Sunday, 9 February 2003
The Influence of Initial Conditions on the SPC 2001 Ensemble Cloud Model Forecasts
As an extension to the Storm Prediction Centerís 2001 Spring Experiment, a cloud model ensemble is used to determine its utility as a forecasting tool. Based on the Day 2 outlook, soundings are extracted from three mesoscale models over a 160 x 160 km area. These soundings serve as initial conditions for two cloud-scale ensemble models. One ensemble contains a mix of soundings from the Operational Eta and a locally run version of the Operational Eta using the Kain-Fritsch convective parameterization, and the other ensemble contains a mix of soundings from the same locally run version of the Operational Eta and the Rapid Update Cycle model. Previous work has only examined the results of all the models combined. This paper addresses the question of how much each mesoscale model influences the verification results. Ensemble model results are characterized by five storm-length categories: no storms, short-lived storms, medium-lived storms, long-lived storms, and supercells. Except for long-lived storms and supercells, combining initial conditions from all mesoscale models yields the best results. For long-lived storms and supercells, verification results are heavily influenced by initial conditions from the Operational Eta.