A Case of Rapid Continental Mesoscale Cyclogenesis. Part I: Model Sensitivity Experiments

Abstract

Abstract A rapid mesoscale cyclogenesis event took place over the southeastern United States during 28–29 March 1984. This small-scale cyclone, whose initial radius of circulation was approximately 120 km, was associated with a 3-h pressure fall of 11 mb, rainfall exceeding 60 mm, and numerous tornadoes. The development of this mesoscale cyclone was poorly forecasted by the operational Limited-Area Fine-Mesh Model (LFM). Later experiments with the Nested Grid Model (NGM) and eta model also experienced similar failure. In this paper, the authors present a series of numerical experiments using The Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model version 4 (MM4) with the goat of determining factors crucial to a successful prediction of the surface cyclogenesis. The control experiment simulated the rapid mesoscale cyclogenesis by using a 40-km grid spacing; explicit prediction of cloud water, rainwater, and cloud ice; subgrid cumulus parameterization developed by Grell; a...