South Pacific tropical cyclone season outlook

Australian outlook

2015–16 South Pacific tropical cyclone season outlook

El Niño likely to decrease cyclone numbers in the western Pacific Ocean

  • The strong 2015 El Niño in the tropical Pacific Ocean reduces the likely number of tropical cyclones for the western South Pacific region.
  • Climate models indicate the El Niño is likely to persist into 2016.
  • Near-average cyclone numbers are likely for the eastern South Pacific but model accuracy is very low.

The South Pacific tropical cyclone season has most cyclones between 1 November and 30 April and averages around seven tropical cyclones in the western region and ten in the eastern region. Tropical cyclones impact Pacific island countries in most years and coastal impacts can still be felt when tropical cyclones remain well offshore.

*Long-term average number of tropical cyclones, calculated using data from 1969–2014, 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 period. The eastern tropical Pacific Ocean has been much warmer than average during this time, exceeding El Niño thresholds. The Southern Oscillation Index, a measure of the atmospheric component of ENSO, has been strongly negative through this period. Climate models suggest the El Niño is nearing its peak and will persist into early 2016. During an El Niño, tropical cyclone numbers in the western region of the South Pacific Ocean tend to be below average.

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.

Past South Pacific tropical cyclone season outlooks

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, respectively.

The July, August and September SOI and NINO3.4 values were used in making the South Pacific tropical cyclone season outlook.

2015 July August September
SOI -14.7 -19.8 -17.7
NINO3.4 SST 1.60 °C 2.07 °C 2.28 °C

The current status of ENSO can be viewed via the Bureau's ENSO Wrap-up. During July–September 2015 the eastern tropical Pacific Ocean was much warmer than average, clearly exceeding El Niño thresholds. The Southern Oscillation Index, a measure of the atmospheric component of ENSO, has also been strongly negative through this period, indicating a significant El Niño event. Climate models suggest the 2015 El Niño will remain strong into early summer, and persist into early 2016. .

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