Laboratory scale investigation of a fire spreading on the windward face of a triangular section hill of variable shape with wind perpendicular to the ridgeline was performed. The work confirmed previous observations that the fire enlarges its lateral spread after reaching the ridgeline entering the leeward face with a much wider front. Reference fire spread velocities were measured and analyzed putting in evidence the importance of the dynamic effect due to flow velocity and its associated horizontal axis separation vortex strength without great dependence on hill geometry. A similar analysis performed to some real fires confirmed the same trend as was observed in the laboratory scale.