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Hurricane Hilary Discussion Number  14
NWS National Hurricane Center Miami FL       EP092023
300 PM MDT Sat Aug 19 2023
 
Hilary appears to be weakening quickly.  The eye is filling
and the cloud tops in the eyewall and rainbands have been warming
during the past several hours.  In addition, the hurricane has
become increasingly asymmetric with dry air continuing to wrap into
the western half of the circulation.  The Air Force Hurricane
Hunters have been investigating Hilary during the past few hours and
found that the minimum pressure has risen to 959 mb.  Blending the
aircraft flight-level wind and SFMR data, as well as some of the
satellite estimates yields an initial intensity of 95 kt, but that
could be a little generous.  Areas of heavy rain are already
spreading across portions of the Baja California Peninsula and the
Southwestern U.S.  Hilary is also producing a large area of high
seas along the coast of Baja California and the Gulf of California, 
with maximum significant wave heights estimated to be higher
than 40 ft.
 
The hurricane is still moving north-northwestward, or 345/15 kt. The
steering currents are well established and consist of a strong
mid-level high pressure area over the south-central U.S. and a mid-
to upper-level low off the central California coast.  The flow
between these features should cause Hilary to accelerate to the
north-northwest or north during the next day or two, with the core
of the system reaching the central portion of the Baja California
Peninsula tonight and southern California Sunday afternoon or
evening.  The NHC track forecast is largely the same as the previous
one and near the middle of the guidance envelope. Users are reminded
that the exact details of the track forecast, including where Hilary
might make landfall, are of little overall importance since strong
winds and heavy rainfall will extend far from the center.  These
hazards will also begin well in advance of the arrival of the
center.
 
Hilary is expected to continue weakening rather quickly while it 
moves northward due to significantly cooler waters, drier air, and 
an increase in vertical wind shear.  However, Hilary is still 
expected to be a hurricane when it makes landfall or moves very near 
the central portion of the Baja California Peninsula.  There is high 
confidence that Hilary will move into southern California as a 
tropical storm.
 
 
KEY MESSAGES:
 
1. Preparations for flooding impacts should be completed as soon as
possible, as heavy rainfall will begin well in advance of the
center. In the Southwestern U.S., the potentially historic
amount of rainfall is expected to cause flash, urban, and arroyo
flooding including landslides, mudslides, and debris flows.
Dangerous to locally catastrophic flooding impacts are expected late
tonight through early Monday.
 
2. Hurricane conditions are expected along the west-central coast of
the Baja California Peninsula within the hurricane warning area
tonight and Sunday morning, and are possible in the Hurricane Watch
area on Sunday.
 
3. Tropical storm conditions are expected to begin Sunday in 
portions of the southwestern U.S. within the Tropical Storm
Warning area.  Winds could be particularly strong and gusty in and
near areas of higher terrain.  Gusty winds are expected to spread
well inland across the western U.S.
 
4. Large swells generated by Hilary will affect portions of the
Baja California Peninsula and southern California over the next
couple of days. These swells are likely to cause life-threatening
surf and rip current conditions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/2100Z 23.8N 114.1W   95 KT 110 MPH
 12H  20/0600Z 26.4N 114.8W   80 KT  90 MPH
 24H  20/1800Z 30.8N 116.2W   60 KT  70 MPH
 36H  21/0600Z 36.4N 117.6W   35 KT  40 MPH...POST-TROP/INLAND
 48H  21/1800Z...DISSIPATED
 
$$
Forecaster Cangialosi
 
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