What You Need to Know:
Name(s): Altocumulus castellanus, Thunder altocumulus
Altitude of Formation: 2,000 – 5,500 m (mid-level)
Signals: Thunderstorms or heavy precipitation to come, medium-level instability in the air
Meaning of the Name: The name ‘castellanus’ relates to the shapes of castle turrets in the clouds. The cloud turrets form above individual cells or cloud clumps.