Weather: DECEMBER, Cold and Snow by Christmas? We tell you why the Polar Vortex could hold Twists
Possible snow by Christmas due to the behavior of the Polar Vortex Before Christmas, snow could arrive on the plains. December is now upon us and therefore the curiosity is growing to know what the beginning of theWinter. Well, thanks to seasonal forecasts, as well as some atmospheric indices, we can already get a general idea of what lies ahead.
The main news concerns the behavior of the Polar vortex, which it could reserve twists with snowfall up to the plain already before the holiday season.
So let’s make the point to understand of what is it, so to clarify and hypothesize one general trend on precipitation and temperatures.
As always happens at this time of year, in high latitudes, beyond the Arctic Circle, one is forming mighty cyclonic structure which takes the name of Polar vortex. We can imagine it as one large area of low pressure, inside which all the cold that is continually produced on the Arctic ice sheet is enclosed and which finds its outlet through the depression centers directed towards the South and therefore as far as Italy. These low pressure centers are i responsible for phases of intense bad weather and drastic drops in temperatures. The behavior of the Polar Vortex, however, it is not always the same.
For instance, if it is strong and compact, the cold remains confined to the North Pole, reason for which on Italy a stable weather with high pressures and milder air. If, on the other hand, the Vortex goes into crisis, the effects can be more or less intense. Sometimes it can literally split into two or more parts, moving with its load icy and unstable currents towards the South. When it splits / weakens the probability that the cold also reaches our Peninsula grows considerably. This configuration was the origin of the most intense waves of frost which invested the whole of Europe (including Italy) in 1929, 1963, 1985, 1996, 2012 just to name a few.
The it causes of this split in the Polar Vortex is to be found in thesignificantly warmer air flow in the upper atmosphere, in technical terms stratwarming.
TREND START OF DECEMBER: As the map of the European Center (below) shows, a inflow of “warmer” air in the stratosphere (between 15 and 30 km in height), defined in technical terms stratwarming, with values up to + 15/20 ° C compared to the average species between North-Eastern Siberia and Alaska.
It is a quite anomalous event in this period of‘year and in fact it could destabilize right away the Polar Vortex with consequences also on the European sector. If this were confirmed, already with the beginning of December freezing air masses descending from the Arctic they could launch their attack on Europe, thus provoking also on Italy an early arrival of the cold and of name at low altitude. A bit like what happened last year, when the snow reached many areas of the Po Valley, whitening cities such as Turin, Milan, Padua, Venice and Bologna.
Abnormal stratospheric heating of the Polar Vortex