Early polar vortex disruption could bring colder weather, but London snow is uncertain

The polar vortex has weakened and shifted position unusually early in November, raising the possibility of a major Sudden Stratospheric Warming event—but it is too soon to tell whether the change will affect London’s winter weather.

Some forecasts indicate that the vortex winds could reverse by mid-November. Such a reversal could lead to a major warming event, which may disrupt the circulation high above the North Pole and increase the possibility of bitter Arctic air moving towards Europe. It does not mean that snow will reach the capital.

The polar vortex is a ring of strong westerly winds in the stratosphere, about 10 to 30 miles above the North Pole. It forms each autumn as Arctic temperatures fall. When the winds are strong, the system helps keep the most extreme Arctic conditions in northern regions. If the vortex weakens or breaks apart, weather patterns can become less stable.

Sudden Stratospheric Warming happens when large atmospheric waves rise from the Earth’s surface and disturb the stratosphere. Most major events occur in mid-winter. A major event can disrupt the polar vortex, increasing the possibility of colder air reaching Europe and snow in the UK.

Jeff Knight, the Met Office’s lead climate scientist, told the BBC that the current disruption appeared to be the earliest in 75 years of observations, adding that most experts considered it very unusual. The earliest date recorded for a major Sudden Stratospheric Warming event is November 28, in both 1969 and 2025.

The longer-range Met Office outlook is for a wet and windy start to winter in the UK, followed by colder periods in early 2027. That pattern is consistent with expectations associated with El Niño, a climate pattern developing over the Pacific Ocean. Knight suggested El Niño could have “helped load the dice” for a potential warming event.

A Sudden Stratospheric Warming event in early 2018 helped trigger atmospheric changes associated with the “Beast from the East”, which brought bitter winds and heavy snow to London. That episode provides context, but does not establish that similar conditions will occur this winter.

Freezing and snowy weather is not guaranteed. The Arctic has not yet reached the temperatures typical of mid-winter, and the polar vortex itself has only recently developed. Experts say it is too early to determine whether the current weakening will change the outlook for Londoners this winter.

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