Christmas thaw

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Christmas thaw is the name of the mild, wet weather period that occurs in Central Europe as a climatological singularity in almost seven out of ten years between December 24th and 29th.

root cause

The trigger for the Christmas thaw is the polar night that sets in in Scandinavia at the end of November . It then leads to the formation of a cold spike. With an easterly current on the southern edge of the high, icy mainland air is carried out onto the Atlantic. Over the Atlantic, which is still mild at this time of year, low-pressure areas usually form , which in the second half of December again lead mild air towards the mainland, the so-called Christmas thaw.

Effects

During the Christmas thaw, warm, humid sea air blows into Central Europe from west to south-west. It brings abundant rainfalls and allows a layer of snow that was previously formed in early winter to melt down in part up to the peaks of the low mountain ranges. Since rainwater and meltwater cannot seep into the ground, which is usually still frozen, the rivers often flood during this time .

The warm, humid air masses cannot always prevail everywhere. A sharp border often runs right across Central Europe, separating the mild air in the southwest from the cold air in the northeast. It is not uncommon for dangerous freezing rain to fall along this air mass limit .

Singularity

The singularity was defined as such by Hermann Flohn in the 1940s.

literature

  • Peter Bissolli, Christian-Dietrich Schoenwiese: Calendar -related weather phenomena in a new light. In: Naturwissenschaftliche Rundschau , 44 (1991) 5, ISSN  0028-1050 , pp. 169-175.

Individual evidence

  1. ↑ Hartmut readers: Dictionary General Geography . Diercke Verlag, Munich 1997, p. OA
  2. ↑ The weather week: Christmas thaw On: SRF from December 22, 2018
  3. ↑ H. Flohn, P. Hess: Large weather singularities in the annual weather pattern of Central Europe (= statistical-synoptic investigations 2). In: Meteorological and Hydrological Service of the German Democratic Republic: Meteorologische Rundschau 2, 1949, pp. 258–263.