What Locks the Position of Nighttime Convection Initiation Center in Hainan Island?

Abstract Current understanding of the position of nighttime convection initiation (CI) center over Hainan Island remains significantly limited. This study comprehensively clarifies what locks the position of the nighttime CI center in Hainan Island. The nighttime CI occurrence over Hainan Island requires warm and moist environmental winds, which primarily generate strong convergence in the southwestern‐to‐eastern offshore region, where nighttime CI occurrence is first locked. Concurrently, the intrinsically phase‐locked inertial oscillation of sea breezes over the South China Sea causes strong convergence between sea breezes and land breezes in the southern‐to‐eastern offshore region, where nighttime CI occurrence is second locked. Ultimately, the coupling between upper‐level easterlies and low‐level environmental winds induces strong vertical wind shear over the southwestern and southern sides of the island, where CI development is highly suppressed. These triple mechanisms collectively lock the nighttime CI center into the southeastern offshore region of Hainan Island.