The images below show the tropical pacific at times of La Nina conditions and times of neutral conditions.
Under La Nina conditions, the sea surface temperatures are cooler across the eastern tropical pacific, and as a consequence the atmospheric circulation is pushed further west. The area where air rises, and where convective rainfall occurs is therefore further west across Indonesia and Australia, rather than over the Pacific Ocean.
The tropical Pacific under La Nina conditions, and its impact on atmospheric circulation patterns.
The tropical Pacific under normal conditions, and the resulting atmospheric circulation patterns.
Finally the graphic below shows some of the clearer impacts that La Nina has on the weather around the globe. The graphic highlights areas where it may be wetter or drier or cooler or warmer than when there is no La Nina.
Map showing areas that may become wetter or drier or colder or warmer than normal when a La Nina is occurring