Ac virga

Formation of altocumulus due to the clash of different air masses at higher levels indicated by the contrast between warm air to the south and the much cooler air to the NW as seen in the fourth thumbnail (850Mb height Temperature) with the cooler air moving towards the Maltese Islands. These clouds were producing precipitation which was not reaching the ground hence Ac virga. In fact, the weather sounding indicated cloud formation at around 500mb (altitude of 5.8km) followed by warm and very dry air underneath it hence the rapid evaporation or sublimation of falling precipiation. The mode of precipitation was likely rain mixed with snow due to cloud temperature of around -10C and surrounding temperature of around 0C at the time. The first thumbnail shows a close-up of such cloud while the second thumbnail shows another view of Ac virga. Of note is that exactly the same clouds kept on forming continually during the second half of that day.

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