Issued at 800 PM PDT Sun Aug 01 2021

WTPZ43 KNHC 020236

Hurricane Hilda Discussion Number 10
NWS National Hurricane Center Miami FL EP082021
800 PM PDT Sun Aug 01 2021

Hilda's satellite appearance is showing effects of easterly vertical
wind shear this evening. Recent imagery shows a sharp edge to the
upper-level outflow on the eastern side of the system. A 2130 UTC
AMSR2 microwave pass reveals that the eyewall is no longer closed,
as the inner core convection has been eroded on the eastern side of
the circulation. Microwave data also indicate the vortex has become
vertically tilted, with the mid-level center displaced about 10-15 n
mi to the west-northwest of the low-level center. Thus, the initial
intensity is lowered slightly to 70 kt for this advisory, in best
agreement with the objective UW-CIMSS Dvorak estimates.

Hilda is still moving west-northwestward at 285/8 kt, to the south
of a ridge over the western U.S. and northern Mexico. A turn to the
northwest is expected on Monday as the ridge weakens, likely in
response to T.D. Ten-E located to the east-northeast of Hilda. A
northwestward motion should continue through midweek before the
ridge becomes reestablished and Hilda turns westward through the
rest of the forecast period. There is greater track uncertainty
later in the week due to possible interaction with another system
that could redevelop from the remnants of T.D. Nine-E. The official
NHC track forecast has been adjusted to the right of the previous
one at 48 h and beyond based on the latest guidance, but it still
lies slightly left of the multi-model consensus aids TVCE and HCCA.

Environmental conditions are not expected to become any more
favorable for strengthening during the next couple days, so Hilda's
intensity has likely peaked. Moderate northeasterly shear is
forecast to persist for the next 36-48 h, and the NHC forecast track
brings Hilda north of the 26 deg C isotherm by the time these
upper-level winds subside. Once over cooler waters, Hilda is
forecast to quickly spin down and weaken to a tropical depression by
96 h. The NHC intensity forecast has again been lowered by 5-10 kt
from the previous one at all forecast times, but it still lies
slightly above the IVCN and HCCA consensus aids through 72 h. The
system is forecast to degenerate to a remnant low by day 5.


INIT 02/0300Z 15.1N 121.6W 70 KT 80 MPH
12H 02/1200Z 15.5N 122.5W 70 KT 80 MPH
24H 03/0000Z 16.2N 123.4W 65 KT 75 MPH
36H 03/1200Z 17.3N 124.3W 60 KT 70 MPH
48H 04/0000Z 18.4N 125.3W 50 KT 60 MPH
60H 04/1200Z 19.5N 126.6W 40 KT 45 MPH
72H 05/0000Z 20.3N 128.3W 35 KT 40 MPH
96H 06/0000Z 21.0N 132.3W 25 KT 30 MPH
120H 07/0000Z 21.5N 136.0W 20 KT 25 MPH...POST-TROP/REMNT LOW

Forecaster Reinhart/Pasch

Source: Hurricane Hilda Forecast Discussion Number 10