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Tropical Storm Hilary Discussion Number 2
NWS National Hurricane Center Miami FL EP092023
400 PM CDT Wed Aug 16 2023
Hilary has not changed much this afternoon. A large burst of
convection, with cloud top temperatures colder than -85 degrees C,
continues to obscure the low-level circulation and some outflow has
developed on the southern semicircle of the storm. Subjective and
objective satellite intensity estimates range from 30 to 43 kt and
the initial intensity is remains at 35 kt.
The storm is moving to the west-northwest at 13 kt. Hilary is
forecast to gradually turn, first to the northwest by day 2 and
then to the north-northwest by day 3 with the same general forward
motion. This is likely driven by a building ridge over the United
States and a trough off the coast of California. The short-term
track prediction has shifted to the right of the previous forecast,
largely due to an adjustment in the rather uncertain initial
position. It is closest to the simple consensus aid, TVCE.
Strengthening is still expected due to the conducive atmospheric
conditions and warm sea surface temperatures. Hilary is forecast to
be in an area of weak vertical wind shear through 72-96 hours and
remain over warm waters through 72 hours. Therefore, steady to
rapid intensification is anticipated and the official forecast
shows Hilary becoming a hurricane in 24 hours. However, the system
is broad and it could take slightly longer to initially consolidate
and strengthen. Beyond day 3, Hilary is forecast to cross over a
gradient of cooling ocean waters which should induce a weakening
trend. The system is still expected to be post-tropical by the end
of the forecast period.
It is important to remind users to not focus on the exact forecast
track and intensity of Hilary, especially in the latter parts of the
forecast period. Due to the nearly parallel angle of approach to
the Baja California peninsula, small changes in the cross track
position may result in large changes to when and where the system
ultimately approaches the coast. Regardless, wind and rainfall
impacts are likely to extend far from the center of Hilary.
KEY MESSAGES:
1. Hilary has the potential to bring impacts to the Baja California
Peninsula and portions of the southwestern United States this
weekend. Although it is too soon to determine the location and
magnitude of rainfall and wind impacts, interests in these areas
should monitor the progress of Hilary and updates to the forecast.
2. Large swells from Hilary will spread northward along the coast
of southwestern Mexico and the Baja California Peninsula during the
next days.
FORECAST POSITIONS AND MAX WINDS
INIT 16/2100Z 13.7N 103.7W 35 KT 40 MPH
12H 17/0600Z 14.5N 105.4W 50 KT 60 MPH
24H 17/1800Z 15.6N 107.6W 65 KT 75 MPH
36H 18/0600Z 16.8N 109.6W 75 KT 85 MPH
48H 18/1800Z 18.2N 111.3W 90 KT 105 MPH
60H 19/0600Z 20.0N 112.8W 105 KT 120 MPH
72H 19/1800Z 22.3N 113.7W 105 KT 120 MPH
96H 20/1800Z 27.8N 115.2W 70 KT 80 MPH
120H 21/1800Z 34.3N 118.3W 40 KT 45 MPH...POST-TROP/INLAND
$$
Forecaster Bucci
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