Various cloud undulations due to various wind shear as shown in the weather sounding. The photographed photo seemed to have been composed of two cloud layers. The top part certainly being altocumulus undulatus (is proved in another photo in the first thumbnail) due to wind speed shear at mid-levels of the atmosphere whereby the westerly wind was increasing speed with height. The lower cloud layer was possibly stratocumulus undulatus due to wind direction change. In the latter case, the cloud formed was capped by a subsidence inversion. The photographed clouds which also produced some light rain in places were caused by a positive vorticity at 500mb height (this is the area coloured in red which indicates that clouds are likely to form due to vertical air motion) as shown in the 3rd thumbnail and was corresponding with clouds formed in the visible satellite image. A relatively strong westerly jet stream was present over Northern Africa and the Maltese Islands, not that common during Summer as usually it is further north.