I know it’s a zombie, but in case now that it’s resurrected other people read the rest of the thread and come across the quoted post:
I have personally known at least two cats who jumped off a second story: one from a porch roof, one out of a window which he’d torn the screen out of. (Never use fiberglass screens if you’ve got cats. Use the older metal screens.) Neither of them was hurt (though I wouldn’t count on that; these were young healthy cats who landed on soft lawn); but they were both very definitely loose. (They both came back home; they were indoor-outdoor cats in any case.)
Also, google “high-rise syndrome.” There are plenty of cats who have jumped or fallen from higher than that. Results are all too often not good at all.