Formation of small ball like clouds due to convection within the thin layers of the atmosphere. The sounding attached clearly shows instability at that level (despite an upper high at 500mb) with the base of the cloud possibly being around 10km. Of note is a storm system over Eastern Spain which could have created turbulence that initiated these cloud formations. The first thumbnail is a cirrus vertebratus cloud taken on the same day which shows a fish-bone like cloud structure due to lots of humidity in the upper levels of the atmosphere. High pressure was present over the Maltese Islands.