Courtney's Cloud Corner: Anvil Clouds

Anvil clouds or Cumulonimbus Incus clouds are a type of clouds that expands from the parent cumulonimbus cloud. As the Cumulonimbus cloud continues to grow to great heights, the cloud will hit the end of troposphere and the beginning of the stratosphere. These different “-sphere’s” are layers of the earth’s atmosphere. In the troposphere, the temperatures will decrease with rising height. In the stratosphere, the temperatures will start to gradually increase with height. It's the temperature change that will make the growing cumulonimbus cloud stop as if it hit a wall and expand horizontally. It is the horizontally expanding cloud that is called the anvil.

Anvil clouds can also be combined with overshooting top. Overshooting tops are when the updraft within the cloud is strong enough to pass the troposphere barrier.  This is unlike the anvil which will stop growing vertically as soon as it reaches the top of the troposphere. Since they are both attached to the parent cumulonimbus cloud, take caution, as they will be associated with severe weather.