The time-evolution of optical degradation in the near nozzle region of a heated axisymmetric jet is measured using conditional sampling techniques. A novel linearized stability experiment is performed in order to identify the flowfield states most applicable for conditional sampling techniques. The results of the conditional sampling experiment exhibit a condition where two distinct flowfield states are evident. Potential explanations for the observance of these two distinct states are proposed, with the most probable explanation being due to pi-jumps that can arise between the phase of the excitation signal and the phase of the flowfield events.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.