In the last two or three years high pressure blockades dominated the West European December months and many countries including the UK, the Netherlands and Germany could enjoy White Christmases.
Christmas Day 2010: some lovely sunshine over a frozen and snow-covered Dutch landscape. In the Netherlands people had been iceskating [national sport and cultural tradition] on lakes since the last days of November, exceptionally early on in the season.
Although different meteorologists had predicted a similar scenario for December 2011 our regulars knew better – as for 2011-2012 there is no scientific reason to assume another cold European winter.
And indeed science seems to show a connection to that complex reality we have outdoors. It’s mild and if anything else rainy. So there may be little news in predicting a wet and a green Christmas for Europe – but we still feel we have to, as we’re entering the reliability range of normal meteorological models – and these confirm your fears.
As we are saddened ourselves and because we feel it hurts the general Christmas spirit we’ll refrain from claiming the forecast victory. Instead we’ll do something else. We’ll elaborate the situation for those countries most disappointed – and we’ll try to make things up with you by searching for some good news on the sidelines. But first some general background to this winter weather:
Half way through the month we’ve seen one simple pattern – and models indicate that will dominate for the rest of the year: a positive phase in the North Atlantic Oscillation (NAO) as the below graph by NOAA shows.
In winter time you can forget about detailed weather charts. For Europe the above line says it all: depressions around Iceland, sometimes moving east over the North European mainland. And for Schotland, Ireland, England, France, the Netherlands, Belgium, Germany, Denmark, the south of Norway, Sweden and Finland and all the way east towards the Czech Republic, Poland and the Baltic States a dominant west circulation.
Meanwhile high pressure systems linger a bit down south, moving back and forth between positions over the Azores in the Atlantic and sometimes reaching all the way up to the south of France. That may mean some occasional fair weather for countries like Spain and Portugal but nowhere anything that would remind of winter – that is snow and ice, except for inland Scandinavia, Russia and Ukraine and of course the European mountain ranges, like the Alps.
The Christmas forecast: mild, not sure about wet
The below chart shows a plot [by a German weather website] of NOAA’s Global Forecasting System (GFS) for the upcoming Christmas, December 25 at 18 hours GMT. The pattern is very similar to the current situation and that expected for the week ahead – with alternating depressions moving east over the North Atlantic.
The specific timing of the passing of troughs and related weather fronts is for now impossible to tune to any specific date. The current model run shows the polar front running between Iceland and Scotland and then over the North Sea towards the Czech Republic. Countries directly underneath that large weather front can expect high precipitation. Countries below (that is to west and to south) the line have very mild air higher up in the atmosphere and the countries above (that is north and east) the line have colder, polar air. [One other interesting feature is a trough to the northeast. If it were actually positioned like this it would blow in some cold Arctic air over parts of Finland, Estonia and Latvia – and -who knows- may then even bring a snow shower on Christmas Day.]
At ground level the temperature differences are less pronounced, as a westerly wind blows mild Atlantic air over the soils of the European plains. The below GFS temperature chart shows this wind has actually blown all real winter completely off the continent, behind the Ural mountains, into Siberia.
There are some pockets of frost though…
Want to go see snow nearby? Go to Norway, the Alps – don’t trust the Highlands
That’s not just in the Alps, but [under the current GFS run – don’t trust such detail too much] perhaps also in some low-lying terrains of Central Europe – as the high pressure system over France sticks out its tongue in a northeasterly direction, leading to some air stagnation directly underneath [so less Atlantic influence] and perhaps a weak northeasterly wind directly to the south of the ridge.
Of course this does not guarantee anything like a White Christmas. A single frosty day doesn’t cool the surface enough – and of course you’d need to be lucky enough to be having actual snow falling that day as well. Less of a worry if you move uphill – the Alps that is. Guaranteed as always, around this time of year.
But beware to gamble on the lower mountain ranges of Europe. Especially below the polar front [that’s where the high altitude air is warm] the snowline can be as high as 2000 meters. Under the current Christmas run the Scottish Highlands for instance are on the wrong side of the front, and can expect temperatures somewhere around 10 degrees Celsius – and apparently accompanied by some nasty rain. With a sweeping front that could change in a couple of days, but perhaps quite a gamble for your family cottage. In the case that you are British and are indeed hoping to see some snow best thing is not to drive north, but jump on the ferry – to Norway.
These mountains stick up high into the polar air – so the more you rise the colder it gets. There will definitely be snow there.
Or you could of course do as we plan to. Sit it out [so you don’t emit too much – and keep the climate cool (right?)], at least enjoy these dark long nights, and hope for the return of some genuine winters before too long. On all accounts…
A merry Christmas to you all!
(And that of course goes to all you non-Europeans as well. In your cases it’s even more appreciated that you made it to the end of this article!)
© Rolf Schuttenhelm | www.bitsofscience.org