Numerical calculations of vortex breakdown generated within a closed circular cylinder by rotation of one of the end walls have been performed. The solutions are used to compute steady streak‐line patterns for dye introduced both symmetrically and asymmetrically about the symmetry axis upstream of the breakdown bubble. Beginning from such a steady state, the end‐wall angular speed is impulsively increased and the asymmetric streak‐line pattern is observed during a portion of the subsequent period of unsteady flow.