Polar Vortex disruption expected after January stratospheric warming
A Sudden Stratospheric Warming (SSW) event evolving over the Arctic through mid-January 2026 is forecast to weaken and displace the Polar Vortex, according to ECMWF and NOAA extended-range guidance. The disturbance is expected to propagate downward over the following weeks, raising the probability of Arctic air outbreaks and colder-than-normal conditions in parts of North America and Europe during the second half of January 2026.
Image credit: Stratobserve
Forecast models suggest a Sudden Stratospheric Warming (SSW) event could develop over the Arctic during mid-January 2026.
Temperature anomalies between the 10 and 30 hPa levels show a rapid increase in the polar stratosphere, indicating a disruption of the wintertime circumpolar circulation that confines cold air to high latitudes.
Forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Global Forecast System (GFS) indicate a continued warming trend in mid-January, leading to a stretched and displaced Polar Vortex.
While model guidance does not yet indicate a full reversal of stratospheric winds at 10 hPa, the disturbance is strong enough to alter hemispheric wave patterns and affect surface weather later this month.
Such disruptions typically require 1 to 3 weeks to propagate downward into the troposphere. Current ensemble data suggest that this process could produce enhanced atmospheric blocking near Greenland and the North Atlantic, favoring northerly and north-easterly flow into Europe.
The resulting cold anomalies are most likely across Scandinavia, the British Isles, and parts of Central and Eastern Europe during the second half of January.
The developing stratospheric anomaly is forecast to support deeper troughing over western and central regions of North America, allowing Arctic air to extend periodically into the northern Plains, Great Lakes, and northeastern United States. The pattern is expected to remain variable, with alternating mild and cold phases rather than a uniform freeze across the continent.
Ongoing weak La Niña conditions in the tropical Pacific are reinforcing the large-scale circulation favorable for SSW development. Historically, La Niña winters have increased planetary-wave activity that can disturb the stratospheric vortex.
The current combination of La Niña forcing and polar stratospheric warming increases the likelihood of repeated cold intrusions and intermittent snowfall events through late January.
While high-latitude circulation weakening is evident, regional surface impacts depend on the magnitude of stratosphere-to-troposphere coupling and concurrent teleconnections such as the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). Model ensembles trend toward a negative AO phase after mid-January.
While forecast confidence remains moderate as of early January, stratospheric temperature anomalies continue to strengthen, and the Polar Vortex remains displaced from the pole.
If downward coupling proceeds as forecast, colder air masses, enhanced snow activity, and increased jet stream waviness are expected to emerge gradually from mid- to late January 2026 across the Northern Hemisphere.
References:
1 Polar Vortex 2026 Update: New Stratospheric Warming Detected, Winter Shift Likely in January – SWE -January 2, 2026
2 Rare sudden stratospheric warming forecast to develop over the Arctic in late November 2025 – The Watchers – November 20, 2025
I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.
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