Dynamic hurricane season prediction experiment with the NCEP T382 CFS CGCM

A series of experimental forecast runs with the NCEP CFS CGCM were made to examine the feasibility of dynamical hurricane season prediction as one of the Climate Test Bed internal projects in 2007/2008. A series of forecast experiments with initial conditions in mid-April and mid-July during 1981-2008 were made in the T382 spectral resolution to evaluate tropical storm statistics in the CFS at the highest possible spatial resolution. Statistics and tracks of tropical storms in the Northern Hemisphere basins are examined and compared to observations. The main focus will be on the seasonal cycle and interannual variability over the Atlantic, Eastern Pacific and Western North Pacific basins.

Tropical storms in the CFS runs were identified using the tropical storm detection method devised by Carmago and Zebiak (2002). Storms depicted in the CFS have very realistic tracks in all four basins in the Northern Hemisphere and a robust seasonal cycle. Comparisons of interannual variability in storm activities indicate that the CFS has reasonable skill and captures the shift to a more active storm era in the Atlantic basin during the post-1995 period. Also discussed will be some preliminary findings on the causes of model bias in storm origins and tracks, and the 2009 season prediction.