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WeatherBlog 5/2012 | Uncertain Christmas weather

Hot flashes in the stratosphere could cause a cold January...

by Lea Hartl 12/19/2012
The current weather situation offers large east/west and cold/warm contrasts and remains difficult to predict. A sudden warming of the stratosphere could determine the further course of winter.

The current weather situation offers large east/west and cold/warm contrasts and remains difficult to predict. A sudden warming of the stratosphere could determine the further course of winter.

Current weather conditions

The Alps are still in a roughly westerly flow, which ensures mild and humid weather and accumulated precipitation in the well-known westerly accumulations. A cold high over Russia is blocking the withdrawal of the Atlantic lows from the westerly drift, which are bobbing around off the British Isles and constantly shoveling new warm air masses from the south and southwest towards us. While people here in Germany worry about a white Christmas and are annoyed by the hourly changing forecasts, many people in Russia and Ukraine are suffering from the extreme cold. There have been 37 deaths from the cold in Ukraine since the beginning of the month. In eastern Russia, the temperature has dropped to -50 degrees and below in recent days.

Further outlook

As some of you may have already noticed, the outlook is still quite uncertain in general and even for the weekend, which is no longer particularly far away. In principle, the west of the Alpine region will remain rather damp and mild for the time being, while it will probably get colder in the east. However, it is difficult to say exactly where the east will begin in this case and whether or when it will warm up there again. The decisive factor is the air mass boundary between the cold area in the east mentioned above and the rest, which is influenced by the west. The models change their opinion with each run as to where exactly this air mass boundary will be over the next few days. Otherwise, a warm front should reach us on Friday, which will (again) mainly benefit the western Alps. From the current perspective, the weekend will remain unsettled, with Saturday tending to promise "better" weather.

Interesting facts in the crystal ball

We are moving away from Central Europe and towards larger contexts: The maps of the northern hemisphere from a bird's eye view offer interesting possibilities for the further development of the general weather situation (remember: everything is in the distant future and can therefore turn out differently). If we look at the temperature forecasts for the stratosphere in the area of the pole, we can see that it is usually rather cold there.

Now there is a phenomenon called major warming, which is much less snappy: psudden stratospheric warmingg. The stratosphere warms by up to 50 degrees within a short period of time. This upsets things and usually leads to a polar vortex split and a generally highly disturbed circulation. This rather dramatic event (imagine temperature fluctuations of 50 degrees in your own garden) is caused by disturbances in the troposphere, which spread vertically and nudge the stratosphere above, causing it to go haywire. See map 1 and 2 for more information.

If that were to happen, we would probably lose the current westerly highway and be more likely to be influenced by cold, polar air masses. If everyone wants a nice base of westerly weather for Christmas, we could perhaps enjoy it in January with sunshine and cold in the dreamy ideal case.

This article has been automatically translated by DeepL with subsequent editing. If you notice any spelling or grammatical errors or if the translation has lost its meaning, please write an e-mail to the editors.

Show original (German)

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