The 2011–12 Australian region cyclone season was a below average tropical cyclone season, with 7 cyclones forming rather than the usual 11. It began on 1 November 2011, and ended on 14 May 2012. The regional tropical cyclone operational plan defines a "tropical cyclone year" separately from a "tropical cyclone season"; the "tropical cyclone year" began on 1 July 2011 and ended on 30 June 2012.
The scope of the Australian region is limited to all areas south of the equator, east of 90°E and west of 160°E. This area includes Australia, Papua New Guinea, western parts of the Solomon Islands, East Timor and southern parts of Indonesia.
Tropical cyclones in this area are monitored by five Tropical Cyclone Warning Centres (TCWCs): the Australian Bureau of Meteorology in Perth, Darwin, and Brisbane; TCWC Jakarta in Indonesia; and TCWC Port Moresby in Papua New Guinea. The Joint Typhoon Warning Center issues unofficial warnings for the region, designating tropical depressions with the "S" suffix when they form west of 135°E, and the "P" suffix when they form east of 135°E.
Seasonal forecasts
During each tropical cyclone year, Australia's Bureau of Meteorology National Climate Centre (BoM), the Guy Carpenter Asia-Pacific Climate Impact Centre, New Zealand's National Institute of Water and Atmospheric Research (NIWA) and partners issue seasonal forecasts for the Australian region and its various subregions. Since a tropical cyclone can move through a region, the actual number of tropical cyclones in a region include any that form in or move into a region from another.
Bureau of Meteorology
In October 2011, ahead of the tropical cyclone season starting on 1 November, the BoM issued seasonal forecasts for the whole Australian region, one for each of the subregions Western, North-Western, Northern and Eastern Australia with each one covering the whole tropical cyclone year. For each forecast they took into account, the current neutral ENSO conditions to weak La Niña conditions that had been observed during that summer. For the whole region they predicted that there was an 80% chance that the season would be above average.
For the Western region between 90°E and 125°E, the BoM forecast that the area would see activity near to or slightly above the average, with a 35% chance of a below average cyclone activity. For the North-Western subregion between 105°E and 130°E, it was predicted that there was a 60% chance of above average tropical cyclone activity, while TCWC Perth noted that there was a likelihood of two tropical cyclones and one severe tropical cyclone impacting Western Australia. The Northern Territory which was defined as being between as being 125°E and 142.5°E had a 60% chance of being above average, while the Eastern region had a 65% chance of having an above average tropical cyclone season. During February, after Cyclones Heidi and Iggy had threatened Western Australia, it was reported that there was a likelihood of at least one more coastal impact and a significant risk that it could be a severe tropical cyclone. The BoM also issued a seasonal forecasts for the South Pacific region between 142.5°E and 165°E and one for the Eastern Southern Pacific region between 165°E and 120°W. The outlook called for a westward shift in tropical cyclone activity with a 65% chance that the Western Pacific Region will see more than the average number of tropical cyclones while there was a 40% chance that the Eastern Pacific Region will see above average number.