No, they aren't. And the vapor doesn't appear because the sound barrier is being broken, although that may cause it to precipitate (pun intended).
As the divergent pressures from the top of the wing and the bottom of the wing down, one of the side effects is to suddenly change the dew-point of the air where they intermix.
Remember.... p=vrnt.... Compressing air makes it hot, lowering the pressure cools it.
So you're looking at a micro-scale thunderstorm event where a dry-line high pressure area meets a cold front.
But I'm just a cook. ;) What do I know?
/johnny
I think you meant pv=nrt.