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Meteorologists are warning that the polar vortex high above the Arctic could weaken or even split in early November, potentially making it the earliest such disruption since records began in 1958. Forecast models now favor a sharp weakening of the stratospheric winds—possibly a sudden stratospheric warming (SSW)—within the next 10 days, a period when the vortex is usually strengthening ahead of winter.
A sudden stratospheric warming event happens when temperatures in the stratosphere rise quickly, sometimes by as much as 120 degrees in just a few days, leading to a dramatic weakening or reversal of the strong westerly winds that normally keep cold air trapped near the North Pole. If a major SSW happens in early November, it would break the previous record of November 28, 1968.
The effects of this possible early disruption could be felt in North America and Europe later in November or into December, with a greater chance for high-pressure systems and some colder spells. However, experts caution that an SSW does not guarantee immediate cold weather at ground level.
For the United States, especially the Midwest, any cold outbreaks would likely occur from late November into December if the atmospheric disruptions line up. Still, the event does not promise a persistent cold pattern. Instead, the region may see alternating warm and cold periods heading into winter.
Complicating the forecast further is a strong Super El Niño, now fully developed over the tropical Pacific. Historically, El Niño winters in the U.S. bring a stronger southern jet stream, more storm activity, and generally milder conditions in the central and eastern parts of the country. This means the typical cold air intrusions associated with a disrupted polar vortex could be counteracted by warmer El Niño effects, resulting in highly variable weather.
While forecasts suggest cooler trends could emerge across the eastern United States as the polar vortex weakens, the timing and intensity of any cold spells remain uncertain due to the complex interaction between the SSW and El Niño.