As the sea surface temperatures in the Equatorial Pacific Ocean are rapidly rising, the National Weather Service (NWS) Climate Prediction Center (CPC) in the United States issued a new warning in August. The probability of this year’s developing El Niño phenomenon reaching the “Very Strong” level has exceeded 90%, with a 69% chance of breaking the historical record since 1950, becoming the strongest El Niño event in history.
This unprecedented tropical ocean energy, when encountering another powerful meteorological system in the high Arctic called the Polar Vortex, will bring significant variability and uncertainty to the winter weather in the United States for the 2026-2027 season.
The operation of the atmosphere in the upper atmosphere is extremely complex, and the interaction between El Niño and the Polar Vortex essentially involves a large-scale atmospheric energy game between tropical ocean heat and polar cold air streams. When these two atmospheric giants clash between the troposphere and stratosphere, the chain reaction they trigger will gradually cascade downward, ultimately shaping the surface weather patterns.
This atmospheric clash unfolds mainly through three closely connected steps:
First, the tropical heat energy triggers atmospheric disturbances. The Pacific Equatorial deep water temperature anomaly is as high as 4°C to 7°C. This continuous source of heat energy will alter the pressure patterns in the troposphere, forcing the Jet Stream to deviate from its normal path and releasing a significant amount of atmospheric wave energy into the upper atmosphere.
Then, the high-altitude polar structure will be disrupted. Normally, the strong Polar Vortex acts as a barrier, trapping frigid air in the Arctic. However, the atmospheric waves propagated by El Niño can severely disrupt the Polar Vortex, leading to the potential occurrence of Sudden Stratospheric Warming (SSW), making its structure unstable.
Finally, the chain reaction will drive cold air southward all the way to the surface. Once there is a sudden stratospheric warming in the troposphere, this disturbance will penetrate downward over the following weeks, causing the Polar Vortex to rupture or shift, ultimately pushing the extreme Arctic cold air southward, pouring into the eastern United States.
Due to the ever-changing nature of atmospheric systems, the collision of these two systems does not yield a single fixed result but rather produces vastly different weather scenarios depending on the final structural changes of the Polar Vortex. The following table presents specific weather patterns that various regions of the United States may face this winter:
Great Lakes Region, Inland New England, and Pacific Northwest:
Snowfall is expected to be less than usual.
San Francisco Bay Area and Most Parts of California:
Equal chances of above or below average precipitation.
Meteorological experts from the University of Miami and Massachusetts Institute of Technology (MIT) emphasize that the complex interactions between the Jet Stream, Polar Vortex, and El Niño involve probabilistic predictions (“increased likelihood” rather than “certain to occur”).
What’s more, the current strong El Niño phenomenon itself contains immense natural heat energy. When such a rare ocean anomaly combines with atmospheric circulation, the combined effects will alter the global atmospheric “teleconnections” mechanism. This remains an open question under close observation and study in the meteorological community.