by EFAS Meteorological Data Collection Centre

The meteorological situation in April 2020 was characterised by higher than normal monthly mean surface pressure in the northwest and centre of the EFAS domain and below normal in the northeast, southeast and southwest of the EFAS domain. Many regions had below normal monthly precipitation totals, whereas monthly totals were above normal in some other regions. The monthly mean air temperature was below the long-term mean in the eastern regions of the EFAS domain whereas there were positive anomalies in the western parts.

At the beginning of April 2020, a low-pressure system was located over northern Scandinavia with a weak secondary system over the Norwegian Sea. The Azores high was shifted northward, located south of Iceland and extended to central Europe.  Furthermore, a weak high-pressure system was situated over the southern central Mediterranean region and low-pressure systems over the western Iberian Peninsula and the eastern Mediterranean region. The second one moved to the Aegean Sea and disappeared there but brought intense precipitation to this region. The low-pressure system from the Iberian Peninsula moved in the next about twelve days eastward over the Mediterranean Sea towards the south-eastern part of EFAS domain and merged on its way with another low-pressure system from northern Africa associated with several intense precipitation events along its track. The low-pressure system over northern Scandinavia moved to the Arctic Ocean and the secondary system strengthened and moved across central Scandinavia also to the Arctic Ocean, brought significant precipitation amounts and, partly, strong winds along its way. The high-pressure system moved to eastern Europe while strengthening. A low-pressure system developed over the Atlantic Ocean and moved via Iceland and north Scandinavia to the Arctic Ocean. Its strong winds influenced especially Great Britain and Ireland, Iceland and parts of Scandinavia. The Azores high established itself at its normal position. Then a low-pressure system, formed near Newfoundland, moved via the Atlantic Ocean, including the cut-off of a weak secondary system, towards Scandinavia, where it intensified and caused strong winds. It moved further towards Russia and disappeared there some days later. The secondary system moved southward to the region between the Azores and Iberian Peninsula, merged with another low-pressure system from the Atlantic Ocean and moved to the Bay of Biscay and dissipated there. A zone of high-pressure established in the meantime from the North Sea to the Balkans with several cores, while an upper-level trough caused intense rainfall around the Adriatic Sea. The northern core in the high-pressure zone developed to a separate high-pressure system over Scandinavia, while a low-pressure system formed over northwest Africa and moved to the western Mediterranean region and a low-pressure system from the Atlantic Ocean to the same region, associated with heavy precipitation events. The first one disappeared soon while the second one could be tracked to the central Mediterranean region. During the same days, a low-pressure system developed over southern Russia and moved to the Arctic with notable precipitation amount along its track. By the end of the month, one low-pressure system developed east of the Baltic Sea and another one over the Atlantic Ocean. Both moved eastward and brought large-scale precipitation.

In April 2020, the highest precipitation totals were observed around the Iberian Peninsula and in western Norway, but also around the Aegean Sea, southeast of the Black Sea and in Russia (Figure 1). On the other hand, no or nearly no precipitation fell in a region from central and eastern Europe to the Black Sea, northward of the Caspian Sea and the southeast of the EFAS domain. Monthly precipitation totals above the long-term means were observed at the Iberian Peninsula, northwest Africa, western Norway and in Russia (Figure 2). Negative precipitation anomalies were reported from the majority of the EFAS domain. The monthly mean air temperature ranged from -12.1°C to 26.1°C with the highest values in the southern parts and lowest in the northern and mountainous parts of the EFAS domain (Figure 3). Air temperature anomalies ranged from -4.5°C to 12.3°C (Figure 4). Monthly mean air temperature below the long-term means were noted in Portugal, Iceland and the region from northern Scandinavia towards northeast Africa, while abnormally high temperatures were reported in central and western Europe, northwest Africa as well as in the southeast and the northeast of the EFAS domain.