Meteorological Situation for May 2020
by EFAS Meteorological Data Collection Centre
The meteorological situation in May 2020 was characterised by abnormally high monthly mean surface pressure over Great Britain and Ireland and the North Sea and abnormally low in the Norwegian Sea and the eastern parts of the EFAS domain. Many regions had below normal monthly precipitation totals, whereas the monthly totals were above normal particularly in some regions in the east of the EFAS domain. The monthly mean air temperatures were below the long-term means in central, eastern and northern Europe while positive anomalies occurred in the other parts of the EFAS domain.
At the beginning of May 2020, a low-pressure system was located over Great Britain and Ireland with weak secondary cores westward over the Atlantic Ocean. The Azores high-pressure system was shifted southward and the African and south-eastern parts of the EFAS-domain were also influenced by high-pressure systems. The main core of the above-mentioned low-pressure system moved to Scandinavia and disappeared but brought significant amounts of large-scale precipitation to the central and northern parts of the EFAS domain. One of its secondary cores intensified over the Atlantic Ocean and was cut-off. It moved southward to the Azores forcing the high-pressure system to move to the Iberian Peninsula. Another high-pressure system extended from the Atlantic Ocean to Iceland and developed a new core there. This core merged with the high-pressure system from the Iberian Peninsula over Great Britain and Ireland. During the same period, an upper-level low-pressure system was cut-off over eastern Europe and moved eastward via the eastern Mediterranean Sea. Floods associated with rainfall caused by this system occurred in Israel. Also, during this period, a low-pressure system moved from Greenland to northern Scandinavia and the remaining trough from the low-pressure system mentioned at the beginning of May extended southward. Particularly, in the first days of the extension, it caused intense precipitation in eastern Europe. The high-pressure system from Great Britain and Ireland moved to central Europe and extended to the central Mediterranean region before it weakened, but another high-pressure system moved from Greenland to Great Britain and Ireland and built a bridge to the Azores high. More relevant in respect of high impact weather were some small low-pressure systems, which were left over from the aforementioned cut-off system at the beginning of May. One system moved via the Iberian Peninsula and brought intense precipitation to western and southern France, which led to local flooding. The low-pressure system over northern Scandinavia was still active in this region, producing several new cores there, which were getting the active ones, associated with strong winds especially over the northern Norwegian Sea. An upper-level low-pressure system moved from the Atlantic Ocean to the central Mediterranean region while weakening but caused heavy rainfall events in the central Mediterranean region. Another low-pressure system developed over the Atlantic Ocean and moved to Great Britain and Ireland causing strong winds and intense precipitation there. In the slipstream of this low-pressure system, the Azores high-pressure system intensified and moved to western Europe and Scandinavia by the end of the month. A large but weak upper-level low-pressure system brought noteworthy large-scale precipitation amounts over eastern Europe.
The highest precipitation totals in May 2020 were observed in the Alps, the Caucasus, eastern Europe and the Norwegian coast (Figure 1). On the other hand, no or nearly no precipitation fell in the regions of England, Belgium, and most of northern Africa in the EFAS domain. The low precipitation totals in Hungary were found also in an independent analysis of the Global Precipitation Climatology Centre (GPCC). Monthly precipitation totals above the long-term means were observed in eastern Europe and locally around the Mediterranean Sea (Figure 2). Negative precipitation anomalies were reported from central and northern Europe and the African region of the EFAS domain.
The monthly mean air temperatures ranged from -9°C to 31.4°C with the highest values in the southern areas and the lowest in the northern and mountainous areas of the EFAS domain (Figure 3). Air temperature anomalies ranged from -5.5°C to 11.2°C (Figure 4). Monthly mean air temperatures below the long-term means were found in central and eastern Europe as well as in Iceland. Above normal air temperatures were reported from western Europe and the African and Asian regions of the EFAS domain.