A rare third year of La Niña is on deck for California, forecasters say, which could bring big changes to the state’s water supply.
A weather-driven La Niña is forecast to begin in early fall and continue through the end of the year, when the ocean waters in the Pacific Northwest and off the coast of California will get more moderate, said Ken Graham, senior scientist with the National Oceanic and Atmospheric Administration.
“The third-year La Niña signal begins in early to mid-September and extends into early and mid-October,” Graham told the Associated Press in an email. “We look for a warm-water to cool-water phase across the northern and central Pacific Ocean.”
Graham said the region is forecast to warm from late fall through the end of the year.
A warmer Pacific ocean will lead to a larger than normal flow of water to California, where there is a water shortage.
“Our forecast indicates that the winter of 2018-2019 will be above average for many reasons,” Graham said. “This is consistent with a stronger El Niño, which in itself is good.”
During La Niña years, the warm water in the northwest Pacific flows south, while the cold water from the west Pacific flows north. La Niña is often followed by El Nino, another long-term weather pattern that favors colder-than-average water in the region, according to the National Oceanic and Atmospheric Administration
A warm Pacific ocean means a warmer and more active weather pattern, which is good news for the state in California where more than half of the water supply is drawn from the Pacific Ocean, according to the state’s water agency.
More frequent and intense storms also favor the state’s weather, as it could cause some of the same problems California is facing now, such as the drought.
“There are numerous reasons why the Pacific waters are more active from La Niña through winter of 2018-19, some of which are still under the discussion,” Graham said. “As the Pacific warms, the potential for increased atmospheric moisture is very large. This leads to increased precipitation in California. While some of this precipitation may be in the form of rain, snowfall and stormwater runoff, much of the precipitation may be as rain, snow or a mixture of rain and snow.”
The water shortage