Rare polar vortex split could bring sub-zero weather to Switzerland

A rare polar vortex split, the earliest recorded since the 1950s, could bring freezing temperatures to Switzerland in early November. Here’s what to expect.

Vortex winds weakening above the North Pole

November is shaping up to be a little chillier than usual as NASA forecasts show previously predicted polar vortex winds are weakening earlier than forecast. 

Polar vortex wind speeds are expected to fall from 12,03 meters per second (equivalent to 43,2 kilometres per hour (km/h)) on October 31, to the equivalent of 32,9 km/h on November 1 and 14,9 km/h on November 3.

A strong polar vortex keeps very cold winds over the North Pole, but a weakened vortex can send freezing temperatures south toward Europe and North America. But there is an additional factor at play.

If a pocket of warm air, known as a sudden stratospheric warming (SSW), forms over the North Pole, it can cause the polar vortex to stretch like a tense rubber band and split. This is what ultimately pushes polar air downward and causes an influx of cold air at ground level. 

Vortex split could send polar weather to Switzerland

A weakened polar vortex and sudden stratospheric warming over the North Pole could then bring a cold snap to Switzerland, expected around November 4.

Meteorologist Klaus Marquart told 20 Minuten that a weakened polar vortex has not occurred so early in the winter since records began in the 1950s. The only other years when a vortex split occurred so early were in 1968 and 2025, and then it began almost a month later, on November 28.

So, what is unusual about the polar vortex split forecast is not that it is happening, but that it is forecast to happen so early in the winter. 

The forecast split is expected to be rather weak, meaning that if it does happen, temperatures will rise again shortly after. Referring to current models, Wetter.com expects the split to subside again by November 11. 

This article originally appeared on IamExpat Germany.