More late season rainfall is headed toward San Diego this week, starting with some drizzle before another atmospheric river is expected to bring several days of wet, overcast conditions into the weekend. The first bout of precipitation is anticipated to begin Tuesday into Wednesday as a ribbon of low atmospheric pressure currently over the Pacific Northwest advances towards the region.
President Donald Trump is obsessed with how California manages its water supply, demanding changes as one price of giving the state billions of dollars in aid to cope with Southern California’s deadly and destructive wildfires. However, Trump’s specific complaints are not grounded in hydrologic or managerial reality — such as his insistence that a lack of water from Northern California was a factor in either the fires’ eruption or the firefighting efforts. Hydrants dried up largely because systems were designed to deal with individual structure fires, not widespread wildfires involving thousands of buildings.
Reservoirs across California recently received good news only weeks after a late January snowpack update from the California Department of Water Resources (DWR) sparked concern. Although a series of atmospheric rivers brought heavy snow to high-elevation areas in parts of northern and central California in November and December, Southern California had an unusually dry start to the winter season. The lack of precipitation fueled wildfires in the region in January and furthered the state’s challenges with drought.
Clarke Knight studies just how far back in history, massive atmospheric river storms wreaked havoc on California.
An approaching storm is expected to soak Southern California this weekend, bringing nearly 2 inches of rain to Los Angeles over four days—nearly the city’s average monthly allotment.
For as long as weather records have been kept, California has been defined by its highly variable climate, with dramatic and sometimes volatile swings between droughts and floods. As human-caused climate change heats up the planet, the state faces even more intense extremes, with increasingly frequent and severe droughts punctuated by stronger and wetter storms.
California is expected to receive more rainfall by Friday from an atmospheric river storm than what Lake Mead in Nevada—the largest reservoir in the U.S.—can hold, meteorologists have said, as the state continues to face the threat of flooding.
All aboard the Pineapple Express this week in California as some coastal ranges could see up to 8 inches of rain before the end of the week, and Los Angeles and San Diego could be in for more monumental flooding.
One reservoir in northern California rose by 5 feet after two atmospheric rivers supplemented the water levels. An atmospheric river began across much of the Pacific Northwest, including Oregon and Northern California, on Friday.
For insight into the numerous atmospheric rivers that brought impressive precipitation accumulations to California this Water Year and how it compares to previous years, the Scripps Institution of Oceanography Center for Western Weather and Water Extremes provides this end of water year 2023 summary.
• Water Year 2022 experienced a total of 61 landfalling ARs over the U.S. West Coast, 15 more than Water Year 2023.
• While WY 2022 experienced more ARs, a much larger majority of the ARs only impacted the Pacific Northwest.
• Water Year 2023 was dominated by a more southerly storm track, bringing stronger and more frequent ARs to California compared to the WY 2022
• This variation in storm track and AR distribution resulted in the Pacific Northwest experiencing below normal precipitation and California experiencing well above normal precipitation during WY 2023, a reversal of WY 2022
Analysis by Chad Hecht, Julie Kalansky, & F. Martin Ralph. This analysis is considered experimental.
Legislation signed into law by California Governor Gavin Newsom earlier this year ensures the state has the science and weather forecasting tools it needs for more flexible reservoir operations. The bill, AB 30, makes breakthrough water management technology standard for the California Department of Water Resources.
The legislation was introduced by San Diego Assemblymember Chris Ward and co-sponsored by the Sonoma County Water Agency and the San Diego County Water Authority. The bill was supported by the Water Authority’s partner, UC San Diego’s Scripps Institution of Oceanography.
The strategy is called forecast-informed reservoir operations, or FIRO, and it complements Gov. Newsom’s California Water Supply strategy released in August 2022 calling for more reservoir storage capacity to capture runoff from big storms, often fueled by atmospheric rivers. The governor and Legislature have already provided funding for state water managers to integrate the strategy.
(Editor’s Note: The San Diego County Water Authority has partnered with the Scripps Institution of Oceanography at UC San Diego to better predict atmospheric rivers and improve water management before, during, and after those seasonal storms.)
