A strong upper-level low pressure system dug south along the West Coast, moving inland directly over southern California. A vorticity maximum rotating around the low, along with the setup of a California Bight Coastal Convergence Zone (between drainage winds off the land and onshore flow from the low) created the perfect conditions for showers, thunderstorms and funnel clouds.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SGX wrote it up.
A strong upper-level low pressure system dug south along the West Coast, moving inland directly over southern California. A vorticity maximum rotating around the low, along with the setup of a California Bight Coastal Convergence Zone (between drainage winds off the land and onshore flow from the low) created the perfect conditions for showers, thunderstorms and funnel clouds. The cold air instability and warm waters resulted in waterspouts and ocean-effect instability showers over the coastal waters and locally onshore during the morning hours. Showers and thunderstorms formed inland from afternoon heating as the low moved onshore, resulting in urban flooding in areas of the Inland Empire. The heaviest amounts ranged from three quarters of an inch to one inch, with other nearby areas receiving one-tenth of an inch to a half of an inch. Impacts included numerous street closures and 10 homes with either external or internal water damage in the Riverside, Colton and Fontana areas. Highway 52 at Interstate 15 in San Diego County was also closed for an hour due to flooding and multiple accidents.|Cold-air instability continued on the 12th, producing several more waterspouts off the Orange County coast.
The national radar mosaic for the moment the first event began.
4 flood, 1 heavy rain. Local standard time, as filed.
A warehouse roof collapsed on the 11000 block of Mulberry Avenue in Fontana due to accumulation of over 1 foot of water. Drains were plugged allowing the water to accumulate. An alert gauge approximately 2 miles north of the location reported 1.02 inches of rain in 25 minutes between 1545 and 1610 PST.
Several streets were flooded due to heavy rain, stranding motorists in their vehicles. Streets affected included Wineville Avenue, Limonite Avenue, 50th Street, Ben Nevis Blvc, Quartz Canyon Road, Fircrest Lane, Agate Street, Mission Blvd, Hastings Blvd, Fleming Street, Glen Street and Villa Woods Drive in Jurupa Valley. No one was injured.
Two homes on Crestview Drive between Mount Shasta and Mount Rushmore Drives sustained damage to the insides of the residences. Eight additional homes on the block sustained damage on the external portion. No injuries and no residents displaced.
Street flooding occurred in Colton Valley between Hermosa and Grand Roads. Roadways were closed in that area.
City of San Diego reported the on ramp for highway 52 and from I -15 was closed in the morning for an hour due to flooded streets and multiple accidents.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2012Every state in 2012This day in weather historyWarnings in California, October 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-30. Each event’s entry at NCEI: 415339, 415340, 415341, 415342, 415365.