Predictions of North Atlantic tropical cyclone activity out to 4 weeks with global MPAS simulations

The very active month of September 2020 included the formation of 10 named storms, the most on record for the month of September, and 5 concurrent tropical cyclones (TCs) in the North Atlantic basin on September 14^th. The Model for Prediction Across Scales (MPAS) is used to explore potential opportunity to predict TC activity out to 4 weeks. First, the MPAS model climatology for September TC activity is established. Next, the predictability of an active September is explored using MPAS simulations with initial atmospheric and oceanic conditions from the global forecast system (GFS) and compared with MPAS climatology. MPAS simulations for 2020 are initialized over the last two weeks of August and run freely through September. The total number of TCs, TC days, accumulated cyclone energy (ACE), and the track density are each evaluated relative to observations. In addition, the simulations resulting in the most and least active month are analyzed in further detail to understand why those model simulations predicted an active or inactive September. Lastly, differences with and without a regionally refined 3 km mesh are explored.