A large-scale circulation of cold air and strong winds known as the polar vortex is forming high above the Arctic for the Northern Hemisphere’s cold season. According to atmospheric data and the National Oceanic and Atmospheric Administration, the stratospheric polar vortex is developing normally for this time of year and is currently somewhat stronger than average.
These zonal winds, located about 10 to 30 miles above the North Pole, serve as one of the primary measurements meteorologists use to track the strength and organization of the vortex. Recent observations show the 2026-27 vortex strengthening as seasonal cooling gets underway. NASA data analyzed in mid-September indicated that winds around 60 degrees north in the lower stratosphere were running above their long-term average for the date.
Latest forecasts show average winds strengthening through the fall, reaching approximately 30 meters per second around December before weakening later in the winter when the forecast becomes more uncertain. By late January, the average falls to roughly 17 to 20 meters per second and generally remains around 10 to 15 meters per second through February. A reversal of those winds can be associated with a sudden stratospheric warming, which represents a major disruption of the polar vortex.
During a Sudden Stratospheric Warming, temperatures high in the stratosphere can rise by several tens of degrees in just a few days. These stratospheric disturbances can take days to weeks to propagate downward into the lower atmosphere, though such an event does not automatically produce a major snowstorm or prolonged cold wave in the United States.
The Climate Prediction Center announced that El Nino is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter of 2026-27. NOAA also noted a 75% chance that the October-December period will reach the threshold for a historic-strength event based on records dating back to 1950. Strong El Nino events can alter atmospheric circulation and influence the jet stream, and long-range analysis indicates the developing strong El Nino could help create a pattern favorable for a midwinter polar-vortex disruption. The report also notes that that might sound like a recipe for a brutally cold winter. The report also notes that the bigger question for winter is what happens after that. The report also notes that the circulation is strongest when the temperature difference between the cold polar region and warmer areas farther south becomes large. The report also notes that for now, that’s not necessarily bad news for the United States. The report also notes that that potential shift is what meteorologists will be watching. The report also notes that the combination can produce snowstorms and blizzards, when Arctic air meets a moisture-rich storm system. The report also notes that the polar vortex naturally develops during late summer and fall as sunlight decreases over the Arctic and the stratosphere begins to cool.
Winter Regional Outlook
- Southern Tier: Wetter than normal, with frequent storms possible from California through Texas, the Gulf Coast and the Southeast. Some storms could bring sleet, freezing rain or heavy, wet snow when cold air moves in.
- West: Changeable conditions are expected, with the Pacific Northwest seeing a less predictable snow season. The southern Rockies could see above-average mountain snowfall.
- Northern Plains, Upper Midwest and Great Lakes: Temperatures are expected to average near normal, but quick cold snaps, snow squalls, blustery winds and brief snowy periods are possible.
- Middle of the country: Expect frequent swings between thawing and freezing conditions, creating rapidly changing road and field conditions.
