Abstract:The three consecutive La Nina events that occurred from 2020 to 2023 have been widespread concerned, and they also led to various global weather and climate anomalies. By statistically analyzing the tropical cyclone datasets from the National Meteorological Centre of China Meteorological Administration and the National Hurricane Center of the United States, we find that the number of tropical cyclones generated in the North Pacific in September 2022 was far more than the historical average over the same period, with the number of tropical cyclones in the Northeast Pacific reaching a new high in the past 70 years. Based on the reanalysis data and the analysis of the dynamic genesis potential index, it is found that the vertical motion in the middle troposphere made a great contribution to the increased number of tropical cyclones in the North Pacific. Further analysis suggests that during the La Nina events, the temperature of warm pool in the Northwest Pacific continued to rise, convective activity near the Philippines enhanced and the southwesterlies over maritime continent strengthened, which forced the subtropical high over the Northwest Pacific to shift northward. The emergence of low-level cyclonic circulation developing from the anticyclonic circulation in the active tropical cyclone area of the Northwest Pacific enhanced the ascending motion of the middle troposphere, which was favorable for the genesis of tropical cyclones. At the same time, the La Nina events led to continuous increase in the meridional temperature gradient over the Northeast Pacific and the meridional Hadley cell got intensified, so the upward movement over the middle and low latitudes strengthened. As the subtropical high located in western Mexico moved eastward, the number of active tropical cyclones in the Northeast Pacific increased.