Tropical Storm GASTON Advisory 9月21日

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Tropical Storm Gaston Discussion Number   2
NWS National Hurricane Center Miami FL       AL082022
Issued by the NWS Weather Prediction Center College Park MD
900 PM GMT Tue Sep 20 2022

Satellite images indicate that deep convection is persisting near
and to the north of the center of the cyclone during the past
several hours. Drifting buoy 44857 recently reported a minimum
pressure of 1009 mb near the center of the low, which is a 8 mb
decrease from earlier today. An ASCAT-C pass from several hours ago
showed maximum winds of about 35 kt in the northeast and northwest
quadrants.  Based on that data, the initial intensity is increased
to 35 kt, making the system Tropical Storm Gaston.

Gaston has turned north-northeastward and is moving a little faster
than before.  The initial motion estimate is 020/15 kt.  A turn to
the east is expected in a couple of days when the tropical storm
moves along the northern periphery of a subtropical ridge.  By the
end of the week, however, Gaston is expected to stall to the west of
the Azores in weak steering currents as high pressure builds near
and to the north of the cyclone.  After that time, a turn to the
northwest or north is expected as Gaston moves in the flow between
Hurricane Fiona and the ridge.  The models have trended a little
faster this cycle, and the NHC track forecast has been adjusted
accordingly.

Gaston is currently moving over relatively warm water, in a region
of upper-level diffluence within a somewhat favorable moist
environment. These factors should allow the system to strengthen
slowly during the next day or two.  However, after that time,
much cooler SSTs, drier air, and an increase in westerly shear
should end the strengthening trend.  The system is expected to
become extratropical on Saturday when it moves over SSTs just
above 20C and merges with a mid- to upper-level trough.  The NHC
intensity forecast is about the same as the previous one and near
the middle of the guidance envelope.

Interests in the Azores should monitor the forecast for Gaston.


FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 34.7N  44.4W   35 KT  40 MPH
 12H  21/0600Z 36.5N  43.3W   40 KT  45 MPH
 24H  21/1800Z 38.3N  40.9W   45 KT  50 MPH
 36H  22/0600Z 39.4N  38.0W   50 KT  60 MPH
 48H  22/1800Z 40.1N  35.3W   50 KT  60 MPH
 60H  23/0600Z 40.3N  33.1W   50 KT  60 MPH
 72H  23/1800Z 40.4N  32.5W   50 KT  60 MPH
 96H  24/1800Z 41.0N  32.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  25/1800Z 44.0N  35.3W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Cangialosi/Kebede