9318751 Sanders This is a collaborative project between Dr. Steven Mullen of the University of Arizona (ATM-9319411) and Dr. Frederick Sanders. The goal is to understand the impact of initial data uncertainty in short-range (1-2 day) and extended range (3-5 day) forecasts of explosive cyclogenesis. This will be accomplished through diagnostic studies and forecast experiments. Both a global spectral model and a limited-area mesoscale model will be used to produce model simulations of cyclone cases. Analyses of observed cases will be examined as well. In addition, the PIs plan to conduct Monte-Carlo ensemble forecasts to evaluate the efficacy of this technique in minimizing the negative impact of forecast variability. Explosive cyclogenesis events, whether over land or ocean, represent potentially dangerous storms in terms of both economics and safety. The principal investigators hope to provide insights into the most promising ways to improve the forecasts of such storms. ***