A system includes a gas turbine system including a compressor, a combustor, a turbine, and an exhaust section. The system also includes multiple sensors coupled to components of the gas turbine system. The system further includes a controller communicatively coupled to the gas turbine system and the multiple sensors and configured to control operations of the gas turbine system, wherein the controller is configured to calculate a surrogate value for turbine exit Mach number based on the feedback from the multiple sensors and to utilize the surrogate value to derive a control action for the gas turbine system.