Shelterbelts appear both intentionally and incidentally in a variety of agricultural and forestry situations. In many cases predicting the downwind microclimate is of practical concern to best facilitate crop growth or forest regrowth. In addition, windthrow can also be a significant problem in cleared areas. Turbulent kinetic energy is known to be an important factor in determining microclimate and windthrow. In this study, we performed a numerical simulation of windbreak flow based on the first-order closure model of Wilson, Finnigan and Raupach (1998). The model was used to simulate flow downstream of windbreaks of varying width to examine patterns of TKE reduction and recovery. The model results were compared with wind tunnel simulations of comparable windbreaks. Results were used to examine the question of whether or not there is an optimal width for downstream turbulence reduction.