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
| Region | Top | Bottom | Left | Right |
|---|---|---|---|---|
| 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 |
Current information
- Weekly tropical climate note
- Southern Oscillation Index (SOI)
- Niño3.4 sea surface temperature index (NINO3.4 SST)
- Tropical cyclone climatology maps
Definitions
South Pacific
References
Research documents
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.
Near average number of tropical cyclones likely in the western Pacific Ocean
- La Niña in the tropical Pacific Ocean has influenced this year’s tropical cyclone outlook.
- All surveyed climate models indicate that the La Niña is likely to persist into early 2021
- Above-average number of tropical cyclones are expected in the western South Pacific region this season (based on 60% probability), with a high level of accuracy.
- Near-average cyclone numbers are also likely for the eastern South Pacific but model accuracy is very low.
The South Pacific tropical cyclone season is typically from 1 November to 30 April. The average numbers of tropical cyclones during the season in the western and eastern regions are six and four, respectively. Tropical cyclones affect Pacific island countries in most years and can impact coastal regions even when they remain well offshore.
This outlook is based upon the status of the El Niño–Southern Oscillation (ENSO) during July to September 2020. A La Niña event is currently underway in the tropical Pacific. Eastern tropical Pacific Ocean sea surface temperatures have been below average since May and remain below average. Atmospheric indicators of ENSO are also indicative of La Niña. All surveyed climate models suggest ocean temperatures will remain at La Niña levels until early 2021.
Ocean temperatures are currently near to above average across the southwestern Pacific Ocean. Climate models predict waters across this region will remain warmer than average in the coming three months, marginally increasing the likelihood of tropical cyclones developing.
Product code: IDCKSPTCSO
