Meteorological Situation for October 2020
by EFAS Meteorological Data Collection Centre
October 2020 was characterised by lower than normal mean sea surface pressure in central and southeast Europe and higher than normal surface pressure around Spitsbergen and towards the eastern regions of the EFAS domain. Monthly precipitation totals were below the long-term means in the east and south of the EFAS domain including the Mediterranean Region, Iceland, and the western slope of the Scandinavian Mountains, while being around or above normal elsewhere. Monthly mean air temperatures were below the long-term means in the western parts and above in the eastern parts of the EFAS domain.
At the beginning of October 2020, a weak low-pressure system was located over southeast Europe associated with high rain amounts in the northern Carpathian Mountains and another near Iceland. A high-pressure system was situated over Russia and the Azores High was shifted slightly westward from its usual position. The corresponding trough of the Icelandic Low extended towards the Pyrenees and the low-pressure system moved to Great Britain and Ireland. Such weather conditions are prone to high precipitation totals in the lee of mountains. So, it was no surprise that high rainfall totals occurred at the Cantabrian Mountains, Pyrenees, Alps, Massif Central, and northern Apennines. Later, as the trough moved eastward, it also rained in the Dinarides and Grampian Mountains. This low-pressure system together with its trough moved northward. A low-pressure system from the Atlantic Ocean was incorporated, causing again notable rain amounts over Great Britain and Ireland and around the North Sea. An upper-level low-pressure system associated with severe weather was cut-off over southeast Europe. In the next days, a steep trough extended from Scandinavia to northern Africa associated with a cold air outbreak. A low-pressure system developed over the Ligurian Sea and moved via the Dinarides and Hungarian Plain to Poland, associated with high precipitation totals. An intense low-pressure system developed over northern Scandinavia and moved via the North Russian Lowlands eastward. In the next days, two low-pressure systems merged over the Atlantic Ocean, to the west of Great Britain and Ireland with an upper-level trough extending towards the Azores. As the trough moved eastward, it caused severe weather at the Iberian Peninsula and strong wind in Great Britain and Ireland. Simultaneously, a low-pressure system developed southeast of Greenland and moved with a strong intensification to Great Britain and Ireland, where it rapidly weakened. Nevertheless, it caused heavy seas in the northern Atlantic and strong winds across Great Britain and Ireland, whereas precipitation amounts were comparatively low. Additionally, a small low-pressure system developed at the frontal zone over the Western Alps, moved south-eastward to the Peloponnese and brought intense precipitation along its track and high snow amounts in the southern Alps. In the last days of October, ex-hurricane “Epsilon” moved to the north Atlantic to the south of Iceland with strong winds and caused also large-scale precipitation in western and central Europe. A previous cut-off upper-level low-pressure system over the Baltics had no significant impacts. Several low-pressure systems developed at the southern edge of the trough from ex-hurricane “Epsilon”, forming a band with strong winds from the Azores to Scandinavia and causing advection of warm subtropical air to central Europe.
In October 2020, the highest precipitation totals were observed around the central Mediterranean region and western Europe (Figure 1). No or almost no precipitation fell in the south of the EFAS domain and around the Caspian Sea. Monthly precipitation totals below the long-term means occurred in the south and east of the EFAS domain, but also at the southern Iberian Peninsula towards the Provence, around the Aegean Sea, Iceland and the western slope of the Scandinavian Mountains (Figure 2). Monthly totals above the long-term means were reported from many regions in central and western Europe and northward of the Baltic Sea.
The monthly mean air temperature ranged from -6.9°C to 31°C with the highest values in the southern parts of the EFAS domain. The lowest temperature values were reported in the northern and mountainous parts (Figure 3). Air temperature anomalies ranged from -6.4°C to 7.7°C (Figure 4). Monthly mean air temperatures below the long-term means occurred in west and southwest Europe and northwest Africa. Positive monthly mean temperature anomalies were reported in other parts of the EFAS domain