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Met Office watches polar vortex for potential early winter cold spell

Summarised from 3 outlets · Updated 6 Nov, 10:42 · Archive

The Met Office is monitoring an unusually early sudden stratospheric warming event that could bring colder weather and snow to the UK this winter.

The Met Office is monitoring a potential unusually early sudden stratospheric warming (SSW) event that could bring colder weather, ice or snow to Essex and the UK in the coming weeks. Experts predict this could be one of the earliest such events on record.

The stratospheric polar vortex is a vast circulation of powerful winds high above the Arctic that helps shape winter weather across the Northern Hemisphere. Changes in its strength and shape can shift the jet stream and alter weather patterns across regions below.

A strong, stable polar vortex typically supports a powerful, relatively straight jet stream across the North Atlantic, bringing milder, wetter and windier weather to the UK. A weaker vortex, by contrast, can make the jet stream more erratic, allowing Arctic air to move south and high pressure to disrupt the usual westerly wind patterns. This increases the chance of colder, drier spells, particularly if winds turn easterly or northerly.

During a sudden stratospheric warming event, polar stratosphere temperatures can soar within days, weakening the vortex's powerful westerly winds. However, an SSW does not automatically mean cold weather will reach the UK. The Met Office says the outcome depends on how the lower atmosphere responds, including the positions of high and low pressure, the jet stream's behaviour and weather patterns over the North Atlantic and Europe.

According to the Met Office, when an SSW affects conditions near the surface, it can weaken the jet stream and encourage blocking high pressure over the North Atlantic, Greenland or Scandinavia. This would disrupt Atlantic weather systems and change the air reaching the UK.

Met Office watches polar vortex for potential early winter cold spell
Image: Colchester Gazette

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In this story: Met Office · Essex · UK · Arctic · Northern Hemisphere · North Atlantic · Greenland · Scandinavia

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