The current positive Indian Ocean Dipole event, which is a climate driver that brings dry and warm weather to Australia, has reached a new high point for 2019.

Differences in sea surface temperature between the western and eastern sides of the tropical Indian Ocean can influence weather patterns in Australia. 

During a positive Indian Ocean Dipole (IOD) event, warmer than usual water sits on the western side of the tropical Indian Ocean, near Africa, while relatively cool water sits on the eastern side, near Indonesia. This pattern usually causes below average rain and above average temperatures in large parts of Australia during winter and spring.

The IOD is currently in a positive phase and this week, it's reached a high point not seen for at least 18 years.

The Bureau of Meteorology monitors the Indian Ocean Dipole using an index that measures the difference in sea surface temperatures between tropical western and eastern Indian Ocean. Positive IOD events are declared when this index exceeds +0.4ºC for a sustained period of time.

The IOD index has been above the positive threshold of +0.4ºC for the past eight weeks and just reached a new high point for 2019.

The latest weekly IOD index value, measured over the week ending on 22nd September, was +1.5ºC. This is the highest IOD index value observed by the Bureau of Meteorology since they started keeping the current set of weekly values in 2001, according to Andrew Watkins, Head of Long Range Forecasts at the Bureau of Meteorology. 

Image: Weekly IOD index values from 2015 to 2019, showing this week's value of +1.5ºC. Source: Bureau of Meteorology.

In light of the strongly positive IOD that's currently underway, the Bureau's latest seasonal outlooks predict warmer and drier than usual weather for most of Australia during the next three months.

The IOD loses its influence on Austalian weather during summer as the monsoon trough moves into the southern hemisphere. So the impacts of this positive IOD event will mainly be felt during the next 2-3 months.