In summary, a strong polar vortex usually corresponds with a strong and stable jet stream, while a weak polar vortex leads to a weaker and wavier jet stream.
When the polar vortex is strong, the jet stream tends to flow more powerfully and steadily in a circular pattern around the poles, effectively containing the cold air within the polar regions.
The Met Office explains: “As the cold air from high up in the stratosphere disperses, it can affect the shape of the jet stream as the cold air sinks from the stratosphere into the troposphere.
In summary, SSW weakens the polar vortex, causing cold Arctic air to move southward, leading to colder weather in the UK.
A weaker jet stream allows more frequent spells of northerly or easterly winds to affect the UK and, in winter, these bring very cold air from the Arctic and continental Europe.”.
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