By Brian K. Sullivan | Bloomberg

After months of anticipation, a weather-changing La Niña has developed in the equatorial Pacific further adding to drought worries in California and the southern US, as well as the croplands in South America, the US Climate Prediction Center said.

Ocean surface temperatures dropped to 0.9F of a degree (0.5C) below normal across the parts of the Pacific tracked by the US, said Michelle L’Heureux, a forecaster at the Climate Prediction Center. In order to declare a La Niña, part of a larger cycle that includes El Niño, the ocean has to cool along with changes in the atmosphere.

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For most of 2024 scientists had been predicting the Pacific would cool, and earlier this week the Philippines’ weather agency also declared that the event is underway.

“La Niña has finally emerged,” L’Heureux said.  “It took its time, but we are there.”

Changes to the atmosphere brought on by cooling in the Pacific Ocean alters weather patterns the world over. In the US, it means more storms strike the Pacific Northwest leaving the southern US, particularly parts of California, drier, while the northern Great Plains gets cooler.

Globally, the phenomenon can raise drought risk in agricultural areas of Argentina and Brazil and bring heavier rainfall across parts of Indonesia and northern Australia. While La Niña has taken months to arrive, L’Heureux said there is a 60% chance it will likely fade by the March, April, and May time frame.

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