The phenomenon is characterized by below-average water temperatures in the equatorial Pacific, leading to changes in upper atmosphere patterns that impact global weather. The atmosphere began exhibiting La Niña-like characteristics in the autumn, but it wasn’t until the end of the year that ocean temperatures truly resembled La Niña, as explained by Becker. Despite its delayed and weakened state, the atmospheric influence of La Niña has already been evident this winter, particularly in California where the northern region has seen abundant rain while the southern part remains unusually dry, resulting in wildfires.
Moreover, La Niña typically brings increased precipitation to the Midwest, with cities like St. Louis, Indianapolis, and Cincinnati experiencing one of the wettest starts to winter on record. However, there have been deviations from the expected La Niña pattern this season, with the South and central US experiencing colder temperatures and frequent winter storms instead of the usual dry and warm conditions.
The weak La Niña is predicted to persist until April before transitioning to neutral conditions, according to the Climate Prediction Center. While the influence of La Niña is still noticeable in the coming weeks, the season may not follow the typical La Niña pattern due to other atmospheric factors at play.
Looking ahead, warmer temperatures are anticipated across the southern US and East from January to March, while cooler temperatures are expected in the northwestern states, in line with La Niña norms. Wetter conditions are likely to persist in the Northwest, Midwest, and parts of the Northeast, increasing the chances of snowfall into early spring. The southern US may see drier conditions overall, with exceptions in the Mississippi Valley and Southeast.
The onset of La Niña was initially forecasted by the CPC in February 2024 when El Niño was still strong, with expectations of increased hurricane activity in the Atlantic. However, the arrival of La Niña was repeatedly delayed, resulting in an extended period of neutral conditions throughout the summer and fall. The delay may be linked to above-average global ocean temperatures that have persisted over recent years.
According to Becker, the year 2024 saw unprecedented global air temperatures, potentially marking the first year in recorded history to surpass a crucial warming threshold. The equatorial Pacific struggled to transition into a La Niña phase due to the persistence of extraordinary heat in both the oceans and the atmosphere. To access further updates from CNN, including news and newsletters, you can sign up for an account on CNN.com.
