It may be simply because you painted these passes real wet and the overlap wasn't good. If you didn't do a full 50% overlap (minimum) then a portion of the pass gets more paint and stays wetter. If you did this and these stripes got more paint they also got more solvent which stayed trapped there a little more than the areas between the stripes did.
That would produce a slightly different "gloss" (or lack of) between the stripes with more paint and the areas between, giving you "tiger stripes".
Whew, that got me dizzy.