This study used a 1.5-layer reduced-gravity numerical model to investigate the nonlinear dynamics of Kuroshio intrusion into the Luzon Strait.The model results suggested that both basin-scale wind curl and lateral friction are the primary factors that control the transformation of the flow,although inertia also plays an important role.Using an idealized model,both the mechanism via which the flow pattern changes depending on the two primary factors and the occurrence of hysteresis were investigated.It was established that the transformation of the Kuroshio flow field between the four previously reported flow patterns(i.e.,leaping across,current looping,eddy shedding,and branch intruding) can be explained under a unified theoretical framework.A diagram is proposed to explain how the flow field transforms between the four patterns from a certain prior state when varying the values of the controlling factors. This study used a 1.5-layer reduced-gravity numerical model to investigate the nonlinear dynamics of Kuroshio intrusion into the Luzon Strait. The model results suggested that both both basin-scale wind curl and lateral friction are the primary factors that control the transformation of the flow , although inertia also plays an important role. Using an idealized model, both the mechanism via which the flow pattern changes depending on the two primary factors and the occurrence of hysteresis were investigated. It was established that the transformation of the Kuroshio flow field between the four previously reported flow patterns (ie, leaping across, current looping, eddy shedding, and branch intruding) can be explained under a unified theoretical framework. A diagram is proposed to explain how the flow field transforms between the four patterns from a certain prior state when varying the values ​​of the controlling factors