[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 232055
TCDAT2

Hurricane Fiona Discussion Number  38
NWS National Hurricane Center Miami FL       AL072022
500 PM AST Fri Sep 23 2022

Fiona is beginning to take on the appearance of an extratropical
cyclone.  The cloud pattern is becoming more elongated and
asymmetrical, with cooler-air stratocumulus clouds near the western
semicircle of the cyclone.  The eye became obscured a few hours ago
and, assuming gradual weakening since the last Hurricane Hunter
aircraft mission into the system, the current intensity is set at
110 kt.

Satellite center fixes indicate that Fiona has been moving very
rapidly toward the north-northeast, or about 030/35 kt.  The
numerical guidance is in good agreement that the cyclone will slow
its forward speed during the next few days while it interacts with
a mid- to upper-level trough.  The center of Fiona is expected to
make landfall in Atlantic Canada by Saturday morning, but wind,
rain, and surge impacts will begin well before that time given the
large size of the hurricane. The NHC track forecast is mainly a
blend of the GFS and ECMWF global model solutions, and similar to
the previous official track prediction.

Fiona is expected to slowly weaken during the next few days due to
increasing shear and dry air entrainment.  In 12 hours, the
system should become embedded within a baroclinic zone, and
be transformed into an extratropical cyclone.  This is also
indicated by simulated infrared satellite imagery from the global
models.  However, there is high confidence that Fiona will remain a
powerful cyclone, with hurricane-force winds, when it moves across
Atlantic Canada.  The system should wind down into a gale center by
the time it reaches the southeastern Labrador Sea.  The official
forecast is near the high end of the model guidance.


Key Messages:

1. Fiona is expected to affect portions of Atlantic Canada as a
powerful hurricane-force cyclone tonight and Saturday, and
significant impacts from high winds, storm surge, and heavy rainfall
are expected. Hurricane and Tropical Storm Warnings are in effect
for much of Atlantic Canada.

2. Large swells generated by Fiona are expected to cause
life-threatening surf and rip current conditions along much of the
east coast of the United States, the northwestern Bahamas, Bermuda,
and Atlantic Canada during the next couple of days.


FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 39.6N  61.0W  110 KT 125 MPH
 12H  24/0600Z 44.0N  60.6W   90 KT 105 MPH...POST-TROP/EXTRATROP
 24H  24/1800Z 47.2N  60.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
 36H  25/0600Z 50.0N  59.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  25/1800Z 54.5N  57.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  26/0600Z 58.5N  57.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  26/1800Z 60.0N  57.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  27/1800Z...DISSIPATED

$$
Forecaster Pasch
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