The foregoing studies have provided considerable insight into the flow patterns and loading due to oscillatory or orbital flow past a cylinder, or the equivalent motion of a cylinder in quiescent fluid. To date, an experimentally-based investigation that provides representations of the instantaneous, quantitative flow patterns about the cylinder, acquired simultaneously with the measured loading, has not been undertaken. At a sufficiently high value of Keulegan-Carpenter number Kc, it is well known that shedding of vortices will occur, but the manner in which these vortices are initially formed and shed from the cylinder has not been addressed. Moreover, the nature of their orbital migration about the cylinder is unclear. An intriguing possibility is the formation of vortices from multiple sites about the surface of the cylinder during the imposed orbital motion of the wave cycle, in contrast to what is known for the case of unidirectional oscillatory flow or, for that matter, for the well known case of Kármán vortex formation from a cylinder in a uniform stream. Moreover, the eventual shedding of a number of vortices from the cylinder during an orbital cycle of the wave motion is expected to produce patterns of multiple, interacting vortices; the issue of whether the trajectories of these vortices follow closely the imposed orbital motion of the wave, or are primarily influenced by mutual induction effects, has not been characterized. An adequate understanding of all of these complex features requires space-time characterization of the instantaneous patterns of vorticity and streamline topology, in conjunction with instantaneous force measurements. The present investigation employs this approach.