Funnel Clouds

One of the most feared and easily recognized storm clouds is the funnel cloud. Produced when a rotating column of air condenses, funnel clouds are the visible part of tornadoes that extend downward from the parent thunderstorm cloud.   But remember, not until the funnel reaches the ground or “touches down” is it called a tornado. Link Source: Means, Tiffany. “Clouds That Spell Severe Weather.” ThoughtCo, Aug. 1, 2021,

Scud Clouds

Scud clouds aren’t dangerous clouds in and of themselves, but because they form when warm air from outside of a thunderstorm is lifted up by its updraft, seeing scud clouds is a good indication that a cumulonimbus cloud (and hence, a thunderstorm) is nearby.  Their low height above ground, ragged appearance, and presence beneath cumulonimbus and nimbostratus clouds mean scud clouds are often mistaken for funnel clouds. But there’s one way to tell the two apart -—look for rotation. Scud do move when caught in the outflow (downdraft) or inflow (updraft) regions but that motion typically isn’t rotation.  Link Source: Means, Tiffany. “Clouds That Spell Severe…

Shelf Clouds

Like wall clouds, shelf clouds also form underneath thunderstorm clouds. As you can imagine, this fact doesn’t help observers differentiate between the two. While one is easily mistaken for the other to the untrained eye, cloud spotters know that a shelf cloud is associated with thunderstorm outflow (not inflow like wall clouds) and can be found in the storm’s precipitation area (not rain-free area like walls clouds).  Another hack to telling a shelf cloud and wall cloud apart is to think of rain “sitting” on the shelf and a tornado funnel “coming down” from the wall.  Link Source: Means, Tiffany. “Clouds That…

Wall Clouds

Wall Clouds Wall clouds form under the rain-free base (bottom) of cumulonimbus clouds. It takes its name from the fact that it resembles a dark gray wall (sometimes rotating) that lowers down from the base of the parent storm cloud, usually just before a tornado is about to form. In other words, it is the cloud from which a tornado spins.     Wall clouds form as the thunderstorm updraft draws in air near the ground from several miles around, including from the nearby rain shaft. This rain-cooled air is very humid and the moisture within it quickly condenses below the rain-free base to create the wall cloud. …


Whoever first exclaimed “The sky is falling!” must have seen mammatus clouds overhead. Mammatus appear as bubble-like pouches that hang on the underside of clouds. As odd as they look, mammatus aren’t dangerous — they simply signal that a storm may be nearby.  When seen in association with thunderstorm clouds, they’re typically found on the underside of anvils. Link Source: Means, Tiffany. “Clouds That Spell Severe Weather.” ThoughtCo, Aug. 1, 2021,