Cu congestus

The day started bright. However, by early afternoon, cumuliform clouds started to bubble up due to daytime heating and lack of surface wind. However, due to weak heating (as it was Winter and the sea was seasonably cool at 15C), only low-level instability had built-up aided by a cold pool of air aloft as shown in the freezing level chart of the fourth thumbnail. The first thumbnail shows the extension of the whole cloud with a dark base towards the church whilst the second thumbnail shows nimbostratus virga clouds that developed in the late afternoon of the following day as this cold pool led to the development of a Mediterranean cyclone (from the family of mid-latitude cyclones), not to be confused with a Medicane as the low pressure over the area further developed. The main cloud and the first thumbnail show cumulus congestus radiatus praecipitatio cloud which developed due to a convergence line on land under variable winds as shown in the wind map of the fifth thumbnail. The third thumbnail is the weather sounding illustrating the air profile at the time. As can be noticed there was a steep lapse rate leading to cumuliform cloud formations but with little instability. Should the airmass had been very unstable, as often is the case during early Autumn in Malta, the photographed clouds had the potential to grow into huge cumulonimbus clouds capable of producing severe weather and large hail due to lots of wind shear. However, the night featured fast moving thunderstorms that produced a considerable amount of small hail in Gozo. Despite their very dark almost black base, the cumulus clouds were estimated have been only about one kilometre thick being composed all of water droplets. It is thaught that the impressive dark base was due to the presence of higher-level clouds, potentially altocumulus, as was observed in the extreme background of the first thumbnail.

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