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Tropical Storm Gaston Discussion Number  22
NWS National Hurricane Center Miami FL       AL082022
900 PM GMT Sun Sep 25 2022
 
Gaston this evening consists of a well-defined, low-level swirl
absent of any deep convection. All of the earlier activity
dissipated shortly after 1200 UTC and if deep, organized convection
does not quickly return near the center, Gaston could soon become
post-tropical. Both subjective and objective Dvorak estimates have
been decreasing, though there were enough derived motion winds
between 925-850 mb (around 50 kt) to lower the intensity down to
just 40 kt for this advisory.
 
Gaston has continued to turn leftward, with the latest estimated
motion now south of due west at 260/9 kt. A deep-layer
southwest-to-northeast oriented ridge is becoming established
northwest of Gaston, which should maintain the system on a
west-southwest heading for the next several days until the
closed-circulation opens up into a trough. The guidance took another
southward shift this cycle, and the NHC track forecast follows the
guidance in bending the track a bit more southward, following the
reliable consensus aids.
 
Gaston has lost its earlier baroclinic support that maintained
instability aiding last night's convective resurgence. The global
and regional hurricane models are in good agreement that Gaston will
fail to produce any additional convective bursts in an environment
of strong northerly vertical wind shear, 24-25 C SSTs, and
significant synoptic forcing for descent on the upwind side of a
upper-level trough. Gaston is now forecast to become a post-tropical
cyclone in 12 hours, but this could occur as quickly as tonight if
convection does not return soon. The post-tropical low should
gradually fill thereafter, opening up into a trough by 60 hours.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/2100Z 39.1N  37.5W   40 KT  45 MPH
 12H  26/0600Z 38.6N  39.0W   35 KT  40 MPH...POST-TROPICAL
 24H  26/1800Z 38.0N  40.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  27/0600Z 37.4N  43.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  27/1800Z 36.9N  46.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  28/0600Z...DISSIPATED
 
$$
Forecaster Papin
 
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