The deep cyclogenesis causing a range of severe weather events took place over the Mediterranean Sea from 11- 15 November 2004. The first phase of the event was analysed by a series of numerical experiments using the MM5 forecast model. Factor separation method was applied to investigate the cyclogenetic and cyclolytic influences of orography, upper-level potential vorticity and latent heat flux from the sea as well as their mutual synergies in the cyclone initiation and movement in the lee of Atlas Mountains.
Results of model simulations show that pure orographic effect is responsible for generation of the low-level shallow vortex in the lee, while upper-level PV anomaly is a dominant effect in the later stage of lee formation. In addition, upperlevel PV anomaly is crucial for advection of the system to the Mediterranean Sea, where the cyclone experienced a severe deeping in the mature stage of its development
