Unusually early sudden stratospheric warming weakens polar vortex

Forecasters are watching an unusually early sudden stratospheric warming event that has weakened the polar vortex above the Arctic. The polar vortex is a ring of strong winds in the stratosphere that usually traps cold air over the North Pole in winter. Sky News described it as a band of westerly winds 10 to 50 kilometres up that circles the Arctic.

ITV weather presenter Alex said the event was highly unusual and could be felt later this month. If the warming develops into a major event, it would be the earliest on record, normally occurring at the end of winter rather than November. Alex said high pressure to the north and low pressure to the south could squeeze winds into an easterly direction, bringing cold but largely dry weather. ITV reported that a major stratospheric warming last year did not produce the expected cold.

Sky News science and technology editor Tom Clarke said forecasters were looking at the collapse of the polar vortex and the prospect of freezing conditions. Sky News reported that the event could shift the low-altitude jet stream and allow high pressure to build across North America and northern Europe. It is the earliest such event on record, and Sky News reported it is occurring during one of the most powerful El Niños ever seen, leaving forecasters in uncharted territory.

Channel 5's weather journalist Nathan Rao said the polar vortex is a spinning circle of very cold air over the Arctic. He said sudden stratospheric warming can dislodge or split the vortex, which is sometimes linked to colder UK weather but not always. This is the earliest sudden stratospheric warming ever recorded, and Channel 5 said the usual six-week lag would point to any cold spell arriving later in the winter, before the new year. Rao said the timing could fit a white Christmas if the vortex splits and cold weather follows.

BBC weather's Matt Taylor said the polar vortex is like a donut of strong winds that circle the North Pole in the stratosphere. BBC News reported that this year's changes are happening earlier than usual and could bring an earlier than expected taste of winter. It said the event may be linked to a strong El Niño. BBC News reported that if it becomes a major sudden stratospheric warming, it would be the earliest in 75 years of observations. Matt Taylor said the early timing and a relatively mild Arctic in late autumn add uncertainty to the forecast.

All four channels linked the phenomenon to the 2018 Beast from the East. Sky News reported that the 2018 storm brought temperatures as low as minus 14 Celsius to southern England and caused widespread disruption, with snow closing schools and blocking roads. Forecasters say the current event may not produce the same severity, partly because it is early in the season and the Arctic is still cooling. BBC News also reported that a long period of blocked flow could bring a lack of rain, which would matter for parts of southern England in severe drought.