Abstract. We present a physical, laboratory-scale analog of large-scale atmospheric circulation and develop an observatory for it. By combining observations of a hydro-dynamically unstable flow with a 3D numerical fluid model, we obtain a real-time estimate of the state of the evolving fluid which is better than either model or observations alone. To the best of our knowledge this is the first such observatory for laboratory simulations of planetary flows that functions in real time. New algorithms in modeling, parameter and state estimation, and observation targeting can be rapidly validated, thus making weather and climate application accessible to computational scientists. Properties of the fluid that cannot be directly observed can be effectively studied by a constrained model, thus facilitating scientific inquiry.