What kind of storm clouds should concern me?

Example of a shelf cloud
Example of a shelf cloud(Sandra Berry)
Published: May. 18, 2022 at 6:03 PM EDT|Updated: May. 20, 2022 at 6:59 PM EDT
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(WHSV) - We are heading into the summer months which means more storms! There are different kinds of storm clouds that can be concerning and some that are not.


These kind of clouds can create quite the sight in the sky. These clouds form the same way funnel clouds do, with sinking air.

Typically these kind of clouds form at the bottom of the anvil in a cumulonimbus cloud. It’s very common for these kind of clouds to be associated with severe thunderstorms. When the anvil of a cumulonimbus cloud begins to spread out, mammatus clouds form.

As these clouds spread out, they allow warm air to move upwards into the bottom of the cloud. Warm air rises and cold air sinks, so when warm air rises upward into the cloud, parts of the cloud begin to sink as they stay cooler than some other parts of the cloud. This creates the pouch pattern they have.

While these clouds are associated with severe thunderstorms, they are harmless. When you see these kind of clouds, it often indicates a thunderstorm is weakening.

This mammatus cloud was taken in Winchester in August 2019.
This mammatus cloud was taken in Winchester in August 2019.(Dennis Atwood)


Shelf clouds originate from the bottom of a storm cloud. Storms have updrafts and downdrafts. With an updraft, warm air is pulled upwards helping create or sustain a thunderstorm while a downdraft is the cool air that comes down from the cloud.

Typically, a downdraft then forms another updraft since warm air rises and cold air sinks. As cool air coming down from the cloud begins to lift, it then condenses which forms the shelf cloud. Shelf clouds are harmless themselves but typically indicate strong storms. Shelf clouds form at the leading edge of a thunderstorm.

Shelf clouds can even form before a derecho strikes. If you see a shelf cloud coming your way, it probably means you are about to get hit by a strong thunderstorm.

Shelf cloud from August 2020
Shelf cloud from August 2020(Aubrey Urbanowicz)


Wall clouds are clouds that drop below the regular storm cloud. They are a lowering of a solid deck of clouds and indicate the beginning phase of potential funnel clouds and tornadoes forming.

They are located in the updraft of a cloud. What happens is the warm air from the updraft entrains the cold air which increases the dew point and causes air below the cloud to condense.

Wall clouds can be a good warning for a possible tornado developing. If you do see this cloud, look for rotation. If you find that the cloud is rotating, it means a tornado is trying to form. If these clouds are heading your way, take cover! Typically when this happens, a tornado warning is issued as radar detects the rotation.


Scud clouds are commonly confused with tornadoes. Scud clouds form below a storm cloud and are wispy in appearance. They can be very narrow which causes the confusion and to be mistaken as a tornado.

Scud clouds are harmless, but they do form with strong thunderstorms. Scud clouds can form as a warmer and more moist updraft occurs relatively close to the ground. The air essentially condenses before it reaches the clouds and forms the wispy, loose clouds.

Scud clouds are commonly found on the leading edge of a storm. Scud clouds can also form when an updraft pulls precipitation cooled air from a downdraft. Scud clouds can move at differnent speeds than the actual thunderstorm. To double check that the clouds are scud, look for the absence of rotation.

Scud cloud in our area from August 2018.
Scud cloud in our area from August 2018.(James)

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