Abstract Winter storms present a major erosional hazard to subaqueous deltas globally, but the associated dynamic mechanisms are still not well understood. Using high‐resolution in situ data collected over a 3‐week period in the abandoned Yellow River subaqueous delta, this study employs three‐dimensional quadrant analysis to examine turbulent structures and sediment response. The findings reveal a distinct cross‐stream asymmetry during winter storms, marked by strengthened positive ejections and negative sweeps—a pattern that is further enhanced when wind and currents are aligned. Storm‐induced changes in turbulent structure produce extended turbulent bursts that substantially facilitate sediment mobilization, while vertical sediment flux increases exponentially with the degree of turbulence asymmetry. Overall, this study demonstrates that storm‐driven modification of three‐dimensional turbulent structure is the primary mechanism for increased sediment export and morphodynamic evolution of subaqueous deltas.