Active northwest cloud bands may bring above average rainfall over the next few months across large areas of western and southern Australia. This is one of the main outcomes from the seasonal outlook for April to June 2020 released this week by the Bureau of Meteorology.

Chance of rainfall being above median for April-June 2020. Source: Bureau of Meteorology

The two main climate drivers in Australia, El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD), are likely to remain neutral over the next months. As a consequence, they both will have limited influence on Australian weather and climate through Autumn. 

However, climate models are indicating warmer than average sea surface temperatures across northern Australia and parts of the eastern Indian Ocean. This may actively enhance northwest cloud bands, stretching from the northwest of the country down towards the southeast. These extensive layers of clouds can interact with mid-latitude weather systems, such as cold fronts and cut-off lows, and produce widespread and heavy rainfall. 

As a result, the three-month April to June rainfall is likely to be above average for Western Australia, western and southern parts of the Northern Territory, most of South Australia, western and central Victoria, and northwest Tasmania. 

Drier than average conditions are likely over much of the Queensland coast, especially the Northern Cape York Peninsula. This is again due to warmer than average ocean temperatures, but in this case across the western Pacific. This setup generally increases cloudiness and rainfall over that region and suppresses rainfall across parts of Queensland and the tropics.  

No significant signal either way to above or below average rainfall is expected for the rest of the country.