The Navy coupled analysis and forecasting system is used to model the air-sea interaction during the onset of 2002 Indian summer monsoon. The Navy Global Coupled System consists of global circulation models of the atmosphere (NOAGPS) and the ocean (POP), together with the data assimilation procedures that produce the assessments of atmosphere and ocean state on daily basis. We investigate the ability of the system to predict the development of the 2002 monsoon, and the role of “bogus monsoon onset” that developed in middle May 2002 and contributed to the delay of the monsoonal rainfall in June.