Wind direction with respect to the orientation of the mountain chain is the most important parameter when detecting Lee Cloudiness of either types. The wind direction need not necessarily be perpendicular to the mountain chain but there must be a normal component. In the Pyrenees region most wind directions can produce High Lee Cloudiness (only east winds were found not to do so, but this is more due to general climatology). The orientation of the developed High Lee Cloud is consistent with the direction of the wind flow causing it. The image shows Lee Cloud formation at the Pyrenees and at the Cantabrian Mountains: Wind flow from the south results in High Lee Cloudiness north of the mountain ridges. The cloud features are parallel to wind direction at the eastern part (Pyrenees and the eastern part of the Cantabrian Mountains), but show some deviation in the west (north of Cantabrian mountains); caused by a different circulation system. In this case there are north-westerly winds. The Lee Cloudiness is formed to the east of the Pyrenees, oriented to the southeast. Further southwards, Lee Cloudiness can be found at the Iberian mountains. Lee Waves formed over mountains in Sicily are orientated perpendicular to the wind direction.

Jet axis and thickness

High Lee Cloudiness often occurs along the right (anticyclonic) side of a jet stream, and sometimes in the jet exit region. Often it can be observed in baroclinic zones on the leading side of the synoptic-scale thickness ridge. In this image Lee Cloudiness at the Carpathians mountains is situated along the right (anticyclonic) side of the jet axis, indicated by the zero line (solid) of shear vorticity.

Stability (Showalter index)

The Showalter index ranges from 3 to 12 which indicates a stable atmosphere.

Looking more closely at stability (Showalter index is only the mean value of a layer) radiosondes mostly show a stable layer on top of a conditionally unstable layer. Above there is again a conditionally unstable layer. (see Meteorological physical background ).