In this workshop we address the challenge of combining stochastic data-driven mathematical modelling with effective data assimilation techniques in high-dimensional operational systems. The aim of the event is to expose cutting-edge results in stochastic analysis and modelling with nonlinear filtering and data assimilation for application in geophysical fluid dynamics. We seek to foster collaborations which could eventually bridge the gap between fundamental research in stochastic PDE analysis and data-driven operational methodologies.