Polar Vortex Weakens Earlier Than Ever Recorded: What It Means for Winter

The polar vortex, the ring of fast winds that normally keeps the coldest air locked over the Arctic, is weakening at a point in the season that forecasters describe as unprecedented. According to the Met Office, it is the earliest such weakening in at least 75 years of modern records.

The immediate effect on the UK looks limited, scientists told The i Paper, but the event raises the chances of colder spells later in winter. Researchers cited by Smithsonian Magazine say they do not yet know how it will interact with this year's very strong El Niño.

What is happening above the Arctic?

Smithsonian Magazine describes the polar vortex as a ring of westerly winds that forms about 10 to 30 miles above the Earth's surface. It usually peaks in December and January and weakens later in the season. This year it is already disrupted, and forecasts cited by Bloomberg suggest it could collapse within the next week.

HuffPost UK reported that the BBC said the vortex had weakened and shifted position in recent days, with some forecasters predicting a reversal of its winds by mid-November. The Met Office said the vortex is being stretched in opposite directions, a pattern called wave two activity, and that this is considerably stronger than average for the time of year.

What is a sudden stratospheric warming?

A sudden stratospheric warming, or SSW, happens when temperatures in the stratosphere spike within a few days, according to Smithsonian Magazine. The jump can weaken or even reverse the vortex's winds and sometimes splits it apart, allowing cold air to be pushed south.

Why is the timing so unusual?

Researchers have kept reliable records of these events since 1958. NOAA meteorologist Laura Ciasto told USA Today that only two other SSWs have been documented in November, Smithsonian reported. The earliest previous disruption came on Nov. 28, 1968, according to Scientific American.

Jeff Knight, a lead climate scientist at the Met Office, told the BBC that if the weakening develops into an SSW, it would be the earliest in the 75 years of observations. HuffPost UK noted that earlier forecasts had put the chance of an SSW at about 25%, but the outlook has shifted since.

Could El Niño be behind it?

The cause is not yet clear. Amanda Maycock, a climate scientist at the University of Leeds, told The i Paper that the very strong El Niño in the Pacific is one potential contender. She said the likelihood of an SSW is higher than normal during El Niño, and that a record-breaking event could have contributed to the early timing. The Met Office has called this El Niño the “strongest in living memory.”

What does this mean for winter weather in the UK and the U.S.?

For the UK, the short-term picture is modest. Matthew Patterson of the University of St Andrews said such an event does not guarantee cold weather but “changes the odds.” He added that the impact is probably weaker than if it came in December or January, when the winds are stronger. Maycock said there is a risk of a cold snap towards the end of next week, though it is unlikely to be extreme. HuffPost UK noted that there is also less cold air available in Northern Europe than at the usual time of year for such an event.

Later in winter is a different question. Maycock said long-range forecasts show a very high chance of another such event. The Met Office says SSWs have been linked to cold, snowy spells such as the Beast from the East in 2018, and that they can bring a long spell of dry, cold weather. Maycock warned that cold, calm and dry conditions during the months when rain normally falls would reduce water storage recharge and might prolong the drought that still affects much of the UK.

In North America, Smithsonian reported that El Niño years usually mean milder winters, but a vortex split could bring cooler temperatures. A 2021 disruption pushed cold air into Texas, contributing to the Great Texas Freeze, which caused more than 200 deaths and left more than 4.5 million homes and businesses without power. The magazine stressed that this does not mean the same will happen now. AccuWeather meteorologist Alex DaSilva said El Niño will still be the primary driver of this winter, and the company is still forecasting a “very warm” Northeast and northern Midwest.

What do scientists still not know?

Quite a lot. Simon Lee, a polar vortex researcher at the University of St. Andrews, told Bloomberg that when several exceptional events coincide, it is hard to know what to expect, and a rapidly warming climate makes it harder. Patterson told The i Paper that El Niño can affect weather through several pathways, bringing cold through the stratosphere or storms through the lower atmosphere. Researchers will keep watching temperature and wind patterns, including for any further disruption later in the winter.

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Around Prague, based on reporting by HuffPost UK, Smithsonian Magazine, The i Paper