Westerly wind bursts can trigger the beginning of a shift from La Nina to El Nino

A shift to El Nino in 2026 could spell rising global temperatures, humidity and moisture levels, but it’s too early to know whether an event would develop.

A warm wind shift is unfolding in a remote part of the equatorial Pacific Ocean.

And despite its geographical isolation, it could signal the start of a planetary change in ocean temperatures and weather patterns.

This change has scientists concerned that the planet could break temperature records in the years to come - because it raises the odds of a planet-warming El Nino in 2026.

Daniel Swain, a climate scientist with the University of California Agriculture and Natural Resources, said that if a significant El Nino event develops, global temperatures could be well above the long-term average for two years.

“This is concerning, because that would probably mean that we set another new global temperature record and possibly by a significant margin,” Swain said.

What a westerly wind burst is

Typically, winds blow from east to west across the tropical Pacific Ocean, forming a predictable pattern called trade winds.

These trade winds cause some of the planet’s warmest ocean water to pile up in the western Pacific, near Papua New Guinea and the Philippines.

But a few times a year on average, winds weaken and reverse direction, blowing from west to east at about 25km/h for a few weeks - forming a westerly wind burst.

This wind shift can bring changes in rainfall and temperatures across the tropical Pacific islands and spark tropical cyclones.

Importantly, it can also trigger the beginning of a shift from La Nina to El Nino - with important consequences for the planet’s weather patterns.

El Nino and La Nina are opposite phases of the natural climate pattern called the El Nino-Southern Oscillation - Earth’s most important source of year-to-year climate variability.

The planet is currently experiencing La Nina conditions, during which cooler-than-average ocean waters pool in the eastern and central Pacific. That’s been the case for five out of the past six years.

A shift to El Nino in 2026 could spell rising global temperatures, humidity and moisture levels as storm-steering jet stream winds change.

During El Nino, warm ocean waters build in the eastern and central equatorial Pacific.

Eventually, this warmth is transported out of the tropics and towards the poles, influencing weather patterns worldwide.

Winds from a westerly wind burst push warm water east from an area south of Guam called the West Pacific Warm Pool, home to the planet’s warmest ocean waters.

This happens as the phenomenon spurs slow-moving and large oceanic waves called Kelvin waves.

“Unlike the waves you see at the beach, Kelvin waves do not curl over and then crash. They are more like the waves in your bathtub, which slowly slosh around,” said Michelle L’Heureux of the National Oceanic and Atmospheric Administration.

Kelvin waves take two to three months to cross the Pacific. So, if this westerly wind burst causes one, it would be sometime in early 2026 that warmer ocean water reaches the eastern Pacific, near Peru and Ecuador in South America.

For an El Nino event to develop next year, several more westerly wind bursts would probably need to occur, with each shifting more heat from west to east across the Pacific.

One key cause of westerly wind bursts is the Madden-Julian Oscillation, a pulse of clouds and rain that rotates around the global tropics every one to two months on average.

Although the westerly wind burst is an important first step toward steering the climate system in the direction of El Nino, Swain cautioned that it’s too early to know whether an event would develop next year.

According to the latest outlook from Noaa, neutral conditions (neither La Nina nor El Nino) are favoured to develop early next year, before odds for El Nino grow steadily, reaching higher than 40% at mid-year.

“It can sometimes take longer to develop than the models think,” Swain said.

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