[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 201452
TCDAT2

Hurricane Fiona Discussion Number  25
NWS National Hurricane Center Miami FL       AL072022
1100 AM EDT Tue Sep 20 2022

Fiona has not changed much in organization on satellite images over
the past several hours, with the eye obscured on visible satellite
imagery.  Upper-level outflow is still somewhat restricted over the
western semicircle of the system.  A recent SSMIS microwave image
suggested that the hurricane may be undergoing an eyewall
replacement.  Observations from Air Force and NOAA Hurricane Hunter
aircraft indicate that the central pressure has not changed much
from earlier this morning.  Flight-level and SFMR-observed surface
winds from the aircraft do not support an intensity higher than 100
kt, so the intensity is held at that value for this advisory.  This
is also in agreement with Dvorak satellite estimates from TAFB and
SAB, and recent NOAA Synthetic Aperture Radar data.

Numerical guidance indicates that Fiona will continue to be
influenced by moderate west-southwesterly shear during the next
couple of days.  However the models also indicate that the
thermodynamic environment will be conducive for intensification
over the next 48 hours, as Fiona passes through a moist air mass
and over warm SSTs of 28-29 deg.  The official intensity forecast
continues to call for Fiona becoming a category 4 hurricane, in
agreement with the corrected consensus model guidance, HCCA.
Beyond 72 hours, the hurricane is expected to interact with a
vigorous mid-latitude trough moving into the Atlantic from the
northeastern United States.  This should start the process of
extratropical transition by 96 hours, with the transition complete
by the end of the forecast period.  Fiona is expected to remain a
deep and strong cyclone after extratropical transition.

Fiona continues to move north-northwestward, at about 330/8 kt.
The track guidance has changed very little from the previous
advisory.  Over the next couple of days, the hurricane should
continue to move around the western periphery of a mid-level high
pressure system centered to its east.  in 48-96 hours, Fiona is
expected to move north-northeastward to northeastward with
increasing forward speed along the southeast side of a strong
mid-tropospheric trough.  The official track forecast is similar to
the previous NHC prediction and in close agreement with the HCCA
guidance.


Key Messages:

1.  Heavy rainfall and localized life-threatening flash flooding
should continue over portions of the Dominican Republic today.
Heavy rains should continue to impact the Turks and Caicos through
this afternoon with continued life-threatening flooding. Localized
additional flash and urban flooding is possible in Puerto Rico.

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. Interests in Bermuda should continue to monitor the progress of
Fiona.


FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 22.0N  71.4W  100 KT 115 MPH
 12H  21/0000Z 23.0N  71.7W  105 KT 120 MPH
 24H  21/1200Z 24.4N  71.8W  110 KT 125 MPH
 36H  22/0000Z 26.1N  71.2W  115 KT 130 MPH
 48H  22/1200Z 28.3N  70.2W  120 KT 140 MPH
 60H  23/0000Z 31.1N  68.4W  115 KT 130 MPH
 72H  23/1200Z 34.7N  65.2W  110 KT 125 MPH
 96H  24/1200Z 45.0N  60.0W   85 KT 100 MPH
120H  25/1200Z 52.0N  59.0W   55 KT  65 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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