Experimental Tropical Cyclone Forecasts Using a Variable-Resolution Global Model

• DOI: 10.1175/mwr-d-15-0159.1
• Publication Date: 2015-07-31T20:14:36Z
• Authors: Colin M. Zarzycki; Christiane Jablon...
• Keywords: Atlantic hurricane; Horizontal resolution

Abstract Tropical cyclone (TC) forecasts at 14-km horizontal resolution (0.125°) are completed using variable-resolution (V-R) grids within the Community Atmosphere Model (CAM). Forecasts integrated twice daily from 1 August to 31 October for both 2012 and 2013, with a high-resolution nest centered over North Atlantic eastern Pacific Ocean basins. Using CAM version 5 (CAM5) physical parameterization package, regional refinement is shown significantly increase TC track forecast skill relative unrefined (55 km, 0.5°). For typical integration periods (approximately week), V-R able nearly identically reproduce flow field of globally uniform forecast. Simulated intensity generally too strong beyond 72 h. This bias robust regardless whether forced observed or climatological sea surface temperatures not mitigated in suite sensitivity simulations aimed investigating impact model time step CAM’s deep convection parameterization. Replacing components default physics Cloud Layers Unified by Binormals (CLUBB) produces statistically significant improvement longer lead times, although structural differences forecasted TCs exist. recurvature Hurricane Sandy into northeastern United States 60 h earlier than Global Forecast System (GFS) identical initial conditions, demonstrating configuration. Computational costs associated dramatically decreased simulations, that techniques promising tool future numerical weather prediction applications.