A Study on the Possible Brown Ocean Effect: Impacts of an Antecedent Tropical Cyclone on the Rapid Intensification of the 1999 Odisha Supercyclone

Odhisa, a state of India, bore the disastrous consequences of two consequent Tropical Cyclones (TCs), TC 04B and TC 05B (Odisha 1999 supercyclone), which formed over the Bay of Bengal and experienced landfall in October 1999, with a time gap of fewer than two weeks, over the same region. It is suggested that the first TC, TC 04B, provided an “ocean‐like situation” over the coastal land region, thus delivering the appropriate land conditions that would facilitate the intensification of the following second tropical cyclone, TC 05B; a clear illustration of the “Brown Ocean effect.” Two Weather Research Forecasting (WRF) simulations were conducted, with the control and experimental runs differing solely in the following aspect: the initial cyclonic vortex corresponding to the first TC at the initial time was removed in the experimental run, whereas it was retained in the control run. Both simulations were analyzed to reveal the “Brown Ocean Effect” role. The experimental run result indicates that the minimum central sea level pressure of the second TC was 35 hPa higher than the second TC simulation in the control run. The heavy rainfall associated with TC 04B led to increased soil moisture conditions, providing the second TC (TC 05B) with the necessary conditions for its intensification by the “Brown Ocean Effect.” The results of this study appear to strongly suggest that the “Brown Ocean Effect” could provide one of the main reasons for the extraordinary intensities associated with the 1999 Odisha supercyclone. Plain Language Summary Whenever two tropical cyclones cross over the same coastal region, one after the other, within 2 weeks, there is a possibility that the second tropical cyclone is a more intense tropical cyclone due to the “Brown Ocean Effect.” The rainfall from the first tropical cyclone leads to increased soil moisture conditions, which makes the coastal region more ocean‐like. The higher soil moisture conditions associated with the first tropical cyclone create the necessary conducive environment for the second tropical cyclone to attain much higher intensity. Odisha, a state in India, experienced two such tropical cyclones TC 04B and TC 05B, the latter also known as Odisha 1999 supercyclone, during October 1999, with both tropical cyclones crossing more or less the same coastal region within 11 days of one another. In this study, we investigate the possibility of the “Brown Ocean Effect” through an atmospheric model, playing a role in the ex