Cu congestus

Formation of local cumulus congestus clouds over the Maltese Islands due to the tail-edge of a cooler airmass effecting the Maltese Islands following a long spell of heat with MAX temp around 36C and a very warm sea of around 27C. An upper-level trough had digged in over Sicily causing severe thunderstorms over the Messina Straits. Due to a light North wind, some of the instability over Sicily arrived towards the Maltese shores generating the photographed cumulus clouds. This weather situation is more common around mid-August, also known as “L-Gherejjex ta` Santa Marija“ whereby cooler air from the Balkans due to a high pressure extending from the Atlantic towards Central Europe was driven towards our shores contrasting with the warmer sea temperature generating cumuliform clouds. Rain showers were observed in the vicinity of Malta and Gozo but not over Malta`s landmass. The weather sounding on the first thumbnail showed instability at the air column, perhaps the lack of moisture was a key factor behind the cumulus clouds not being able to grow into cumulonimbus and for the Sicilian thunderstorms to weaken rapidly before reaching our shores. The second thumbnail shows the freezing level indicating the extent of the cooler airmass whilst the third thumbnail is the surface pressure chart of a typical “Gharixa ta` Santa Marija“ which drives the cooler air from the Balkans. Finally, the fourth thumbnail is the visible satellite image showing massive thunderstorm clouds over Italy and only local cumulus over the Maltese Islands which always remained at the edge of this cooler airmass.

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