Formation of roll cloud which seems to have been made from cumulus. This particular cloud formation may have been due to a small area of low pressure to the east of Malta (refer to thrid thumbnail) generating a NE wind which met a more Northwesterly wind. The circulation of air from this low pressure (clearly seen on the actual wind map of the 3rd thumbnail) might have acted as an outflow boundary to create such cloud. Furthermore, a line of bad weather was present over the area. A photo taken some 20 minutes later shows that the roll cloud had disintegrated into small cumulus-like cloud cells. The weather sounding showed moist air but with little instability perhaps explaining the very benign looking roll cloud having disintegrated quickly. The surface low pressure itself had formed due to cold air aloft.