Beautiful picture, Apple!
It's funny. In order to find my image of three crisply delineated clouds, I had to sort through a lot of pictures like the one you've shared!
Interestingly, "cloud" (like many other nouns that are primarily count nouns) can also be used as a noncount noun. Here are some examples from COCA:
- "The day was warm and windy with thin streaks of cloud painted across the sky"
- ". . . the heavens utterly unobstructed by even the thinnest ribbon of cloud."
- "Between black blots of cloud, the stars were stunningly bright but did nothing to illuminate the street."
- ". . . itself topped by a purely white stratum of cloud."
- ". . . the world below lost in an ocean of cloud and vapor."
Fortunately, we also have the adjective "cloudy" and attributive-noun constructions like "cloud cover."