Formation of stratocumulus stratiformis opacus clouds consisting of large round masses merged together to form a cloudy sky rather than overcast because the individual clouds were still identifiable. The photographed cloud cover was associated with a low pressure area originating from Africa that kept on intensifying as it met colder air over Western Europe and which resulted in heavy storms over Sardinia due to the clash between this milder air and colder air.
However, despite its intensity, no cumulonimbus clouds had formed over the Maltese Islands due to the airmass stability especially at upper-levels and the fact that the sea was seasonably cool at around 18C, therefore not able to provide much energy and moisture into the system. The first thumbnail is a photo of cumulus congestus radiatus cloud street taken on the evening of the previous day as the cold airmass entered the Maltese Islands from the WSW following a hot day though the surface pressure chart on the fourth thumnail only showed an upper-level cold front. The second thumbnail is the weather sounding taken on the morning of 3May18 showing only a little instability at the surface; if there had been a warmer low level airmass and an even warmer surface temperature, conditions might have become ripe for thunderstorms. The following thumbnails show the presence of only low-level clouds in the Maltese Islands through grey clouds in the infrared satellite image meaning the clouds were “warm” and the wind field in the Western and Central Mediterranean on the day due to the rather deep low pressure system over the southern Tyrennhian Sea.