Cumulonimbus Incus - a big one

Cumulonimbus, originally uploaded by Sparrows' Friend.

Snow showers all day. This was taken late afternoon. Click on the image for a larger version.

I spotted this from my window. It's a cumulonimbus with an anvil. "Incus" is Latin for anvil, a characteristic shape of this enormous cloud, which holds a staggering amount of water. The flattened top is formed from ice crystals at the top of the troposphere, where it can't go any higher. These clouds can be up to 11 miles high.

The cloud was to the south-west, probably over Felixstowe and Harwich.