Ns praecipitatio

Formation of a whole nimbostratus cloud as seen from the Upper Barracks in Valletta looking westwards. Its base was rendered very diffuse by the continuously falling moderate rain at the time which also reduced visibility as clearly evident in the photo. The first and second thumbnails show other cloud photos taken late afternoon from Paola looking towards the west and the east respectively. The clouds on the first thumbnail is very unclear as many various clouds were observed in the day. What’s sure is that there was cumulus in the background with the clouds in the centre could be either parts of nimbostratus clouds (note that light rain was still falling in the area) or more likely cumulus clouds whose tops was rendered diffuse by higher clouds. The second thumbnail looks like stratocumulus nimbostratomutatus clouds as the nimbostratus thinned enough following the end of the rain event and undergoing the effects of turbulence. The third thumbnail is the weather sounding showing high humidity and a mostly stable atmospheric profile especially at altitudes above 800mb or 2km. However, the photographed nimbostratus could have had an even lower base. Also from the weather sounding notice that there was quite some wind shear at the lower levels which explains the buffeting observed on the clouds of the second thumbnail. Nimbostratus and indeed the day’s various clouds were the result of a warm conveyor belt pumping a stream of warm and moist air at high altitudes from West Africa towards the North Mediterranean as depicted by the Jet Stream chart on the fourth thumbnail and revealed by cloud covering on the fifth thumbnail showing the visible satellite image. The sixth thumbnailed surface pressure chart showed a number of frontal systems close to the Maltese Islands leading to a variety of clouds but always an overcast sky. Localized heavy rain fell on Central Malta during the night with an alleged 100mm of rain in just a few hours over Mosta. The same weather situation hence the same cloud cover persisted for the following 2 days.

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