[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 170859
TCDAT2

Tropical Storm Fiona Discussion Number  12
NWS National Hurricane Center Miami FL       AL072022
500 AM AST Sat Sep 17 2022

While the center of Fiona is moving westward over the northeastern
Caribbean Sea, the strongest winds and heaviest rains associated
with the storm are still displaced to the east of the center by some
westerly shear. Tropical storm conditions are ongoing over portions
of the Leeward Islands. Earlier data from an Air Force Hurricane
Hunter aircraft indicated the minimum pressure had fallen slightly
to 1000 mb, but the aircraft winds on the final passes did not show
signs of additional strengthening. A blend of the latest satellite
intensity estimates and the earlier aircraft data support an initial
intensity of 50 kt for this advisory. NOAA and Air Force Hurricane
Hunter aircraft are scheduled to investigate Fiona this morning.

The center of Fiona was adjusted a bit south of the previous track
based on aircraft and radar data, and the initial motion is westward
at 275/11 kt. A westward to west-northwestward motion is expected
through Sunday, which brings the center of Fiona near or just south
of the Virgin Islands and Puerto Rico and toward the eastern portion
of the Dominican Republic. Although some of the track guidance
shifted a bit right this cycle, the adjusted initial position
resulted in little net change to the NHC track forecast with regard
to Fiona's closest approach to Puerto Rico. However, it is noted
that the latest track forecast is somewhat slower than the previous
one based on the latest guidance trends. After passing near or over
the Dominican Republic, a northwestward and northward turn is
expected next week over the southwestern Atlantic. The forecast
track at days 3-5 was nudged a bit eastward based on the consensus
aids.

Fiona is expected to encounter slightly more favorable environmental
conditions over the next 24-48 h. In particular, the westerly shear
that has plagued Fiona for days is forecast to weaken, which could
allow the cyclone's structure to improve and become more vertically
aligned. The latest intensity guidance is stronger than the previous
cycle, and the NHC forecast has been adjusted upward during the
first 36 h of the period. Fiona could be at or near hurricane force
when it passes near Puerto Rico later this weekend, and a Hurricane
Watch has been issued to account for this potential. If current
trends continue, further increases to the intensity forecast may be
necessary on future cycles. Some brief weakening is possible due to
interaction with the mountainous terrain of Hispaniola, but
re-strengthening seems likely once Fiona moves over the southwestern
Atlantic next week. The NHC intensity forecast has been raised on
days 3-5 in line with the latest consensus aids.


Key Messages:

1. Tropical storm conditions will continue to affect portions of the
Leeward Islands through this morning. Tropical storm conditions
will reach the U.S. and British Virgin Islands this morning and
spread westward across Puerto Rico later today and tonight. Fiona
could be near hurricane strength as it moves near Puerto Rico late
tonight and on Sunday, and a Hurricane Watch has been issued.
Additional watches or warnings could be required later today for
portions of the Dominican Republic.

2. Heavy rains from Fiona will spread west to British and U.S.
Virgin Islands and Puerto Rico today, the Dominican Republic Sunday,
and the Turks and Caicos Monday night. This rainfall is likely to
produce considerable flood impacts including flash and urban
flooding, along with mudslides in areas of higher terrain,
particularly in Puerto Rico.

3. 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  17/0900Z 16.4N  63.3W   50 KT  60 MPH
 12H  17/1800Z 16.7N  64.8W   55 KT  65 MPH
 24H  18/0600Z 17.1N  66.3W   60 KT  70 MPH
 36H  18/1800Z 17.7N  67.7W   60 KT  70 MPH
 48H  19/0600Z 18.6N  68.9W   65 KT  75 MPH...INLAND
 60H  19/1800Z 19.7N  69.9W   65 KT  75 MPH...OVER WATER
 72H  20/0600Z 20.8N  70.6W   65 KT  75 MPH
 96H  21/0600Z 23.0N  71.5W   75 KT  85 MPH
120H  22/0600Z 26.0N  71.5W   80 KT  90 MPH

$$
Forecaster Reinhart
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