The Japan (East) Sea (JES) is a region of intense air-sea interactions. Recent observations show deep open ocean convection occurring south of Vladivostok near the subpolar front to a depth of roughly 1000 m during the winter of 2000, with even more intense convection during the extremely cold winter of 2001. In this region, wintertime cold continental air outbreaks, combined with strong very cold mountain-gap winds give rise to deep convection and Intermediate Water Formation. We have reproduced the 2000 event in a three dimensional numerical model and examine its onset and evolution, thus shedding some more light on this important process. The study demonstrates that the confluence of warm and cold water masses at the subtropical front south of Vladivostok is the preferred location of deep convection events in JES, as the confluence-induced downwelling assists in the deeper penetration of the convective turbulence generated by strong wintertime cooling.