A turbine performance diagnostic system creates a performance report for one or more turbines and includes an assessment module that receives operating data from at least one turbine and produces a performance report from the operating data. The assessment module includes a change detection module configured to determine when at least one parameter has changed beyond an associated threshold and generate an alarm and a root cause analyzer coupled to the change detection module that predicts a root cause of the alarm utilizing a Bayesian Belief Network (BBN). The performance report includes an indication of the predicted root cause.