User blog comment:Miskos3/Fairy Tail Chapter 490: Fairy Tail Zerø, Review/@comment-27281341-20160620122358/@comment-7418318-20160620123041

Knowing of Natsu does not necessarily include which magic he uses.

Or it could even be that he used heat-based magic exactly because he knew that Natsu could partially coutner it. Mest was the one who messed with him and Brandish, not Natsu, Happy and Lucy, so maybe he intentionally chose a means to hit Mest harder than the others.

Or he was just so enraged he didn't think much at all. ^^