A mackarel sky over Valletta as a low pressure system was approaching from the SW. Such clouds indicate deteriorating weather conditions which is what happened in the following days and hence are the very first clouds to appear long before the arrival of the actual weather system. Such clouds form when additional water vapour droplets freeze into the ince crystals which are then whipped by very fast moving winds in the upper-levels. In fact, the weather sounding (1st thumbnail) showed that these clouds had formed at an altitude above 10km whereby the wind at that altitude was a roaring 270kmh satisying the conditions for these clouds to form. The final process that shapes the cloud is the precipitation of these ice-crystals making the photographed sun distorted as if it was shining through some sort of lens. Of course, such cloud never produces precipitation on the ground because the precipitating ice cyrstals evaporate long before then.