For the second straight year, the world heads into a new La Niña weather event. This would tend to dry out parts of an already parched and fiery American West and boost an already busy Atlantic hurricane season.
Just five months after the end of a La Niña that started in September 2020, the U.S. National Oceanic and Atmospheric Administration announced a new cooling of the Pacific is underway.
The West’s historic, multi-year drought is threatening water supply, food production and electricity generation. It has drained reservoirs at incredible rates and fueled one of the most extreme wildfire seasons the region has ever experienced.
A weather-roiling La Niña appears to have emerged across the equatorial Pacific, setting the stage for worsening droughts in California and South America, frigid winters in parts of the U.S. and Japan and greater risks for the world’s already strained energy and food supplies.
The phenomenon—which begins when the atmosphere reacts to a cooler patch of water over the Pacific Ocean—will likely last through at least February, the U.S. Climate Prediction Center said Thursday. There is a 57% chance it be a moderate event, like the one that started last year, the center said.
The Center for Western Weather and Water Extremes, or CW3E, at Scripps Institution of Oceanography, released its report October 11 on atmospheric rivers during Water Year 2021.
The report, “Distribution of Landfalling Atmospheric Rivers over the U.S. West Coast During Water Year 2021: End of Water Year Summary” shows that more atmospheric rivers landed on the U.S. West Coast in Water Year 2021 than in Water Year 2020. But the majority of those storms reached the Pacific Northwest, not California, where drought conditions have impacted water supply.
Yale researchers are charting the course of mighty “rivers” in the sky that are holding steady in the face of climate change — for now.
In future decades, however, climate-induced changes to these atmospheric rivers could drastically increase extreme precipitation events in some parts of the world, they report in a new study published in the journal Nature Climate Change.
Atmospheric rivers — long, winding filaments of intense water vapor — account for as much as 90% of the moisture sent toward the North and South poles.
The White House announced Tuesday that it would work to revise building standards for flood-prone communities across the country in the face of climate change, while launching tools to make climate information more accessible to the public.
Lake Tahoe’s water level dropped to a four-year low on Tuesday as gusty winds and the impacts of California’s devastating drought hit the popular tourist destination.
After days of high winds increased evaporation rates, water levels fell to the basin’s natural rim for the first time since 2017, the end of the state’s last drought. The lake normally sits above the rim, which allows for water to flow into the Truckee River. Levels will probably continue to drop, receding below the rim this week, sooner than expected.
The Center for Western Weather and Water Extremes, or CW3E, at Scripps Institution of Oceanography, released its report October 11 on atmospheric rivers during Water Year 2021.
The report, “Distribution of Landfalling Atmospheric Rivers over the U.S. West Coast During Water Year 2021: End of Water Year Summary” shows that more atmospheric rivers landed on the U.S. West Coast in Water Year 2021 than in Water Year 2020. But the majority of those storms reached the Pacific Northwest, not California, where drought conditions have impacted water supply.
“The report on atmospheric rivers shows the variability in weather across the state from year to year,” said Jeff Stephenson, Water Resources Manager with the San Diego County Water Authority. “Through our partnership with CW3E and the AR forecasting tools they’ve developed, it better prepares us in management of our water resources using regional storage. This storage, in conjunction with developing multiple water supply sources in the San Diego region, has prepared us for years when rainfall levels are below normal in the region.”
Water Year 2021 experienced a total of 69 landfalling ARs over the U.S. West Coast, 4 more than Water Year 2020.
• While WY 2021 experienced more ARs, a much larger majority of the ARs only impacted the Pacific Northwest.
• California only experienced AR conditions (IVT >250 kg m–1 s–1) from 36 separate ARs during WY 2021, compared to 43
during WY 2020.
Distribution of Landfalling Atmospheric Rivers over the U.S. West Coast During Water Year 2021: End of Water Year Summary. Graphic: Center for Western Weather and Water Extremes
The lack of AR activity over California for two consecutive water years has resulted in a substantial lack of precipitation.
• A large portion of California received <30% of the normal precipitation for both Water Year 2020 and 2021.
• Coastal Washington and Oregon was the only location in the Western U.S. to receive near or above normal precipitation
during both water years, which is also the region that received a majority of the AR activity.
The San Diego County Water Authority partnered with the Scripps Institution of Oceanography, Center for Western Weather and Water Extremes, at UC San Diego in 2020 to better predict atmospheric rivers and improve water management before, during, and after those seasonal storms. The Center and its partners share best practices in forecast-informed reservoir operations, increased research around atmospheric rivers and droughts, and develop strategies for mitigating flood risk and increasing water supply reliability.
For additional details and graphics go to: https://bit.ly/3mKhkcR
This week, a historically dry period in California will come to bear at Lake Tahoe, where the water level is expected to sink below the basin’s natural rim. That’s the point at which the lake pours into its only outflow, the Truckee River.
It’s not a crisis, researchers and conservationists say, but it marks another extreme swing for Tahoe amid historic drought, wildfires and erratic weather, all intertwined with climate change and becoming more prominent aspects of the alpine environment.
