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.
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Phenomenon: The ‘wave’ clouds unfurl over an airport near Birmingham, Alabama last week
On a roll: The strange clouds which appeared over Birmingham, Alabama are called a Kelvin-Helmholtz instability
People across the southern state captured pictures and video of the unusual sight and sent them to local weather stations asking, ‘What are these tsunamis in the sky?’
The Cloud Appreciation Society explains the quirky weather phenomenon. They are the result of turbulence in a layer of Cirrus cloud where air currents exist of differing speeds or directions – making the cloud resemble a wave rolling along the top of the water.
The incredibly uncatchy name is a combination from Lord Kelvin – a Scottish baron who along with a German physicist Hermann Helmholtz – came up with an explanation for the freak occurrence.
Eerie: The Kelvin-Helmholtz instabliity is named after the Scottish and German scientists who explained it
Natural beauty: The clouds were captured as they rolled over the skies in Birmingham, Alabama last week
