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Tropical Depression Hilda Discussion Number  25
NWS National Hurricane Center Miami FL       EP082021
200 PM PDT Thu Aug 05 2021
 
Stubborn Hilda refuses to go away. Convection has been pulsing since 
the previous advisory with cloud tops fluctuating between -30C and 
-60C in the northeastern quadrant. However, this convection hasn't 
mixed higher winds downward into the boundary based on a 1634Z 
ASCAT-A scatterometer pass, which showed 30-31-kt wind vectors north 
of the center and outside of the convection.  The initial intensity 
is being maintained at 30 kt for this advisory based on the 
aforementioned ASCAT surface wind data. Gradual weakening should 
occur now that Hilda is firmly located over sub-23 deg C sea-surface 
temperatures and will be moving into a drier and more stable air 
mass. Visible satellite imagery already shows an extensive field of 
cold-air stratocumulus clouds being entrained into much of the 
low-level circulation. Hilda is forecast to degenerate into a 
remnant low tonight or early Friday, and open up into a trough by 
the weekend, well east of the Hawaiian Islands.
 
The initial motion estimate is 300/11 kt. Hilda should continue on 
a west-northwestward trajectory for the next couple of days, being 
steered by a deep-layer subtropical ridge to the north. The latest 
NHC track forecast is essentially just an update of the previous 
advisory track, and lies down the middle of the tightly packed 
consensus models.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/2100Z 21.5N 131.2W   30 KT  35 MPH
 12H  06/0600Z 22.2N 132.8W   25 KT  30 MPH
 24H  06/1800Z 23.0N 135.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  07/0600Z 23.7N 137.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  07/1800Z 24.4N 139.3W   15 KT  15 MPH...POST-TROP/REMNT LOW
 60H  08/0600Z...DISSIPATED
 
$$
Forecaster Stewart
 
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