The US National Oceanic and Atmospheric Administration's Climate Prediction Center says there is a 60 percent chance that a weak La Niña will develop this fall and could last until March.
La Niña is part of a natural climate cycle that can cause extreme weather across the planet, and its effects vary from place to place.
Although there are no guarantees about how La Niña may end, some general trends are beginning to emerge. According to experts, the northern parts of South America could receive more rain than usual. The southern United States and parts of Mexico may be drier than average. The northern United States and southern Canada may be wetter than average.
La Niña is the cold phase of the El Niño Southern Oscillation, a natural global weather pattern that includes changes in winds and ocean temperatures in the Pacific Ocean and can cause extreme weather across the planet.
El Niño is the warm phase and occurs when the trade winds that normally blow across the Pacific Ocean toward Asia weaken, allowing warm ocean water to accumulate along the western edge of South America. But during La Niña, trade winds intensify and cold water rises from the deep sea, causing ocean temperatures to cooler than average in the eastern Pacific.
Cooling ocean temperatures and changes in the atmosphere affect the position of the jet stream — a narrow band of air that moves quickly from west to east around the planet — and move it north. The jet stream is located over the ocean and can draw on its moisture, influence the path of storms and increase precipitation.
Recently, Earth experienced a La Niña “triple dip” between 2020 and 2023. “We have had three consecutive winters with La Niña conditions, which is unusual, as the only other such case was in 1973-1976,” said Michele L'Heureux. , climate scientist at NOAA. MI L'Heureux points out that La Niña tends to last longer and be more frequent than El Niño.
“It's unusual, but it's not without precedent,” Ben Cook, a climate scientist at NASA's Goddard Institute for Space Studies, affiliated with Columbia University, said of predictions of a possible La Niña event this year.
Mr. Cook noted that recurring La Niña events could be stressful for regions that have recently faced drought, such as East Africa. “If we are headed toward another La Niña, that means these very adverse conditions will continue,” he said.
Weather effects of La Niña
The woman said that the effect of the La Niña phenomenon on weather conditions varies depending on the location and season.I Happy. Some areas of South America, such as eastern Argentina, may be drier than average, while Colombia, Venezuela and northern parts of Brazil may be wetter than normal.
“It all depends on where you are. This is partly because Central and South America has a monsoon cycle, a rainy season and a dry season, and La Niña changes the intensity and location of the monsoon cycles.”I Happy.
Snowfall in the United States is difficult to predict and depends largely on the storm and its track, said Samantha Borisoff, a climate scientist at NOAA's Northeast Regional Climate Center based at Cornell University.
MI However, Borisov noted that New England, New York and the Great Lakes region tend to have more snow during La Niña winters, but that is by no means a guarantee. Areas of the southern and southeastern United States are far from the active storm track and tend to be drier and warmer than normal.
La Niña, El Niño, and climate change
According to scientists, the relationship between climate change and the La Niña and El Niño phenomena is not entirely clear.
Climate models tend to suggest that El Niño is more frequent and La Niña less frequent, but not all models agree, says Paul Roundy, a climate scientist at the University at Albany, State University of New York. Computer models also have difficulty distinguishing between natural variations in the El Niño and La Niña phases and the impact of climate change on warming of the oceans and atmosphere.
“I cannot conclude that climate change is not causing more El Niño events,” Roundy said. It's just that nature itself has such strong fluctuations. So we may have several episodes of La Niña, and maybe in 40 or 50 years we will see the opposite. »
