What is this? (Paint related)

Ouch!
Yep, I will have to say "Lemon" peel!

Did you do the 50-75% overlap during each pass? Looks like you drysprayed it. Too much air pressure-not enough material or wrong reducer didn't allow the paint to flow and/or you moved too fast. How hot was it when you sprayed the paint?

You are gonna have to wetsand with 600 and reapply! That is some serious peel! I really don't think there is enough paint to wetsand and buff. You could always wetsand and apply a clearcoat over it. Alot less work! Since it is Urethane you can get a gallon af urethane clear and be done! Just be careful on the crowns when sanding so you don't take the color off! I would tape the crowns with 1/4" blue fineline tape before you start sanding. Wetsand all of the peel out then clear it.

Wetsanding and buffing will remove too much materials then you won't have enough mills to protect it from the elements. You can get a gallon of clear and hardener for less than $100... Use a SUPER SLOW reducer and be sure you overlap each pass by at least 50% better at 75%.