[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 250231
TCDAT3

Tropical Storm Gaston Discussion Number  19
NWS National Hurricane Center Miami FL       AL082022
300 AM GMT Sun Sep 25 2022

Gaston has been interacting with an upper-level trough just to its
west for the past several hours, which has helped to regenerate deep
convection over the northern semicircle. This has bought Gaston some
more time as a tropical cyclone. A pair of recent scatterometer
overpasses revealed a swath of 35-42 kt winds over the northern
semicircle of the tropical storm, which indicates that it is
stronger than previously estimated. Assuming some undersampling by
the scatterometer, the initial intensity has been adjusted to 45 kt
to reflect this new data.

The upper trough that is helping to maintain the deep convection is
forecast to lift northward later this morning and be replaced by a
ridge, which should induce strong northwesterly shear over Gaston.
The combination of this shear, relatively cool SSTs of about 24
degrees C, and the presence of dry air should cause Gaston's current
convection to dissipate today, resulting in the system becoming
post-tropical. The NHC intensity forecast was adjusted higher
through 24 h due to the adjusted initial intensity and is unchanged
from the previous forecast after that time.

Gaston continues its westward motion at 10 kt to the south of a
mid-level ridge. By Monday, the cyclone is forecast to turn
west-southwestward and possibly southwestward as the ridge builds
its northwest. The latest NHC track forecast is little changed from
the previous one and closely follows the track consensus guidance.


Key Messages:

1. Tropical storm conditions over the western Azores should diminish
by midday as Gaston moves away from the islands.

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


FORECAST POSITIONS AND MAX WINDS

INIT  25/0300Z 38.6N  33.4W   45 KT  50 MPH
 12H  25/1200Z 38.9N  35.3W   45 KT  50 MPH...POST-TROPICAL
 24H  26/0000Z 38.7N  37.6W   35 KT  40 MPH...POST-TROPICAL
 36H  26/1200Z 38.4N  39.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  27/0000Z 37.9N  41.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  27/1200Z 37.2N  44.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  28/0000Z 36.8N  46.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  29/0000Z...DISSIPATED

$$
Forecaster Latto
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