La Niña conditions can occur in autumn and early winter, but predictors say they will likely be weak and short-lived.
La Niña is the cold stage of the El Niño Southern Oscillation (ENSO), a natural climate pattern of atmospheric and seawater temperature changes in the tropical Pacific Ocean. During La Niña, the Jetstream moves north, bringing wet and cold winters to the northern United States, while the southern United States experiences dry and warm winters. La Niña also tends to intensify hurricane activity over the Atlantic.
The conditions for this phase were developed temporarily last winter, but have not been stuck long enough to be considered by historical records as the official La Niña event. The latest ENSO forecast from the National Weather Service shows that we will be able to participate in similar things in the coming months.
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La Niña’s condition period is preferred during autumn and early winter, with a 21% chance of qualifying for the current period from July to September. Then, if the three-month period overlaps between September and January, the likelihood rises to over 50%. Still, predictors are not expecting major weather changes.
“If La Nina is formed, it’s likely to be weak. That means La Nina will not have a strong effect on the winter,” Emily Becker, a research professor at the University of Miami and lead writer for the National Oceanic and Atmospheric Administration ENSO blog, told Live Science in an email.
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The ENSO cycle causes a warm El Niño phase, then on average a cold La Niña phase every 2-7 years, each phase lasts about 9-12 months. However, the timing of these phases varies and are difficult to predict.
The phase is defined by changes in sea surface temperature in the Niño region of the East Central Pacific Ocean and changes in atmospheric conditions affecting jet rivers in the Pacific Ocean. El Niño conditions occur when sea surface temperature is 0.9 degrees Fahrenheit (0.5 degrees Celsius) higher than the long-term average, but La Niña conditions occur when sea surface temperature is 0.9 f below the long-term average.
We were scheduled to enter Alaninha last summer, but the condition didn’t occur until December. That late start meant that La Niña had no time to gain strength before the start of winter.
Ocean temperatures warmer than last year’s average could have played a role in the delay. The Earth was located in El Niño between May 2023 and March 2024, contributing to record-breaking heat during that period. But no matter what ENSO is doing, the planet continues to get warmer with climate change.
Last winter’s La Niña spell did not appear in the record book as temperatures did not fall below the 0.9 f threshold for at least five consecutive overlapping seasons, or three months. The latest data suggests that La Niña conditions are likely not to be the official La Niña in these next three periods, over autumn and winter.
“It’s very likely that there will be another winter like 2024-25, and there will be a few months of La Niña condition and it’s not enough to qualify as a La Niña event with historic records,” Becker said. “But last winter’s impact looked like what we would expect during the moderately strong La Niña.”
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