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A 10-km version of the NCEP Eta Model has been run over a roughly 1000 km 1000 km domain centered over the upper Midwest for 20 cases where heavy warm season rainfall occurred from mesoscale convective systems to investigate the response of the precipitation forecasts to improvements in the depiction of mesoscale features at initialization time. Modifications to the initial conditions included (i) use of a cold pool initialization scheme, (ii) inclusion of mesonetwork surface observations using the model's own vertical diffusion formulation to allow the surface data to be assimilated into a deeper layer through a simulated initialization period, and (iii) addition of water vapor at points covered by radar echo to ensure relative humidities greater than 80%. All of these modifications were implemented in runs using both the operational Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) convective parameterizations. In addition, simulations were also run with a doubling of the convective time step, alternation of the two convective schemes within one run, and exclusion of a convective scheme in another run. For all 20 cases, 14 variants in the model initilization/moist physics were used, creating a high grid resolution (10-km grid spacing) ensemble.
Gallus et al. (Sat,) studied this question.