An experimental coupled forecast system at the National Meteorological Center - Some early results

An experimental coupled ocean-atmosphere model forecast system has been implemented at the National Meteorological Center (NMC) for routine multi-season climate forecasts. The ocean initial conditions for the forecasts are provided by an ocean data assimilation system which uses a basin model of the Pacific Ocean integrated with a four-dimensional variational data assimilation system. Pacific basin ocean reanalyses for the period 1982—1992 provided both the initial conditions and the verification fields for the coupled model forecasts. The coupled model consists of a modified T40 version of NMC’s operational medium range forecast model coupled to a Pacific basin ocean general circulation model. Hindcast experiments starting on the first of every month from October 1983—1993 have been made to establish the skill of this system in forecasting sea surface temperature variability in the tropical Pacific with lead times of up to several seasons. The system consistently out performs persistence forecasts even at short forecast lead times, and is able to forecast most of the sea surface temperature variability that occurred in the tropical Pacific during 1984—1993.