The Morton effect (ME) is characterized by an asymmetric journal temperature distribution, slowly varying thermal bow and intolerable synchronous vibration levels. The conventional mass imbalance model is replaced by a more accurate thermal shaft bow model. Rotor permanent bow and disk skew are synchronous excitation sources and are incorporated in the dynamic model to investigate their influence on the ME. A hybrid beam/solid element finite element shaft model is utilized to provide improved accuracy for predicting the rotor thermal bow and expansion, with practical computation time. ME is shown to be induced by initial shaft bow and disk skew. The conventional mass imbalance approach is shown to have some limitations.