Hurricane Hilary triggers California's first tropical storm watch ever, with heavy rain and flash flooding forecast

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Nicholas Grondin, University of Tampa

(THE CONVERSATION) Hurricane Hilary headed for Mexico’s Baja peninsula as a powerful Category 4 storm, and was on track to speed into Southern California at or near tropical storm strength as early as Aug. 20, 2023. The storm is so unusual that for the first time ever, the National Hurricane Center issued a tropical storm watch for both San Diego County and Orange County, as well as Catalina Island.

Hurricane scientist Nick Grondin explains how Hurricane Hilary, with help from El Niño and a heat dome over much of the country, could mean dangerous flash flooding, wind damage and potentially mudslides in the U.S. Southwest.

How rare are tropical storms in the Southwest?

California has only had one confirmed tropical storm landfall. It was in September 1939 and called the Long Beach Tropical Storm. It caused about US$2 million dollars in damage in the Los Angeles area – that would be...