2012–2013 Australian Tropical Cyclone Season Outlook

Odds favour a near average cyclone season for most Australians

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Chance of above average tropical cyclone (TC) activity

Region	Summary	Chance of above average	Long-term average number of TCs*	Forecast skill
Australian region	Below average	37%	11	High
Western region	Near to slightly below average	43%	7	Low
North-western sub-region	Near to slightly below average	42%	5	Moderate
Eastern region	Near to slightly below average	43%	4	High
Northern region	Near average	48%	3	Very low

*averages may change when the dataset is updated.

This outlook is based upon the status of the El Niño - Southern Oscillation (ENSO) over the preceding July to September period. In 2012, neutral to borderline El Niño conditions were present during these months. Historically, these conditions have favoured an average to below average number of tropical cyclones in the regions around Australia.
Related information: Tropical cyclone average conditions.

Regional Outlooks

The statistical outlook indicates all regions can expect near average tropical cyclone activity, with the odds slightly favouring fewer than average tropical cyclones this season (1 November and 30 April).

• Tropical cyclone activity over the full Australian region (5°S-40°S, 90°E-160°E) is likely to be below average during the 2012–2013 season. The outlook indicates a 37 per cent chance of having more tropical cyclones than average over the Australia region (63 per cent chance of having less). Such odds mean that for every ten years with similar ocean patterns to those currently observed, about three to four years would be expected to have an above average number of tropical cyclones, while about six to seven years would be expected to have a below average number of tropical cyclones. Past outlooks have shown that the Australian region outlook has high skill.

• The Western region experiences, on average, around seven tropical cyclones in the eastern Indian Ocean during the tropical cyclone season. This year's forecast indicates near to slightly below average tropical cyclone activity with a 43 per cent chance of above (57 per cent chance of below) average cyclone activity. In the past, the skill level for forecasts in the Western region has been low. On average, around 30 per cent of tropical cyclones in the western region will have an impact on the coast at some stage in their life.

• The North-western sub-region (the area from 105°E to 130°E, where tropical cyclones can impact upon coastal Western Australian communities) has decreased odds (42 per cent) of an above average (58 per cent chance below average) tropical cyclone season. Typically, five cyclones form or pass through this area each season and around 40 per cent of tropical cyclones in the north-western sub-region will have an impact on the coast at some stage in their life. Model skill in this region is moderate.

• The Northern region does not have tendency towards above or below average tropical cyclone activity this season, and the skill level for this outlook is very low. In an average year the northern region sees two or three named storms and one or two tropical low pressure systems that become cyclones after moving into the western or eastern regions. A relatively high number (75 per cent) of tropical cyclones in the northern region impact the coast at some stage in their life.

• The Eastern region forecast indicates a 43 per cent chance that an above average (57 per cent chance of below average) number of tropical cyclones will form in the region, with a high confidence level based upon historical skill. Around 25 per cent of the tropical cyclones in the eastern region cross the coast, with fewest crossings in El Niño years.

Chance of exceeding average number of tropical cyclones

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 Australian tropical cyclone season outlook.

2012	July	August	September
SOI	-1.7	-5.0	+2.7
NINO3.4 SST	0.53°C	0.73°C	0.51°C

The current status of ENSO can be viewed via the Bureau's ENSO Wrap-up. Tropical Pacific Ocean temperatures showed signs of a developing El Niño until September. However, as of mid-October, conditions have generally eased away from El Niño thresholds. Despite this shift, the tropical Pacific remains warmer than average. Other ENSO indicators, such as the trade winds and tropical cloud patterns also remain at values typical of neutral conditions; the monthly SOI value for September was +2.7.

Research references

Model: Kuleshov, Y., L. Qi, R. Fawcett and D. Jones, 2009: 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.

Further Information

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