South Pacific 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.
South Pacific countries
This Outlook provides general guidance for the South Pacific region. For specific guidance for an individual country, please contact their National Meteorological and Hydrologic Service.
South Pacific region outlook accuracy
The statistical model used for this outlook has a high level of accuracy predicting cyclone numbers in the western region, but a very low level of accuracy for the eastern region.
South Pacific tropical tropical cyclone outlook region bounds
|Whole South Pacific region||5° S||40° S||142.5° E||120° W|
|Western region||5° S||40° S||142.5° E||165° E|
|Eastern region||5° S||40° S||165° E||120° W|
- 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.
Average number of cyclones likely in the western Pacific Ocean
- Near average number of tropical cyclones are expected in the western South Pacific region this season.
- ENSO-neutral to weak La Niña-like conditions in the tropical Pacific Ocean have influenced this year’s tropical cyclone outlook.
- Most climate models indicate that neutral conditions are likely to persist into 2018.
- Near-average cyclone numbers are also likely for the eastern South Pacific but model accuracy is very low
The South Pacific tropical cyclone season typically extends between 1 November and 30 April. The average numbers of tropical cyclones during the season in the western and eastern regions are seven and four respectively. Tropical cyclones affect Pacific island countries in most years and can impact coastal regions even when they remain well offshore.
* Long-term average number of tropical cyclones, calculated using data from 1969–2016, 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) during the preceding July to September. Eastern tropical Pacific Ocean sea surface temperatures began cooling during August and remain below average, although they have yet to exceed La Niña thresholds. Atmospheric indicators of ENSO remain neutral. A majority of international climate models expect ocean temperatures to cool to La Niña thresholds by December, but they mostly predict a return to neutral ocean temperatures by the end of summer.
The statistical model used for this outlook has a high level of accuracy predicting cyclone numbers in the western region, but a very low level of accuracy for the eastern region. This outlook is for the southern hemisphere tropical cyclone season which runs between 1 November and 30 April.
Product code: IDCKSPTCSO