LOS ANGELES — Over a span of three days, parts of northern California experienced unprecedented flooding, with more than 12 inches of rain falling in some areas. This extreme weather had widespread effects, including evacuation orders due to a fire in Los Angeles County, the issuance of California’s first tornado warning in San Francisco, and rough sea conditions that damaged a wharf in Santa Cruz.
California has recently faced a series of severe weather events that have highlighted its susceptibility to natural disasters. Strong storms on Tuesday led to massive waves anticipated to reach up to 35 feet near Santa Cruz, prompting the National Weather Service to issue a high surf warning until the evening and advising the public to stay clear of the coastline and piers.
According to Chandler Price, a meteorologist with the National Weather Service in San Diego, these weather patterns are both typical and atypical for a La Niña winter, a climate phenomenon that often results in extreme weather globally. In California, this usually brings wetter conditions in the north and dryness to the south.
“Thus far, we’ve seen this pattern fairly well,” Price noted, adding that the tornado occurrence in the Bay Area was an unusual event. “We haven’t witnessed that in a long time,” he said.
The tornado warning was issued in response to a storm that generated wind gusts reaching 60 mph and affected nearly 1 million people in San Francisco and neighboring San Mateo County. The tornado caused damage in Scotts Valley, about 70 miles south of San Francisco, overturning vehicles and uprooting trees and utility poles, resulting in injuries. While California does experience tornadoes, they rarely affect populated regions.
In San Francisco, local meteorologists clarified that strong straight-line winds—not a tornado—had caused trees to crash onto vehicles and streets and led to roof damage throughout the area. Additionally, the storm brought considerable snowfall to the northern Sierra Nevada mountains.
F. Martin Ralph, the director of the Center for Western Weather and Water Extremes at the University of California, San Diego, explained that climate change is likely to make atmospheric rivers—long corridors of moisture in the atmosphere—a more significant contributor to California’s annual precipitation. However, he noted that the days between these intense storm events are becoming drier. Although these storms play a crucial role in the state’s water supply, they also pose risks.
“Excessively strong storms that occur in succession can lead to flooding,” he remarked, emphasizing their role in California’s weather extremes.
Tragically, during the recent storms around Santa Cruz, one individual was killed when trapped under debris, and another was pulled into the ocean. The intense surf conditions also caused part of a municipal wharf under construction in Santa Cruz to splinter off, resulting in three individuals falling into the water; one managed to swim to safety, while the remaining two were rescued.
A sequence of atmospheric rivers is forecasted to continue affecting California throughout the week. While this atmospheric activity is not particularly unusual for this time of year—often bringing high winds, heavy mountain snowfall, and intense rains—David Lawrence, a meteorologist and emergency response specialist at the National Weather Service, noted a unique aspect to the current system: the storms are occurring in close succession with little time between them.
Ahead of the Thanksgiving holiday, California experienced severe storms as well, which drenched areas like Santa Rosa with over a foot of rain within three days—a new record.
Interestingly, the storms have largely bypassed southern California, leaving the region with dry weather that raises fire risks. One recent incident, known as the Franklin Fire, resulted in approximately 20,000 individuals receiving evacuation notices, forcing Pepperdine University students to take shelter. Strong Santa Ana winds, notorious for pushing dry air from the interior toward the coast, fueled the blaze.
Much of the destruction occurred in Malibu, a picturesque community in Los Angeles famed for its scenic bluffs and the iconic Zuma Beach. The fire resulted in damage to or destruction of 48 structures and is one among nearly 8,000 wildfires that have scorched over a million acres in California this year.
The Santa Ana winds, peaking in December, have also contributed to higher than average temperatures in southern California. Price noted that unseasonably warm Christmas temperatures of around 80 degrees Fahrenheit are not uncommon in the area, but this year saw some unusually high temperature records being broken even in mountain areas, which are typically less impacted by these winds.
