[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 211009
TCDAT2

Hurricane Fiona Discussion Number  28
NWS National Hurricane Center Miami FL       AL072022
500 AM EDT Wed Sep 21 2022

An Air Force Reserve Hurricane Hunter aircraft has recently
reported 700-mb flight-level winds of 128 kt, and reliable surface
winds estimates from the SFMR of 115 kt.  The central pressure
inside the 25 n mi wide eye has fallen to 939 mb.  Based on these
data, the initial intensity is set at 115 kt, making Fiona a
category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.

There is little change to the intensity forecast philosophy since
the last advisory. The vertical wind shear over Fiona is expected
to remain low to moderate during the next couple of days.  During
that time, the hurricane will be traversing warm sea surface
temperatures and remain in a moist environment.  These conditions
should allow for some additional strengthening during the next 12
to 24 hours, and the new intensity forecast calls for a peak
intensity of 120 kt during that time.  After that time, difficult-
to-predict eyewall replacement cycles are likely to cause some
fluctuations in intensity.  Starting near 72 h, Fiona is expected to
interact with a vigorous mid-latitude trough, which should lead to
transition into an intense extratropical low between 72-96 h.
After 96 h, the system is expected to weaken.

The initial motion is now 360/7.  Fiona should move generally
northward around the western periphery of a mid-level ridge during
the next 12-24 hours.  After that time, the hurricane is forecast
to turn north-northeastward and begin to gradually accelerate as
the aforementioned trough approaches from the northwest.  There
were no no significant changes to the guidance from the last
advisory, and the new forecast track is an update of the previous
track.


Key Messages:

1.  Heavy rains south of Fiona will continue to impact the Turks and
Caicos through this morning with additional flooding possible.

2. Tropical storm conditions are possible on Bermuda by late
Thursday.

3. Fiona is expected to affect portions of Atlantic Canada as a
powerful hurricane-force cyclone late Friday and Saturday, and could
produce significant impacts from high winds, storm surge, and heavy
rainfall. Interests in these areas should closely monitor the
progress of Fiona and updates to the forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0900Z 23.9N  71.8W  115 KT 130 MPH
 12H  21/1800Z 25.0N  71.7W  120 KT 140 MPH
 24H  22/0600Z 26.9N  71.1W  120 KT 140 MPH
 36H  22/1800Z 29.3N  69.8W  120 KT 140 MPH
 48H  23/0600Z 32.3N  67.4W  120 KT 140 MPH
 60H  23/1800Z 36.5N  63.3W  115 KT 130 MPH
 72H  24/0600Z 42.0N  60.9W  105 KT 120 MPH
 96H  25/0600Z 50.0N  60.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  26/0600Z 56.0N  59.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Beven
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