Crown fire initiation is studied by using laboratory experiments, a semi-empirical model, and a detailed physical based on large eddy simulation (LES) to gain a better understanding of transition from ground to crown fire. In the experiments, we investigated the effects of height of crown fuel, wind speed, and crown fuel configuration on crown fire initiation. The experimental setup was designed to model an isolated clump of crown fuels such as a single tree or group of shrubs. Three wind velocities (0, 1.5, and 1.9 m s−1) and three vertical distances (25, 35, and 45 cm) were used. Crown and air temperature within the elevated fuel bed were measured. Crown bulk density and fuel moisture content were constant. As crown base height increased, crown fire initiation success decreased. Both non-zero wind speeds reduced crown fire initiation success because of reduced heating. A semi-empirical model based on convective and radiative heat exchange was developed to predict the crown fire initiation above a prescribed ground fire. The predicted results for different wind speeds and crown base height were in good agreement with the experimental measurements. A recently developed three dimensional (3D) LES was used to model the experiments and to highlight the physical processes of turbulent flow, heat transfer and fuel combustion involved in fire propagation.