Stochastic representations of model uncertainties at ECMWF: state of the art and future vision by Leutbecher, M, Lock, S, Ollinaho, P, Lang, S, Balsamo, G, Bechtold, P, Bonavita, M, Christensen, H, Diamantakis, M, Dutra, E, English, S, Fisher, M, Forbes, R, Goddard, J, Haiden, T, Hogan, R, Juricke, S, Lawrence, H, MacLeod, D, Magnusson, L, Malardel, S, Massart, S, Sandu, I, Smolarkiewicz, P, Subramanian, A, Vitart, F, Wedi, N, Weisheimer, A