Formation of an isolated cumulonimbus cloud with what looks like a roll cloud attached with its underside. Such cloud may have developed as potentially sinking air spread throughout the cloud surface inhibiting the ingestion of rising air into the cloud`s updraft. As the descending air raises the moist air, condensation occurs hence creating this roll-shaped cloud due to wind shear. The first thumbnail shows a closeup of this cloud. The weather situation was a cut-off upper low over a warm sea surface generating instability hence the formation of isolated storm clouds around the Maltese Islands.