Early polar vortex weakening may bring drier UK winter, not snow

The polar vortex, the band of strong winds that circles the Arctic each winter, has weakened unusually early this year, in what scientists say is the earliest such event on record.

What is happening

The polar vortex develops every autumn as temperatures fall in the Arctic. Strong westerly winds form in the stratosphere, roughly 10 to 30 miles (15-50km) above Earth's surface, locking the coldest air near the pole. Atmospheric disturbances can cause the air high up to warm, weakening the vortex winds. This is known as sudden stratospheric warming (SSW).

Most SSW events occur from mid-winter, but forecasts show the vortex winds could reverse by mid-November this year. If the winds reverse, it will be known as a major SSW event. The current earliest major SSW events occurred on 28 November in 1969 and 2025.

Jeff Knight, lead climate scientist from the Met Office, told the BBC: "It would appear to be the earliest on record looking back over the 75 years we've been observing…with most experts agreeing this is a very unusual event."

Snow or drought

Professor Andrew Charlton-Perez, meteorologist at the University of Reading, told the BBC: "The typical response to a SSW is for colder and drier conditions over Europe and the UK."

He said snow is unlikely in the coming weeks because there is still too much heat in the oceans, land and atmosphere left over from summer. The link between an SSW and snowy weather would be stronger later in the winter.

Charlton-Perez said the "concerning thing would be if this event ends up bringing the typical drier weather pattern and lack of rain" associated with a sudden stratospheric warming over the coming months. With most of England and Wales still in drought, experts say a wetter winter is needed to fill up extremely low reservoirs.

Why it matters

The early disruption of the polar vortex presents meteorologists with a situation for which there are few modern comparisons. Experts stress that it is too early to know whether recent changes in the polar vortex will change the winter outlook.

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Sources

• bbc.com: Could the earliest weakening of the polar vortex on record bring UK snow? - BBC Weather
• express.co.uk: Professor tells BBC the 1 'most concerning' impact of polar vortex — not snow | UK | News | Express.co.uk

This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.