[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 160239
TCDAT2

Tropical Storm Fiona Discussion Number   7
NWS National Hurricane Center Miami FL       AL072022
1100 PM AST Thu Sep 15 2022

Although Fiona remains a strongly sheared tropical storm, deep
convection has been inching closer to the center of circulation
during the past several hours.  Cloud tops remain quite cold on the
system's east side.  The initial intensity is held at 50 kt based on
the earlier aircraft data.  Another Air Force reconnaissance
aircraft is scheduled to investigate Fiona overnight.

Satellite and aircraft fixes indicate that Fiona has been slowly
losing latitude over the past 24 hours or so, and the initial motion
is estimated to be 265/13 kt.  A low- to mid-level subtropical ridge
to the north of Fiona should steer the system generally westward for
the next few days, taking the storm across the northern Leeward
Islands Friday night and near the Virgin Islands and Puerto Rico on
Saturday through early Sunday.  A turn to the west-northwest and
then the northwest near Hispaniola seems likely late this weekend
and into early next week as the system nears a weakness in the
subtropical ridge. The NHC track forecast has been adjusted
to the left this cycle, based on the initial position and trending
toward the latest model guidance.

Fiona has been quite resilient even though it continues to be
affected by westerly vertical wind shear and intrusions of dry air.
The models suggest that the upper-level wind pattern could become a
little more conducive for strengthening during the next couple of
days, which might allow the storm to become more symmetric and
strengthen slightly.  However, after that time, the intensity of
Fiona will become highly dependent on how much the storm interacts
with Puerto Rico and Hispaniola.  Since there is uncertainty on the
details of the exact track, the NHC intensity forecast during the
days 2-5 time frame is uncertain.  This prediction lies near the
middle of the guidance envelope at most forecast times.


Key Messages:

1. Tropical storm conditions are expected in the Leeward Islands
within the warning area by Friday evening.  Tropical storm
conditions are possible within the watch area across the Virgin
Islands beginning on Saturday, and then reaching Puerto Rico late
Saturday and Saturday night.

2. Heavy rains from Fiona will reach the Leeward Islands Friday
afternoon, spreading to the British and U.S. Virgin Islands and
Puerto Rico Saturday into Sunday morning, and reaching eastern
Hispaniola Sunday.  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 move near Hispaniola early next week, and
watches could be required for parts of the island on Friday.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 16.0N  56.9W   50 KT  60 MPH
 12H  16/1200Z 16.2N  58.9W   50 KT  60 MPH
 24H  17/0000Z 16.5N  61.4W   50 KT  60 MPH
 36H  17/1200Z 16.8N  63.7W   55 KT  65 MPH
 48H  18/0000Z 17.1N  65.5W   55 KT  65 MPH
 60H  18/1200Z 17.3N  67.0W   55 KT  65 MPH
 72H  19/0000Z 17.8N  68.5W   55 KT  65 MPH
 96H  20/0000Z 19.5N  70.4W   55 KT  65 MPH...INLAND
120H  21/0000Z 21.5N  72.0W   60 KT  70 MPH

$$
Forecaster Cangialosi
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