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The life cycle of Bay of Bengal cyclone GIRI, characterized by a rapid intensification during 36-h interval, is investigated. The cyclone under study underwent a period of explosive cyclogenesis from 0000 UTC 21 October to 1200 UTC 22 October 2010. During this period, the sea level pressure minimum at the center of cyclone dropped by 52 hPa. European Centre for Medium Range Weather Forecasts (ECMWF) model data is used to perform the analysis of Q-vectors, K-Index and potential vorticity (PV) perturbation in order to diagnose the life cycle of this unusual cyclone. The analysis reveals that during the period of explosive development, the 500–700 hPa column-averaged Q-vector convergence (regions of quasi-geostrophic forcing for ascent) directly above the surface cyclone had strengthened, which in turn affected the lower to middle-tropospheric ascent and associated surface cyclogenesis. The …