Australian tropical cyclone season outlook

2013–2014 Australian tropical cyclone season outlook

Near average cyclone season most likely for Australia

Chance of above average tropical cyclone (TC) activity

Region Summary Chance of
above average
Long-term average
number of TCs*
Australian region Near average 57% 11
Western region Near average 53% 7
North-western sub-region Near average 55% 5
Eastern region Near average 53% 4
Northern region Near average 52% 3

*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 2013, neutral conditions were present during these months in the Pacific. Neutral conditions are also forecast to continue through the southern Summer. In the absence of El Niño or La Niña (i.e., neutral years), tropical cyclone numbers around Australia are most often close to average, though individual years can be above or below the long term mean.

Regional Outlooks

The statistical outlook indicates all regions can expect near average tropical cyclone activity this coming 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 near average during the 20132014 season. The outlook indicates a 57% chance of having more tropical cyclones than average over the Australia region (43% chance of having less). Such odds mean that for every ten years with similar climate patterns to those currently observed, about five years would be expected to have an above average number of tropical cyclones, while about five years would be expected to have a below average number of tropical cyclones. Past outlooks have shown that the Australian region outlook has a high level of accuracy. On average, 11 tropical cyclones occur over the full Australian region, with four crossing the coast. In neutral ENSO years, such as this, the Australian region has seen as many as 18 and as few as eight tropical cyclones throughout the cyclone season, but it is most common to have near average cyclone activity.

  • 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 average tropical cyclone activity is most likely with a 53% chance of an above (47% chance of below) average number of cyclones. On average, around 30% of tropical cyclones in the western region will have an impact on the coast at some stage in their life cycle. In the past, the accuracy level for forecasts in the Western region has been low.

  • The North-western sub-region (the area from 105°E to 130°E, where tropical cyclones can impact upon coastal Western Australian communities) also has a near normal outlook for tropical cyclones this season (55% chance of above average). Typically, five cyclones form or pass through this area each season. Around 40% of tropical cyclones in the north-western sub-region have an impact on the coast at some stage in their life cycle. Model accuracy in this region is good

  • The Northern region does not have tendency towards above or below average tropical cyclone activity this season. 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%) of tropical cyclones in the northern region impact the coast at some stage in their life cycle. Historically, the level of accuracy for the Northern region tropical cyclone outlook is low, though still better than chance.

  • The Eastern region forecast indicates a 53% chance that an above average (47% chance of below average) number of tropical cyclones will form in this region. Historically, the level of accuracy of the model is low in this region. Around 25% of the tropical cyclones that form in the eastern region cross the coast.

The tropical cyclone Australian regions

Chance of exceeding average number of tropical cyclones

Past Australian tropical cyclone season outlooks

Cyclone impacts

Before a tropical cyclone forms it is difficult to predict its exact strength and path, including whether it will make landfall. Along the east and west coasts fewer than half of the cyclones impact onshore areas, with the majority staying out to sea. Conversely, along the north coast more than half of the cyclones impact the coast. Tropical cyclones which remain out to sea can still cause storm surges, gales and areas of heavy/flooding rainfall over land.

Even after a tropical cyclone has passed, or has decayed below tropical cyclone strength, significant flooding may occur. The impacts of flooding may be more widespread than the area impacted by the cyclones damaging winds. The Bureau's flood warning services are an integral part of the response to tropical cyclones.

During the cyclone season, ensure you are well informed of any warnings from the Bureau of Meteorology and instructions from local Emergency Services authorities.

Diagram of storm tide height

Emergency services agencies

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.

2013 July August September
SOI +8.1 -0.5 3.9
NINO3.4 SST -0.31°C -0.28°C -0.03°C

The current status of ENSO can be viewed via the Bureau's ENSO Wrap-up. Tropical Pacific Ocean temperatures have been neutral since October 2012. This means that the sea surface temperature patterns in the Pacific are neither La Niña nor El Niño and is therefore not driving the Australian Region toward significantly more or fewer tropical cyclones than average. As such, the forecast is suggesting a season closer to average.

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 various sub Regions this relationship, and thus forecast skill, can vary. Some regions have much higher forecast skill than others. The North-western sub-region has good skill, while the Western and Eastern regions both have low skill and the northern region has very low skill. Regardless of the region or the skill of the statistical model, there is currently nothing in the broad climate drivers to suggest anything but a typical tropical cyclone season for Australia and the sub Regions.

Further information