The effects of stable atmospheric-density stratification, vortex core size, and turbulent scale on the descent of aircraft-trailing vortices are investigated using numerical solutions of a second-order closure turbulence model. A Boeing 747 vortex descent is simulated numerically and compared to reported measurements of descent distance, velocity, and circulation profiles. It is concluded that the pair was halted in its descent by a diffuse region of countersign vorticity primarily outboard and above the vortex cores. It is shown that the core size and turbulent macroscale have significant effects on vortex behavior through their influence on turbulence production, diffusion, and dissipation.