So, changes in the polar vortex in the stratosphere can affect the strength of the jet stream and as a result whether we get milder or colder weather in winter. This has been linked to many spells of cold winter weather in recent years. Sometimes the polar vortex can even break down entirely, in an event called a ‘ Sudden Stratospheric Warming’. 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. With a stronger jet stream, stormy and very wet weather tends to occur. In a typical UK winter, the jet stream brings winds from the west giving us our mild, damp climate. The jet stream is a fast moving ribbon of air around 5 to 7 miles (8 to 11km) above the earth that drives weather systems from the Atlantic towards the UK.Ĭonversely, when the polar vortex weakens, the jet stream also tends to weaken and become distorted. The Arctic stratospheric polar vortex (hereafter referred to as the polar vortex) is known to affect Northern Hemisphere winter weather on subseasonal-to-seasonal timescales 7,8,9,10,11.Persistent. "Forecast models struggle with predicting a splitting of the vortex more than a week in advance.How does the Polar Vortex affect our weather?Ī strong polar vortex favours a strong jet stream. The polar vortex might split further in about 10 days, "but it's unclear if this will happen," Butler said. During that time, it began to (but didn't completely) split, Cohen said. 5, the polar vortex's counter-clockwise winds reversed direction (a clue that a sudden atmospheric warming event had happened) and the vortex wandered from its usual location centered over the North Pole, toward Europe and the North Atlantic, Butler said. Related: Images of melt: Earth's vanishing ice caps It's also possible that the extreme bomb cyclone (a rapidly-forming winter storm with hurricane-strength winds) in the North Pacific a few days ago, contributed to the SSW, "but that will have to be investigated further," she said. This high-pressure, low-pressure duo is known to disrupt the stratosphere, where the polar vortex lives. "Over the last few weeks, there was a persistent high-pressure system over much of the North Atlantic and northern Europe/Asia, and a low-pressure system over the North Pacific," Butler told Live Science in an email. It's possible the SSW was caused by a high-pressure, low-pressure system, said Amy Butler, a research scientist at the National Oceanic and Atmospheric Administration Chemical Sciences Laboratory in Boulder, Colorado. SSWs happen an average of six times every 10 years, and right now we're experiencing a big SSW, The Washington Post reported. SSWs happen when large-scale atmospheric waves associated with weather systems reach into the stratosphere and disrupt the polar vortex, causing it to slow down and heat up as much as 90 degrees Fahrenheit (50 degrees Celsius) within a few days.Ĭohen noted that SSWs can be triggered by weather conditions associated with the Arctic's disappearing sea ice. It's also accepted that so-called sudden stratospheric warming (SSW) events can weaken the polar vortex and make it teeter around. Not everyone agrees with this increased-Siberian-snow-and-wobbly-polar-vortex connection, but it is clear that a weakened polar vortex leads to colder winters in certain parts of the Northern Hemisphere.
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