Extremely warm spring-time maximum temperatures in Australia can have adverse effects on agriculture, the economy, and contribute to early fire season onset. A recent study of extreme spring heat events suggested that there is more to learn about how maximum temperatures develop over the individual spring months. A better understanding of the drivers of high spring maximum temperatures could lead to more skilful prediction of spring heat extremes across Australia.

Our goal is to explore the atmospheric dynamics and teleconnections that contribute to high maximum temperatures in Australia through the months of spring. We use linear regression and Rossby wave analysis techniques, including wave activity flux, in reanalysis and POAMA, one of the Bureau of Meteorology’s seasonal prediction systems, to understand the tropical and extratropical sources of those teleconnections, and the roles of Australia’s key climate drivers on monthly maximum temperature development.

Results highlight the importance of an upper-troposphere anticyclone over southern Australia to high maximum temperatures in each month of spring; barotropic cyclones to the southwest and southeast of Australia are also important. These circulation patterns and Australian spring temperature extremes are found to be more closely related to extratropical drivers in early spring and remote tropical drivers in later spring. Variability of Pacific SSTs is found to be primarily associated with Australian-region atmospheric circulation and maximum temperature; however, the Indian Ocean is also shown to play an important role.

The POAMA forecasts were found to be too dominated by variability coming out of the Pacific, diminishing the role of the Indian Ocean in driving Australian heat. We test this hypothesis with experiments to isolate the impacts of the Indian and Pacific Oceans on Australia’s spring temperatures.  Better simulation of the Indian Ocean atmospheric circulation and associated teleconnections to Australia could lead to improved maximum temperature forecasts.