Several dozen kilometers above the Arctic, the winds that usually accompany winter's arrival are showing unusual weakness.
Each autumn, a vast circulation of cold air forms around the North Pole. This is the polar vortex, a region where powerful winds generally rotate from west to east. It normally strengthens as winter approaches. This year, observations and weather forecasts are showing something unusual: its winds slowed sharply at the beginning of November.
Diagram comparing a stable polar vortex, on the left, with a disrupted one, on the right, showing cold air circulating farther down toward the mid-latitudes.
Credit: NOAA / Climate.gov, public domain.
At around 30 kilometers above the ground, in a layer called the stratosphere, the winds form a belt around the polar air. When this circulation holds firm, it helps maintain a relatively stable organization of air masses at high altitudes. Like a natural barrier containing frigid air in the north.
However, this belt can be disrupted by large atmospheric waves that transport energy from the lower layers. The air above the Arctic then warms rapidly, and the winds lose strength. In some cases, they even end up rotating in the opposite direction. Meteorologists then refer to this as sudden stratospheric warming.
The phenomenon is attracting particular attention this November 2026. Scientists at the European Centre for Medium-Range Weather Forecasts have reported an exceptionally early disruption. Data used by an independent polar vortex monitoring service indicated nearly calm winds in early November, compared with the roughly 26 meters per second normally observed at this time of year.
The November 8 forecasts go further: the various European model calculations anticipate a reversal of the winds before November 22. But a forecast remains a forecast. It proves neither that the phenomenon will reach its full intensity nor that it will produce the same consequences as in previous winters.
And what about the weather near us? A disruption at high altitude can sometimes alter the circulation of lower-level winds several weeks later. Cold air from the north can then reach certain regions of Europe, Asia, or North America. Yet the countries affected and the duration of the cold remain impossible to determine from this observation alone.
One might think that a weakened vortex automatically means snow. That is not the case. Some sudden stratospheric warming events do not lead to any significant cooling at the surface. Weather also depends on many air movements much closer to the ground.
Another question remains open: why is this disruption happening so early? Researchers have suggested a possible influence from El Niño, linked to the warming of tropical Pacific waters, without being able to establish this connection. The next observations will mainly show whether the winds actually reverse, and then whether this change spreads into the lower layers of the atmosphere.