The Madden-Julian Oscillation (MJO), also called the 40-day wave, is a tropical weather pattern that is a very important climate driver for northern Australia, but can also influence rainfall patterns across southern Australia. Depending on the phase and time of year, the MJO can influence if it is likely to be wetter or dryer.

The MJO is characterised by a band of clouds, rainfall and winds moving eastward across the tropical Indian Ocean into the western Pacific Ocean.

When the MJO is in its enhanced phase it can increase the rainfall across southern Australia. However, when the MJO is in its suppressed phase it can reduce rainfall and bring drought conditions across southern Australia.

The following videos explain the impact of MJO and how it behaves.

Key points