"I read a study of the turbulence in the area between the shuttle and the tank, a few years back. and remember that the turbulence in this portion of the stream is very high. I don't remember the relative wind information, but do remember that near the nose it is very slow."
Yes the area between the tank and the obiter would have quite a bit of turbulence, becuse of the high reynolds number there. The area around the nose would be where the shock front is generated, in front of the nose would be effected as the streamlines from the tank and boosters would develope there.
The debris itself is riding the streamlines, except where it bumps the shock cone. It's being accelerated away from the tank, until it encounters the streamlines developed by the obiter, there it's slowed in the radial direction, so it passes under and wacks the underside of the wing.