Super El Niño expected to shape U.S. winter weather patterns

A rapidly intensifying El Niño, forecast to reach "Super" strength by October, is set to dominate U.S. winter weather, NOAA officials said. The phenomenon, characterized by unusually warm Pacific Ocean waters, typically shifts the jet stream southward, bringing cooler, wetter conditions to the southern tier of the country and warmer, drier weather to the north.

Meteorologist Nat Johnson of the National Oceanic and Atmospheric Administration described the developing event as "something that’s very unusual, if not a once-in-a-lifetime type of (strength)." While a strong El Niño raises the odds of these patterns, NOAA cautioned that it does not guarantee extreme outcomes.

The Climate Prediction Center’s December-through-February outlook shows above-average temperatures likely across much of the northern United States, from the Pacific Northwest to the Midwest, and possible warmth over more than half of the contiguous states. Precipitation forecasts indicate wetter than normal conditions for Southern California, the southern tier of states and the East Coast, with the highest confidence in the Southeast. Conversely, the northern tier is expected to be drier, reducing the likelihood of snow in those regions.

The shift in storm tracks may also increase the risk of severe thunderstorms in Florida during winter, while other Gulf Coast areas could see reduced activity, according to climate scientist Michael Tippett of Columbia University. Researchers note that long-term climate warming has already contributed to declining snowfall across much of the United States.