Southwestern Indian state, Kerala experienced extreme devastating statewide flood event of the century during 2018 monsoon season. In this study, an attempt has been made to bring out the salient dynamical factors contributed to the Kerala flood. There were 3 active spells over Kerala during 2018 Monsoon season. All the three spells were accustomed with the intrinsic factors of low frequency components of the active spells such as strength of monsoon Low Level Jet (LLJ), Monsoon depressions in the Bay of Bengal, favorable Madden-Julian oscillation (MJO) phases and Western Pacific systems. Though all the common ingredients remain same, the third spell is distinct with the less evaporation flux over Western and Central Arabian Sea and unusual moisture transport from maritime continent through South Equatorial Indian ocean (SEIO) towards the Kerala coast across Equator. Strong meridional pressure gradient force created by the combined effect of high pressure anomaly oriented Northwest-Southeast direction across tropical Indian ocean and anomalous low pressure along monsoon trough might have contributed to this unusual moisture transport across SEIO originating from west of Australia. The anomalous high pressure in South Indian ocean was greatly influenced by the position of the Mascarene high. Subtropical Indian ocean dipole (SIOD) also exhibits an influential role by altering tropical Southern Indian ocean dynamics in favor of the unusual moisture transport. The position of the monsoon depression and presence of typhoons in Western Pacific might have aided to this moisture transport. However, the normal moisture transport from Central Arabian sea towards Kerala coast by virtue of the strong LLJ along with additional moisture transport directly from South of maritime continent through SEIO across the Equator towards Kerala coast might have played a dominant role in the historical flood event over entire Kerala state.

印度西南部喀拉拉邦在 2018 年季风季节经历了本世纪的极端破坏性全州洪水事件。在这项研究中，试图找出导致喀拉拉邦洪水的显着动力因素。在 2018 年季风季节期间，喀拉拉邦有 3 个活跃期。这三个期都适应了活跃期的低频分量的内在因素，如季风低空急流（LLJ）的强度、孟加拉湾季风洼地、有利的马登-朱利安振荡（MJO）相位和西太平洋系统。虽然所有的共同成分都保持不变，第三个阶段的特点是阿拉伯海西部和中部的蒸发通量较小，并且从海洋大陆通过南赤道印度洋 (SEIO) 向跨越赤道的喀拉拉邦海岸输送了不寻常的水分。由横跨热带印度洋的西北-东南方向的高压异常和沿季风槽的异常低压共同作用产生的强烈的经向压力梯度力可能导致了这种来自澳大利亚西部的 SEIO 异常水分输送。南印度洋异常高压受马斯卡林高压位置影响较大。亚热带印度洋偶极子 (SIOD) 也通过改变热带南印度洋动力学有利于不寻常的水分输送而发挥重要作用。西太平洋季风洼地的位置和台风的存在可能有助于这种水分输送。然而，由于强低空急流，从阿拉伯海中部向喀拉拉邦海岸的正常水分输送，以及从海洋大陆南部通过 SEIO 穿过赤道向喀拉拉邦海岸直接输送的额外水分，可能在过去的历史洪水事件中发挥了主导作用。整个喀拉拉邦。