If you are still hoping for white Christmas, this could be a good time to re-plan your wardrobe. This year, in many parts of Northern Europe and in the USA temperatures are so high, that snow on Christmas is as likely as getting only best presents.
While this new warm weather already started to disrupt seasonal patterns of flora and fauna, according to the Guardian, strangely enough, many British newspapers have continued to warn about “coldest winter for 50 years with months of snow”.
But as you leave your winter coat to dust in the closet yet again, let’s see what’s really going on.
Usually we attribute such warm temperatures in the Northern Europe, which is parallel to Canada, to the Gulf Stream.Riser and Lozier suggest the lack of cold this December is due to “a complex interaction between the surface ocean, massive upper atmospheric currents and differences in pressure on either side of the Atlantic”. But there are many other factors, influencing the weather: El Nino, Atlantic water temperatures, Winds high up in the atmosphere over the equator, Easterly winds, are only a few of them.
El Nino got a lot of media attention, because it is a reoccurring weather event related to the higher ocean temperatures in the equatorial Pacific. But the Met Office suggests that the UK will be subtly affected by its impact.
But the most interesting answer is related to the so-called Arctic oscillation, described as “a change in air pressure at the North Pole that affects how far south cold air travels from the Arctic.”
In order to understand Arctic oscillation, let’s quickly look at the marvel of the polar vortex. Who knew, but there are two of them – one around the North Pole, and one around the South Pole. They both are persistent, cold mega-cyclones, circling the poles with a stream of extremely swift cold air forming their borders.
“But the pattern varies — high pressure in the Arctic can push the winds away from the pole and down to the mid-latitude regions of the planet, where most people live. Other times, the pressure at the Arctic can be so low that the vortex is especially tight, and a greater portion of cold air than normal is trapped near the pole,” explains CNBC.
And such variations form the Arctic oscillation. When the pressure at the Arctic rises, it is referred to as negative phase, while the low pressure characterises a positive phase.
Now, the Arctic oscillation is remarkably positive, and the polar vortex has been sturdier than average. The cold air that usually cools down the northern regions of Europe remains around the Arctic, keeping the snow away this Christmas.
But this situation is global, resulting in milder temperatures not only in Northern Europe, but also in the Eastern United States and even in East Asia, according to a meteorologist Judah Cohen, the author of the Arctic Oscillation Analysis and Forecasts. However, he added a glimpse of hope noting that this pattern is shifting, and “temperatures are likely to cool from their very elevated levels”.