Method and apparatus for wave flushing cached writeback data to a storage array. A cache manager operates to initiate a wave flushing operation whereby sets of writeback data in a cache memory are sequentially written to each of a plurality of logical groups radially concentric with respect to the storage medium. During the wave flushing operation, a write transducer is radially advanced across the medium in a single radial direction across boundaries between immediately adjacent groups. The write operations thus form a traveling wave across the medium, analogous to a wave in a sports stadium formed by spectators standing up and sitting down in turn. Each logical group preferably corresponds to a selected transducer seek range, such as an associated RAID stripe. Seeks are preferably bi-directional within each group, and uni-directional between adjacent groups. A dwell time (service time interval) for each group can be constant, or adaptively adjusted.