Europe March 2020 Outlook (Why was winter so mild?)

Written by on February 24, 2020 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Winter 2019-20 could not be any different to the winter of a decade ago. In fact it’s the polar opposite to 2009-10 which was one of the coldest. 2019-20 will go down as one of the warmest for the entire hemisphere never mind North America or Europe. Cities such as Oslo and Helsinki received their first snowless January while Kiev and St Petersburg had their warmest February. According to a friend, Chisinau, Moldova has not see any snow the entire winter!! For Edinburgh it was the wettest February in 78 years.

As stated time and time again this winter, the culprit points straight to the record strong and and incredibly resilient stratospheric polar vortex which drove a positive Arctic Oscillation throughout this winter.

Credit: Weatherbell

Little arctic air can escape from the arctic when you’ve for a near perfect donut-like polar vortex sitting directly over the pole and circled by 120+mph winds at 10hpa.

Credit: Georgios Papavasileiou

The 3D view of the PV structure just a week ago is almost perfect.

At the close of 2019, the polar vortex reached it’s coldest and strongest in 40 years. This was followed by a record strong Arctic oscillation not once but twice in February with low pressure dominant north of the arctic circle.

 

WHAT HAS DRIVEN THE UNUSUALLY STRONG POLAR VORTEX AND ARCTIC OSCILLATION?

There is plausible reason to suggest that a record strong positive Indian Ocean Dipole back in autumn and early winter along with a strong ‘warm phase’ of the Madden Julian Oscillation contributed to a lack of high latitude blocking. A lack of high pressure in the high latitudes have resulted in a lack of pressure put on the PV.

During December, the IOD was record positive while the MJO too was strong but firmly stuck within the warm phase of 5. Through January, phase 6 dominated and although rotating into a more blocky and favourable phase 7 for UK cold late January into early February, the record strong PV and AO had overwritten any MJO influence.

+AO/NAO SHALL SEE OUT THIS WINTER

The below chart nicely represents the general pattern structure at 500mb this winter in response to the PV and AO. Note the deep negative below Iceland and strong positive over Iberia. That’s a textbook positive North Atlantic Oscillation, reflective of the strong +AO.

A record strong vortex and Arctic oscillation has led to a turbulent North Atlantic also with one deep low after the next crossing both Pacific and Atlantic, further enhancing the flood of mild maritime air across the continents.

ANY STRATOSPHERIC WARMING & COLD WEATHER IN SIGHT?

Given what we’ve seen, are seeing and what the models are portraying for the forseeable future, the answer is no to late cold!

The below graphic says everything and by that I mean there’s no hint at a strat warming…

The latest CFSv2 weeklies continue with the +AO/NAO signature with pronounced Iceland low over Azores high holding firm through the opening week of March, however the models show the northward expansion of the Azores high and weakening of the Icelandic low week 2 on which would finally break this cycle. If high pressure builds into northern France, England, I wouldn’t be surprised if we got a spell of unusually warm weather during the 2nd half of the month.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

While warmer than normal is likely for the UK and Western Europe in March I expect warmer than normal for the majority of the continent.

CFSv2 2m temperature anomaly for March.

Credit: Tropical Tidbits

March precipitation anomaly

Credit: Tropical Tidbits

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