Look at this cloud shot:
It's an interesting cloud pattern, sort of abstract. It's not as dramatic as I remember it, and even if I darken the blue it still won't be what I wanted to convey.
But look what happens when I convert to black and white:
That is a much more dramatic treatment and the black and white starkness pushes it over toward a more artistic presentation. That's what I was looking for.
Here is a wide shot of the sky, in B&W, showing multiple cloud formations and therefore multiple opportunities to crop into a nice abstract.
And here is an in-camera crop (using a zoom) of one interesting section:
You need to do something a little special in the B&W conversion to get those dark skies. You need to add a filter. Yellow, Orange and Red filters blacken the deep blue sky, creating the dramatic effect. Alfred Eisenstadt always shot his B&W landscapes with a yellow or orange filter for just this reason. You get very dramatic skies.