Vucetic, Visnja (Meteorological and Hydrological Service of Croatia)
The severe bora wind on the Adriatic coast has been in the centre of interest for the last fifteen years, especially since the Alps experiment (ALPEX-SOP) in March and April 1982. Many authors analysed the Adriatic bora from various points of view since it provides the strong effect and the frequency of such a phenomenon manifested by violent and poften devastating surface winds and sea waves. These researches made possible the better understanding of the physics of bora conditions, the processes favourable for bora onset and mechanisms for the generation of downstream turbulence. A detailed statistical study of Adriatic severe bora (Bajic, 1989; Vucetic 1991) presented that the location with the most frequent and longest duration of severe bora in Senj.
The lowest pass (Vratnik Pass) rises close to Senj and the mountain range upstream of the Senj bora belongs to a region where the mountain barrier is the narrowest. Because of that, violent bora occurs in this region and the strong channelling effects are responsible for the Senj bora longevity and strenght. However, it is known that there are many other places along the Adriatic coast where the relief allows strong channelling effects and causes the severe bora. This paper discusses various processes (frontal passages with a cold air outbreak, cyclogenesis and gravity wave break in the mountain waves) in the atmosphere, according to ours and foreign investigators, which could be responsible for the generation of severe bora along the Adriatic coast.