Oh my friend I'm glad you asked.

Those are truly wonderful pictures.

Personally I wish they were a touch darker/more contrasty.

Something I've picked up from a fellow professional photographer is of you're sitting with your cell phone, you're sunglasses can act as a ND filter and stop down your exposure while giving definition to some of the things that are kissing definition in the highlights.

So like a dslr can add filters in front you can just hold your sunglasses in front and shoot through them. Especially if they're polarized. It'll instead of tinting it a color just remove the out of phase light and make your clouds pop real nice.

The trick is to frame up your shot of what you want, tap your screen so it gets a autofocus and exposure reading, then you put your sunglasses in front and click the photo