In late September of 2002, the first recorded major sudden stratospheric warming occurred over Antarctica, leading to sudden breakdown of the cold polar vortex and the collapse of the ozone hole. Our diagnosis reveals that the warming was associated with propagation of a Rossby wavepacket from a prominent tropospheric blocking ridge over the South Atlantic into the stratospheric polar-night jet that had already weakened unusually. The blocking developed from anomalies that had formed as a component of another Rossby wavetrain that appeared to be forced in mid-September by anomalous deep cumulus convection in the South Pacific Convergence Zone.