birdbrain,
Your comment,
"Please excuse my ignorance, but, how did an A300 manage to find the wake of a 747 so soon after t/o ???"
It was there, and the co-pilot made a perfect formation join up on the center of an invisible, horizontal tornado. (the "Heavy" B 747's vortex)
Shortly after T/O ATC released AA 587 to go direct to the departure fix. AA 587's shorter turning radius, compared to the B 747, turned it inside the "Heavy's" track to the same fix. The wind direction moved the B747's vortex into AA 587's projected flight path, with the resultant intercept.
Fraternally