Eastern UK could see higher chance of snow if polar vortex weakens further

Eastern parts of the UK could have a greater chance of snow if the weakening polar vortex alters the jet stream and allows colder air to move south, BBC meteorologist Simon King has said. He described the possibility over the following days and weeks, rather than giving a specific date or local forecast.

King said the circulation of winds high above the Arctic had weakened and shifted position in recent days. The vortex had stretched and briefly split into two smaller circulations, he wrote in a BBC weather blog.

The polar vortex is a ring of strong winds in the stratosphere, around 10 to 30 miles above the Earth’s surface. It helps keep some of the coldest air near the polar region. The winds usually strengthen as autumn takes hold across the Arctic.

Some forecasts showed the winds might reverse by mid-November. King said that if the weakening continued and the winds eventually reversed, the event would be classed as a major sudden stratospheric warming, or SSW. A reversal on its own was not described as sufficient to establish that event.

SSW events involve temperatures rising rapidly high in the atmosphere and can weaken the winds that circle the pole. The westerly winds may turn easterly. King said changes in the stratosphere can affect the jet stream, potentially favouring a blocked weather pattern. That could bring drier conditions and colder northerly or easterly winds carrying Arctic air, as well as increasing the possibility of snow, particularly in eastern UK.

The timing has drawn attention because such disruptions are more commonly associated with mid-winter. Jeff Knight, the Met Office’s lead climate scientist, told the BBC that the development appeared to be the earliest on record in 75 years of observations and was very unusual.

Met Office presenter and meteorologist Aidan McGivern said El Niño can enhance waves in the troposphere, the layer of the atmosphere where the jet stream operates. Those waves can travel upwards into the stratosphere and disturb the circulation around the pole, potentially displacing, deforming or splitting it.

The Met Office’s longer-range outlook had pointed to a turbulent start to winter, with colder conditions becoming more likely later in the season, broadly in line with El Niño expectations.

King’s comments set out a conditional risk, not a prediction that snow will fall. The possible impact depends on whether the vortex continues to weaken, how the jet stream responds and whether colder air reaches the UK.

Information on this page is refreshed from the connected theuk.fyi services when the interactive page loads.