Effect of Mountains on Genoa Cyclogeneses

Four cases of cyclogenesis in the Gulf of Genoa (so-called Genoa cyclogeneses) have been simulated using a high resolution prediction model. Integrations are performed for a 48 hour period, using observed boundary conditions, and for each case with and without mountains in the model. It is found that in two of these cases cyclogenesis happens irrespective of the presence of mountains. However, mountains have a strong modifying influence, in ridging at the surface to the northwest and to the southwest of the Alpine obstacle, and at mid-troposphere in ridging in central Europe north of the Alps. Of the two cases in which cyclogenesis does not happen without mountains, in one case a very realistic simulation of the surface development is obtained. In mid-troposphere, although simulated geopotential heights are even less than observed, the intensity of the cutoff process north of the Genoa region is not sufficiently realistic. It is suggested that, therefore, the problem is either in an insufficient intensity of blocking north of the obstacle, or in a process of a more large scale nature.