Polar vortex weakens unusually early, raising uncertain cold-snap risk for Europe

Observed weakening high above the Arctic

The Met Office and Météo France are tracking an unusual disturbance in the polar vortex, a band of strong winds that normally circles the North Pole at heights of about 15 to 50 kilometres during winter. The disturbance was detected in early November 2026, and the two agencies say its consequences for European weather remain very uncertain. Météo France adds that the outcome will depend on how the disturbance evolves in the coming days. Scientists report that stratospheric winds have slowed sharply, and the vortex has stretched and briefly split into two smaller circulations around the Arctic. Forecast models point to a possible reversal of those winds, which would allow colder air to move towards the south.

An earlier break than in past records

Météo France told AFP that models agree on a significant disturbance of the upper atmosphere at the start of November, a development it says has never occurred before late November since the 1950s. The Met Office says the weakening is the earliest in the 75 years since modern records began. Jeff Knight, lead climate scientist at the Met Office, said as much to the BBC.

“It would appear to be the earliest on record looking back over the 75 years we've been observing.”

Knight added that most experts agree this is a very unusual event. Météo France notes that disturbances of this kind usually happen in January or February, when the vortex is typically weaker, so the timing is what sets this episode apart.

Possible links to El Niño

Professor Amanda Maycock, a climate scientist at the University of Leeds, names the strong El Niño developing in the Pacific as one of the leading candidate explanations. The Met Office describes this El Niño as the strongest in living memory. Maycock notes that during an El Niño event the chance of a sudden stratospheric warming is higher than normal, and she suggests the record strength of this event may have helped bring the weakening forward. The reasons for the early timing are not yet clear, and the pattern could partly reflect natural variability in weather systems. Grahame Madge, a Met Office spokesperson, told AFP that the effects could be less pronounced than in mid-winter, because the air source regions in Siberia and the Arctic are not yet as cold as they will be in February.

What could follow for Europe

Météo France estimates that the temperature gap between northern and southern Europe could strengthen within several weeks, with colder weather in the north and milder conditions in the south. Severe Weather Europe's analysis points to high pressure over southwest Europe and low pressure in the northeast for late November, with below-normal temperatures and more snow in the east. For December, the same analysis sees a signal for colder weather and more snow across much of Europe, except the north and northeast. Some forecasts show the winds reversing by mid-November, which would let Arctic air move south.

The Met Office notes that a weakened vortex can disturb the westerly winds and bring drier weather, and these outlooks may shift as the models evolve.