In meteorology, weather conditions that occur with above-average probability on a certain date are called singularities or weather regularities. One such singularity is the much-hated Christmas thaw. While everything is often still frosty and Christmasy white just before the holidays, it starts to thaw when the presents are given, it gets warm, it rains and not even an array of colorful fairy lights can alleviate the dreariness of muddy front gardens? In seven out of ten years, such a weather pattern can be observed between December 24 and 29. Before Christmas Eve, cold air masses from the Arctic or the continental east determine our weather. This cold air flows across Central Europe and out into the Atlantic, where it meets warm, humid sea air.
As with Christmas gatherings with unloved relatives, things do not always run smoothly when air masses come into contact with each other: A pronounced low-pressure center forms over Western Europe. Lows rotate cyclonically, which means that in the northern hemisphere the air moves counterclockwise in a circular path around the center of the low.
Accordingly, the Alps are exposed to a strong southwesterly flow: warm air from the Mediterranean and Atlantic region penetrates as far as southern Germany, causing melting snow, often accompanied by heavy rain and subsequent New Year's flooding. In addition to the Christmas thaw, there are several other similar weather phenomena that occur regularly. We are familiar with many of them in connection with so-called "lost days", such as the dormouse or the ice saints. As is so often the case, exceptions prove the rule. Not all singularities are always fulfilled, sometimes Indian summer is already in July and the dog days in August literally fall through. Unfortunately, even scientifically proven country rules are not particularly useful for accurate weather forecasting and only provide a rough guide at best. The origins of singularity research date back to the 1920s and are based on recurring disturbances in the annual temperature cycle, which do not disappear even in the long-term average. By cataloging the major weather patterns and their statistical analysis, it was possible to prove What grandma feels in her bones, the farmer already knows anyway. It is known that the occurrence of singularities has to do with the solar cycle or the number of sunspots. But to find out what holds the world and the weather together at its core, we might have to sell a few souls to the devil first.
