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Hurricane Hilda Discussion Number   7
NWS National Hurricane Center Miami FL       EP082021
200 AM PDT Sun Aug 01 2021
 
Hilda's strengthening last evening was short lived.  Infrared and 
water vapor imagery show high-level clouds from a weather 
disturbance to the east impinging on the eastern side of Hilda's 
circulation, suggestive of moderate easterly shear.  In fact, 
85-GHz SSMIS data from 0241 UTC shows that the microwave 
presentation has degraded significantly, with most of the deep 
convection displaced to the west of the low-level center.  Hilda's 
initial intensity is being held at 75 kt based on Dvorak CI numbers 
of 4.5 from TAFB and SAB, although that estimate could be generous.

Hilda continues to move west-northwestward, or 285/9 kt, to the 
south of a subtropical ridge which is expected to build westward 
over the Pacific during the next few days.  Despite the placement 
of this ridge, the dynamical models indicate that Hilda is likely 
to have some degree of binary interaction with the disturbance to 
its east and thus take on a northwestward heading on days 2 and 3.  
After the interaction, the ridge should then cause Hilda to turn 
back toward the west-northwest and then west by days 4 and 5.  
While there are some model outliers, the spread among the guidance 
has actually decreased over the past 24 hours.  The updated NHC 
track forecast is not too different from the previous forecast, 
except that it is a little slower to account for recent model 
trends.

The moderate easterly shear affecting Hilda is unlikely to abate 
much during the next couple of days, especially as the distance 
between the hurricane and the disturbance to the east decreases.  
Still, Hilda will remain over relatively warm waters during that 
period, and the models suggest that the hurricane will either 
maintain its current intensity or strengthen slightly through 48 
hours.  Hilda is then expected to move over waters colder than 26 
degrees Celsius, causing a steady weakening trend through the end 
of the forecast period.  The new NHC intensity forecast is a little 
lower than the previous forecast to account for the current 
structure of the cyclone and the latest model solutions, although 
the forecast intensities are not as low as what is shown by the 
HCCA and IVCN consensus aids.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0900Z 14.5N 119.6W   75 KT  85 MPH
 12H  01/1800Z 14.8N 120.8W   80 KT  90 MPH
 24H  02/0600Z 15.3N 122.1W   80 KT  90 MPH
 36H  02/1800Z 15.9N 123.3W   80 KT  90 MPH
 48H  03/0600Z 16.7N 124.3W   75 KT  85 MPH
 60H  03/1800Z 17.6N 125.4W   65 KT  75 MPH
 72H  04/0600Z 18.7N 126.9W   55 KT  65 MPH
 96H  05/0600Z 20.1N 130.9W   45 KT  50 MPH
120H  06/0600Z 20.7N 135.3W   35 KT  40 MPH
 
$$
Forecaster Berg
 
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