[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 202057
TCDAT2

Hurricane Fiona Discussion Number  26
NWS National Hurricane Center Miami FL       AL072022
500 PM EDT Tue Sep 20 2022

Deep convection around Fiona's eye is intense, but is in a rather
asymmetrical pattern at this time.  Upper-tropospheric outflow
remains somewhat restricted over the western semicircle of the
system.  The last Air Force Hurricane Hunter fix in the
center of the hurricane around 17Z showed a slight fall of
central pressure from earlier in the day, but the flight-level and
SFMR-observed surface winds indicated that the maximum winds were
still near 100 kt.  This is also in agreement with the latest
Dvorak satellite estimates from TAFB and SAB.  Another Air Force
Hurricane Hunter mission into Fiona is scheduled for 00Z to see if
Fiona is strengthening again.

Vertical wind shear over Fiona, as diagnosed by the SHIPS model, is
predicted to remain moderate for the next few days.  However, the
hurricane is likely to remain in a moist unstable air mass and over
a warm ocean for the next couple of days which is likely to offset
the influence of shear.  In general, the intensity model guidance
continues to show strengthening for about the next 48 hours, and so
does the official forecast.  Fiona is expected to become a category
4 hurricane in a day or so.  By 96 hours, global model guidance
indicates that the system will be transformed into a vigorous
extratropical cyclone near Atlantic Canada.

The hurricane is still headed toward the north-northwest with an
initial motion estimate of 330/7 kt.  The track forecast scenario
is generally unchanged from the previous advisory.  Fiona should
turn northward while moving along the western side of a mid-level
anticyclone during the next day or so.  In 2-3 days, an intense
mid-tropospheric trough will be moving off the northeast United
States coast.  This feature should cause Fiona to accelerate toward
the north-northeast and northeast during the latter part of the
forecast period.  The official forecast follows about the same
trajectory as the previous one, but is just a tad slower.  This is
in good agreement with both the simple and corrected consensus
predictions.


Key Messages:

1.  Heavy rains around the center of Fiona will continue to impact
the Turks and Caicos through this evening with continued
life-threatening flooding.  Localized additional flash and urban
flooding is possible in Puerto Rico and the Dominican Republic.

2. Hurricane conditions are affecting portions of the Turks and
Caicos islands, while tropical storm conditions should affect
portions of the southeastern Bahamas during the next few hours.

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

4. 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  20/2100Z 22.6N  71.8W  100 KT 115 MPH
 12H  21/0600Z 23.6N  72.0W  110 KT 125 MPH
 24H  21/1800Z 25.0N  71.9W  115 KT 130 MPH
 36H  22/0600Z 26.9N  71.3W  115 KT 130 MPH
 48H  22/1800Z 29.4N  70.1W  120 KT 140 MPH
 60H  23/0600Z 32.4N  67.8W  115 KT 130 MPH
 72H  23/1800Z 36.9N  63.5W  105 KT 120 MPH
 96H  24/1800Z 46.5N  60.0W   85 KT 100 MPH...POST-TROP/EXTRATROP
120H  25/1800Z 55.0N  58.0W   55 KT  65 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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