Abstract: In this study, RI (rapid intensification) tropical cyclones with atypical convection (upshear concentrated convection) in the Northwest Pacific were screened using reanalysis data and infrared cloud images. A group of slow intensification (noRI) typhoons with typical convection (downshear concentrated convection) was gathered for comparison. The RI group has a stronger center of surface latent heat flux on the left side of the VWS (vertical wind shear) direction. To further explore possible mechanisms, the atypical convection case Lekima was selected for sensitivity numerical experiments. Diagnostic results indicate that surface latent heat flux on the left side of the VWS direction helps establish convective instability in the region. Consequently, the influence of the “ventilation effect” is weakened because of the “boundary layer entropy recovery” mechanism caused by surface latent heat flux. Under easterly VWS, convection activity can be enhanced in regions with high surface latent heat flux during the transition from downshear to upshear, thereby stimulating strong upper outflow channels. The establishment of outflow channels (outflow blocking mechanism) can resist environmental easterly flow, weakening the strength of VWS and allowing typhoons to develop vertically.