Description

Kelvin-Helmholtz waves are vertical waves in the atmosphere generated by wind shear. If enough moisture is present, a characteristic cloud, the Kelvin-Helmholtz wave cloud (also known as Fluctus), can be formed. The wind shear is the result of stronger upper winds being separated from weaker lower winds by a stable layer between. This thermodynamically stable layer is typically a temperature inversion.

When the upper layer of air is moving at a higher speed than the lower level air, it may scoop the top of an existing cloud layer into these wave-like rolling shapes. The clouds themselves occur within the stable layer at altitudes above 16,500 ft.