Polar vortex is ‘spinning backwards’ above Arctic after major reversal event

The new polar vortex blog hosted (but not written) by NOAA says ‘some winters come and go without a single interesting thing happening in the stratosphere’, but this one wasn’t one of those. The blog also notes: ‘Odds of polar vortex collapse boosted during El Niño…But not all the El Niños’. The article below says ‘Changes to the polar vortex influence the jet stream, which can in turn impact weather across the Northern Hemisphere’ (caption to NOAA graphic).
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The polar vortex circling the Arctic is swirling in the wrong direction after surprise warming in the upper atmosphere triggered a major reversal event earlier this month, says Live Science.

It is one of the most extreme atmospheric U-turns seen in recent memory.

In the past, disruptions to the polar vortex — a rotating mass of cold air that circles the Arctic — have triggered extremely cold weather and storms across large parts of the U.S.

The current change in the vortex’s direction probably won’t lead to a similar “big freeze.” But the sudden switch-up has caused a record-breaking “ozone spike” above the North Pole.

The polar vortex is most prominent during winter months and extends into the stratosphere — the second layer of the atmosphere up to around 30 miles (50 kilometers) above the surface. The vortex spins counterclockwise with wind speeds of around 155 mph (250 km/h), which is around the same speed as a Category 5 hurricane, according to the U.K. Met Office. A similar vortex also encircles Antarctica during the southern winter.

Polar vortices occasionally reverse temporarily. These events can last for days, weeks or months and are caused by sudden stratospheric warming (SSW), when the temperatures in the stratosphere climb by as much as 90 degrees Fahrenheit (50 degrees Celsius) in the space of a couple of days, according to the Met Office.
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The current reversal event in the Arctic began on March 4. However, the winds are starting to slow down, hinting that the vortex will return to its normal trajectory soon, Spaceweather.com reported.

“It was a substantial reversal,” Amy Butler, a climate scientist at the National Oceanic and Atmospheric Administration (NOAA) and author of NOAA’s new polar vortex blog, told Spaceweather.com. The speed of the reversed winds puts the event in the top six on record, she added.

Full article here.