Californians should prepare for another La Niña year as the stubborn weather pattern in the tropical Pacific is expected to persist for a third straight year, forecasters say.
The latest outlook, released Thursday by the National Weather Service’s Climate Prediction Center, increased the odds of La Niña persisting through November to 91%, a near certainty. The pattern can also persist into winter, with 80% chance of La Niña from November to January and 54% chance from January to March.
La Niña is the coldest phase of the El Niño-Southern Oscillation climate model and is a major driver of weather patterns across the globe, including temperature, rain and snowfall, jet streams and tropical cyclones. .
In the southwestern United States, La Niña seasons tend to be drier, which could cause problems for the drought-ravaged region.
“That doesn’t mean for sure it’s going to be 100% dry, but it does tip the scales towards dry,” said Mike Halpert, deputy director of the Climate Prediction Center. “If you had been wet for a while now, drier than average wouldn’t matter – but that’s becoming very important this year due to the dryness that’s already in place. Another dry winter certainly won’t be not good news for California.”
According to the Times Drought Tracker, more than 97 percent of the state is currently experiencing severe, extreme, or exceptional drought, the three worst categories. The state’s reservoirs are at about 41% capacity.
If the predictions materialize, it would be only the third time La Niña has persisted for three consecutive years since records began in the early 1950s, Halpert said. The only other such “triple dips” occurred from 1973 to 1976 and from 1998 to 2001.
“We saw it, obviously, but not a lot,” he said.
The outlook mirrors that of the World Meteorological Organization, which also predicts another La Niña this year. This forecast includes a 70% chance that La Niña will continue from September to November and gradually decrease to 55% from December to February.
“It is exceptional to have three consecutive years with a La Niña event,” WMO Secretary-General Petteri Taalas said in a forecast post, noting that it would be the “first La Niña triple dive of the century.”
The effects of the model are not limited to the southwest. La Niña is known to bring wetter and snowier conditions to parts of the northern United States, more frequent tornadoes in the south-central United States, and increased hurricane season activity in the Atlantic.
Overall, La Niña can reduce crop yields in the Horn of Africa, southeastern South America and other regions, and produce colder and drier conditions in western Antarctica, among other effects.
On the west coast of the United States, La Niña can also reduce the number of atmospheric rivers, which could be concerning in California, which receives much of its precipitation in winter. A dry season this year forced officials to cut state water project allocations to just 5 percent.
Halpert said the relationship between man-made climate change and La Niña remains a topic of interest.
“We believe that La Niña and El Niño have been around for hundreds, thousands of years, so it’s not like climate change has any manifestation on the actual phenomena,” he said. “A more relevant question is whether climate change alters the frequency of both events, and to be honest, that’s really still an open research question.”
According to the WMO, climate change is already amplify the effects of certain natural events such as La Niña.
“All natural climate events now occur against the backdrop of human-induced climate change, which is increasing global temperatures, exacerbating extreme weather patterns and impacting seasonal precipitation patterns,” Taalas said.
Last fall, particularly dry conditions helped spread several wildfires through September and October in California, including the Windy Fire and the KNP Complex Fire, which destroyed ancient redwood trees.
And while La Niña generally only has a slight impact on temperatures in Southern California, a distinct climate perspectives published by the Climate Prediction Center shows a higher likelihood of above normal temperatures across much of the United States through November.
California has about a 33% to 50% chance of being warmer than average, depending on the outlook. Although it does not include temperature forecasts for December and next year, a warm La Niña winter could affect the timing and availability of water in the state, as warmer temperatures can bring down more precipitation as rain instead of snow.
“We’re often asked, when you’re in a drought and we’re forecasting dry conditions, what do you do?” Halpert said. ” There’s not too much. There are water restrictions – and basically the old mantra of ‘hope for the best but prepare for the worst’.