Formation of a long straight line of cumulus clouds created by a common convection mechanism in an elongated area. As per 2nd thumbnail, this convergence line was a cold front that was moving southeastwards towards the Maltese Islands ushering in an even stronger Mistral wind. As per weather sounding shown in the third thumbnail, the atmosphere was not particularly unstable. This led to only this cloud formation caused by cumulus congestus and a quick rain shower which afterwards led to a completely clear sky. The first thumbnail show the same cloud 15 minutes earlier still at a distance. The fourth thumbnail shows the actual satellite image of the clouds that passed over Malta and this corresponds exactly with the photo taken and the surface pressure chart hence proving without doubt that the photographed cumulus radiatus (actually made up of cumulus congestus clouds arranged in a line) was the result of this particular cold front.