Ac lacunosos

The word `lacunosus` is a latin word meaning `full of holes`. The photographed cloud was closely related to Altocumulus Lacunosus hence given this subtitle althaugh it could be undulatus as well because of undulations in the background. In fact, the weather sounding (1st thumbnail) indicated some wind shear which would have been able to develop such clouds. The first 2 thumbnails are 2 photos of the same cloud cover with the purpose of enabling the expirienced meteorological person to decipher the cloud structure more closely. The cloud`s holes were probably developed due to sinking air pockets because of falling precipitation dragging air with it. The 3rd and 4th thumbnails show moderate rainfall approaching the Islands and the cloud cover as seen from a visible satellite respectively. The warmer air inland might have resulted in some of the rain evaporating hence leaving behind sinking pockets of cooler air within the altocumulus cloud layer resulting in this sub-species. Of course, the cloud fringes would have been created because of the rising humid air replacing the sinking air causing the areas of dark grey in the cloud cover. The whole cloud system has developed because of a large trough (7th thumbnail) extending to Sicily and sending cooler air towards the Central Mediterranean while meeting the warmer air on the way. Since the air at the surface seems to have been capped, only mid to high-level clouds developed. Later in the day, this became Nimbostratus cloud with continuous rainfall hence lowering the temperature to unusually low values for the time of day as indicated in 6th thumbnail. The weather sounding confirmed instability on the day and layers of air with various humidity levels which might also have contributed to the way the altocumulus cloud had formed. Such formation of altocumulus cloud is not very common in Malta but synonyms with the warm (Summer and Autumn) season rather than with Winter clouds.

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