Cold ends in western Europe, starts in south east

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 200km long (the cold spell was not long enough). The last Elfstedentocht took place in January 1997.

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).

In the end, the frontal precipitation in Germany was not that strong and only weak freezing rain was reported, mainly in central and 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

Airmass RGB Annotated Airmass RGB

 

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 40kts.

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

Additional content

Strong winds over the Aegean Sea seen in HRV animation on 16 February 2021
Terra MODIS True Color RGB of the low-level vortex over the Ionian Sea
Temperatures have dropped to -15 degrees in the north of the country – Essential (World in News)
Freezing rain forecasting: experiences and case study webcast (EUMeTrain)
Black Ice Case in January 2017 webcast (EUMeTrain)