Tropical Storm Fiona Forecast Discussion Number 11

By | September 17, 2022

324 
WTNT42 KNHC 170245
TCDAT2

Tropical Storm Fiona Discussion Number  11
NWS National Hurricane Center Miami FL       AL072022
1100 PM AST Fri Sep 16 2022

The center of Fiona moved across the island of Guadeloupe a few
hours ago and it is now over the far northeastern Caribbean Sea.
Deep convection has been increasing near the center, and reports
from the Air Force Hurricane Hunters indicate that Fiona is a
little stronger.  The maximum SFMR winds recorded on the flight so
far were 50 kt and peak flight-level winds measured were 61 kt.
This supports nudging the initial intensity back up to 50 kt.  The
minimum pressure of 1002 mb is based on a surface observation from
Guadeloupe. Tropical-storm-force winds and heavy rains are expected
to continue across the Leeward Islands through Saturday afternoon.

Fiona continues to move just north of due west, or 280 degrees, at
13 kt on the south side of a deep-layer ridge.  A west to
west-northwest motion is expected during the next day or so, and
that should take Fiona near the Virgin Islands and Puerto Rico
during that time.  The cyclone is expected to slow down and make a
turn to the northwest when it is near or over the Dominican Republic
on Monday as it moves toward a weakness in the ridge.  A northward
motion near the southeastern Bahamas is expected during the early
and middle portions of next week.  The models generally show a
similar theme, but there are notable differences in where, when, and
how sharply Fiona makes the northwestward and northward turns.  The
NHC track forecast is essentially the same as the previous one
through 60 h, but a touch to the east of the previous track from
days 3 to 5.  This forecast lies close to the various consensus
aids.

Fiona is still feeling some effects of westerly vertical wind shear
and dry air entrainment, but the models suggest that the storm could
be moving into a region of higher moisture and slightly less shear.
These conditions should support slow strengthening and Fiona could
be near hurricane strength when it approaches the Dominican
Republic.  Some weakening is expected due to the interaction with
the mountainous terrain of Hispaniola, but re-strengthening is
forecast when it moves north of that island.  Fiona is expected to
reorganize over the southwestern Atlantic and become a hurricane in
about 4 days with additional strengthening after that.  The NHC 
intensity forecast is a little higher than the previous one at days 
4 and 5, but still below the IVCN and HCCA models.


Key Messages:

1. Tropical storm conditions will continue to affect portions of the 
Leeward Islands through Saturday morning.  Tropical storm conditions 
will spread westward across the U.S. and British Virgin Islands on 
Saturday and Puerto Rico late Saturday and Saturday night.  Tropical 
storm conditions are possible over Dominica overnight. 

2. Heavy rains from Fiona are beginning in the Leeward Islands, and 
will spread to the British and U.S. Virgin Islands and Puerto
Rico Saturday, reaching the Dominican Republic Sunday, and Haiti
and the Turks and Caicos Monday through Tuesday.  This rainfall
may produce considerable flood impacts including flash and urban
flooding, along with mudslides in areas of higher terrain.

3. Fiona is expected to strengthen gradually over the northeastern
Caribbean Sea, and it could be near hurricane strength as it
approaches the southern or eastern coast of the Dominican Republic
Sunday afternoon.  A Tropical Storm Warning has been issued for 
portions of the island and additional watches or warnings could be 
required on Saturday.

4. Fiona is forecast to strengthen after moving across Hispaniola
early next week, and interests in the Turks and Caicos Islands and
southeastern Bahamas should continue to monitor forecasts for the
storm.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 16.6N  62.2W   50 KT  60 MPH
 12H  17/1200Z 17.0N  63.9W   55 KT  65 MPH
 24H  18/0000Z 17.4N  65.8W   55 KT  65 MPH
 36H  18/1200Z 17.8N  67.4W   55 KT  65 MPH
 48H  19/0000Z 18.4N  68.6W   60 KT  70 MPH...INLAND
 60H  19/1200Z 19.4N  69.6W   55 KT  65 MPH...OVER WATER
 72H  20/0000Z 20.4N  70.5W   60 KT  70 MPH
 96H  21/0000Z 22.3N  71.8W   65 KT  75 MPH
120H  22/0000Z 24.7N  72.0W   75 KT  85 MPH

$$
Forecaster Cangialosi


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