Tropical Climate Update

Climate driver influence on northern wet season

The current seasonal climate drivers of El Niño and positive Indian Ocean Dipole (IOD) both have a significant influence on rainfall and temperature patterns across northern Australia during the wet season months of October to the following April. Rainfall is typically much lower than average during the early wet season months of October to December. Since 1960, the lowest rainfall observed across northern Australia (taken as north of latitude 26 °South) occurred in 2019 when a strong positive IOD was underway. The second lowest was in 1963, another positive IOD year. Based on recent observations and current model outlooks, the positive IOD of 2023 may potentially be close in strength to the 2019 event, which was the strongest on record.

El Niño also influences wet season rainfall beyond December. It historically leads to later than normal monsoon onset at Darwin and delayed and reduced tropical cyclone activity across the broader Australian region. Overall wet-season rainfall totals are normally below average for parts of far northern Australia, including the Northern Territory Top End and Queensland's Cape York Peninsula.

Current long-range forecasts are broadly in line with these historical precedents and indicate a high likelihood of warmer than average temperatures across northern Australia in the coming months.

Elevated fire danger remains across the tropics.

In northern Australia, 'build-up' like conditions continue. Over the coming week, warmer than average temperatures are expected to persist, with heatwaves forecast for some localised areas, and increased humidity, isolated showers and thunderstorms are possible across the tropics.

While current conditions across the tropics are relatively calm (from a severe weather perspective), elevated fire danger ratings are still in place in many areas. This includes the Barkly region in the NT, where a bushfire of more than 2 million hectares has forced the closure of the Barkly Highway. The warmer and drier conditions are likely to see these fire dangers remain for some areas in the near term.  

Looking further ahead with the Bureau's new 7-day tropical cyclone forecast, there is a chance of a tropical low entering the Australian Region by Monday 23 October, potentially the first of the season. It is likely this will form well away from the Australian coast, but it will be named '01U' if it forms and enters the region.

The Bureau's recently released Severe Weather Season and Tropical Cyclone Long-range Forecast, indicates that Australia can expect fewer tropical lows and cyclones this severe weather season due to the active El Niño and positive Indian Ocean Dipole (IOD) events; however, it is important to remember that tropical lows and cyclones can still occur and preparedness for the season (October 2023 to April 2024) is necessary for communities in the tropics. Since reliable records began in 1970, at least one tropical cyclone has crossed the coast each season.

Madden–Julian Oscillation remains weak

The MJO is currently weak or indiscernible. Climate models surveyed by the Bureau are forecasting a generally negligible signal during the coming week.