[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 210247
TCDAT2

Hurricane Fiona Discussion Number  27
NWS National Hurricane Center Miami FL       AL072022
1100 PM EDT Tue Sep 20 2022

Data from a NOAA Hurricane Hunter aircraft that has been
investigating Fiona this evening show that the hurricane has
strengthened since this afternoon.  The aircraft has measured peak
700-mb flight-level winds of 120 kt, and SFMR winds of around 110 kt
earlier in the evening. Based on those data, the intensity was
increased to 110 kt on the intermediate advisory at 0000 UTC.  Since
that time, the satellite presentation has continued to improve with
the eye becoming better defined and the surrounding ring of deep
convection expanding with colder cloud top temperatures. The
pressure has fallen a few more millibars and is now down to 947 mb,
however the plane has not found any higher winds during several
passes through the northeastern and northern portion of the eyewall.
It is worth noting that the latest subjective and objective
satellite estimates suggest a stronger intensity, and this may be a
case in which the winds are lagging the improved satellite
presentation, which is not too uncommon.

The vertical wind shear over the hurricane is expected to remain low
to moderate during the next couple of days.  During that time, the
hurricane will be traversing SSTs of 29-30 degrees Celsius, and
remain in a moist environment.  These conditions should allow for
some additional strengthening during the next 12 to 24 hours, but
after that time, difficult-to-predict eyewall replacement cycles are
likely to cause some fluctuations in intensity.  By day 3, the
system is forecast to interact with a vigorous mid-troposphere
trough and the system is expected to become a large and powerful
extratropical cyclone near Atlantic Canada.

The latest satellite and aircraft fixes indicate that the hurricane
is now moving just west of due north or 350/7 kt. Fiona should move
generally northward around the western periphery of a mid-level
ridge during the next 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. Very little cross-track changes were made to the latest
NHC forecast, but it is slightly slower than the previous advisory
to be in better agreement with the bulk of the dynamical models.


Key Messages:

1.  Heavy rains south of Fiona will continue to impact the Turks and
Caicos through tonight 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  21/0300Z 23.2N  71.8W  110 KT 125 MPH
 12H  21/1200Z 24.3N  71.9W  120 KT 140 MPH
 24H  22/0000Z 26.0N  71.5W  120 KT 140 MPH
 36H  22/1200Z 28.1N  70.8W  120 KT 140 MPH
 48H  23/0000Z 30.8N  69.0W  120 KT 140 MPH
 60H  23/1200Z 34.3N  65.6W  115 KT 130 MPH
 72H  24/0000Z 39.5N  61.8W  105 KT 120 MPH
 96H  25/0000Z 48.3N  59.7W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  26/0000Z 55.4N  58.7W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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