Sc opacus

Formation of stratocumulus stratiformis opacus perlucidus virga or praecipitatio cloud as a cold front was moving across the Maltese Islands. This cloud formation could be proved to have formed as a result of this cold front by comparing the satellite image with the surface pressure chart on the third and fourth thumbnails respectively. The photographed cloud formation could be distinguished from altocumulus by its cloud elements arrangement having a very large width compared with altocumulus and indeed by its very prominent virga or weak rain shaft in the background. In fact, the first thumbnail is a single shot of the same cloud highlighting a potential precipitation streak in the background and definitely virga from the base of the cloud on the right hand side. Light rain drops were also felt whilst taking this photo. The varieties opacus and perlucidus were chosen becuase the cloud was thick enough to hide the position of the sun (in fact it was producing precipitation which the variety translucidus does not) and it also had small clear gaps in between. The second thumbnail is the weather sounding showing the atmospheric profile at the time with very low instability hence difficulty for the rising air to keep up the momentum to continue rising. Despite the presence of wind shear, this cloud formation never acquired the ‘undulatus’ features.

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