ERIE, Pa. (KDKA) – While clouds are nothing new to Western Pennsylvania, we don’t usually see amazing clouds like this.

These super rare wave-shaped clouds were photographed yesterday in Erie.

Photo Credit: Jamie Morath Heynes

KDKA meteorologist Ray Petelin weighed in on what caused the clouds to form.

“Those are Kelvin-Helmholtz clouds. A very rare cloud pattern that is caused by velocity shear,” he said.

Photo Credit: Jamie Morath Heynes

“Velocity shear occurs when winds are traveling at different speeds at different heights in the atmosphere.”

“In the case of these cloud patterns, the winds are moving faster at the top of the cloud, than the winds at the bottom of the cloud, just like how waves are created on water. While these cloud patterns are very rare, the most often occur when it is windy.”