She’s baaaaaaack. The National Oceanic and Atmospheric Agency’s Climate Prediction Center said last week that a La Niña has developed in the Pacific Ocean and is set to last through the winter and into next spring. That’s bad news for the record drought in the West.
This is the second year in a row that a La Niña has formed, marking what’s (adorably) known as a “double dip La Niña.” The term is used to describe abnormally cool waters in the eastern tropical Pacific. When those water cool off, they alter the atmosphere and weather around the world.
Last winter’s La Niña is a warning of what could be in store: the cold spell in the tropical Pacific helped to create drier conditions across the West, which exacerbated the drought in the region before the dry summer even hit. Later this week, NOAA is set to release its weather outlook for the U.S. through the winter, and La Niña will certainly play a role in what the agency thinks is in store.
“Our scientists have been tracking the potential development of a La Niña since this summer, and it was a factor in the above-normal hurricane season forecast, which we have seen unfold,” Mike Halpert, deputy director of NOAA’s Climate Prediction Center, said in a news release. “La Niña also influences weather across the country during the winter, and it will influence our upcoming temperature and precipitation outlooks.”
The colder-than-normal waters associated with La Niña influence the jet stream, the river of air that flows from west to east around the world. In North America, the jet stream tends to take on a more wavy pattern, ushering in storms to the Pacific Northwest and trapping cold air over western Canada while leaving the Southwest warmer and more parched than normal. El Niño, which is the opposite of La Niña, basically flips that pattern. But sadly, that’s not what’s in store.
It’s important to note that La Niña doesn’t guarantee a warm, dry winter for the Southwest. Rather, it increases the odds of one. La Niña events only happen every couple of years, and scientists also only have eight instances on record of double dips to look at. However, some studies do suggest that drought conditions can actually strengthen during the second consecutive La Niña winter.
What is for sure is the West really doesn’t need drier weather this winter. More than 50% of the western U.S. is currently in extreme or exceptional drought, according to the Drought Monitor. This summer saw several worrisome drought milestones, including the water levels in Lake Mead falling to such low levels that it triggered the Colorado River’s first-ever water restrictions. La Niña’s impact on weather patterns could hit states like Arizona, New Mexico, and Colorado as well as parts of Southern California especially hard.
Even areas that wouldn’t be affected by drier weather may still experience problems. In some areas of the Northwest, La Niña is likely to bring wetter conditions. But since much of that region saw a record-breaking fire season, there’s a danger that strong storms dumping rain and snow could lead to mudslides and flooding as the soil isn’t able to absorb the water. And because climate change has a tendency to change the intensity of rainfall, creating bursts of precipitation, these effects could be even more pronounced than usual.
“A lot of times when we talk about whether it was a wet year or dry year, you average the whole season,” said John Fasullo, a scientist at the National Center for Atmospheric Research, told the Guardian. “But with climate change, you have greater amounts of rainfall being delivered in shorter bursts.”