Formation of cumulus and cumulonimbus clouds due to a negatively-tilted upper level low stretching towards the Maltese Islands combined with a cold pool of air at upper-levels. This 500mb chart directly corresponds with the clouds seen in the visible satellite image. In combination with strong solar heating, it managed to produce such isolated clouds with the weather clearly remaining clear in the background. The first thumbnail shows newly developing cumulus clouds within the base line of the condensation level. The cloud was confirmed as Cbs due to life-threatening lightning strikes that struck the area. The second thumbnail is an altocumulus undulatus cloud photo taken on the same day showing wave-like formations, althaugh stratocumulus could not be excluded. This formation was due to some speed shear as indicated in the sounding.