Five-day tropical cyclone track forecasts in the North Atlantic basin

Statistical analyses of the most recent 40 yr of hurricane track (1956-95) are presented, leading to a version of the North Atlantic climatology and p ersistence (CLIPER) model that exhibits much smaller forecast biases but si milar forecast errors compared to the previously used version. Changes to t he model involve the inclusion of more accurate historical tropical cyclone track data and a simpler derivation of the regression equations. Nonlinear systems analysis shows that the predictability timescale in which the aver age errors increase by a factor e is approximately 2.5 days in the Atlantic basin, which is larger than that found by similar methods near Australia. This suggests that 5-day tropical cyclone track forecasts may have some ben efit, and therefore a version of CLIPER extended to 5 days to be used as a baseline to measure this skill is needed.