[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 240254
TCDAT2

Post-Tropical Cyclone Fiona Discussion Number  39
NWS National Hurricane Center Miami FL       AL072022
1100 PM AST Fri Sep 23 2022

Satellite images and observations from an Air Force Hurricane
Hunter aircraft indicate that Fiona is now an intense
extratropical cyclone.  The system's appearance has evolved into
a comma-shaped cloud pattern with a frontal band extending well to
the south and southwest.  Data from the Hurricane Hunters indicate
that the radius of maximum winds is on the order of 100 miles or
more.  Although the minimum central pressure is a very low 933 mb,
the maximum winds have decreased to near 90 kt.

The cyclone has been moving very rapidly northward or around 360/40
kt on the eastern side of a deep-layer trough.  Fiona should slow
its forward speed while it interacts with the trough during the
next couple of days.  The official track forecast has been adjusted
a little to the west of the previous one for the next 12-24 hours,
and is on the western side of the track model suite.  Fiona's
center should move over eastern Nova Scotia shortly, and then
traverse the eastern Gulf of Saint Lawrence, eastern Labrador and
move over the southeastern Labrador Sea.  It should be repeated
that strong winds, heavy rains, and storm surges are occurring well
away from the center.

Gradual weakening is anticipated during the next couple of day, and
Fiona's winds should drop below hurricane strength in 24 hours or
so.  The system should wind down to a marginal gale center after
moving into the southeastern Labrador Sea, and the global models
indicate that the system should dissipate to the west of Greenland
in about 4 days.  The official intensity forecast remains on 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 overnight, 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  24/0300Z 44.5N  60.8W   90 KT 105 MPH...POST-TROPICAL
 12H  24/1200Z 47.5N  60.7W   70 KT  80 MPH...POST-TROP/EXTRATROP
 24H  25/0000Z 51.2N  60.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 36H  25/1200Z 54.6N  58.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  26/0000Z 58.0N  57.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  26/1200Z 60.6N  57.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  27/0000Z 63.0N  57.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  28/0000Z...DISSIPATED

$$
Forecaster Pasch
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