Prosper in a dynamic world
Search

The positive IOD is finally over

The Bureau of Meteorology has today declared the end of the persistent positive Indian Ocean Dipole (IOD) event, which contributed to the driest three-month period on record in 2023. 

The IOD is an index that measures the difference in sea surface temperature anomalies between the western and eastern sides of the tropical Indian Oceans. 

The IOD index is positive when cooler-than-average water lies off the coast of Indonesia and warmer than average water sits near the Horn of Africa. 

Positive IOD events typically cause below average rain and above average daytime temperatures over large areas of Australia during winter and spring, particularly over central and southern parts of the country. 

 This positive IOD event was the second strongest on record peaking at +1.92°C in October 2023, falling short of the 2019 event which reached as high as +2.15°C. 

Both the positive IOD and El Niño were declared in September 2023, which led to the driest three-month period on record during the middle of 2023. 

The map below shows the exceptionally dry period between August and October 2023, particularly in southeast Qld, parts of NSW and the NT, WA and SA.


Image: Australian rainfall deciles for the three months leading up to November 2023 

While these climate drivers had a noticeable influence in winter and early spring, their influence has waned in summer for much of Australia.  

The map below shows that above average rainfall fell across central and eastern Australia between November and February, while the WA coast saw below average rainfall.

Image: Australian rainfall deciles for the three months leading up to  February 2024.

However, the positive IOD has contributed to several impacts this summer: 

  • Reduced number of early season cyclones, lows and cyclones across the Western Region. 
  • Extreme heat in WA and parts of the NT during late December and early January. 
  • Lack of northwest cloud bands which stretch from the northwest of Australia to the southeast, reducing cloud cover, thunderstorms and rain in these areas at times. 

This year’s event was also unusually long, lingering into February thanks to the late arrival of the monsoon trough and the strength of the event.  

The monsoon trough was around a month late under the influence of El Nino arriving on Thursday 11th January. However, it was not the latest arrival on record, which was on the 25th January 1973. 

The warming of the oceans near Jakarta and the arrival of the monsoon in Australia has caused the positive IOD to lose strength during the last few weeks.  

The latest weekly value to February 4 was +0.3°C, which is below the positive threshold of +0.4 °C for the second consecutive week. 

Image: Weekly IOD index since the beginning of 2019, showing the IOD is now neutral. 

While the positive IOD has lost its grip on Australia, El Niño is continuing in the Pacific Ocean, but it has passed it peak. For more information on our climate forecasts and briefings, please contact us at apac.sales@dtn.com.  

Latest news

Satisfy your weather obsession with these news headlines from around the nation, and the world.

Lightning Tracker WA: Real-Time Tracker for Western Australia | Radar, Alerts & Weather Map

Lightning tracker WA technology by DTN APAC helps industries across Western Australia stay one step ahead of severe weather events. From mining to aviation, we deliver precision insights through real-time lightning detection tools. Visualise strikes, monitor thunderstorms, and respond faster with radar and satellite intelligence tailored to the region’s unique weather risks. Track Lightning Strikes […]

Why have NSW businesses flooded and when will the rain stop?

An unprecedented May deluge has impacted businesses across eastern NSW this week, with some rain gauges eclipsing their previous monthly records in the space of just three days. So why is eastern NSW seeing so much rain this week? In an average May, the NSW Mid North Coast and Hunter regions would see about 50 […]

Historic flooding as eastern NSW deluge continues

Flood records are being broken in parts of eastern NSW this week as relentless rainfall continues to dump water into already overflowing rivers and creeks, affecting businesses and industries through road and transport closures and disruptions due to flooding. A steady stream of moisture-laden onshore winds has been causing persistent rain over eastern NSW since […]

Indian monsoon onset on the doorstep

Heavy rainfall and squally thunderstorms will intensify over southern India with the arrival of the southwest Indian monsoon this week. The Indian Meteorological Department (IMD) is responsible for tracking the advance of the monsoon over the Indian sub-continent. The latest map issued by the IMD shows the northern limit of the southwest monsoon just to […]