Hydrographic data collected on board ORV Sagar Kanya in the southern Bay of Bengal during the BOBMEX-Pilot programme (October -- November 1998) have been used to describe the thermohaline structure and circulation in the upper 200m water column of the study region. The presence of seasonal Inter-Tropical Convergence Zone (ITCZ) over the study area, typically characterized with enhanced cloudiness and flanked by the respective east/northeast winds on its northern part and west/southwest winds on its southern part, has led to net surface heat loss of about 55W=m2. The sea surface dynamic topography relative to 500 db shows that the upper layer circulation is characterised by a cyclonic gyre encompassing the study area. The eastward flowing Indian Monsoon Current (IMC) between 5°N and 7°N in the south and its northward branching along 87°E up to 13°N appear to feed the cyclonic gyre. The Vessel-Mounted Acoustic Doppler Current Profiler (VM-ADCP) measured currents confirm the presence of the cyclonic gyre in the southern Bay of Bengal during the withdrawing phase of the southwest monsoon from the northern/central parts of the Bay of Bengal.