<Li> Pannus: accompanied by a lower layer of fractus species cloud forming in precipitation . </Li> <Li> Pileus (species calvus only): small cap - like cloud over parent cumulonimbus . </Li> <Li> Velum: a thin horizontal sheet that forms around the middle of a cumulonimbus . </Li> <Ul> <Li> Incus (species capillatus only): cumulonimbus with flat anvil - like cirriform top caused by wind shear where the rising air currents hit the inversion layer at the tropopause . </Li> <Li> Mamma or mammatus: consisting of bubble - like protrusions on the underside . </Li> <Li> Tuba: column hanging from the cloud base which can develop into a funnel cloud or tornado . They are known to drop very low, sometimes just 20 feet (6 m) above ground level . </Li> <Li> Flanking line is a line of small cumulonimbus or cumulus generally associated with severe thunderstorms . </Li> </Ul>

Which type of cloud produces thunderstorms and hail