Seasonal climate forecasts for agriculture: Towards better understanding and value

Two approaches to obtaining more valuable seasonal climate forecasts for Australian agriculture are described. The first involves obtaining a better understanding of the climate system by exploring the individual synoptic weather events that make up seasonal climate. An examination of rainfall events in north-west Victoria indicates that there is one dominant synoptic system that is responsible for the majority of useful rainfall: the cutoff low. An exploration of the physics of these systems reveals that the moisture sources are most likely to be from the oceans north of Australia, while the frequency and intensity might be controlled by ocean temperatures to the south. The second approach involves an examination of the potential value of different forecast systems using a century-long simulation of the growth of a wheat crop in north-west Victoria. It is concluded that a perfect forecast of the growing season rainfall total is likely to provide less than half the potential value of an ideal forecast system.