From June 2012, the Bureau of Meteorology is upgrading the Water and the Land (WATL) computer generated rainfall forecasts. The revised maps use a higher resolution model that more precisely reflects the influence of topography and local effects on the rainfall in your area. These improvements are possible because the skill level in computer generated forecasts is improving.
The above maps show low resolution (left side) and high resolution (right side) rainfall around Cairns, Queensland. The high resolution map shows small areas of no rainfall (white) or heavy rainfall (green and blue) that are not shown in the low resolution map, and the higher resolution map shows smaller areas of extreme rainfall. In the low resolution map, the effect of averaging over a larger area results in large areas with uniform rainfall. The high resolution map is able to show more variation within a given area.
The gridded data will be available at 0.5° resolution (about 50km on the ground) which is roughly double the resolution from the previous gridded data. The data that is used to the make the maps WATL rainfall maps is derived from a technique known as the "probability matched ensemble mean" to reassign the ensemble mean rain rates, to give the most likely rainfall forecast.
This upgrade in resolution was undertaken in response to requirements for the NexGenFWS (Next Generation Forecasting and Warning System).
For more detail see: About Forecast Rainfall.