Polar Vortex Wobbles Two Weeks Ahead of Record Temps, France’s Weather Impact Remains Uncertain

Over the Arctic, the winds in the stratosphere collapsed within a few days at the end of October 2026. Models forecast a possible reversal around November 10, which would represent the earliest major stratospheric warming ever recorded. Yet we must understand what this criterion measures and why a cold spell in France is not automatic.

The wind measured at 60°N and 10 hPa fell from 22 to 5 meters per second between October 25 and November 2

The polar stratospheric vortex is a ring of westerly winds that circles the pole in the stratosphere, around 30 kilometers above the surface. It normally strengthens in autumn, when the polar night cools the Arctic. Therefore, its abrupt weakening comes as a surprise.

According to the NASA Ozone Watch series, the mean wind at 60°N was 22.13 m/s on October 25 and 5.44 m/s on November 2. The average for that date is around 25.6 m/s, and the previous minimum was 13.7 m/s. Consequently, the vortex is already outside any known reference for the season.

On November 4, the Met Office described an elongated vortex, disrupted by waves coming from two opposite directions. This configuration, termed “Wave 2,” favors a separation into two lobes. Simultaneously, the stratosphere warms above the pole.

An inversion around November 10 would surpass the late-November episodes of 1958 and 1968 recorded by NOAA

A sudden stratospheric warming becomes “major” when the mean wind at 60°N shifts from west to east. Yet, several members of the ensemble from the ECMWF (the CEPMMT) foresee this reversal between November 9 and 11. The Met Office, however, regards it as weak and brief, with no certainty that it will occur.

The NOAA compendium, which covers reanalyses dating back to the late 1950s, places the earliest episodes on November 30, 1958 and between November 27–29, 1968. From there, a confirmed inversion by mid-November would gain more than two weeks. However, this record only applies to that database, updated through 2023.

The NOAA CPC labeled the phenomenon as a “rare” disturbance on October 30. It also anticipated a negative Arctic Oscillation, a sign of weakened surface west-to-east flow, with possible effects lasting about two months.

The possible descent of the anomaly to the surface would take two to six weeks, with no guaranteed cold spell or snowfall

Such warming affects daily weather only if the anomaly descends into the troposphere. According to the Met Office, this coupling generally develops over two to six weeks, and it does not occur with every episode. Thus, the first potential effects would not appear before late November or December.

When the coupling works, the jet stream slows and becomes more wavy. Arctic air can then descend into North America, Europe, or Siberia, depending on the position of the lobes.

In the face of a powerful El Niño, the seasonal forecast keeps a milder winter as the main scenario

The vortex is not the only factor guiding the season. Indeed, the CPC had given on October 8 more than an 83% chance of a strong to very strong El Niño for January–March 2027. With the Indian Ocean Dipole, it weighs on large-scale circulations.

France’s meteorological service favored a November–January quarter milder than normal, without ruling out cold spells. No organization cited anticipates a broad-based cold spell across Europe. Ultimately, mid-November will indicate whether the inversion is confirmed and whether the lower atmosphere takes over.