Towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. Convective rain, or showery precipitation, occurs from convective clouds, e.g. cumulonimbus or cumulus congestus. Cumulonimbus clouds are the final form of growing cumulus clouds. Convective rain, or showery precipitation, occurs from convective clouds (e.g., cumulonimbus or cumulus congestus). Cumulus congestus clouds, which appear as towers, will often grow into cumulonimbus storm clouds. Stratocumulus Cumulogenitus out of cumulus or cumulonimbus clouds, disrupted by decreasing convection. Cumulus congestus will mature into cumulonimbus calvus under conditions of sufficient instability. This cumulus evolved into a large cumulonimbus. They are an intermediate stage between cumulus mediocris and cumulonimbus. Mammatus are not exclusive to supercells and can be associated with developed thunderstorms and cumulonimbus. The updraughts inside a cumulonimbus associated with a supercell thunderstorm can reach . Like other precipitation in cumulonimbus clouds hail begins as water droplets. It also forms from the outflow of tropical cyclones or the anvils of cumulonimbus clouds. Like other precipitation in cumulonimbus clouds, hail begins as water droplets. Thunderstorms occur in a type of cloud known as a cumulonimbus.