A method for monitoring performance of a gas turbine system comprises providing a plurality of combustor cans; placing a plurality of temperature sensors circumferentially around an exhaust plane of the plurality of combustor cans; operating the plurality of combustor cans while varying a plurality of gas turbine operating parameters, where exhaust gas issues from each combustor can of the plurality of combustor cans during operation; measuring temperature of the exhaust gas in the exhaust plane using the plurality of temperature sensors to obtain a plurality of individual temperature measurements; determining a correlation of the individual temperature measurements of exhaust gas temperature with corresponding individual combustor cans of the plurality of combustor cans issuing the exhaust gas; and developing a swirl model, where the model uses the correlation to predict swirl values in the exhaust plane as a function of the operating parameters.