When severe storms move into our area, some may glance up at the sky to see what’s coming our way. Once in a while, you may catch a cloud that appears to be lowering towards the ground and think it’s a funnel cloud. Not so fast, it might actually be SCUD cloud.

SCUD Clouds

SCUD clouds may look like funnel clouds, but they actually form much differently. They form in areas of increase relative humidity as air rises in a thunderstorm.

The term SCUD is actually an acronym standing for “Scattered Cumulus Under Deck”.

Scud cloud near Greenland. Notice the cloud feature’s non-smooth appearance. Image: Kama Davis

While they look ominous, SCUD clouds are harmless and do not produce severe weather.

The biggest differences between a SCUD cloud & a funnel cloud are SCUD clouds DO NOT rotate and they are often detached from the bottom of the thunderstorm!

Definition of a SCUD cloud. Image: American Meteorological Society Glossary of Meteorology

Funnel Cloud

Unlike SCUD clouds, funnel clouds develop from a rotating updraft and are connected to the base (or bottom) of the thunderstorm.

Funnel cloud north of Sallisaw, OK. Image: Logan Burress

A funnel cloud is not a tornado unless it touches the Earth’s surface. Therefore, a tornado can be a funnel cloud but not all funnel clouds are tornadoes.

Definition of a funnel cloud. Image: American Meteorological Society Glossary of Meteorology

One trick to tell a funnel cloud from a SCUD cloud is if the cloud features on the edges are smoothed. Funnel clouds are smooth due to the rotation, while SCUD clouds are not smooth.

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