The panoramas at top and bottom show attention-getting mammatus clouds over San José Pinula, Guatemala and Lasham, Hampshire, U.K., respectively. Mammatus clouds such as these can form when downdrafts in a thunderstorm complex push against a storm cell's base. On occasion they're observed on the underside of cumulonimbus anvil clouds . It may look as though a funnel could decent from a droopy mammatus, but tornadogenesis occurs in rotating storm systems, not from protruding clouds. Top photo taken on February 12, 2015; bottom photo taken on May 12, 2015.