The anvil shape happens because as clouds reach the tropopause, a relatively stable area that acts like an atmospheric “lid,” they fan out horizontally.

The anvil shape is one of nature’s most striking warnings. When a cumulonimbus cloud’s top flattens out and spreads into a wide, thin layer, it forms what meteorologists call an “anvil.” ...

That cloud is popularly known as an anvil cloud, because of its shape. The technical name for this type of cloud is cumulonimbus incus. It is often associated with lightning and heavy rain or hail.

Towering, dense clouds with a flat, anvil-shaped top. Develops from cumulus clouds and can reach great heights, often associated with thunderstorms.

Drivers on their morning commute were treated to views of a massive, unusually-shaped cloud as the Sun rose over the Houston area Thursday morning. The aptly nicknamed anvil cloud towered over the ...

This image shows an anvil shaped Cumulonimbus cloud at sunset in the Caribbean. When a cloud is maturing, or growing vertically, there comes a point when the air can no longer rise, ...

Flying high over the ground in a plane, a thunderstorm's anvil cloud might be the last thing you want to see, but it's exactly what a group of scientists conducting an airborne mission were ...

HOUSTON — Anvil clouds can often look like an alien spacecraft trying to land, We’ve had emails suggesting there is a UFO in the sky and immediately when I see the picture, it’s an anvil cloud.

Towering, dense clouds with a flat, anvil-shaped top. Develops from cumulus clouds and can reach great heights, often associated with thunderstorms. Indicates severe weather, such as thunderstorms ...

Dear Tom,I have seen cumulonimbus clouds (thunderheads) with classic anvil formations at the top. What air mass is above the anvil causing it to flatten?Scott, Bloomingdale, Ill. Dear Scott, The tr… ...

Towering, dense clouds with a flat, anvil-shaped top. Develops from cumulus clouds and can reach great heights, often associated with thunderstorms.