Observational data from the Arabian Sea Monsoon Experiment (ARMEX-Phase IIA) in the southeastern Arabian Sea (SEAS) showed intense warming with the SST up to 31.5°C during April – May 2005. Analysis of 5–day repeat cycles of temperature and salinity profiles from an ARGO float (ID No. 2900345) in a 3°x1° box closer to ARMEX-II buoy (8.3°N, 72.68°E) in the SEAS during January – September 2005 revealed evolution of warm pool (SST>28°C) in spring 2005. The Argo data derived D20 (depth of 20°C isotherm) showed the influence of remote forcing during January – May, and local wind forcing during southwest monsoon. Low salinity waters (<34.0) occupied the top 30 m during January – February followed by temperature inversions (up to 0.5°C) in the 30-60 m depth range. From the peak spring warming, the SST dropped gradually by 3.5°C by end-July with the advent of southwest monsoon followed by a decrease in net heat gain upto 100 W/m². The merged weekly products of sea surface height anomalies and the NLOM simulated surface currents showed complex surface circulation consisting of seasonal Lakshadweep High/Low in winter/summer. The examined oceanic and atmospheric variables showed an intraseasonal variability with 41 to 63 day period, coinciding with the Madden-Julian Oscillation.