Tropical Storm FIONA Advisory vie, 23-09

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Hurricane Fiona Discussion Number  36
NWS National Hurricane Center Miami FL       AL072022
500 AM AST Fri Sep 23 2022

Fiona is feeling the first effects of the mid-latitude westerlies,
with the eye becoming less distinct during the past few hours and
the central convection becoming more ragged.  In addition,
satellite imagery shows a cold front approaching the cyclone from
the west.  However, these changes have not yet caused much change
in strength. An earlier Air Force Reserve Hurricane Hunter mission
found the central pressure was 936 mb, and it reported 132-kt
700-mb flight-level winds in the southeastern eyewall.  The maximum
surface wind estimates from the SFMR were under 100 kt, so the
initial intensity of 110 kt is a compromise between the SFMR winds
and the higher intensity suggested by the flight-level wind.

Fiona is accelerating to the north-northeast with the initial
motion now 030/22 kt.  Interaction with the strong deep-layer
trough moving eastward into the northwestern Atlantic should cause
the hurricane to speed up further during the next day or so,
reaching peak speeds of 30-35 kt as it approaches Nova Scotia.
As stated in the previous advisory, Fiona should merge with the
trough soon after 24 hours, slow down a bit, but continue moving
northward across Atlantic Canada to the Labrador Sea during the
balance of the forecast period.  There are no significant changes
to the track guidance for this advisory, and the new track forecast
is an update of the previous forecast.

Fiona should start to undergo extratropical transition during the
next 12 h, with the transition likely to be complete just after the
24 h point.  While the cyclone will weaken some during the
transition, it is expected to remain a powerful hurricane-force
cyclone as it crosses Nova Scotia into the Gulf of St. Lawrence.
Continued weakening is expected after that, and winds could drop
below gale force by day 5 when the post-tropical low is over the
Labrador Sea. The new intensity forecast had some minor adjustments
from the previous forecast and it follows the overall trend of the
intensity guidance, including the global models.


Key Messages:

1. Hurricane conditions are expected on Bermuda overnight.
Conditions should diminish below tropical storm force during the
day on Friday.

2. Fiona is expected to affect portions of Atlantic Canada as a
powerful hurricane-force cyclone late Friday and Saturday, and
significant impacts from high winds, storm surge, and heavy rainfall
are likely. Hurricane and Tropical Storm Warnings have now been
issued for much of Atlantic Canada.

3. 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 Bahamas, Bermuda, and Atlantic
Canada during the next few days.


FORECAST POSITIONS AND MAX WINDS

INIT  23/0900Z 33.8N  66.8W  110 KT 125 MPH
 12H  23/1800Z 37.9N  63.9W  110 KT 125 MPH
 24H  24/0600Z 43.2N  62.0W  100 KT 115 MPH
 36H  24/1800Z 47.0N  61.1W   75 KT  85 MPH...POST-TROP/EXTRATROP
 48H  25/0600Z 50.1N  59.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 60H  25/1800Z 53.8N  58.4W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  26/0600Z 57.5N  58.3W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  27/0600Z 62.5N  57.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  28/0600Z 65.0N  57.0W   30 KT  35 MPH...POST-TROP/EXTRATROP

$$
Forecaster Beven