Friday January 13, 2023

Scientific American

California is taking a beating from what the National Weather Service has called a “seemingly never ending parade” of strong storm systems, which started late last December and are still coming. Called atmospheric rivers, they are long, narrow currents of exceptionally wet air that shoot across the ocean, capable of dumping massive volumes of rain or snow on landfall. Although these storms deliver much of the West’s precipitation, they also cause most of the region’s flooding, with associated economic damages as high as $1 billion a year.

This winter’s spate of storms has killed more than a dozen people in California and has put tens of thousands more under evacuation orders and watches. Rain on December 31, 2022, reached 5.5 inches in downtown San Francisco and flooded all six lanes of Highway 101 in the city of South San Francisco. On January 8 heavy rains and 70-mile-per-hour winds knocked out power for more than 345,000 people in the state’s capital of Sacramento.

More atmospheric rivers are predicted in the coming days, raising fears of flash floods across California—and of catastrophic mud and debris flows where recent wildfires have created 21 burn scars around the state. Its governor Gavin Newsom declared a state of emergency on January 4, and the White House issued a presidential emergency declaration for California on January 8.

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