Prowling thunder

How I love the sound of thunder! Listen! There is a warning under its rumbling and growling! It is like a great grey beast prowling the skies, looking for a place where rain is likely to fall. Then it will make plain the threat of the dark clouds by a roar that (just before the rain comes, beating earth with silvery arrows) starts retreating into deep and distant caves, decreasing there, and finally ceasing.