Large-scale scientific computing applications frequently make use of closely-coupled distributed parallel components. The performance of such scientific applications is therefore dependent on the component parts and their interaction at run-time. This paper describes a methodology for predictive performance modelling of parallel applications composed of multiple interacting components. In this paper, the fundamental steps and required operations involved in the modelling process are identified - including inter-component dataflow analysis, MxN communication performance evaluation and composite performance model evaluation. A case study is presented to illustrate the modelling process and the methodology is verified through experimental analysis.