The National Oceanic and Atmospheric Administration’s Climate Prediction Center has forecasted a 60% chance of a weak La Nina event developing this autumn and potentially lasting until March. La Nina is a natural climate cycle that can cause extreme weather patterns across the planet, with effects varying by location. Some general trends expected include increased rainfall in northern parts of South America, drier conditions in southern regions of the U.S. and parts of Mexico, and wetter conditions in the northern tier of the U.S. and southern Canada. La Nina is the cool phase of the El Nino-Southern Oscillation, a global climate pattern that involves changes in wind and ocean temperatures in the Pacific.
During La Nina, trade winds intensify, leading to the rise of cold water from the depths of the sea in the Pacific. This results in cooler-than-average ocean temperatures in the eastern Pacific, impacting the position of the jet stream. The jet stream, a fast-moving band of air flowing west to east around the planet, can influence storm paths, boost precipitation, and tap into moisture from the ocean. Recent years have seen a series of La Nina events, with a “triple-dip” occurring from 2020 to 2023. Climate scientists note that La Nina events tend to last longer and be more recurrent than El Nino events, with potential impacts on regions dealing with drought, such as East Africa.
The influence of La Nina on weather patterns varies depending on location and season. Parts of South America, like eastern Argentina, can experience drier conditions, while countries like Colombia, Venezuela, and northern Brazil may see increased rainfall. In the U.S., the Northeast and Ohio Valley typically receive higher precipitation levels due to the position of the jet stream, leading to an active storm track. The waviness of the jet stream can also cause more frequent cold outbreaks in central regions, potentially affecting snowfall patterns across New England, New York, and the Great Lakes area. Conversely, southern and southeastern U.S. regions tend to be drier and warmer during La Nina events.
Scientists have highlighted that the connection between climate change and La Nina/El Nino events is not fully understood. While climate models suggest a potential increase in El Ninos and decrease in La Ninas, there is variability among different models. It is challenging to separate natural variations in these climate phases from the impact of warming oceans and atmosphere due to climate change. Despite these uncertainties, experts emphasize the importance of monitoring and understanding these global climate patterns to better anticipate and respond to their impacts.
