[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 291435
TCDAT3

Tropical Storm Philippe Discussion Number   8
NWS National Hurricane Center Miami FL       AL182017
1100 AM EDT Sun Oct 29 2017

Philippe looks the best it ever has, possessing a well-defined
low-level center as seen in high-resolution GOES-16 visible
imagery, along with at least 45-kt sustained winds based on several
recent ship reports. However, the cyclone is sheared with the bulk
of the convective cloud shield having been displaced northeast of
the center due to southwesterly mid-/upper-level winds of 45-75 kt.

Although the exact center of Philippe was difficult to track
overnight, the current position is actually on the previous forecast
track. Philippe has been moving due east at about 25-27 kt for the
past few hours. However, the NHC model guidance is in decent
agreement that the cyclone will turn toward the northeast by this
afternoon ahead of an approaching frontal system and a powerful
deep-layer trough moving quickly eastward across the eastern Gulf of
Mexico and Florida. The cold front is currently located only 90-100
nmi west of Philippe's center, and merger with the front along with
transition to a extratropical low pressure system is expected by 12
hours, if not sooner. As the aforementioned trough becomes more
negatively tilted over the next 24 hours, a strong extratropical low
is forecast to develop near or just east of the North Carolina Outer
Banks, pulling Philippe's circulation north-northeastward to
northward in the 12-24-hour period well offshore of the U.S east
coast. Absorption of Philippe's circulation into the larger
extratropical low is expected to be completed by 24 hours when the
larger low is located over New England. The official forecast track
lies to the right of the previous advisory track, mainly due to the
recent eastward jog, and lies along the eastern edge of the guidance
envelope near a blend of the HCCA and TVCN consensus models.

Some additional slight strengthening is possible during the
next 12 hours or so, mainly due weak baroclinic forcing and the
faster forward speed that is forecast. However, most of the
baroclinic energy associated with the negatively tilted mid-latitude
trough is expected to remain to the west, triggering the development
of the above-mentioned significant extratropical coastal low. In
fact, some of the latent heat from Philippe's circulation will
likely get drawn into the larger extratropical low developing to its
northwest, aiding in that intensification process and increasing the
demise of Philippe after 12 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 27.8N  77.5W   45 KT  50 MPH
 12H  30/0000Z 32.5N  72.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 24H  30/1200Z...ABSORBED BY LARGER EXTRATROPICAL LOW

$$
Forecaster Stewart
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