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Tropical Storm Hilda Discussion Number  21
NWS National Hurricane Center Miami FL       EP082021
200 PM PDT Wed Aug 04 2021
 
Convection associated with Hilda continues to weaken and shrink in 
areal coverage due to modest northwesterly vertical wind shear, 
sub-25C sea-surface temperatures (SSTs), and entrainment of stable, 
cold-air stratocumulus clouds. A 1656Z partial ASCAT-A scatterometer 
pass revealed two 33-kt vectors in the southeastern quadrant in the 
radius-of-maximum winds. Even allowing for some undersampling, this 
indicates that Hilda is barely hanging on to tropical storm status, 
and the initial intensity will remain at 35 kt for this advisory. 

Model analyses show virtually no instability in the center of and 
north of Hilda right now, and with the cyclone forecast to move over 
even cooler water and into increasing westerly wind shear during the 
next 12-24 hours, a rapid decrease in both the convection and 
cyclone's intensity appears to be forthcoming soon. Hilda is 
forecast to become a depression later tonight and a remnant low 
on Thursday. Dissipation is expected by late Friday or Saturday 
well to the east of the Hawaiian Islands. The latest NHC official 
intensity forecast is similar to the previous advisory, and follows 
a blend of the HCCA and IVCN consensus intensity models.
 
Hilda continues on a steady west-northwestward course or 295/08 kt. 
This general motion is expected to continue into  Thursday, 
followed by a more westward motion on Friday and Saturday as a low- 
to mid-level ridge builds to north of Hilda on days 2 and 3. The 
official NHC track forecast is essentially just an update of 
the previous advisory track, and lies along the southern edge of 
the guidance envelope between the tightly packed consensus track 
models to the north and the ECMWF model to the south.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/2100Z 19.4N 128.0W   35 KT  40 MPH
 12H  05/0600Z 20.0N 129.4W   30 KT  35 MPH
 24H  05/1800Z 21.0N 131.4W   25 KT  30 MPH
 36H  06/0600Z 21.8N 133.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  06/1800Z 22.4N 136.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  07/0600Z 23.0N 138.4W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  07/1800Z...DISSIPATED
 
$$
Forecaster Stewart
 
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