Tropical Storm Gaston Forecast Discussion Number 14

By | September 23, 2022
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Tropical Storm Gaston Discussion Number  14
NWS National Hurricane Center Miami FL       AL082022
900 PM GMT Fri Sep 23 2022

Convection has been sputtering in recent hours in the core of
Gaston.  It appears the effects of strong vertical wind shear, dry
middle-level humidities and cool sea surface temperatures have
weakened the storm.  Satellite Dvorak estimates from both TAFB and
SAB suggest the storm is now 45 kt while and earlier scatterometer
pass showed a decent area of 50-55 kt winds.  The initial intensity
has been lowered to 50 kt to represent a blend of these estimates.

Gaston is moving southward at about 8 kt toward the central
Azores.  A building mid-tropospheric ridge to the north is
expected to turn the storm towards the southwest early tomorrow. 
The ridge will eventually steer Gaston westward in about a day
or so, and this motion is forecast to continue until the end of the
period.  The official forecast track is very similar to the
previous advisory prediction except being slightly farther east in
the first 12 hours due to the present location and motion.

The tropical nature of Gaston seems to be winding down quickly.
Simulated satellite imagery from global models suggests the storm
will become fully post-tropical in about 36 hours.  Statistical
model guidance insists that, despite strong to moderate vertical 
wind shear and dry air, Gaston should only gradually weaken.  The 
NHC intensity forecast reflects this and is close the multi-model
consensus guidance and slightly lower than the previous forecast.
However, it is entirely possible Gaston could weaken more rapidly 
than expected.

Key Messages:

1. Tropical storm conditions are expected over portions of the
western and central Azores.

2. Gaston is expected to produce heavy rainfall over the western
and central Azores Friday into Saturday.  This rainfall may
result in landslides and areas of flooding.


FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 39.6N  28.7W   50 KT  60 MPH
 12H  24/0600Z 38.8N  29.1W   50 KT  60 MPH
 24H  24/1800Z 38.5N  30.8W   50 KT  60 MPH
 36H  25/0600Z 38.7N  33.2W   45 KT  50 MPH...POST-TROPICAL
 48H  25/1800Z 38.9N  35.4W   45 KT  50 MPH...POST-TROPICAL
 60H  26/0600Z 38.9N  37.3W   45 KT  50 MPH...POST-TROPICAL
 72H  26/1800Z 38.9N  39.1W   40 KT  45 MPH...POST-TROPICAL
 96H  27/1800Z 38.5N  43.1W   35 KT  40 MPH...POST-TROPICAL
120H  28/1800Z...DISSIPATED

$$
Forecaster Bucci

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