Formation of the undulatus variety within the altocumulus stratiformis cloud cover. The undulations have formed because of a change in wind direction within the cloud layer as indicated by the weather sounding on the second thumbnail. The altocumulus clouds covered the altitudes of between around 2.6km and 3.2km whilst the wind at those altitudes was SE veering clockwise SW Force 3 hence generating clockwise movement within the cloud cover making larger undulations than the shear suggests as the air was moist revealing it all. In the same photo high-level clouds probably cirrostratus nebulosus and cumulus congestus clouds could be observed. The first thumbnail shows another variety of the altocumulus stratiformis clouds being perlucidus because of its small blue gaps within the cloud cover which was taken on the evening of the previous day, that is the 7Aug.
Both these cloud formations had the same mechanism as indicated in the third thumbnail being an upper-level trough along with a cold pool extending around the Maltese Islands. On both days, thunderstorms have occured in the vicinity of the Maltese Islands but because these clouds were already present in the morning, these inhibited the hot air rising from the ground via cumulus clouds from over-coming the convective inhibition indicated hence joining together to form embedded thunderstorms. The fourth and fifth thumbnails are the visible satellite images taken in the morning and evening showing the associated cloud cover and dissipation becuase the cold pool actually dissipated during the day.