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Post-Tropical Cyclone Hilary Discussion Number  20
NWS National Hurricane Center Miami FL       EP092023
200 AM PDT Mon Aug 21 2023
 
The circulation of Hilary has become quite diffuse tonight, making 
it difficult to track a coherent low-level center over the complex 
topography of southern California and Nevada. Satellite imagery 
indicates the storm has lost all tropical characteristics, as strong 
upper-level southerly winds have stripped away most of the 
associated shower activity well to the north. Hilary no longer 
satisfies the criteria of a tropical cyclone, and thus it has become 
post-tropical. Based on recent surface observations, the estimated 
maximum sustained winds are reduced to 30 kt for this advisory.
 
Despite its post-tropical classification, the system is still 
expected to produce heavy rainfall, significant flooding, and gusty 
winds as it races northward across the western United States today. 
Users should refer to products issued by their local National 
Weather Service office for more specific information on these 
threats. The circulation of post-tropical Hilary has been 
significantly disrupted by land interaction, and the system is 
likely to dissipate later today.
 
This is the last tropical cyclone discussion issued by the National
Hurricane Center on post-tropical Hilary. Future information on this
system can be found in discussions issued by the Weather Prediction
Center beginning at 800 AM PDT, under AWIPS header TCDEP4, WMO
header WTPZ44 KWNH, and on the web at www.hurricanes.gov.
 
 
KEY MESSAGES:
 
1. Across the Southwestern United States, the ongoing and historic
amount of rainfall is expected to cause life-threatening to locally
catastrophic flash, urban, and arroyo flooding including landslides,
mudslides, and debris flows today. Localized flooding impacts, some
significant, are also expected across northern portions of the
Intermountain West into Tuesday morning.
 
2. Strong and gusty winds are expected to persist across portions
of the western United States today, particularly in and near areas
of higher terrain.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0900Z 38.3N 117.9W   30 KT  35 MPH...POST-TROPICAL/INLAND
 12H  21/1800Z 42.0N 117.4W   25 KT  30 MPH...POST-TROP/INLAND
 24H  22/0600Z...DISSIPATED
 
$$
Forecaster Reinhart
 
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