Prof. Dr. Jaak Jaagus, University of Tartu
Dr. Mait Sepp, University of Tartu
Prof. Dr. habil. Zbigniew Ustrnul, Jagellonian University, Institute of Meteorology and Water Management
Cyclones, which have formed over the Mediterranean, the Black Sea or the Caspian Sea (southern cyclones) and have influenced weather conditions in northern Europe, particularly in Estonia are focus of the present work. Southern cyclones are much longer-lasting and deeper than the cyclones originating from the same areas over southern Europe, but not moving to northern Europe. Southern cyclones are rather rare in northern Europe comprising 10% of all cyclones, but by carrying warm and moist subtropical air northwards, they have a lot of potential to significantly design weather conditions in affected areas and to cause severe weather events. Sometimes southern cyclones can bring very high precipitation amounts and are also capable of generating very long-lasting thunder events. In the hilly south eastern part of Estonia there was detected the highest number of thunder days, in western Estonian archipelago was observed the lowest number of thunder days related to southern cyclones but the longest duration of thunder events. In most of the years, southern cyclones had caused a much higher number of lightning strikes per day than other events and therefore it can be said that the southern cyclones-induced thunderstorms are more intense than others.