Formation of a line of cumulus clouds developing into cumulonimbus capillatus incus and then moving eastwards by a westerly upper-level wind. Althaugh the photographed cloud looks like it formed in the vicinity, it developed over the SE tip of Sicily due to daytime heating acting as a trigger on the an upper-level cold pool of air as indicated by the 500mb chart on the third thumbnail which had already reached Sicily but had yet to arrive over the Maltese Islands. The satellite images on the fourth and fifth thumbnails taken at that time confirm this. The first thumbnail photo puts the described cloud into perspective as it was actually seen without zooming when compared against the local cumulus clouds in the foreground whilst the second thumbnail is the Sicilian cloud zoomed in to reveal it steam-like characteristics rising from a hot ground towards the much cooler upper air. Finally, the sixth thumbnail shows the surface wind field over Sicily converging over the point where sea breezes meet hence are forced to rise upwards to form cumuliform clouds.