Record Strong Polar Vortex /+AO/NAO Pushes Arctic Sea Ice to 10-Year High But Makes For Warm, Wet, Stormy Winter Across Europe

Written by on February 14, 2020 in Rest of Europe with 0 Comments

With barely 2 weeks remaining of meteorological winter 2019-20, I think it’s safe to say that warmth, a lot of rain and big storms have been dominant.

Europe as well as the UK and Ireland has likely seen one of it’s warmest winters on record with summer-like warmth hitting central countries including Switzerland at a time when it’s meant to be the coldest.

A record strong stratospheric polar vortex has brought probably the coldest Arctic winter in over a decade and so it should be of no surprise that Arctic sea ice cover has reached a 10-year high with the greatest coverage since 2010.

Credit: weather.com

Though it remains below normal overall.

Credit: weather.com

The cold/strong vortex has been mirrored from stratosphere down through the troposphere supporting a strong and persistent +AO/NAO setup which hosts low pressure within the polar region and a strong zonal jet stream running west to east underneath. A strong zonal jet protects the mid-latitudes from polar air.

Credit: weather.com

This setup has been responsible for extremes of warmth, flooding rain, record high pressure and now the parade of exceptionally deep Atlantic cyclones.

Winter arrived early in November through the mid latitudes but then disappeared in December when the stratospheric polar vortex reached it’s strongest levels in 40 years. This allowed temperatures to reach a near all-time record low over Greenland with -66C recorded at Summit Station.

While Greenland as well as Alaska shivered beneath the -96C polar vortex at 10mb over Reykjavik, Iceland, the mid-latitudes observed record warmth with Scotland observing a new UK December high of 18.7C at Achfray, Highland. This surpassed the previous UK December record high of 18.3C recorded at Achnashellach set back in 1948.

Slight weakening of the PV commenced the Atlantic storm train!

The polar vortex peaked in strength around New Year but gradually weakened through January allowing some stretching and release of Arctic air south, mainly into North America.

The southward dislodge of arctic air out of Alaska and the Yukon into the Lower 48 clashed with tropical air lifting north out of the Caribbean, this dramatically increased the thermal gradient forcing the jet stream to strengthen thus shifting the mid latitude pattern into stormy mode.

Cold and warm clash over North America and North Atlantic.

Tropical Tidbits

Creates super Pacific and Atlantic jet stream!

+AO/NAO has resulted in big surface pressure swings this winter.

This push of air mainly from the south and west has delivered one of the mildest winters on record.

Credit: Stuart Markham

An intense low exiting Newfoundland at the end of January helped pump upper level high pressure on the other side of the Atlantic and brought crazy warmth across many parts of Europe. Like squeezing a balloon, the push of the deep low off Newfoundland helped pump heights downstream to beyond 1050mb over the UK. This became the UK’s highest surface pressure since 1957. That record high was abruptly followed by back to back sub-950mb lows and commenced a particularly stormy period over the Atlantic.

As you can see from the below GFS pressure/temperature pattern for February 12, the PV has once again strengthened and approaching record strength once again.

Tropical Tidbits

The cold, consolidated stratospheric polar vortex delivers a textbook reflection down at 500mb.

Deep lows circling the Arctic, sub Arctic and indeed mid latitudes from Pacific across North America and Atlantic to Europe.

Tropical Tidbits

With a vast low height field covering the mid and northern latitudes, deep lows spinning off Greenland and Iceland and a 265 mph jet tearing zonally through the central-north Atlantic have explosively developed and propelled deep lows from the Southeast US to between Iceland and Scotland.

Storm Ciara was the 2nd sub-945mb depression to impact Iceland and the UK in a matter of days bringing widespread severe gales and heavy rain across Ireland and the British Isles as well as mainland Europe.

In the wake of Ciara, a cold tight westerly air stream connecting Canada with the UK helped bring the snowiest weather to the UK this winter.

As of this writing, Storm Dennis is rapidly developing and expected to approach the lowest non-tropical central pressure on record for the North Atlantic tomorrow.

Hopeful of some winter before we reach spring? I see little chance of that I’m afraid.

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