In the context of increasingly energetic typhoons and rapidly evolving coastal sea states, the likelihood of destructive rogue waves in nearshore environments is expected to rise. This study conducts a high-fidelity, phase-resolved numerical investigation of the rogue waves generated off the western coast of Lamma Island during Typhoon Mangkhut (2018). A fully nonlinear Enhanced Spectral Boundary Integral (ESBI) model, implemented on GPU architecture, enables long-duration simulations of directional wave evolution over realistic bathymetry. Across multiple random-phase realizations, 92 coastal rogue waves are identified using a wavelength-based crest–trough criterion, and their geometry is analyzed through two-dimensional Proper Orthogonal Decomposition (POD). The leading POD mode reveals a coherent core structure shared across events, whereas comparison with the linear New Wave theory shows that, despite accurately predicting transverse crest width, it fails to capture the pronounced longitudinal sharpening and asymmetry produced by strong nonlinear interactions. These results provide a physics-based characterization of coastal rogue-wave morphology and offer valuable guidance for improving coastal hazard assessment and engineering design in extreme weather conditions.