To provide critical spotting information to fire managers and the developers of operational wildfire behavior models, a physics-based spotting model has been developed and used to characterize potential spotting hazard in complex wildland urban interface (WUI) fires. The spread of large-scale fires is a result of two types of phenomena: contiguous spread and spotting. Spotting is the phenomenon by which burning material, called firebrands, are lofted by the plume, transported via the fire-influenced wind field, and deposited to ignite new fires ahead of the contiguous fire front. Spotting behavior depends on the strong coupling between fire, atmosphere, topography, and fuels and is therefore difficult to characterize without adequate methods of accounting for this coupling. In order to predict spotting, the physical firebrand model has been integrated into HIGRAD/FIRETEC, a premier physics-based model for the prediction of contiguous fire spread. Incorporating the firebrand model into HIGRAD/FIRETEC provides a mechanism to predict spotting locations in a wide range of conditions including rugged terrain, gusty winds, and non-homogeneous fuels. The coupled effects of fuel types/conditions, fuel heterogeneity, atmospheric wind speed/gust/turbulence, topography, and human-made structures could be studied through the HIGRAD/FIRETEC_SPOT model and be characterized. It is found that the flame/plume structure with wind conditions around fire is critical for predicting spotting behavior. It is recommended to study of plume structure/wind patterns and critical factors on them such as topology and atmospheric conditions for further firebrand research. The knowledge obtained from this project and further investigation will be practical information for fire and land management personnel.