A high performance modelling system is proposed for simulating multi-scale flows with an unprecedented range of multidisciplinary physical applications. Computer simulations of global weather at horizontal resolutions in the order of a kilometre (i.e. nonhydrostatic) will become operational for numerical weather prediction (NWP) beyond 2020. Existing NWP models operate at hydrostatic scales and are not equipped to resolve convective motions where nonhydrostatic effects dominate, thus impairing the fidelity of forecasts. While NWP strives to extend the skill towards finer scales, nonhydrostatic research models endeavour to extend their realm towards the global domain. The two routes of development must cross, but the approach how to merge the diverse expertise is far from obvious. The proposed work will synthesise the complementary skills of two exceptionally successful modelling systems: ECMWF's Integrated Forecasting System (IFS) and the nonhydrostatic research model EULAG formulated by the principal investigator. The IFS is one of the most comprehensive Earth-system models available in the world, while EULAG offers unprecedented expertise in multidisciplinary computational fluid dynamics (CFD) ranging from simulations of laboratory flows to magneto-hydrodynamics of solar convection. The essence of the proposal is a pioneering numerical approach, where a nonhydrostatic global model is conditioned by global hydrostatic solutions within a single code framework. The key technology are EULAG's numerical procedures expressed in time-dependent generalized curvilinear coordinates, pairing the mathematical apparatus of general relativity with modern CFD. The new model will predict with greater fidelity extreme weather events that are critical to the protection of society while sustaining Europe’s role as the world leader in operational NWP. Moreover, this model will be one of the most advanced computing tools available to the European community for research and education.