Upon analyzing the weather sounding on the second thumbnail, it is not clear whether the clouds should be classifed as altocumulus or stratocumulus stratiformis perlucidus. Since the photographed cloud just before sunset had smaller cloud elements, it was decided to go for altocumulus, also since the weather sounding was showing an inversion at the height of about 2000 metres hence this could be low-level altocumulus stratiformis perlucidus as described. As per third thumbnail, the weather situation was dominated by a wintry Azores high pressure system hence the cooling evening air contrasting with a warmer surface might have initiating the cumuliform cloud formation which once hitting the stable layer in the atmosphere, the clouds spread out and bits of it evaporating to produce the pearl like effects. The first thumbnail is another photo taken during that night super full moon indicating an even thinner cloud cover which at the height of about 2000 metres, the cloud cover was very subjective either being upper stratocumulus or low-level altocumulus but always within the same species and variety.