THE ADRIATIC FRONTAL BORA TYPE

The bora of 9 April 1982 on the northern Adriatic associated with the most pronounced cold air outbreak during the ALPEX SOP is presented and classified as the "frontal bora type" in terms of environmental large scale characteristics. The main local characteristics of this type are a sudden increase of bora speed and a brief duration. ln spite of the changes of the mesoscale flow characteristics in the shallow bora layer, as well as a stronger flow above the wind reversal level, the application of Smith's (1985) steady state hydraulic theory proved useful to describe the basic features of this phenomenon. The calculated hydraulic parameters are compared to those of the strong bora case of 11 March 1982 on the middle and southern Adriatic characterized by a deep bora layer, stronger incoming flow and lower effective mountain heights. Although real atmospheric structure pinpoints to the numerous factors which could be incorporeted in the bora model, it is shown that the application of hydraulics is successful in many respects, and particularly as a guide toward classification of bora types and the essential differences in bora onset, intensity, duration and weather characteristics at different localities along the Adriatic coast.