Early polar vortex split may impact UK snow and drought
06 November 2026
The polar vortex is the band of strong winds that circles around 30km above the Arctic each winter. It has weakened unusually early this season, in what is known as a sudden stratospheric warming (SSW). Scientists say a disruption this early is unprecedented in modern observations.
Professor Andrew Charlton-Perez, a meteorologist at the University of Reading, and Head of the School of Mathematical Physical and Computation Sciences, is a researcher on changes in the Arctic stratosphere and the impact of sudden stratospheric warmings on UK weather and forecasts, provides expert comment.
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Professor Andrew Charlton-Perez said:
"We've never seen anything like this before. Our best records go back to 1979, when satellite observations began, and we have reasonable records back to the 1940s. In all that time, we haven't seen a sudden stratospheric warming earlier than very late November.
"This is unusual because the polar vortex has to form first, before it can it interact with the atmospheric waves that travel up from the lower atmosphere, and those waves are what cause these events to occur. Our records are relatively short and SSWs are still quite rare, only usually happening about once every two years, but this is certainly new territory from what we know.
"It's too early to say whether the current record strong El Niño event in the Pacific is the cause of this without more analysis. El Niño usually weakens the vortex and can make an SSW more likely in late winter, during January or February. But the vortex was not unusually weak before this event began. It is still so early in the colder seasons for the northern hemisphere that the vortex hadn't had much time to form or be impacted by the effects of El Niño.
UK snow or drought?
"An SSW normally means the UK is, on average, colder and drier, with more settled conditions and often blocking high pressure.
"Because this is so early in the season, I think snow now in the UK is unlikely, and the forecasts don't currently suggest it. There is still too much heat in the oceans, land and atmosphere left over from summer to make snow likely. Later in the winter, the link between an SSW and snowy weather would be stronger.
"Perhaps a bigger concern would be a long dry spell. Our water resources in some parts of the UK are very low after an exceptionally dry and warm summer. Some parts of the UK are still in drought or even severe drought, and we need more than 120% of our usual rainfall every month over the winter to come out of it. If this event or other SSW events during winter bring prolonged periods of dry weather, it could stop our reservoirs from refilling over the winter. That could have extremely significant impacts on water supplies for homes, businesses and farmers next summer.”
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