The photographed clouds over Castille are known as cirrocumulus because of their very thin and barely visible white cloud elements owing to their immense height with an altitude base of well 8.3km as per weather sounding on the third thumbnail. It was also widely spread over the sky hence their stratiformis classification and finally undulatus because of the water-like ripples in the cloud cover. The ripples being the parallel cloud wavelets were formed because of a strong jet stream inducing wind shear at upper levels. The high clouds initially in the form of grains were blown by the strong upper winds similar to how the wind acts over a body of water to produce waves. The first thumbnail photo shows the cirrocumulus clouds in finer detail. The second thumbnail is another photo taken in the same evening of cirrus radiatus clouds, again notice the repeting nature of the cloud. No surface weather feautures were observed but the Maltese Islands were inside a warm conveyor belt as evident by the 500mb chart on the fourth thumbnail. It seems that such clouds form inside the warm side of a mid-latitude cyclone or during rising warm air events.