Australian tropical cyclone season outlook

The tropical cyclone season runs from 1 November to 30 April


Lower number of cyclones likely for Australia

  • Fewer number of tropical cyclones are expected in the Australian region for the 2018–19 cyclone season (November–April)
  • The possible development of El Niño in the tropical Pacific Ocean and near average ocean temperatures to the north and east of Australia have influenced this year’s tropical cyclone outlook.
  • On average, there are 10 to 13 tropical cyclones each season in the Australian region, four of which typically cross the coast.
  • El Niño typically reduces the number of coastal crossings, but at least one tropical cyclone has crossed the Australian coast each season since reliable records began in the 1970s.
  • During El Niño years, the first tropical cyclone to cross the coast is typically during the second week of January. This is generally later than seasons which are ENSO-neutral when the first cyclone landfall typically occurs in late December.
  • Cyclone formation is rarely spread evenly throughout the season; often quiet periods are followed by bursts of activity.
  • Tropical lows that do not intensify into cyclones, or lows that are the remnants of older cyclones, can still cause widespread rainfall and dangerous flooding. These impacts can extend beyond the tropics into southern areas of the country.

Outlook influences

This outlook is based on the status of the El Niño–Southern Oscillation (ENSO) over the preceding July to September. Sea surface temperatures in the tropical Pacific Ocean have continued to warm all year and have been above average since June.  Eight climate models surveyed by the Bureau have forecast tropical Pacific Ocean temperatures to remain above average throughout summer, with three predicting El Niño thresholds to be exceeded.   The Southern Oscillation Index has remained negative since the middle of July and exceeded El Niño thresholds during September.  However, trade winds and cloudiness in the central Pacific are yet to show a strong El Niño signal. Ocean temperatures are currently 0.5 to 1 °C warmer than average to the north and east of Australia but remain average to the west.

 

Outlook by region

The outlook indicates that less tropical cyclones are likely  in the Australian region and all sub-regions for 2018–19.

  • The Australian region has a 37% chance of more tropical cyclones than average, meaning a 63% chance of less tropical cyclones than average. Typically, around four tropical cyclones cross the Australian coast in a season. Outlook accuracy for the Australian region is high.
  • The Western region is likely to experience a below-average number of tropical cyclones this season, with a 56% likelihood of fewer than average. The likelihood of more cyclones than average is at 44%. Typically between about 15% and 40% of tropical cyclones in the Western region affect coastal areas. Outlook accuracy for the Western region is low.
  • The Northwestern sub-region has a 41% chance of more tropical cyclones than average and a 59% chance of fewer tropical cyclones than average. Typically, five cyclones form in or pass through this area each season. Around 40% of tropical cyclones, or their associated tropical lows, affect coastal areas of the Northwestern sub-region. Outlook accuracy for this region is moderate.
  • The outlook for the Northern region suggests an average number of tropical cyclones with a 46% chance of more than average and a 54% chance of fewer tropical cyclones than average. In a typical year the Northern region experiences around three cyclones, and one or two tropical lows that later become cyclones after moving into the Western or Eastern regions. About three-quarters of the tropical cyclones in the Northern region impact coastal regions. Outlook accuracy for this region is very low.
  • The Eastern region outlook shows a below-average season is most likely, with a 40% chance of more tropical cyclones than average and a 60% chance of fewer. About a quarter of tropical cyclones in the Eastern region make landfall. Outlook accuracy for this region is low.

 

Product code: IDCKAUTCSO