La Niña officially arrives, may shape winter weather patterns
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A few months later and weaker than expected, the tropical Pacific Ocean has officially tipped into La Niña conditions, which can influence weather patterns globally, NOAA declared Thursday.
Why it matters: La Niña winters are often drier than average across the southern tier of the U.S., with more rain and snow favored in the Pacific Northwest, among other knock-on effects.
The big picture: La Niña is a periodic ocean and atmosphere cycle in the equatorial tropical Pacific that features cooler-than-average waters along the equator.
- This, in turn, alters weather patterns over that region, with the effects rippling outward for thousands of miles.
- The La Niña this year, which follows a strong El Niño in 2023 into early 2024, is now expected to be brief and relatively weak.
- La Niña, the cooler sibling of El Niño, is forecast to persist through the February to April period and transition back into neither El Niño or La Niña conditions during the March to May timeframe, NOAA stated.
Yes, but: Throughout the spring, summer and into early fall, NOAA forecasts called for a potentially moderate La Niña to develop before the end of the Atlantic hurricane season.
- Instead, the atmosphere over the tropical Pacific resembled a La Niña weather pattern, NOAA meteorologist Michelle L'Heureux told Axios, but the ocean didn't meet the definition.
The intrigue: L'Heureux, who leads the team that forecasts such climate events, said it's possible that widespread warm water anomalies across the tropical oceans hindered La Niña's formation.
- If this is the case, La Niña events may become more muted and harder to predict as the oceans and air temperatures continue to warm.
- "It is not entirely clear why the La Niña was so late to form and I'm sure that will be a subject of future research," L'Heureux told Axios via email.
- "The model forecasts that we rely upon were clearly too cold when we look back at what has transpired since we issued the [La Niña] Watch in spring 2024."
The bottom line: La Niña has arrived as the consummate socialite: late and with a hint of mystery.
