Previous studies have suggested that the vertical mesovortex couple plays a critical role in tropical cyclogenesis. This couple consists of midlevel and low-level mesoscale vortices, whose formation is believed to result from different physical mechanisms. However, existing tropical cyclone datasets primarily document post-formation stages, and a substantial gap remains between the well-observed life cycles of mature tropical cyclones and the poorly documented mesoscale processes preceding formation. To address this gap, a flexible, objective detection and tracking framework was developed based on ERA5 reanalysis, termed the Mesovortex Analysis of Structure and Tracking (MAST), and a corresponding multi-decadal dataset was constructed for the western North Pacific (WNP) basin covering 1984–2023. Technical validation shows that MAST successfully detects 96 % of the mesovortex couple associated with observed tropical cyclogenesis events at the formation time, with more than 50 % of cases identifiable as early as 48 h prior to formation. A comparative analysis further reveals systematic differences in the vertical tilt evolution of the mesovortex couple: genesis cases exhibit a steady reduction in tilt with time, whereas non-genesis cases maintain a persistently large tilt of approximately 200 km. The MAST framework extends the long-term record of mesoscale vortex evolution during the pre-formation stage and provides a valuable resource for understanding tropical cyclogenesis, numerical model evaluation, and machine-learning-based genesis prediction.