Polar vortex weakening and possible UK snow, Digi Mart USA News (United Kingdom): High above the Arctic, powerful winds usually circle the North Pole each winter, helping trap some of the coldest air on Earth. This circulation, known as the polar vortex, has weakened and shifted position in recent days.
While such disruptions can occur during winter, scientists say an event this early in November is unprecedented in modern observations. Similar disruptions in past years have sometimes been followed by colder weather affecting parts of Europe and North America.
However, because this is happening so early in the season, there are few historical examples to compare with, and it could add even more uncertainty to current winter forecasts.
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 to 50 km) above Earth’s surface, locking the coldest air near the pole.
Atmospheric disturbances can cause the air high up to start warming, which weakens the vortex winds. This sudden stratospheric warming (SSW) can eventually lead to the strong westerlies reversing into easterly winds.
In the following days and weeks, these changes can alter the position of the jet stream, increasing the chance of a blocked weather pattern in which drier conditions develop with colder northerly or easterly winds bringing Arctic air southward. It can also boost the possibility of snow, especially in eastern parts of the UK.
Most SSW events tend to occur from mid-winter, but the current weakening of the strong winds is dramatic, with some forecasts even showing a reversal of the polar vortex winds by mid-November. Due to this weakening, the vortex has stretched and briefly split into two smaller circulations around the Arctic.
If the winds continue to weaken and reverse as forecast, this will be known as a major SSW event. Jeff Knight, lead climate scientist at 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.” The current earliest major SSW event occurred on 28 November in 1969 and 2025.
The reasons for such an early event are not clear, and it could simply be part of the natural variability of weather patterns. However, in a typical El Niño year, a weakening of the polar vortex often occurs toward the end of winter.
While the warmer waters of the Pacific in El Niño directly disrupt weather in tropical areas, pulses of energy in the atmosphere, known as planetary waves, can also cause disturbances in polar regions. These waves can push the polar vortex out of position and break the circulation apart.
With the current record El Niño taking forecasters into uncharted territory for disruption to global weather patterns, Knight suggested it could have “helped load the dice for this SSW event. However, because this is so rare, there’s not enough evidence.” A link between a strong El Niño and an early onset of an SSW event is unclear and will need further research.
Long-range forecasts issued by the Met Office show the UK is more likely to see a stormy start to winter, followed by a colder spell to end the season, which is consistent with expectations from an El Niño pattern. However, this unusually early SSW event was not widely expected.
Professor Andrew Perez-Charlton, meteorologist at the University of Reading, said: “The typical response to a SSW is for colder and drier conditions over Europe and the UK.” He added: “Because we haven’t seen a SSW event quite like this before, it is harder to anticipate a cold spell at the moment.”
The Arctic is not yet as cold as it becomes later in winter, and the polar vortex itself has only recently developed. Any influence it may have on weather patterns could therefore be weaker than during a mid-winter disruption.
Because the air is not yet at mid-winter temperatures, cold and snowy weather for the UK is far from guaranteed.
While snow is not likely in the coming weeks, a possible continuation of drier-than-average conditions would be concerning for the replenishment of reservoirs. Long-term forecasts are based on large-scale climate signals and how they have affected weather patterns in previous years.
Much of the outlook for this autumn and winter has focused on the influence of the exceptionally strong El Niño, pointing to a stormier start to winter, with the potential for colder and drier conditions from January.
For Perez-Charlton, the “concerning thing would be if this event ends up bringing the typical drier weather pattern and lack of rain” associated with sudden stratospheric warming over the coming months. With most of England and Wales still in drought, the country needs a wetter winter to fill extremely low reservoirs.
For now, experts stress that it is too early to know whether recent changes in the polar vortex will alter the winter outlook.
