Vol. 129, No. 1 * Pages 1–105 * January - March 2025

In general, there would be one monsoon depression affecting the South China Sea every summer. Such depressions are relatively short-lived and mostly last for a few days. In early June 2023, there was a relatively long-lived monsoon depression over the South China Sea with a lifespan of around 10 days. The paper documents the life of this monsoon depression, including the meteorological observations. This depression is found to have the typical structure of a monsoon depression, namely, very weak winds near the center and higher wind speed with intense convection associated with a burst of southwest monsoon in its periphery. The strong southwest monsoon was also observed as a boundary layer jet in the upper air observations. The study is unique from the perspective that there are more meteorological observations over the northern part of the South China Sea, including the weather buoys and oil platforms, which provide unprecedented meteorological observations of the depression. It is hoped that this paper could stimulate further studies of monsoon depressions in this region in the future.