Abstract A three-dimensional, prognostic numerical model of the North Pacific Ocean, possessing an actual coastal configuration and ten layers (but constant depth), has been developed in order to show the physical nature of large-scale normal and abnormal characteristics of this ocean in response to various normal and anomalous seasonal meteorological conditions. Based on the simulated energetics, emphasis is given to the identification of the major physical processes and essential dynamic mechanisms responsible for the generation, evolution and dissipation of large-scale anomalies in the North Pacific Ocean. The model is based on time integrations of the finite-difference forms of the primitive equations. The oceanic circulation is driven by atmospheric forcing, namely, the surface wind stresses and the differential heating over the ocean. The flux form of numerical scheme for energy conservation and the rigid-lid approximation for filtering out the external inertia-gravity wave are used in the formulati...