CW3E Event Summary: Hurricane Hilary 20-21 August 2023

August 24, 2023

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Hurricane Hilary Brings Heavy Rain, Flooding and High Winds to Southern California

• Hilary made landfall as a Category 1 hurricane in Baja California and weakened into a tropical storm before crossing into California
• The cyclone produced heavy rain and high winds across Southern and Central California on 20 and 21 August
• Much of Southern California and Southwestern Nevada received > 2 inches of precipitation with stations in the Transverse Range measuring > 10 inches
• Several stations set new daily precipitation records for the month of August while Death Valley set its all-time single day precipitation total at 2.20 inches
• Precipitable water observed during this event in San Diego was 2.38 inches, tying for the second highest recorded value per Storm Prediction Center records
• Many streamflow stations throughout Central and Southern California saw streamflows > 90th percentile of climatology because of the record-breaking rainfalls
• Heavy rainfall resulted in widespread flash flooding and debris flows that damaged roadways
• High winds caused trees to fall and resulted in power outages for more than 50,000 people across Central and Southern California
• Per the National Oceanic and Atmospheric Administration Hilary was the first tropical storm to pass over California since Nora in 1997

Summary provided by M. Steen, C. Castellano, S. Roj, P. Iñiguez, J. Cordeira, and J. Kalansky; 24 August 2023

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