A cumulonimbus cloud with full of pouches hence mammatus just after the passage of a cold front when the weather was clear after the front. It was much more spectacular at sunset but unfortunately I only managed to catch a late shot of this magnificent cloud. The cloud formed just after the thunderstorm caused by a cold front moved away from the Islands as can be seen in the third thumbnail and confirmed by the rain radar image of the fourth thumbnail. The second thumbnail is the weather sounding showing lots of upper-level instability and moisture hence perhaps the reason behind this cloud as for every action there must be an equal and opposite reaction, in this case the faster the air was rising, the faster is its descent after bumping into the stratosphere. The first thumbnail is altocumulus undulatus clouds just before the storm approached the Island.