The first thumbnail is a non-panoramic photo of the cloud in the main photo. Formation of altocumulus translucidus, identified as such because the position of the sun was visible but could also have been identified as stratiformis or perlucidus, with grey radiatus clouds in the background seeming merging into long lines that seem to be converge near the horizon. A shallow open-wave upper-level trough was present over Northern Africa as per 500mb chart and the visible satellite image showed these altocumulus clouds approach the Maltese Islands from the SW. The weather sounding on the second thumbnail indicated that very little instability was present at mid-levels of the atmosphere. Later on it seemed that the cloud thickened as it became grey and transformed into altostratus opacus without producing precipitation.