[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 231443
TCDAT2

Hurricane Fiona Discussion Number  37
NWS National Hurricane Center Miami FL       AL072022
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Fri Sep 23 2022

Fiona is pulling away from Bermuda and racing toward Atlantic
Canada.  Although the core of Fiona missed Bermuda, the Bermuda
Weather Service reported that there were wind gusts up to 100 kt on
the island early this morning.  The Air Force Hurricane Hunters have
been investigating the major hurricane and have found that it
remains powerful and very large.  The maximum flight-level wind at
700 mb was 144 kt in the southeast quadrant and the peak SFMR wind
was 109 kt.  Based on these data, the initial intensity is nudged up
to 115 kt, which makes Fiona a very dangerous category 4 hurricane
on the Saffir-Simpson Hurricane Wind Scale.  Satellite images show
that Fiona still has a relatively well-defined eye and deep
convection over the eastern portion of the circulation, but dry air
and westerly vertical wind shear are beginning to affect the system.

Satellite and aircraft fixes indicate that Fiona is moving very
quickly to the northeast at about 30 kt.  The hurricane is expected
to turn slightly to the left and slow down as it interacts and
merges with a nearby mid- to upper-level trough.  The center of
Fiona is expected to make landfall in Atlantic Canada late tonight
or early Saturday, but wind, rain, and surge impacts will begin
well before that time given the large size of the hurricane.  The
models suggest that Fiona will slow down significantly, but
continue a generally northward motion through the weekend and into
early next week.  The NHC track forecast lies close to the middle of
the guidance envelope.

Although Fiona is expected to begin weakening soon given the
increasing shear and dry air entrainment, there is high confidence
that Fiona will be a powerful cyclone when it moves across Atlantic
Canada.  The system is forecast to complete extratropical
transition when it merges with the trough just before or around the
time it makes landfall.  The NHC intensity forecast lies near the
high end of the guidance in the short term, but falls in line with
the IVCN and HCCA models after that.


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. Tropical storm conditions will likely continue for a few
more hours in Bermuda.

3. 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 Bahamas, Bermuda, and Atlantic
Canada during the next couple of days.


FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z 35.9N  64.2W  115 KT 130 MPH
 12H  24/0000Z 40.8N  61.4W  105 KT 120 MPH
 24H  24/1200Z 45.5N  60.6W   85 KT 100 MPH...POST-TROP/EXTRATROP
 36H  25/0000Z 48.4N  59.4W   65 KT  75 MPH...POST-TROP/EXTRATROP
 48H  25/1200Z 51.5N  57.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
 60H  26/0000Z 55.2N  57.1W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  26/1200Z 58.3N  56.9W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  27/1200Z 61.6N  55.7W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  28/1200Z...DISSIPATED

$$
Forecaster Wpc Forecaster
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