Australian tropical cyclone season outlook

Pacific outlook

2014–15 Australian Tropical Cyclone Outlook

Average to below-average cyclone season most likely for Australia

Chance of above average tropical cyclone activity

Region Outlook summary
(near, below or above average)
Chance of
above average
Long-term average
number of tropical cyclones
Australian below average 34% 11
Western near average 43% 7
Northwestern sub-region below average 38% 5
Eastern region near average 42% 4
Northern region near average 46% 3

*Long-term average number of tropical cyclones may change slightly from one year to the next as a new season of data is added to the calculation.

This outlook is based upon the status of the El Niño–Southern Oscillation (ENSO) over the preceding July to September period. The Pacific Ocean has remained neutral during these months but the ocean temperatures have been near El Niño thresholds. The Southern Oscillation Index, a measure of the atmospheric component of ENSO, has been negative through this period. Climate models suggest there is still double the normal chance of El Niño occurring this summer (i.e., 50% chance).

Regional Outlooks

The statistical outlook indicates that regions can expect average to below-average tropical cyclone activity this coming season.

  • The Australian region is likely to experience below average tropical cyclone activity during the 2014–15 season. The outlook indicates a 34% chance of having more tropical cyclones than average over the Australian region (meaning a 66% chance of having fewer tropical cyclones than normal). Past outlooks have shown that the Australian region outlook has a high level of accuracy.

  • The western region experiences an average of seven tropical during the tropical cyclone season. The outlook indicates near-average tropical cyclone activity is most likely this season, with a 43% chance of an above average (57% chance of below average) number of cyclones. Typically between one and three tropical cyclones in the western region will have an impact upon the coast. In the past the accuracy for forecasts in the western region has been low.

  • The northwestern sub-region, where tropical cyclones can impact coastal Western Australian communities, has a below average outlook for tropical cyclones this season (38% of above average, meaning a 62% chance of below average). Typically, five cyclones form or pass through this area each season. Around 40% of tropical cyclones in the northwestern sub-region impact on the coast at some stage in their life cycle. Forecast accuracy in this region is good.

  • The northern region also has a near average outlook for this season. In an average year the northern region usually sees two or three named storms and one or two tropical lows that become cyclones after moving into the western or eastern regions. About three quarters of the tropical cyclones in the northern region impact the coast. Forecast accuracy in this region is low.

  • The eastern region outlook indicates a near average tropical cyclone season is most likely (42% chance of above average, 58% chance of below average. About a quarter of tropical cyclones in the eastern region make landfall. Forecast accuracy in this region is low.

Interpreting the outlook

Percentages such as a 40% chance of having more tropical cyclones than average (60% chance of having fewer) mean that for every ten years with similar climate patters to those currently observed, four years would be expected to have an above-average number of tropical cyclones and six years would be expected to have a below-average number of tropical cyclones. On average, 11 tropical cyclones occur over the full Australian region, with four making landfall. Although there are often fewer tropical cyclones on average over the Australian region during El Niño years, there has never been an El Niño year without at least one tropical cyclone making landfall over the Australian coast.

Past Australian tropical cyclone season outlooks

Cyclone impacts

Before a tropical cyclone forms it is difficult to predict its exact strength and path, including whether it will make landfall. Along the east and west coasts fewer than half of the cyclones impact onshore areas, with the majority staying out to sea. Conversely, along the north coast more than half of the cyclones impact the coast. Tropical cyclones which remain out to sea can still cause storm surges, gales and areas of heavy/flooding rainfall over land.

Even after a tropical cyclone has passed, or has decayed below tropical cyclone strength, significant flooding may occur. The impacts of flooding may be more widespread than the area impacted by the cyclones damaging winds. The Bureau's flood warning services are an integral part of the response to tropical cyclones.

During the cyclone season, ensure you are well informed of any warnings from the Bureau of Meteorology and instructions from local Emergency Services authorities.

Diagram of storm tide height

Emergency services agencies

About the outlooks

This outlook is produced using statistical relationships between tropical cyclone numbers and two indicators: the Southern Oscillation Index (SOI) and the Niño3.4 sea surface temperature index (NINO3.4 SST). These indicators provide a measure of the strength of the atmospheric and oceanic state of the El Niño-Southern Oscillation (ENSO), respectively.

The July, August and September SOI and NINO3.4 values were used in making the Australian Tropical Cyclone Outlook.

2014 July August September
SOI -3.0 -11.4 -7.5
NINO3.4 SST 0.18 °C 0.20 °C 0.45 °C

The current status of ENSO can be viewed via the Bureau's ENSO Wrap-up. At the beginning of the 2014-15 tropical cyclone season the tropical Pacific was near El Niño thresholds, which has influenced this year's Tropical Cyclone Outlook. Sea surface temperatures in the NINO3.4 region have been warmer than average for several months and the Southern Oscillation Index has been consistently negative since early July (sustained negative values of -8 or below can be an indication that an El Niño is developing). Typically when the Pacific approaches or exceeds El Niño thresholds, the Australian region experiences less tropical cyclone activity.

Over the entire Australian Region, this statistical relationship has proven to be highly accurate, or a skilful way to forecast tropical cyclone activity. However, across the various sub Regions this relationship, and thus forecast skill, can vary. Some regions have much higher forecast skill than others. The Northwestern sub-region has good skill, while the Western and Eastern regions both have low skill and the Northern region has very low skill.

Further information