The polar vortex is a stratospheric area of low pressure across the North Pole that forms during autumn. As it grows, westerly stratospheric winds strengthen at mid-latitudes in the northern hemisphere and allow cold air to build up across the North Pole.
These westerly stratospheric winds are what is known as the jet stream. The jet stream typically drives UK weather, with areas of low pressure from the Atlantic bringing the cloudy and wet weather that we are used to. However, the strengthening of the jet stream through autumn and winter as a result of the expanding polar vortex is why we see stormier conditions during late autumn and winter compared with other periods of the year.
An example of the link between a strong polar vortex and stormier weather came just last week. Many parts of the UK had frequent spells of wet and windy weather between Monday and Thursday. This included Storm Brendan, which brought strong winds and heavy rain to southern and western areas in particular.
This coincided with the polar vortex being almost at record strength. And just as the polar vortex weakened later last week, so the weather calmed down.
