Meteorologists are monitoring a potential sudden stratospheric warming (SSW) this November that could displace the polar vortex and send Arctic air into the United States. MIT climatologist Judah Cohen says a confirmed November SSW would be unprecedented in the satellite era and could trigger colder, snowier conditions starting in December. La Niña would still influence the path of cold air, but the polar vortex's behavior is likely to be the primary factor in how cold it gets. If the stratospheric warming couples strongly to the surface, odds tilt toward a colder winter; if coupling is weak, the season may remain milder.
La Niña vs. the Polar Vortex: Rare Stratospheric Warming Could Reshape U.S. Winter
Meteorologists are monitoring a potential sudden stratospheric warming (SSW) this November that could displace the polar vortex and send Arctic air into the United States. MIT climatologist Judah Cohen says a confirmed November SSW would be unprecedented in the satellite era and could trigger colder, snowier conditions starting in December. La Niña would still influence the path of cold air, but the polar vortex's behavior is likely to be the primary factor in how cold it gets. If the stratospheric warming couples strongly to the surface, odds tilt toward a colder winter; if coupling is weak, the season may remain milder.
03:37 PM, 11/15/2025Environment
Possible November stratospheric warming could alter the winter outlook
Researchers are watching an unusual development in the polar stratosphere that could change the winter forecast across much of the United States. Climatologist Judah Cohen, a research scientist at MIT, warns the atmosphere is at a "critical juncture" and that events in November could become a "fork in the road" for the rest of the winter season.
Several weather models are signaling a potential sudden stratospheric warming (SSW) this November — a rapid temperature rise high above the North Pole that can paradoxically lead to colder conditions at the surface. If an SSW occurs and couples down to the troposphere, it can displace the polar vortex and steer Arctic air southward into the U.S.
"It is the largest type of disruption that occurs to the polar vortex," Cohen said, noting that polar stratospheric temperatures can climb more than 100°F in a matter of days during an SSW.
If confirmed, a November SSW would be notable: modern satellite records show no prior November events, though historical reconstructions suggest possible occurrences in 1958 and 1968. Cohen cautions that pre-satellite stratospheric data are less reliable, so a verified November SSW now would be extraordinary in the modern record.
How the polar vortex and La Niña could interact
The relationship between a displaced polar vortex and La Niña is complex. Cohen explains that the polar vortex's configuration largely determines how cold it gets, while La Niña helps steer where the cold air travels. There is no simple "winner" between the two; instead, their interaction shapes regional impacts.
Two broad scenarios are possible:
- Strong coupling: If the stratospheric warming strongly influences the troposphere and the jet stream, the U.S. could see an extended period of colder and/or snowier conditions beginning in December and possibly persisting into early January.
- Weak or short-lived coupling: If the SSW does not effectively couple to the surface, the U.S. may remain relatively mild overall, increasing the likelihood of a more moderate winter.
Forecast uncertainty remains high. Models can indicate an SSW is developing, but whether and how it propagates downward to impact surface weather depends on complex atmospheric dynamics. Meteorologists will watch the evolving pattern closely in the coming weeks.
Context: This analysis originally appeared in USA TODAY. Judah Cohen’s comments reflect current model signals and the range of plausible winter outcomes; updates will follow as observations and model guidance evolve.