SCIENTISTS IDENTIFY EARLY NOVEMBER WEAKENING OF POLAR VORTEX

Scientists say the polar vortex has weakened and shifted above the Arctic in recent days, describing disruption this early in November as unprecedented in modern observations. The circulation has stretched and briefly split into two smaller circulations around the Arctic. Met Office lead climate scientist Jeff Knight said: "It would appear to be the earliest on record looking back over the 75 years we've been observing…with most experts agreeing this is a very unusual event." Scientists have not established why the weakening has occurred so early.

The polar vortex develops each autumn as Arctic temperatures fall, with strong westerly winds forming in the stratosphere. These winds circulate roughly 15–50km above Earth's surface and help keep the coldest air near the North Pole. Atmospheric disturbances can warm the air at that height, weakening the circulation through a process known as sudden stratospheric warming. Scientists classify an event as a major sudden stratospheric warming when the winds reverse from westerly to easterly.

The observational record places the earliest previous major events on 28 November, in both 1969 and 2025. Similar disruptions have sometimes preceded colder weather in parts of Europe and North America. Changes in the circulation can alter the jet stream and establish weather patterns that bring Arctic air southwards. Scientists have few historical examples from this early in the season against which to assess the current disruption.