A 3-year investigation is underway into the performance of applications used in the Australian Community Climate and Earth System Simulator on the petascale supercomputer Raijin hosted at the National Computational Infrastructure. Several applications have been identified as candidates for this investigation including the UK MetOffice’s Unified Model (UM) atmospheric model and Princeton University’s Modular Ocean Model (MOM). In this paper we present initial results of the investigation of the performance and scalability of UM and MOM on Raijin. We also present initial results of a performance study on the data assimilation package (VAR) developed by the UK MetOffice and used by the Australian Bureau of Meteorology in its operational weather forecasting suite. Further investigation and optimization is envisioned for each application investigated and will be discussed.