Australian tropical cyclone season outlook
About the outlooks
This outlook uses the statistical relationships between tropical cyclone numbers and two indicators: the Southern Oscillation Index (SOI) and the Niño3.4 sea surface temperature anomaly. These two indicators provide a measure of the atmospheric and oceanic state, respectively, of El Niño-Southern Oscillation (ENSO).
The July, August and September SOI and NINO3.4 values were used in making the tropical cyclone season outlook.
Interpreting the outlook
Percentages such as a 60% chance of having more tropical cyclones than average (or a 40% chance of having fewer) mean that for every ten years with similar climate patterns to those currently observed, six years would be expected to have an above-average number of tropical cyclones and four years would be expected to have a below-average number.
The long-term average number of tropical cyclones per season in the Australian region (since 1969–70) is eleven, with four typically making landfall. Since the year 2000, there have been an average of nine tropical cyclones in the Australian region each season.
During El Niño events, there are typically less tropical cyclones than average, while more tend to occur during La Niña events. As always, it is essential that all local communities prepare for the cyclone season regardless of the outlook.
Australian region outlook accuracy
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 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.
Australian tropical cyclone outlook region bounds
|Australian region||5° S||40° S||90° E||160° E|
|Western region||5° S||40° S||90° E||125° E|
|NW sub-region||5° S||25° S||105° E||130° E|
|Northern region||5° S||40° S||125° E||142.5° E|
|Eastern region||5° S||40° S||142.5° E||160° E|
- Weekly tropical climate note
- Southern Oscillation Index (SOI)
- Niño3.4 sea surface temperature index (NINO3.4 SST)
- Tropical cyclone climatology maps
Model: Kuleshov, Y., L. Qi, R. Fawcett and D. Jones, 2008: Improving preparedness to natural hazards: Tropical cyclone prediction for the Southern Hemisphere, in Advances in Geosciences, 12 Ocean Science, (Ed. Gan, J.), World Scientific Publishing, Singapore, 127-143.
Data: Kuleshov, Y., R. Fawcett, L. Qi, B. Trewin, D. Jones, J. McBride and H. Ramsay, 2010: Trends in tropical cyclones in the South Indian Ocean and the South Pacific Ocean, Journal of Geophysical Research 115, D01101, doi:10.1029/2009JD012372.
More cyclones than average likely for Australia
- An average to above-average number of cyclones are expected for the 2016–17 Australian tropical cyclone season (November–April).
- Neutral to weak La Niña conditions in the tropical Pacific Ocean and warmer than average ocean temperatures to the north and east of Australia have influenced this year’s tropical cyclone outlook.
- During neutral years, the first tropical cyclone to make landfall typically occurs in late December. In La Niña years, the first cyclone to make landfall over Australia typically occurs earlier, around the first week of December.
- The Australian region typically experiences more tropical cyclone activity during La Niña years
This outlook is based upon the status of the El Niño-Southern Oscillation (ENSO) over the preceding July to September period. Sea surface temperatures in the tropical Pacific Ocean are showing some La Niña-like characteristics but have not reached La Niña thresholds . The majority of climate models predict these ocean conditions to continue into summer with only one model predicting La Niña thresholds to be exceeded. Ocean temperatures are currently 1–2 °C warmer than average to the north and east of Australia which is favourable for tropical cyclone development. The Southern Oscillation Index, a measure of the atmospheric component of ENSO, has been positive through this period and exceeded La Niña thresholds in the last two weeks of September.
Outlook by region
The outlook indicates that an above-average number of tropical cyclones are most likely in the Australian region and Northwestern sub-region for 2016–17. All other regions are likely to have a near average number of tropical cyclones.
- The Australian region has a 67% chance of having more tropical cyclones than average, meaning a 33% chance of having fewer tropical cyclones than average. Typically, around four tropical cyclones cross the Australian coastline in a season. Outlook accuracy for the Australian region is high.
- The Western region is likely to experience an average number of tropical cyclones this season, with the likelihood of an above average season at 59%. The chance of a below average season is 41%. Typically between about 15% and 40% of tropical cyclones in the Western region create coastal impacts. Outlook accuracy for the Western region is low.
- The Northwestern sub-region has a 63% chance of more tropical cyclones than average and a 37% chance of fewer tropical cyclones than average. Typically, five cyclones form in or pass through this area each season. Around 40% of tropical cyclones in the Northwestern sub-region effect coastal areas at some stage in their life cycle. Outlook accuracy in this region is moderate.
- The Northern region outlook suggests an average number of tropical cyclones with a 56% chance of more tropical cyclones than average and a 44% chance of fewer tropical cyclones than average. In an average year the Northern region typically experiences three cyclones, and one or two tropical lows that later become cyclones after moving into the Western or Eastern regions. About three-quarters of the tropical cyclones in the Northern region impact coastal regions. Outlook accuracy in this region is very low.
- The Eastern region outlook also indicates a near average tropical cyclone season is most likely, with a 58% chance of above average and 42% chance of below average numbers. About a quarter of tropical cyclones in the Eastern region make landfall. Outlook accuracy in this region is low.
Product code: IDCKAUTCSO