The 2012–13 Australian region cyclone season was a slightly below average tropical cyclone season event in the ongoing cycle of tropical cyclone formation. It officially started on 1 November 2012, and officially ended on 30 April 2013, despite Cyclone Zane being an active system at the time (it dissipated a day later on 1 May). 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 2012 and ended on 30 June 2013.
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 145°E, and the "P" suffix when they form east of 145°E. __TOC__
Seasonal forecasts +Tropical cyclone predictionsRegionChance ofabove averageAveragenumberActualactivity Whole37%1110 Western43%75 North-Western42%55 Northern48%32 Eastern43%34 Southern Pacific53%155 Western South Pacific35%84 Eastern South Pacific55%113Source:BOM's Seasonal Outlooks for Tropical Cyclones. RegionNormalnumberNumberpredictedActualactivity GCACIC Whole12 – 151210/11 GCACIC Western9 – 1096 GCACIC Eastern5 – 645 NIWA109 – 108Sources:
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 2012, ahead of the 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 and the near El Niño conditions that had been observed during that summer. For the whole region they predicted that the season would be below average, with a 63% chance that it would be below average and a 37% chance that it 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 below the average, with a 43% 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 58% chance of below 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. There was no tendency towards an above or below average tropical cyclone season for the Northern Territory which was defined as being between as being 125°E and 142.5°E, while the Eastern region had a 57% chance of having a below average tropical cyclone season.
The BoM also issued seasonal forecasts for the South Pacific region between 142.5°E and 120°W, one for the Western Southern Pacific region between 142.5°E and 165°E and one for the Eastern Southern Pacific region between 165°E and 120°W. They noted that the current neutral ENSO conditions would historically suggest the South Pacific region as a whole would experience near average tropical cyclone activity during the coming season. However, because of the warmer than average sea surface temperatures that were experienced in the central equatorial Pacific during July, August and September 2012, the western Southern Pacific had a 65% chance for average to below average tropical cyclone activity. For the Eastern part of the region the BoM predicted that it had a 55% chance of above average tropical cyclones, while for the overall region, they predicted that the region would experience a near average amount of tropical cyclones with a 53% chance of having an above average number of tropical cyclones.
Others During October 2012, the New Zealand National Institute of Water and Atmospheric Research (NIWA) and its partners issued a tropical cyclone outlook, for the South Pacific region between 135°E and 120°W. The outlook predicted that the region would see a near average or slightly above average amount of tropical cyclones with between 9 and 12 systems predicted to develop or move into the region. NIWA also predicted that countries west of the International Date Line, including Papua New Guinea, the Solomon Islands, Vanuatu, New Caledonia and Fiji were likely to experience an average to slightly above normal risk of a tropical cyclone.
During December 2012, the Guy Carpenter Asia-Pacific Climate Impact Centre (GCACIC), issued a seasonal forecast for the whole basin and one each for the regions to the east and west of 135°E. This season the GCACIC predicted that tropical cyclone activity in the entire Australian region and the western Australian region was likely to be near-normal and predicted 12 and 9 tropical cyclone respectively. For the eastern Australian region, the GCAIC predicted that tropical cyclone activity would be below average and only predicted 4 tropical cyclones to develop.
Seasonal summary
Systems Tropical Cyclone Mitchell
On 27 December, Tropical Low 04U developed within a monsoon trough about north-northwest of Karratha. The following day, a significant central dense overcast developed over the low and banding features began forming to the northwest of the center. Development was further aided by an anticyclone situated just to the east, providing dual outflow channels. Later on 28 December, the JTWC classified the system as a tropical storm as the banding features consolidated around the low's center and a scatterometer pass revealed winds of 55 to 65 km/h (35 to 40 mph). Some intensification was expected as the storm tracked generally southward along the edge of a subtropical ridge before moving over cooler waters. On 29 December, TCWC Perth classified the system as Tropical Cyclone Mitchell, the first named storm in the western region for the season. The storm ultimately attained peak winds of and a pressure of 990 mb (hPa; 29.23 inHg) before weakening below tropical cyclone strength on 30 December. The system persisted for two more days off the coast of Western Australia before dissipating well to the west of Perth on 1 January 2013.
Severe Tropical Cyclone Narelle
On 4 January, a tropical low developed within a monsoon trough over the Timor Sea. Over the following several days, the system gradually tracked westward and intensified, being classified Tropical Cyclone Narelle on 8 January. Turning southward into a region of low wind shear, Narelle intensified into a severe tropical cyclone on 9 January. Over the following two days, the cyclone's structure fluctuated, temporarily featuring an eye, before it maintained its organization and intensified further on 11 January. The storm attained its peak intensity later on 11 January as a Category 4 cyclone with winds of . Around the same time, the JTWC assessed Narelle to have been a Category 4-equivalent storm on the Saffir–Simpson hurricane scale with winds of . The following day, Narelle passed approximately northwest of Exmouth as it moved on a south-southwesterly course. The system steadily weakened and ultimately fell below tropical cyclone strength on 15 January well to the west of Geraldton.
Early in the storm's existence, Narelle brought strong winds, heavy rain, and high winds to many areas in Indonesia. More than 10,000 homes were flooded and many others were damaged by thunderstorms. A total of 14 people were killed by the storm, and 17 others were listed as missing. In Western Australia, scattered strong thunderstorms caused minor damage and produced a possible tornado. Moisture from the storm spread into South Australia, producing light rain and bringing relief to areas suffering from a severe drought.
Tropical Low 06U
On 12 January, a weak tropical low formed over the Arafura Sea. The system was last noted the following day, having a pressure no lower than 1004 mb (hPa; 29.65 inHg). The United States Navy continued monitoring the system until it was last noted on 16 January.
Tropical Cyclone Oswald
On 17 January, an area of low pressure developed over the Gulf of Carpentaria. Situated within a region of low wind shear and high sea surface temperatures, conditions were favorable for gradual development of the system. The following day, TCWC Darwin began monitoring the system as a tropical low. Early on 19 January, the system made landfall southwest of Borroloola. By 20 January, the system completed a clockwise loop before re-emerging into the Gulf of Carpentaria. Once back over water, the system quickly organized and strengthened into a tropical cyclone early on 21 January. Radar imagery from Mornington Island depicted a well-defined low-level circulation with defined banding features wrapping into the center. Situated in a very moist air mass and over the warm waters of the Gulf, some intensification was expected before Oswald struck the Cape York Peninsula. Approximately 12 hours after being named, the storm made its second landfall north of Kowanyama with winds of and the final advisory was issued by TCWC Brisbane. Although over land, the system was able to maintain a defined circulation and gradually reorganized as it moved southwestward. By 23 January, deep convection redeveloped over the circulation and a strong monsoonal flow became established to its north.
Although a relatively weak storm, Oswald produced torrential rains over much of Queensland. Rainfall peaked in Tully where approximately of rain fell, with falling over a 48‑hour span. The township of Scherger received a record-breaking in just 24 hours. These rains caused widespread flooding in the state that shut down many roads and isolated communities. The town of Ingham was completely cut off due to high waters. Residents in the town were advised to stock up on emergency supplies as the Herbert River rose rapidly after of rain fell in the town in just three hours. In Cairns, winds up to left many homes without power and waves up to prompted the cancellation of most coastal activities. Additionally, a brief tornado or waterspout with winds of touched down near Hay Point. Across the affected region, damage from severe weather and flooding amounted to at least A$2.4 billion (US$2.5 billion). The name Oswald was retired and was replaced with Oran.
Tropical Low Peta