Abstract: The El Niño events in the tropical Pacific usually suppress precipitation in fall over the northern Bay of Bengal through cross-basin air-sea interactions. However, a significant enhanced precipitation was observed during the super El Niño event in fall 2023 and triggered severe localized flooding. This study reveals that the anomalous precipitation event mainly originated from the synergistic effect of anomalous westerly wind activity and tropical cyclone in the Bay of Bengal, which are resulted from the sea surface temperature (SST) anomalies due to westerly anomaly-SST gradient positive feedback mechanism. In September 2023, the northern Bay of Bengal experienced significant westerly winds in low-altitude atmospheric circulation field, which drove surface warm water towards the east coast and formed a westward SST gradient, affecting the wind field through sea surface pressure gradient, thus allowing the anomalous westerly winds and anomalous SST distribution to be maintained. At the same time, tropical cyclone activity is obviously enhanced. Superposition of the southeasterly circulation of the tropical cyclone and the anomalous westerly winds formed a low-level jet with a central wind speed of more than 20 m·s⁻¹, whose warm moisture transported from ocean surface synergistically interacted with the tropical cyclone precipitation and ultimately caused anomalous precipitation surge in the northern Bay of Bengal in September. Moreover, the tropical storms and typhoons in the Bay of Bengal in October-November were the strongest in the past 20 years in terms of duration and intensity, which in turn caused significant increase in precipitation. These results demonstrate the complexity of the multi-scale air-sea interactions regulating precipitation changes in the monsoon region of the Bay of Bengal, and provide a new perspective for predicting localized meteorological hazards under tropical climate change.