Shelf clouds vs. wall clouds: What’s the difference?

Several iWitness7 viewers captured photos of shelf clouds moving into the Miami Valley, and many have asked what’s the difference between a shelf cloud and a wall cloud.

PHOTOS: Shelf cloud formations captured by iWitness7 viewers

“Shelf clouds form when a cold downdraft pushes strong winds out ahead of a strong thunderstorm,” according to Storm Center 7 Meteorologist McCall Vrydaghs. “This is known as the gust front. The cool air associated with this downdraft forces warm air up and over.”

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The process creates  wedge-shaped appearances. On very humid days the cloud can look ragged and dip low to the ground.

“It is important to note these cloud formations are indicative of strong winds,” Vrydaghs said. “You will usually feel a drop in temperature along with increased winds as this cloud and storm approaches.”

Wall clouds, on the other hand, are typically rain-free and will form with a strong updraft of a supercell thunderstorm.

“This rapid rise in air creates a lower pressure below the storms main updraft, forming this wall cloud,” Vrydaghs said. “Sometimes the rotation and vertical motion within this cloud can create a tornado.”