<p>Typhoon Hinnamnor (2022) was the only tropical cyclone (TC) during 1982–2023 that maintained strong or higher intensity north of 25°N while undergoing two rapid intensification (RI) events under marine heatwave (MHW) conditions. These RI events differed significantly in both duration and intensification rates. This study investigated the role of MHWs in modulating these events, with a focus on variations in ocean stratification and atmospheric circulation. The results revealed that the first RI lasted 18 h, during which typhoon Hinnamnor intensified from a strong tropical storm to a super typhoon, which was driven primarily by oceanic thermal conditions. The anomalous MHW deepened the warm subsurface waters, leading to sustained accumulation of upper ocean heat content (UOHC), which fueled the RI. The cyclone’s rapid movement and moderate intensity helped preserve the abnormally thick barrier layer (BL), which maintained the UOHC via a subsurface “heat pump” effect, thus supporting continued intensification. In contrast, the second RI lasted only 6 h and involved a one-category intensification from a strong typhoon to a super typhoon, influenced by both oceanic and atmospheric factors. The prolonged and intensified MHW maintained a high UOHC, while strong upper-level divergence, increased mid-level moisture and low-level convergence enhanced deep convection, triggering the RI. However, a shallow mixed layer confined warm anomalies to the surface, whereas the cyclone’s slower movement, stronger winds, and thinner BL induced cold water upwelling. This “cold suction” effect depleted the UOHC, prematurely terminating the RI. These findings highlight the complex interplay between oceanic and atmospheric factors in shaping TC intensification under MHW conditions, emphasizing the critical role of upper ocean stratification in improving TC intensity forecasts.</p>