The first of two back-to-back atmospheric rivers began drenching the San Francisco Bay Area on Wednesday and arrived in Los Angeles in time to snarl the Thursday morning commute. The Los Angeles and San Diego areas will be in the bullseye for heavy rain on Thursday, with flooding possible to the north. The "Pineapple Express"—called that because its long plume of moisture stretched across the Pacific to near Hawaii—will be followed by an even more powerful storm Sunday, reports the AP. Brian Ferguson with the Office of Emergency Services characterized the situation as "a significant threat to the safety of Californians," with concerns for impact over 10 to 14 days from the Oregon line to San Diego and from the coast into the mountains. "This really is a broad sweep of California that's going to see threats over the coming week," he said.
- The National Weather Service issued a flood watch into Friday morning for the Bay Area and the Central Coast. Forecasters said the Central Coast could see waves up to 18 feet high on Thursday and Friday.
- Service on San Francisco's iconic cable cars was halted as a safety precaution.
- In the far south, all of San Diego County was under a flood watch Thursday. Forecasters said some areas could see 2 inches of rain, with up to 3 inches in the mountains and winds gusting to 40mph or more. The storm came a week after heavy flooding that inundated homes and overturned cars.
The second storm in the series has the potential to be much stronger, said Daniel Swain, a climate scientist at the University of California, Los Angeles. Models suggest it could intensify as it approaches the coast of California, a process called bombogenesis—aka a bomb cyclone—in which a spinning low-pressure system rapidly deepens, Swain said Tuesday. That scenario would create the potential for a major windstorm for the San Francisco Bay Area and other parts of Northern California as well as heavy but brief rain, Swain said.
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