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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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