The large-scale circulation departure patterns associated with the interannual variability of (July–June) rainfall in Java are studied on the basis of ship observations (1911–73) in the Indian Ocean and surface station records. Circulation mechanisms of interannual variability can, in part, be understood as modulations of the average annual cycle. Abundant rainfall years are characterized by an anomalously strong Northwest monsoon, and drought years by approximately inverse circulation characteristics. In December–January of the wet years, anomalously high pressure near Southeast Asia along with anomalously low pressure over Indonesia entail an enhanced meridional pressure gradient, stronger northeasterly flow over the South China Sea and Bay of Bengal, and enhanced northwesterlies over the Indonesian waters. The increased northerly wind component to the north and intensified westerlies over the equatorial Indian Ocean result in enhanced convergence and cloudiness over Indonesia, while surface wa... Abstract The large-scale circulation departure patterns associated with the interannual variability of (July–June) rainfall in Java are studied on the basis of ship observations (1911–73) in the Indian Ocean and surface station records. Circulation mechanisms of interannual variability can, in part, be understood as modulations of the average annual cycle. Abundant rainfall years are characterized by an anomalously strong Northwest monsoon, and drought years by approximately inverse circulation characteristics. In December–January of the wet years, anomalously high pressure near Southeast Asia along with anomalously low pressure over Indonesia entail an enhanced meridional pressure gradient, stronger northeasterly flow over the South China Sea and Bay of Bengal, and enhanced northwesterlies over the Indonesian waters. The increased northerly wind component to the north and intensified westerlies over the equatorial Indian Ocean result in enhanced convergence and cloudiness over Indonesia, while surface wa...