The Met Office has issued new predictions suggesting that a disturbance in the North Pole could bring snow, fog and freezing frost to the UK even earlier than previously thought.
The forecaster says a Stratospheric Polar Vortex is set to be 'displaced' from the North Pole, which could bring much colder conditions to the UK and Europe despite it being 'exceptionally early' in the season for such a wintry blast. Snow is still not confirmed at this point.
Sudden Stratospheric Warming Signs
The Met Office has set out how a Stratospheric Polar Vortex high above the North Pole is 'currently being disturbed', with signs of 'sudden stratospheric warming' which can bring colder weather. The meteorologists said that this is an 'exceptional development for this early in the season' and that it could be linked to the current El Niño weather phenomenon in the Pacific.
The Met Office said: "During autumn, the stratosphere above the North Pole becomes increasingly cold as the Northern Hemisphere receives less sunlight. The growing temperature contrast between the Arctic and lower latitudes helps strengthen a ring of westerly winds around the pole, known as the stratospheric polar vortex."
It added: "The stratospheric polar vortex high above the North Pole is currently being disturbed, with signs that a sudden stratospheric warming (SSW) is developing. It is an exceptional development for this early in the season and there is an intriguing connection with the current exceptional El Niño in the tropical Pacific."
El Niño Connection
The Met Office said: "This wave two activity is considerably stronger than average for the time of year. Forecasts suggest the vortex will subsequently become increasingly displaced from the North Pole."
Met Office presenter and meteorologist Aidan McGivern said: "El Niño is basically enhancing the waves that go on in the troposphere, the wriggly jet stream. Those waves can then propagate upwards into the stratosphere, knocking, bumping and disturbing that circle of winds around the polar stratosphere, causing it to be displaced, pushed off the pole, deformed or even split."
It is a good example of a "teleconnection", the Met Office adds, where atmospheric changes in one part of the world influence weather patterns thousands of kilometres away.
Forecast Outlook
The current disturbance is already producing warming in the stratosphere above the North Pole. Forecasts now show temperatures continuing to rise, while the normally westerly winds surrounding the vortex weaken. If it does happen, its timing would be particularly notable, the forecaster says, adding: "It would be exceptionally early in the season compared with the events meteorologists are more accustomed to analysing later in winter."
Mr McGivern adds: "We know that El Niños increase the chances, through this chain of events, of sudden stratospheric warmings happening, and we know sudden stratospheric warmings increase the chance of colder weather for the UK. So we've got this chain of events that we can start to flag well in advance."
The Met Office adds: "High pressure over the UK could bring quieter, drier conditions with an increased likelihood of frost and fog. Blocking farther north could encourage easterly winds, while high pressure to the west could make northerly winds more likely. Historically, an SSW increases the chance of colder UK weather, but the outcome is far from guaranteed."
That uncertainty is particularly important with such an early-season event because there is generally less cold air available across the Northern Hemisphere than later in winter. For now, therefore, this is not a forecast of an impending UK cold spell. Instead, meteorologists will be closely monitoring the polar vortex and whether changes in the stratosphere eventually work their way down into the part of the atmosphere where day-to-day weather takes place.
