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

K. Horvath (1) , L. Fita (2) , R. Romero (2) , B. Ivancan-Picek (1) , I. Stiperski (1)

1 DHMZ - Croatian Meteorological and Hydrological Service
2 UIB - Universitat de les Illes Balears = Universidad de las Islas Baleares = University of the Balearic Islands

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.

Domaines: Sciences de la Terre

K. Horvath, L. Fita, R. Romero, B. Ivancan-Picek, I. Stiperski. Cyclogenesis in the lee of the Atlas Mountains: a factor separation numerical study. Advances in Geosciences, 2006, 7, pp.327-331. ⟨hal-00296933⟩