![]() ![]() But a lot of the moisture from last week’s storms in California made it to Minnesota, dropping a foot and a half of snow. Mountains usually wring the water out of atmospheric rivers. It’s unusual that there are so many storms and that they are super juicy. This convergence is the heart of the matter. The atmospheric rivers are coming in a row, and they are really strong and really wet. La Niña can nudge the storm track more toward Northern California, and it now favors atmospheric-river landfalls on this part of the coast. ![]() The storm track is a wind current, like the jet stream, that carries the river of moisture from west to east. What else is driving these powerful storms in California? And are they unusual?Īll sorts of chaos is happening in the atmosphere, but sometimes it stays in a certain configuration for a while-so the storm track is stuck. El Niño and La Niña can tip the scales toward wet or dry, depending on what else is going on along the coast. It’s kind of a crapshoot it could go either way. Northern California is on the cusp of the wet-dry pattern. The simple narrative is not necessarily true. Why didn’t the forecast hold up this year? This is the third year of La Niña, and expectations were set up by the first two years, when winters were not very wet. The simple narrative is that El Niño is wet, and La Niña is dry. Often we try to use El Niño and La Niña-large climate patterns in the Pacific Ocean-as proxies for the forecast. ![]() Weather forecasters didn’t expect such a wet winter in California. To learn more about why these storms are hitting California, as well as their potential dangers and benefits, Scientific American spoke with extreme weather expert Katerina Gonzales, who studied atmospheric rivers as a graduate student at Stanford University and is now a postdoctoral associate at the University of Minnesota. 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. 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. 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. 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. 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. 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. 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. 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. ![]()
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