Model Consensus

Abstract

Consensus forecasts from the control runs of several operational numerical models are compared to 1) the control-run forecasts of the individual models that compose the consensus and to 2) other consensus forecasts generated by varying the initial conditions of the various individual models. It is found that the multimodel consensus is superior to the individual control runs and to the consensus forecasts constructed from ensembles of runs generated by varying model initial conditions. The source of the forecast improvement by model consensus is not the result of a simple cancellation of errors as a result of an overall positive bias in one model and an overall negative bias in another. Rather the main improvement stems from overlapping differences in the sign of the errors associated with forecasts of individual traveling disturbances. The results suggest that variations in model physics and numerics play a substantial role in generating the full spectrum of possible solutions that can arise in a given numerical forecast.