We present a model-based system for tracking rotating fluids, and apply it to a laboratory study of atmospheric circulation. Tracking is accomplished by filtering uncertain and high-dimensional states of a nonlinear general circulation model with optical measurements of the physical fluid's velocity. Realtime performance is achieved by using a nonuniform discretization of the model's spatial resolution, and by using time-snapshots of model-state to construct spatially-localized reduced-rank square-root representations of forecast uncertainty. Realtime performance, economical and repeatable experimentation, and a direct connection to planetary flows implies that the proposed physical-numerical coupling can be useful for addressing many perceptual geophysical fluid dynamics problems. To the best of our knowledge, such a system has not hitherto been reported.