the possibility of strong winds and
heavy rainfall and monitor statements from their local weather
office.


FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 25.6N  66.3W   45 KT  50 MPH
 12H  06/0000Z 27.7N  66.4W   45 KT  50 MPH
 24H  06/1200Z 30.9N  66.3W   45 KT  50 MPH
 36H  07/0000Z 34.2N  66.6W   50 KT  60 MPH
 48H  07/1200Z 37.6N  66.6W   50 KT  60 MPH
 60H  08/0000Z 41.8N  66.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  08/1200Z 47.4N  68.0W   40 KT  45 MPH...POST-TROP/INLAND
 96H  09/1200Z...DISSIPATED

$$
Forecaster Berg
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