A rare third year of La Niña is on deck for California, forecasters say

Californians should brace for another year of La Niña as the intractable climate 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 Forecasting Center, has raised the probability of La Niña lasting through November to 91%, a near-certainty. The pattern can also persist into winter, with an 80% chance for La Niña from November through January and a 54% chance from January through March.

La Niña is the cooler phase of the El Niño-Southern Oscillation climate pattern and is a significant contributor to weather patterns around the world, including temperature, rain and snowfall, jet streams, and tropical cyclones.

In the southwestern United States, seasons tend to be drier in La Niña, which could create problems for the drought-stricken region.

Map graphic showing what happens in the Pacific during a La Niña.

In La Niña, stronger trade winds push warm surface waters into the western Pacific.

(Paul Duginski/Los Angeles Times)

“It doesn’t mean it’s going to be 100% dry, but it does tip the odds toward dry,” said Mike Halpert, deputy director of the Climate Prediction Center. “If you’ve been wet for a while now, drier than average wouldn’t matter – but it will be very important this year because of the drought already in place. Another dry winter is certainly not good news for California.”

According to The Times drought tracker, more than 97% of the state is currently experiencing severe, extreme or exceptional drought, the three worst categories. The state’s reservoirs are at about 41% capacity.

Should the prognosis materialize, it would be only the third time La Niña has stayed there for three consecutive years since records began in the early 1950s, Halpert said. The only other such “triple dips” were from 1973 to 1976 and from 1998 to 2001.

“We saw it, of course, but not much,” he said.

The outlook mirrors that of the World Meteorological Organization, which is predicting another La Niña for this year as well. This forecast includes a 70% chance that La Niña will last from September to November, gradually decreasing to 55% from December to February.

“To have three consecutive years with a La Niña event is extraordinary,” said WMO Secretary General Petteri Taalas in a post about the forecast, noting it would be the “first triple-dip La Niña of the century.” .

The pattern’s effects are not limited to the Southwest. La Niñas are known to result in wetter, snowier conditions in parts of the northern US, more frequent tornadoes in the southern US, and increased activity in the Atlantic hurricane season.

Globally, La Niña may reduce crop yields in the Horn of Africa, southeastern South America and other regions, among others, and create colder, drier conditions in West Antarctica.

On the US West Coast, La Niña may also reduce the number of atmospheric flows, which could be a concern in California, where much of its rainfall falls during the winter. A dry season this year forced officials to cut state water project allocations to just 5%.

Halpert said the relationship between human-caused climate change and La Niña remains an interesting topic.

“La Niña and El Niño have been around for hundreds, thousands of years in our opinion, so it’s not like climate change is affecting the actual phenomena,” he said. “A more relevant question is whether climate change is changing the frequency of the two events, and honestly that’s really an open research question.”

According to the WMO, climate change is already amplifying the impact of some naturally occurring events such as La Niña.

“All naturally occurring climate events are now taking place in the context of human-caused climate change, which is increasing global temperatures, exacerbating extreme weather conditions, and affecting seasonal precipitation patterns,” Taalas said.

Last fall, particularly dry conditions contributed to the spread of several September and October wildfires in California, including the Windy Fire and the KNP Complex Fire, which destroyed some old-growth redwoods.

A 3-month outlook shows a higher likelihood of above-normal temperatures into fall.

A three-month forecast released by the National Weather Service’s Climate Prediction Center shows a higher likelihood of above-average temperatures through the fall.

(National Weather Service)

And while La Niña tends to have little impact on Southern California temperatures, a separate climate outlook from the Climate Prediction Center shows a higher likelihood of above-average temperatures across much of the U.S. through November.

California has about a 33% to 50% chance of warming above average, according to the Outlook. While it doesn’t include temperature forecasts for December and next year, a warm winter in La Nina could affect the timing and availability of water in the state, as warmer temperatures can result in more precipitation falling as rain rather than snow.

“We get asked a lot, when you’re in a drought and we’re forecasting dry conditions, what do you do?” Halpert said. “There is not much. There are water restrictions – and basically the old mantra: ‘Hope for the best, but prepare for the worst.’”

https://www.latimes.com/california/story/2022-09-13/la-nina-california-rare-third-year A rare third year of La Niña is on deck for California, forecasters say

Alley Einstein

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