A 10-layer dry numerical model which includes convective adjustment, surface friction, and vertical momentum diffusion is used to identify the mechanical effects of a- mountain on transient eddies during winter. Thermal effect is simplified to the form of Newtonian cooling. Observed winter zonal mean temperature is prescribed as an equilibrium state. The mountain has a simple elliptic shape. The numerical integration was performed for 72 days, but a detailed analysis was done only for the 16-day period from day 21 to day 36.The 16-day mean fields show that the westerly jet tends to flow around, rather than over the mountain and splits into two branches in the lower troposphere. At 500 mb, winds are weakest over the mountain with a distinct splitting of the jet north and south of the mountain. Above 300 mb, the jet flows south of the mountain. These features agree well with those of the 1978-79 winter mean fields (Murakami, 1981a).At 850 mb, significant temperature perturbations originate at the northwest periphery of the mountain and extend clockwise around the mountain until reaching the southern part of the mountain. These low-level disturbances, which are trapped below 700 mb along the periphery of the mountain, are referred to as “edge” disturbances in this paper. These edge disturbances receive their eddy available potential energy via nonlinear interaction with 16- day mean temperature fields. Their eddy available potential energy is not converted into eddy kinetic energy; namely, the baroclinic conversion process contributes little to the development of edge disturbances. They acquire their kinetic energy through flux convergence of geopotential energy due to the nongeostrophic components of winds.At 500 mb, the kinetic energy of the disturbances is weakest, and baroclinic conversion is directed from eddy kinetic to the available potential energy, over the mountain. Here, the major contributing process in the generation of eddy kinetic energy is the horizontal flux convergence of eddy geopotential energy. The disturbances supply (extract) energy to (from) 16-day mean winds outside (over) the mountain.At 200 mb, a belt of large eddy kinetic energy lies south of the mountain, where the strong upper tropospheric jet stream prevails. The barotropic conversion process feeds energy to the 16-day mean westerly flows there. Again, the major generation factor for eddy kinetic energy is the flux convergence of eddy geopotential energy, while other terms, such as, baroclinic conversion are negligible.