The presentation of back trajectory information from synoptic analyses and forecasts can provide additional forecast guidance. A package has been developed to compute backward and forward trajectories in three dimensions,with three velocity components. from the Australia Bureau of Meteorology operational limited area 36-hour forecasts. Three forms of output are available,backward trajectories,forward trajectories, and a contoured field of 36(hour air parcel displacement to a chosen vertical coordinate surface. The package has also been applied to diagnostic studles.