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Atmospheric Rivers in California’s Ancient Past Exceeded Modern Storms

Clarke Knight studies just how far back in history, massive atmospheric river storms wreaked havoc on California.

California City to Get Nearly Month’s Worth of Rain in Four Days

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.

How California’s Storms are Projected To Become More Extreme With Climate Change

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.

Bomb Cyclone To Dump More Water Than in Lake Mead on California

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.

Pineapple Express Headed for California With Flooding, Wind, Snow Expected This Week

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.

How California Reservoir Water Levels Changed After Atmospheric Rivers

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.

Water Year 2023-Atmospheric Rivers-CW3E

The Atmospheric Rivers of Water Year 2023: End of Water Year Summary

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 2023 and Atmospheric Rivers

Center for Western Weather and Water Extremes-atmospheric rivers-water year 2023-Scripps Institution of Oceanography

• 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

Atmospheric Rivers-Water Year 2023 compared to Water Year 2022-CW3E

Atmospheric Rivers-CW3E-climate science-weather

Strong ARs-CW3E-Atmospheric Rivers-climate science

Central California's Water Year-Atmospheric Rivers-CW3E

Water Year 2023-Atmospheric Rivers-CW3E

Analysis by Chad Hecht, Julie Kalansky, & F. Martin Ralph. This analysis is considered experimental.

New California Law Taps Science to Improve Water Management

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.

Forecast-Informed Reservoir Operations strategy will help deal with drought and flood

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.)

FIRO-Scripps-Law-Water Management

New California Law Taps Science to Improve Water Management

Legislation signed into law by California Governor Gavin Newsom 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.

FIRO-Science-water management

Diagram illustrating the FIRO process to develop an adaptive water control manual. Graphic courtesy Scripps Institution of Oceanography Center for Western Weather and Water Extremes

FIRO-Scripps-Law-Water Management

New California Law Taps Science to Improve Water Management

Legislation signed into law by California Governor Gavin Newsom 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.

Forecast-Informed Reservoir Operations strategy will help deal with drought and flood

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.

“We thank Assemblymember Chris Ward for his leadership and vision in supporting next-gen water management and flood reduction efforts that will benefit residents statewide,” said Mel Katz, chair of the San Diego County Water Authority Board of Directors. “The legislation provides an innovative approach to help San Diego County and California thrive in the changing climate.”

Forecast-informed reservoir operations use weather predictions to advise dam operators about how much water to retain or release from reservoirs, enhancing their ability to handle whatever nature serves up while retaining as much water as possible in storage.

FIRO-Science-water management

Diagram illustrating the FIRO process to develop an adaptive water control manual. Graphic courtesy Scripps Institution of Oceanography Center for Western Weather and Water Extremes

Many reservoirs in the West are strictly regulated based on historical averages of winter storms and spring runoff. Under existing rules, the highly variable rainfall from year to year is not directly considered. Complicating the problem, many current guidelines and practices were developed before satellites, radar and advanced numerical models significantly improved weather forecasts.

To address these challenges, researchers at Scripps Institution of Oceanography and elsewhere developed tools that provide weather forecasters with reliable notice of atmospheric rivers a week in advance. Advancing this research could have taken decades, but sophisticated prediction products have evolved in less than 10 years with funding by the San Diego County Water Authority and other water agencies statewide, along with state and federal support.

The Water Authority has partnered with SIO and the Scripps Center for Western Weather and Water Extremes at UC San Diego, to share and support best practices in FIRO, to increase research around atmospheric rivers and droughts, and develop strategies for mitigating flood risk and increasing water supply reliability.

San Diego County Water Authority And its 24 Member Agencies

New California Law Taps Science to Improve Water Management

Legislation signed into law by California Governor Gavin Newsom 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.

“We thank Assemblymember Chris Ward for his leadership and vision in supporting next-gen water management and flood reduction efforts that will benefit residents statewide,” said Mel Katz, chair of the San Diego County Water Authority Board of Directors. “The legislation provides an innovative approach to help San Diego County and California thrive in the changing climate.”

Forecast-informed reservoir operations use weather predictions to advise dam operators about how much water to retain or release from reservoirs, enhancing their ability to handle whatever nature serves up while retaining as much water as possible in storage.

Many reservoirs in the West are strictly regulated based on historical averages of winter storms and spring runoff. Under existing rules, the highly variable rainfall from year to year is not directly considered. Complicating the problem, many current guidelines and practices were developed before satellites, radar and advanced numerical models significantly improved weather forecasts.

To address these challenges, researchers at Scripps Institution of Oceanography and elsewhere developed tools that provide weather forecasters with reliable notice of atmospheric rivers a week in advance. Advancing this research could have taken decades, but sophisticated prediction products have evolved in less than 10 years with funding by the San Diego County Water Authority and other water agencies statewide, along with state and federal support.

The Water Authority has partnered with SIO and the Scripps Center for Western Weather and Water Extremes at UC San Diego, to share and support best practices in FIRO, to increase research around atmospheric rivers and droughts, and develop strategies for mitigating flood risk and increasing water supply reliability