All eyes were trained on the sky over Alabama last week as eerie wave clouds rolled over the state.
The surreal event was captured on camera phones last Friday afternoon in Birmingham and is called a Kelvin–Helmholtz instability.
It normally occurs in regions with vast plains where winds quickly change speed creating turbulence. A fast-moving, lighter density cloud slides on top of a slower, thicker layer, dragging out the surface and creating the wave effect.
On a roll! The incredible tsunami of 'wave' clouds that had all eyes on the skies
