Crenelated appearance of altocumulus clouds indicating mid-level instability over Malta’s southeast side on the SE side of an upper-level trough, click on the third thumbnail, corresponding with the satellite image of the fourth thumbnail. The weather sounding on the second thumbnail indicated both low and upper range altocumulus. Through comparison with the appearance of the photographed cloud, the base was likely to have been at an altitude of 2000 metres being trigerred by a cold front passing at that level. This would have generated the lift required to overcome the convective inhibition hence forming the clouds which were moving towards the NE. The most prominent aspect in the photo was the various visible rain streaks in the form of light isolated rain showers seemingly not reaching the ground due to evaporation in the drier air beneath it. Therefore the photographed panoramic cloud is a perfect example of altocumulus castellanus virga. The first thumbnail is a photo of stratocumulus opacus cloud with some undulations formed on the previous morning from the same upper-level trough which was almost stationary.