Remnants of or cirrocumulus virga clouds due to instability in the atmosphere in a weak high pressure system. It is common that thunderstorm clouds form over North Africa and then are carried towards the Maltese Islands via WNW currents. The slight positive vorticity (red colour) in the 500mb chart on the third thumbnail seems to have prevented the dissipation of the high-level clouds. The first thumbnail shows locally developed cumulus clouds over mainland Malta due to strong daytime heating whilst the second thumbnail is the weather sounding indicating general instability at upper-levels in the area.