La Niña predicted to bring stormy weather

“Since El Niños have the seeds of their own destruction, we are quite confident the tropical Pacific will be on the cool side in a few months.”

The El Niño winter, which delivered abovenormal precipitation to much of California, is drawing to a close.

But as quickly as El Niño emerged, it is expected to fade even faster.

Signs of La Niña have already appeared in the eastern equatorial Pacific Ocean. Cooler than normal sea-surface temperatures recently emerged off the coast of Ecuador and Peru, according to a Climate Prediction Center report published Thursday.

By June, there’s only a 15% chance that El Niño will persist, with an 85% chance of “neutral” or near normal sea-surface temperatures. By August, La Niña is favored, with odds increasing to 80% or more by October.

This transition could significantly impact U.S. weather patterns. La Niña conditions enhance hurricane activity in the Atlantic region during summer and fall, and often result in below normal winter precipitation in Central and Southern California.

Predictability of a forthcoming El Niño or La Niña is usually low in April, but this year is unique, according to Michelle L’Heureux, a climate scientist at the Climate Prediction Center.

“We may be in a rare situation when predictability is higher than normal,” L’Heureux said.

Climate models that simulate ocean temperatures agree that La Niña will form in the coming months. Historically, La Niñas often follow strong El Niños, which gives the computer models additional merit, according to Nick Bond, emeritus Washington state climatologist.

“Since El Niños have the seeds of their own destruction, we are quite confident the tropical Pacific will be on the cool side in a few months,” Bond said.

How La Niña impacts hurricane season

La Niña’s impact on North American weather patterns is most widespread in winter, but the subtropical influence amplifies during summer and fall, peak hurricane season. Over the Caribbean Sea, La Niña reduces wind shear — changes in wind with height, either in direction or speed. Wind shear can rip hurricanes apart, so weak wind shear is a key ingredient for hurricane development and survival.

Record warm waters in the eastern Atlantic and Caribbean oceans are also expected to supercharge hurricanes this season. Long-range forecasts predict stronger and more frequent hurricanes along the Atlantic and Caribbean U.S. coastline this season.

“We anticipate that the 2024 Atlantic basin hurricane season will be extremely active,” researchers from Colorado State University wrote in a seasonal hurricane outlook, released last week.

While Atlantic hurricane activity is usually enhanced during La Niña, hurricanes in the eastern Pacific are often suppressed. During El Niño, hurricane behavior is just the opposite, and contributed to Hurricane Hilary’s close encounter with California last August.

California impacts

The influence of El Niño and La Niña on California’s weather is most significant during winter, when the storm track, also known as the jet stream, is closest to the Golden State.

“(La Niña) basically rings a bell near the jet stream,” L’Heureux said.

However, quickly fading El Niños that transition to La Niña have historically resulted in slightly cooler and wetter than normal spring weather in California.

La Niña is not known to influence California’s summer weather, but by late fall and winter, a slight tilt in the odds toward drier than normal conditions is likely in the southern half of the state. La Niña winters have historically resulted in a mixed bag of precipitation impacts in Northern California.

Three of the past four winters have aligned with seasonal forecasts, but it doesn’t mean the typical El Niño and La Niña patterns play out every winter in California. In 2022-23, a weak La Niña resulted in well above-normal precipitation and a record Sierra Nevada snowpack.