Enhancing daily and medium-range weather forecast skills has been a demanding impetus for basic predictability studies on the atmosphere and now our global environmental concern pushes that impetus further into the realm of climate variations such as El Niño/Southern Oscillation (ENSO). One of the main features of climate variability is the fact that the variability strongly reflects oceanic field variations whose intrinsic time scale is much longer than that of the atmosphere. The J-COPE activity in the ocean modeling subgroup is to develop an oceanic counterpart of weather prediction though the time scale is different. The aim of this research group is to study such basic behaviors of forced-dissipative systems as perturbation growth in unstable fields and statistical stability of nonlinear systems; it leads to a basic understanding of the predictability of model simulations as well as the mechanism of the climate changes.