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Tropical Storm Hilda Discussion Number   3
NWS National Hurricane Center Miami FL       EP082021
200 AM PDT Sat Jul 31 2021
 
A prominent convective band now wraps about halfway around the 
southeast to west side of Hilda's center, and another band is 
taking shape to the north of the center.  With the improved 
organization, Dvorak estimates increased to a consensus T3.0/45 kt 
from TAFB and SAB, and a 0520 UTC ASCAT-B pass confirmed that indeed 
maximum winds are about 45 kt.  This is being set as Hilda's 
initial intensity, although it could be a little conservative since 
objective ADT estimates have trended higher than that since 0600 
UTC.

A mid-tropospheric ridge currently extends from northern Mexico 
westward across the Baja California peninsula to about 120W and is 
steering Hilda west-northwestward at 290/12 kt.  Although this 
ridge is expected to build westward and keep Hilda on a 
west-northwestward course, potential interactions with Tropical 
Depression Nine-E to the west and another low pressure area to the 
east could cause the storm to slow down over the next 3 days and 
oscillate a bit around that general heading.  There is slightly more 
spread among the track models than is typical, with the HWRF a 
notable southern outlier and the GFS and HMON models having some of 
the faster solutions due to greater interaction with T.D. Nine-E.  
That being said, the overall track guidance has trended a little 
slower and farther south on this cycle, and the updated NHC track 
forecast has therefore been adjusted in that direction from the 
previous forecast, lying close to the TVCE multi-model consensus but 
not nearly as far south as the HCCA consensus aid.

Hilda is currently in a light-shear regime and over sea surface 
temperatures of about 29 degrees Celsius, so continued 
strengthening is anticipated in the short term with Hilda likely 
to reach hurricane strength by tonight or early Sunday.  However, 
global models are suggesting that the shear may increase out of the 
east during the next 24 hours, and then Hilda will be near cooler 
waters in 2 to 3 days.  Therefore, Hilda is likely to reach its 
peak intensity in about 48 hours, and the NHC intensity forecast at 
that time is near the upper end of the guidance suite.  Hilda is 
expected to move over even cooler waters after 48 hours, which 
should cause a gradual weakening trend through the end of the 
forecast period.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0900Z 13.3N 115.7W   45 KT  50 MPH
 12H  31/1800Z 13.6N 117.3W   55 KT  65 MPH
 24H  01/0600Z 14.1N 119.1W   65 KT  75 MPH
 36H  01/1800Z 14.6N 120.8W   70 KT  80 MPH
 48H  02/0600Z 15.1N 122.3W   75 KT  85 MPH
 60H  02/1800Z 15.7N 123.7W   70 KT  80 MPH
 72H  03/0600Z 16.3N 124.8W   65 KT  75 MPH
 96H  04/0600Z 17.8N 127.6W   55 KT  65 MPH
120H  05/0600Z 18.9N 131.5W   45 KT  50 MPH
 
$$
Forecaster Berg
 
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