As is known from previous modeling efforts and our knowledge of the physical processes of the ocean, it is difficult to build a ``universal'' ocean model that can treat accurately phenomena on all spatial and temporal scales in the various ocean basins of the world. This is due both to finite computer size and CPU speed, and to an imperfect description of the physical processes, such as turbulence. Thus ocean modeling efforts have diversified into different classes, some concerned only with the turbulent surface boundary layers, some with continental shelves, and many with the meso-scale eddy-resolving circulation in a given part of, or a whole, ocean basin. World ocean models of such high resolution are just on the threshold of being built and tested. Similarly, models that aim to give real-time nowcasts/forecasts using objectively analyzed initial density fields and model-predicted atmospheric forcing, have only recently begun to be tested extensively with real-time observations. In the past, these models have been confined to a limited domain with some open boundaries present, and in the predictive mode could profess to make successful predictions only for a few days without additional information provided at the boundaries and/or from observations made within the domain. Lately, the arrival of new supercomputers and more extensive ocean surveillance (i.e. satellite altimetry and IR sensing) have extended the area and period of prediction, e.g. with the whole global ocean 25-level model being initialized and modeled at a resolution of 1/6 degree (16 km) or better on a 256 processor CM-5.
We can therefore finally afford to start building an eddy-resolving world ocean model that will treat both the thermodynamic and hydrodynamic aspects. The fine resolution versions of such models can be used to do real-time forecasts for periods of several weeks. These forecasts will be quite useful to the fishing industry, ship routing, long range weather prediction and search and rescue operations. The more coarse resolution versions will be used to do long term climate simulation.