Clouds Of The Apocalypse.

At first I thought a stormy cumulonimbus was headed our way, boiling up from the south.

But it became clear that the approaching menace was not the tail of thunderhead's anvil, but what could be a layer of altocumulus undulatus asperatus: an uncommon type of cloud that has only recently been considered to be a new species of cloud - the first to be identified since 1951.