Here, we present three examples of the Alpert–Stein Factor Separation Methodology (hereafter, FS in short) on a medium scale in the atmosphere, often referred to as meso-scale or, in general, meso-meteorology. The first example is that of a deep Genoa cyclogenesis (Alpert et al., 1996a, b) that was observed during the Alpine Experiment (ALPEX) in March 1982, and then studied intensively by several research groups. The second example is that of a small-scale shallow short-lived meso-beta-scale – only tens of kilometers in diameter – cyclone over the Gulf of Antalya, Eastern Mediterranean (Alpert et al., 1999). The third example is that of a much smaller scale, of orographic wind, following Alpert and Tsidulko (1994). In each of these three examples, some factors relevant to the specific problem are selected, and special focus is given to the role played by the synergies as revealed by the FS approach.

A multi-stage evolution of an ALPEX cyclone: meso-alpha scale

A relatively large number of studies have been devoted to cyclogenesis, with particular attention given to the processes responsible for the lee cyclone generation. Early studies of lee cyclogenesis (henceforth LC) focused on observations, and indicated the regions with the highest frequencies (Petterssen, 1956).

More recently, several theories have been advanced to explain the LC features, and they are frequently separated for convenience into two groups, as follows: the modified (by the lower boundary layer) baroclinic instability approach, as reviewed by Tibaldi et al. (1990) and Pierrehumbert (1985), and the directional wind shear suggested by Smith (1984).