It has been proposed that evaporation of precipitation failing from widespread thick masses of nimbostratus derived from cumulonimbus can account for the mesoscale unsaturated downdrafts inferred to occur within certain tropical mesosystems. This paper discusses experiments made with a numerical model suitable for testing this idea. Dynamics of the explicitly described (large-scale) flow are governed by the hydrostatic unfiltered equations specialized to two dimensions. The value of f is for 10°N. Cumulus convection is parameterized through a one-dimensional plume model which allows for vertical transport of water substance in vapor and liquid form. The water budget for the large scale includes vapor and both cloud and precipitation and allows for transformations between these categories. Computations are sensitive to the assigned value of β, the ratio of mass flux upward through the bases of convective clouds to the large-scale upward mass flux through 900 mb. For β=1.0, the initial wave disturb... Abstract It has been proposed that evaporation of precipitation failing from widespread thick masses of nimbostratus derived from cumulonimbus can account for the mesoscale unsaturated downdrafts inferred to occur within certain tropical mesosystems. This paper discusses experiments made with a numerical model suitable for testing this idea. Dynamics of the explicitly described (large-scale) flow are governed by the hydrostatic unfiltered equations specialized to two dimensions. The value of f is for 10°N. Cumulus convection is parameterized through a one-dimensional plume model which allows for vertical transport of water substance in vapor and liquid form. The water budget for the large scale includes vapor and both cloud and precipitation and allows for transformations between these categories. Computations are sensitive to the assigned value of β, the ratio of mass flux upward through the bases of convective clouds to the large-scale upward mass flux through 900 mb. For β=1.0, the initial wave disturb...