ATL: PHILIPPE - Advisories

[cycloneye]

BULLETIN
Tropical Storm Philippe Intermediate Advisory Number 50A
NWS National Hurricane Center Miami FL AL172023
800 PM AST Thu Oct 05 2023

...RAINBANDS MOVING ACROSS BERMUDA...
...TROPICAL STORM FORCE WINDS EXPECTED TO BEGIN EARLY FRIDAY
MORNING...


SUMMARY OF 800 PM AST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...27.5N 66.0W
ABOUT 340 MI...545 KM SSW OF BERMUDA
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES

[cycloneye]

Tropical Storm Philippe Discussion Number 51
NWS National Hurricane Center Miami FL AL172023
1100 PM AST Thu Oct 05 2023

Satellite imagery of Philippe shows little change in structure with
the center still exposed to the west of a growing area of deep
convection. Radar data from Bermuda indicate outer rain bands from
the system are moving across Bermuda. However, the winds so far are
below tropical storm force. The initial wind speed remains 45 kt,
which is near the high end of the latest satellite intensity
estimates.

Philippe is moving northward at 14 kt. The storm is currently
moving between an upper-level cutoff low off the Florida coast, and
a ridge over the central Atlantic. This flow is expected to
accelerate Philippe further northward during the next few days. The
center of Philippe is expected to pass by Bermuda on Friday, and
reach the coast of Maine and Atlantic Canada Saturday night or
early Sunday. This forecast track has been shifted slightly to the
left of the previous advisory, closer to the HCCA and ECMWF models.

Philippe is behaving like a hybrid system. Even though the cyclone
is facing strong wind shear and lower SSTs during the next couple
of days, Philippe may pull most of its energy from an upper-level
cutoff low just to its west. Due to these conditions, some
intensification is predicted during the next day or so. Weakening
is expected as Philippe moves inland over New England and Atlantic
Canada this weekend. The official NHC intensity forecast is near
the middle of the guidance envelope.

Based on the forecast for Philippe to become post-tropical by
Saturday, and after coordination with National Weather Service
offices in New England and the Canadian Hurricane Centre, the
current plan is for hazards in New England and Atlantic Canada to
be handled via local non-tropical statements and not issue tropical
watches or warnings. We will continually assess this plan if the
forecast evolves and tropical watches or warnings become warranted.


KEY MESSAGES:

1. Tropical storm conditions are expected on Bermuda beginning
early Friday morning, and a Tropical Storm Warning remains in
effect. Heavy rainfall is expected to affect the island into
early Friday. This could produce flash flooding.

2. Philippe is expected to move over portions of Atlantic Canada and
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. The
rainfall could produce isolated to scattered instances of urban and
flash flooding.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 28.2N 66.0W 45 KT 50 MPH
12H 06/1200Z 30.5N 65.8W 45 KT 50 MPH
24H 07/0000Z 33.6N 65.9W 50 KT 60 MPH
36H 07/1200Z 36.7N 66.5W 50 KT 60 MPH
48H 08/0000Z 40.5N 66.9W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 08/1200Z 45.7N 69.2W 45 KT 50 MPH...POST-TROP/INLAND
72H 09/0000Z 49.5N 73.0W 35 KT 40 MPH...POST-TROP/INLAND
96H 10/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Tropical Storm Philippe Discussion Number 52
NWS National Hurricane Center Miami FL AL172023
500 AM AST Fri Oct 06 2023

Philippe's structure this morning is consistent of a cyclone in the
initial stages of extratropical transition. While the low-level
circulation center appears better defined than yesterday at this
time, most of the deep convection remains displaced well east of the
center, a result likely caused by nearly 30 kt of SSW vertical wind
shear. There is another cloud band of linear convection to the
northwest of the center, but this appears more related to synoptic
forcing caused by an upper-level cutoff low triggering non-tropical
surface cyclogenesis west of Philippe. The interaction of this low
with Philippe will likely dictate how quickly its completion of
extratropical transition is. The initial intensity this advisory
remains at 45 kt, which remains on the high end of the satellite
estimates.

Philippe appears to be taking a jog to the north-northeast this
morning with some acceleration, estimated at 15/16 kt. The storm is
caught in the flow between the aforementioned cutoff low to its
west, and a amplified mid-level ridge to its east. An additional
complication is the non-tropical surface cyclone forming to the west
of Philippe that may also interact with it over the next day or so.
The end result of this interaction is that there might be a
short-term north-northeastward deviation in Philippe's motion, but
then pivots back north-northwest as the two systems undergo some
binary interaction with each other. The track guidance this cycle
shows this short-term deviation, but end up roughly along the
previous forecast track after 24 hours. The NHC track forecast is
thus only shifted some early on, showing a bit more of short-term
eastward bend before Philippe resumes a northward and then
north-northwestward track, close to the simple and corrected
consensus aids.

While environmental conditions are becoming increasingly hostile for
intensification as a tropical cyclone, Philippe's winds may still
increase slightly over the next 24-36 h as it gets some baroclinic
enhancement from the aforementioned upper-level trough interaction
with the system. This trough interaction is also likely responsible
for initiating its extratropical transition, and the latest forecast
now shows Philippe completing this process and becoming a
post-tropical cyclone in 36 h. Given the current structure, this
could occur sooner after passing by north of Bermuda. Another even
more amplified trough should fully capture this post-tropical
cyclone, and weakening is expected after Philippe moves inland over
New England and Atlantic Canada on Sunday. Whats left of Philippe
will be absorbed by a much larger mid-latitude cyclone that is
expected to occlude over Quebec. The official NHC intensity
continues to lie near the middle of the guidance envelope.

Based on the forecast for Philippe to become post-tropical
on Saturday, and after coordination with National Weather Service
offices in New England and the Canadian Hurricane Centre, the
current plan is for hazards in New England and Atlantic Canada to
be handled via local non-tropical statements and not issue tropical
watches or warnings. We will continually assess this plan if the
forecast evolves and tropical watches or warnings become warranted.


KEY MESSAGES:

1. Tropical storm conditions are beginning on Bermuda and expected
to continue today, where a Tropical Storm Warning remains in
effect. Heavy rainfall is expected to affect the island into early
Friday. This could produce flash flooding.

2. Philippe is expected to move over portions of Atlantic Canada and
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. The
rainfall may produce isolated to scattered instances of urban and
flash flooding.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0900Z 29.5N 65.3W 45 KT 50 MPH
12H 06/1800Z 31.9N 64.9W 45 KT 50 MPH
24H 07/0600Z 35.0N 65.6W 50 KT 60 MPH
36H 07/1800Z 38.1N 66.4W 50 KT 60 MPH...POST-TROP/EXTRATROP
48H 08/0600Z 42.3N 67.3W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 08/1800Z 48.1N 71.6W 35 KT 40 MPH...POST-TROP/INLAND
72H 09/0600Z...ABSORBED BY LARGER EXTRATROPICAL CYCLONE

$$
Forecaster Papin

[cycloneye]

BULLETIN
Tropical Storm Philippe Intermediate Advisory Number 52A
NWS National Hurricane Center Miami FL AL172023
800 AM AST Fri Oct 06 2023

...PHILIPPE BEGINNING EXTRATROPICAL TRANSITION...
...TROPICAL STORM CONDITIONS CONTINUE ON BERMUDA...


SUMMARY OF 800 AM AST...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...29.9N 64.9W
ABOUT 165 MI...265 KM S OF BERMUDA
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NNE OR 20 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES

[cycloneye]

Post-Tropical Cyclone Philippe Discussion Number 53
NWS National Hurricane Center Miami FL AL172023
1100 AM AST Fri Oct 06 2023

The center we were following overnight has become untrackable this
morning and appears to have become absorbed by the nearby frontal
zone. In addition, the overall cloud pattern now has the look of a
classic extratropical cyclone, with Philippe's center resembling
the triple point of an occlusion. Based on these recent
developments, Philippe is being declared a post-tropical cyclone.
The intensity remains 45 kt, mainly based on continuity.

The initial motion is estimated to be north-northeastward, or
020/14 kt, but this movement is becoming less representative as the
larger storm system takes over. Philippe's remnant center and
another non-tropical low to the west are likely to interact and/or
merge with each other during the next day or two, but the overall
system is expected to move northward or north-northwestward at
increasing forward speed into the weekend. This will bring the
center of the post-tropical cyclone to the coast of Nova Scotia or
Maine in about 48 hours, and then inland toward eastern Quebec
before it becomes absorbed by a separate but larger extratropical
low.

The post-tropical cyclone still has an opportunity to strengthen a
bit over the next day or so due to baroclinic influences. Due to
the system's structure and forward motion, the strongest winds are
expected to be on the eastern side of the circulation and will
most likely affect portions of Atlantic Canada. Weakening is
forecast after the system moves inland.

Future information on potential flooding impacts in the Northeast
United States can be found in products issued by the Weather
Prediction Center on the web at http://www.wpc.ncep.noaa.gov, and
in products issued by local National Weather Service Forecast
Offices on the web at http://weather.gov.

Additional information on marine impacts can be found in High Seas
Forecasts issued by the National Weather Service, under AWIPS
header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php.


KEY MESSAGES:

1. The post-tropical cyclone is expected to move over portions of
Atlantic Canada and New England this weekend. Interests in those
areas should be prepared for the possibility of strong winds and
heavy rainfall and monitor statements from their local weather
office. The rainfall may produce isolated to scattered instances of
urban and flash flooding.


FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 30.7N 64.6W 45 KT 50 MPH...POST-TROP/EXTRATROP
12H 07/0000Z 33.1N 64.9W 45 KT 50 MPH...POST-TROP/EXTRATROP
24H 07/1200Z 36.3N 66.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
36H 08/0000Z 40.0N 66.3W 50 KT 60 MPH...POST-TROP/EXTRATROP
48H 08/1200Z 44.9N 67.5W 45 KT 50 MPH...POST-TROP/INLAND
60H 09/0000Z 49.1N 70.9W 35 KT 40 MPH...POST-TROP/INLAND
72H 09/1200Z...DISSIPATED

$$
Forecaster Berg