More ideas from Marieke
"Mammatus clouds are most often associated with the anvil cloud and severe thunderstorms. They often extend from the base of a cumulonimbus, but may also be found under altocumulus, altostratus, stratocumulus, and cirrus clouds, as well as volcanic ash clouds. When occurring in cumulonimbus, mammatus are often indicative of a particularly strong storm or perhaps even a tornadic storm."

MAMMATUS clouds are most often associated with the anvil cloud & severe thunderstorms. They often extend from the base of a cumulonimbus but may also be found under altocumulus, altostratus, stratocumulus, & cirrus clouds as well as volcanic ash clouds^