The Met Office has issued a fresh update on the weakening polar vortex, which could bring disruption to the UK and Europe this winter. The update follows what has been confirmed as the hottest UK summer on record, and comes as an unprecedented El Niño event is set to build in late 2026.
El Niño is a natural climate pattern marked by the warming of sea surface temperatures in the central and east-equatorial Pacific Ocean. A research paper published by the US government's NOAA Chemical Sciences Laboratory concluded that El Niño "tends to promote the breakdown of the polar vortex, especially in late winter".
What is the polar vortex?
The polar vortex is a band of strong westerly winds that circles the North Pole high in the stratosphere, trapping bitterly cold air near the Arctic. When the vortex weakens or is disrupted, it becomes "wavy" and allows cold air to spill southward into mid-latitude regions such as North America and Europe.
If this happens, the UK would likely face extremely windy conditions, with experts saying it could bring cold and snow over the coming months. According to the GFS weather model, October may mark the beginning of months of cold weather.
Sudden Stratospheric Warming risk
The Met Office explained: "Through the latter part of the winter, following a peak in El Niño, the stratospheric Polar Vortex can become weaker, leading to an increased chance of Sudden Stratospheric Warming (SSW) events unfurling, increasing the potential for cold weather."
SSW involves warming between 10km and 50km above the Earth's surface. It can cause cold air to rush downwards, impacting the jet stream and potentially creating a "blocking pattern". If these patterns persist, cold conditions could remain for the rest of the year.
Dr Will Lang, chief forecaster at the Met Office, described the effect as a "subtle shift in the odds" rather than a certainty. He said: "We are going in with a heightened potential for wet weather, heightened potential for potentially stormy conditions, and that leads through to a heightened potential for flooding."
