The initiation of a deep and severe impact Mediterranean cyclone in the lee of Atlas Mountains is investigated by a series of numerical experiments using the MM5 forecast model. Roles of orography, surface sensible heat flux and an upper-level potential vorticity anomaly are identified using factor separation method. Results of model simulations show that orography blocking is responsible for generation of the low-level shallow vortex in the first phase of lee development. Upper-level potential vorticity is a principal ingredient of this event, responsible for a dominant deepening effect in the later stage of lee formation. Analysis of cyclone paths shows that orography tends to keep the cyclone stationary, while upper-level dynamical factors are crucial for advection of the system to the Mediterranean Sea. The most noteworthy influence of surface sensible heat flux is identified as an afternoon destruction of a surface baroclinic zone and associated weaker cyclogenesis.

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deepening effect upperlevel potential vorticity anomaly cyclone stationary orography surface sensible heat flux lowlevel shallow vortex orography blocking surface baroclinic zone factor separation mm5 forecast upperlevel dynamical factors event cyclogenesis

,.Cyclogenesis in the lee of the Atlas Mountains: a factor separation numerical study. 7 (),.

,"Cyclogenesis in the lee of the Atlas Mountains: a factor separation numerical study" 7

,"Cyclogenesis in the lee of the Atlas Mountains: a factor separation numerical study"