Snapshots of the vorticity along the flow for both classes of initial conditions at time 1000, 2000 and 3000. Top: weakly-perturbed vorticity stripe initial conditions rapidly de- cay via a classic two-stream instability into a slowly-relaxing quasi-turbulent state. Bottom: random-wave initial condi- tions gradually fade away. Red indicates positive vorticity, blue negative and black zero.