El Niño Map Predicts U.S. Winter Weather

An emerging El Niño pattern in the Pacific Ocean is expected to bring a greater amount of snowfall than usual to southern U.S. states, meteorologists are predicting, based on historical trends.

The phenomenon of a plume of unusually warm water in the sea—which has occurred periodically, but become more frequent with climate change as average ocean temperatures rise—is forecast to be particularly strong this coming winter, creating a north-south divide in weather patterns.

The National Oceanic and Atmospheric Administration (NOAA) declared the arrival of an El Niño in June, which contributed to the barrage of hurricanes and tropical storms in both the Atlantic and Pacific Oceans—including the first tropical storm to make landfall in California in recorded history.

"Depending on its strength, El Niño can cause a range of impacts, such as increasing the risk of heavy rainfall and droughts in certain locations around the world," Michelle L'Heureux, a climate scientist at NOAA's Climate Prediction Center, said at the time. "Climate change can exacerbate or mitigate certain impacts related to El Niño."

In its latest advisory on the phenomenon, the National Weather Service said there was a 95 percent chance the current El Niño would strengthen and continue through to March next year, with the probability of a "strong" occurrence at 71 percent.

Given its apparent likelihood and persistence through the winter, Jonathan Erdman, a senior meteorologist at The Weather Channel, examined snowfall data across the U.S. since 1950, and found that in years where the ocean pattern was present, southern states tended to experience more snowfall and northern states less than on average.

This split tended to flip for La Niña seasons—the obverse of an El Niño, when Pacific Ocean temperatures tend to be lower than normal—with northern states seeing the most snow. In years when neither phenomenon is present, the snowiest parts tend to be eastern states from Missouri to Maryland.

"In general, t​he classic El Niño winter tends to be wetter than average through much of the southern U.S., from parts of California to the Carolinas, due in part to a stronger, more southern jet stream track," Erdman explained. "A​cross much of the northern U.S., a stronger El Niño tends to produce a warmer winter."

An El Niño has occurred more than 30 times since 1901. This usually results in a rise in global temperatures and the aggravation of extreme weather events.

As surface water temperatures are higher than usual, they are more likely to evaporate into the Pacific jet stream, which runs close to the equator, giving weather systems a greater amount of moisture. As the pattern tends to peak in the colder, winter months, when that precipitation falls, it is more likely to do so as snow or ice.

As the tropical jet stream is pushed farther south than usual by the phenomenon, the areas where it meets colder, Arctic air—causing storms and precipitation—are lower and further away from northern states, meaning they are likely to receive less snow and rain.

In August, long-term weather forecaster Farmers' Almanac predicted blizzards across the Southwest, central and Midwest regions, as well as in New England, attributing the forecast in part to the prevailing El Niño pattern.

While it foresaw above-normal snowfall levels across areas prone to the winter weather, apparently bucking the El Niño trend, it attributed this to the polar jet stream reaching further south, as the tropical jet stream pushes further south at the same time, bringing cold Arctic air down over the northernmost states.

It predicted that southern states will generally see more rain and snow than usual, and that Texas will be hit with "unseasonably cold weather" throughout the first two months of 2024, coupled with a "possible major winter storm" in the middle of January.