Formation of very common stratocumulus stratiformis opacus praecipitatio cloud. The interesting feauture that propped out was the blue light coming out from the cloud gap as if it was shining itself. In thunderstorms sometimes it appears green possibly indicating lots of hail but in this case it was blue perhaps indicating an area of the cloud containing lots of rain drops. The cloud moved eastwards and continued to grow very slowly due to limited instability but with lots of compensating moisture forming a weak thunderstorm cloud as indicated in the first thumbnail taken more than 2 hours later. In fact, the weather sounding on the third thumbnail showed the potential of cumuliform cloud formations at levels between 600 metres and 1600 metres. The lack of wind had stalled the photographed cloud which then grew slowly over the same place producing a heavy shower as per rain radar on the fourth thumbnail. The strong early wintry anticyclone over mainland Europe resulted in relatively lower pressure over the Mediterranean. The second thumbnail is the base of a marginal cumulonimbus cloud taken on the following day as a similar weather setup persisted producing very isolated thundery showers as well as longer periods of widespread light rain from the spreading out of such cloud to become nimbostratus.