The extremely high rainfalls that have fallen on Queensland, Australia have illustrated one of the characteristic weather patterns of La Niña events, namely the westward shift in major rainfall patterns across the Pacific basin. La Niña is associated with a strengthening of the equatorial trade winds that blow from east to west. These trade winds push atmospheric moisture that forms in the Intertropical Convergence Zone (ITCZ) from the Central Pacific into the far Western Pacific. The ITCZ is responsible for transporting a large amount of moisture around the globe, and is most commonly associated with the hurricane/cyclone formation regions. In this image, daily precipitation has been averaged over the course of a year. On the left, the data is from January 1 - December 31, 1999, during a very intense La Niña. On the right, the data is from January 1 - December 31, 1993, during a "normal" year when neither La Niña nor El Niño were present. Notice how the areas of highest daily rainfall are situated directly over the Coral Sea during the normal year, but move far more westward during La Niña. This offset places some of the heaviest rains over the islands of the Pacific and Indian Ocean Basins, areas which are usually spared from the most intense rains during normal years.
This precipitation data comes from the Global Precipitation Climatology Project, a global partnership between NOAA, other governmental organizations, and academia to provide highly accurate analysis of global rainfall patterns, using data from a variety of satellite and ground measurements.