Met-11 Airmass RGB, 15 Feb 2021, annotated

End of the cold spell in western Europe, arrival of cold air in south-eastern Europe

15 February 2021 00:00 UTC-16 February 09:00 UTC

Met-11 Airmass RGB, 15 Feb 2021, annotated
Met-11 Airmass RGB, 15 Feb 2021, annotated

Cold spell in Germany ended with freezing rain on 15 February 2021, while a snowstorm hit Greece and western Turkey.

Last Updated

26 February 2021

Published on

22 February 2021

By Jochen Kerkmann (EUMETSAT) and Andreas Wirth (ZAMG)

February 2021 started extremely cold in northern and central Europe. Large parts of Europe were snow covered (see Figure 1), and the grounds were deeply frozen.  In The Netherlands thousands of enthusiastic ice skaters went ice-skating on the frozen lakes and canals, although the ice was not thick enough for the famous Elfstedentocht (Eleven cities tour), which is a long-distance ice skating tour on natural ice, almost 200 kilometres long (the cold spell was not long enough). The last Elfstedentocht took place in January 1997.

Suomi NPP VIIRS RGB M11-I2-I1
Figure 1: Suomi NPP VIIRS RGB M11-I2-I1 (Natural Color RGB), 14 February. Credit: NASA.

On 14 February, after one week of winter weather, a first Atlantic front reached Western Europe and temperatures in the UK started to rise above 0°C. On the following day, the front crossed Denmark and Germany bringing warm air at higher levels to Central Europe (see Figures 2 and 4, and radiosounding of Essen at 12:00 UTC. However, as the grounds were frozen and the surface air temperatures still around or below 0°C, there was a high probability for so-called freezing rain (black ice), i.e rain that immediately freezes when it gets in contact with the cold, frozen ground. Therefore, the DWD issued a red alert warning for freezing rain (see Figure 3). Note that also Greece had issued a red alert, but for very strong winds (see discussion below).

Figure 2:  Meteosat-11 Airmass RGB, 15 February, 00:00 - 15:00 UTC.
Meteoalarm weather warnings, 15 February 2015
Figure 3: Meteoalarm weather warnings for 15 February 2015 (Credit: Meteoalarm).

In the end, the frontal precipitation in Germany was not that strong and only weak freezing rain was reported, mainly in Central & Northern Germany (Hessen and Niedersachsen, see IR10.8 image with synop reports. Credit: EUMeTrain). Only, minor car accidents were reported on the Hessen radio; no severe accidents or casualties.

The SatRep (Satellite Report) analysis of the situation is presented in Figure 4. It shows the long occlusion north of Denmark, the warm front over Germany and the cold front from Denmark over the Benelux countries to the Normandy. Further to the west, the next cyclone is rapidly developing, forming a nice, spiral occlusion.

 

 

Meteosat-11 Airmass RGB analysis

Annotated Meteosat-11 Airmass RGB compare1
compare2
 

Figure 4: Meteosat-11 Airmass RGB with analysis of Conceptual Models, 15 February 2021, 12:00 UTC.

Other interesting satellite features on this image are the sharp, deep trough over eastern Europe (indicated by red hues), the vortex to the west of the Peleponnes and the cloud streets over the Ionian/Aegean Seas. This leads us to the second red warning on Meteoalarm, namely the very strong winds over the Aegean Sea. Both, the upper-level trough and the massive advection of very cold air from eastern Europe to the Mediterranean, contributed to the storm-force winds over eastern Greece.  For three consecutive days, ferries remained docked at the ports of Piraeus, Rafina and Lavrio in Attica due to winds blowing in the Aegean Sea with intensity of up to 10-11 on the Beaufort Scale.

Figures 5 and 6 provide more detailed views of the cloud streeets, the low-level vortex west of Greece and the wind situation, in and around Greece, in general. The clouds over the sea move very rapidly, and the cold air reaches northern Africa in the afternoon of 15 February. Wind products, such as Cloud Motion Vectors (CMVs, not shown) and ASCAT sea surface winds (Credit: EUMeTrain) indicate wind speeds of up to 40 knots.

Figure 5: Meteosat-11 IR10.8 channel, 15 February 00:00 UTC to 16 February 09:00 UTC.
Figure 6: Animation of Meteosat-11 HRV channel, 15 February 2021, 08:00-15:00 UTC.

On the sequence of HRV images (Figure 6)  the small, low-level vortex west of Greece can be seen in higher details.  This vortex, which has some characteristics of a weak Medicane,  moves slowly southward, following the movement of the upper-level trough.

Note that Greece was not only hit by strong winds, but also by a snowstorm (see white snow surfaces in Figure 6). The most affected areas were those in the north and centre of the country. The snow also covered the Acropolis of Athens, but not for long, with temperatures in the capital hovering around 5 °C


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Strong winds over the Aegean Sea seen in HRV animation on 16 February 2021
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Freezing rain forecasting: experiences and case study webcast (EUMeTrain)
Black Ice Case in January 2017 webcast (EUMeTrain)