A regional climate model (DARLAM) implemented over a substantial region of the South Pacific is nested within a 100-year transient GCM climate change simulation. The regional climate model has a horizontal resolution of 125 km, with nine vertical levels. The output of this model is analysed for the presence of tropical cyclone-like vortices (TCLVs). There are substantial variations in TCLV formation in the model output on both interannual and interdecadal time scales, both in terms of regions of formation and subsequent tracks. A comparison is made to variations in observed tropical cyclone behaviour on these time scales, with an emphasis on validating the mechanisms operating in the model. The model's simulation of TCLV behaviour under changed climate conditions is also described and evaluated, with a particular emphasis on the associations between decadal variations in sea surface temperature patterns and related variations in TCLV formation and movement. A comparison is also made to relationships on similar time scales found in observations.