The 2016–17 Australian region cyclone season was a slightly below-average season in terms of activity, despite a very high number of tropical lows. It featured nine tropical cyclones, three of which intensified further into severe tropical cyclones; though it was much more active than the previous season. The season was the first to have a severe tropical cyclone since the 2014–15 season. It was the period of the year when most tropical cyclones form in the Southern Indian Ocean and Pacific Oceans between 90°E and 160°E. The season officially ran from 1 November 2016 to 30 April 2017, however, a tropical cyclone could form at any time between 1 July 2016 and 30 June 2017 and would count towards the season total. The first named storm, Yvette, developed during 21 December, and the final named storm, Greg, left the region on 3 May as a remnant low. This season was also the second-costliest tropical cyclone season on record in the Australian region basin, behind only the 2010–11 season, with a total of AUD$3.7 billion (US$2.82 billion) in damages incurred by the various storms, mostly from Cyclone Debbie.
During the season, tropical cyclones were officially monitored by one of the five Tropical Cyclone Warning Centres (TCWCs) that operated in this region. Three of the five centres were operated by the Australian Bureau of Meteorology (BoM) in Perth, Darwin, and Brisbane, while the other two were operated by the National Weather Service of Papua New Guinea in Port Moresby and the Indonesian Agency for Meteorology, Climatology and Geophysics in Jakarta, Indonesia. The United States' Joint Typhoon Warning Center (JTWC) and other national meteorological services, including Météo-France, also monitored the basin during the season.
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Seasonal forecasts Region Averagenumber Chanceof more Chanceof less Actualactivity Whole1167%33% 9 Western 759%41% 3 North-Western 563%37% 3 Northern 356%44% 3 Eastern 458%42% 1Source: BOM's Seasonal Outlooks for Tropical Cyclones.
After the least active season on record had occurred during the previous season, the BoM issued five tropical cyclone outlooks for the Australian region during October 2016. Each one of these forecasts was for the entire tropical cyclone year between July 2016 and June 2017 took into account various factors, including the latest neutral to weak La Niña conditions that had been observed in the tropical Pacific Ocean. The outlooks indicated that an above-average number of tropical cyclones were likely for the basin as a whole and the Northwestern sub-region. It was also predicted that the first tropical cyclone landfall on Australia would take place during December 2016. For the Western region between 90°E and 125°E, the BoM forecast that the area would also see activity near its average of 7, with a 59% chance of an above average number of tropical cyclones occurring. TCWC Perth also noted that there was a likelihood of two tropical cyclones and a significant likelihood of at least one severe tropical cyclone impacting Western Australia. They also noted that the number of significant cyclones and flood impacts had been well below average over the last five seasons. For the North-Western sub-region between 105°E and 130°E, it was predicted that activity would be above average, with a 63% chance of above-average tropical cyclone activity. The Northern Territory, which was defined as being between as being 125°E and 142.5°E, had a 56% chance of an above-average season. The Eastern region between 142.5°E and 160°E was predicted to have a near-normal tropical cyclone season, with a 58% chance of above-average tropical cyclone activity.
Seasonal summary
Despite a weak season with only 8 named tropical cyclones, the BoM monitored a total of 30 tropical lows, which is the highest recorded in a season. The 2016–17 season opened with a tropical system in the Western Region on 23 September, just more than a month before the official start of the season. After three months, with the development of some tropical lows, the first named tropical cyclone, Yvette, developed on 21 December. About four-and-a-half months later, on 3 May, the season concluded when Ex-Tropical Cyclone Greg moved out of the basin.
Systems Tropical Low 06U
Tropical Low 06U was first noted during 18 December while it was located in the Arafura Sea, about to the northwest of Darwin in the Northern Territory. Over the next couple of days, the system moved south-westwards and gradually developed further as it moved into the Timor Sea, where it reached its peak intensity with 10-minute sustained winds of and a minimum pressure of . The system subsequently made landfall on the Kimberley and degenerated into a deep monsoonal low, remaining slow-moving over north-western Australia for several days. The low subsequently started to move southwards during 25 December, as it absorbed the remnants of Tropical Cyclone Yvette. The remnants of 06U crossed Southern Australia during 27–28 December, before being absorbed by another area of low pressure which approached 06U from southern Western Australia during 30 December. This system subsequently consolidated in the Great Australian Bight and moved south-eastwards, where it passed to the west of Tasmania before it moved into the Tasman Sea during 31 December.
Tropical Cyclone Yvette
A tropical low developed during 19 December within a monsoon trough of low pressure, about to the north-northwest of Karratha in Western Australia and was designated as 07U. Soon after, the JTWC declared the system as a tropical storm and designated it as 02S. By 21 December, it had strengthened into a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale as persistent deep convection developed, and the BoM named it Yvette. Remaining quasi-stationary under strong wind shear, convection from Yvette soon weakened; simultaneously, the storm started to move southeastwards. By 23 December, the BoM had downgraded Yvette to a tropical low as dry air began to be wrap into the centre. Later the same day, both the JTWC and the BoM issued their final bulletin on Yvette.
Tropical Low 09U
On 3 January, TCWC Perth started to monitor a tropical low to the northwest of the Western Region. The tropical low meandered southwards as it was over in favourable conditions. By 9 January, the system was designated as 09U. Despite unfavourable atmospheric conditions in the area, 09U persisted, tracking slowly eastward until it was last noted early on 15 January, located about to the east of Christmas Island.
Tropical Low 10U
On 7 January, a weak tropical low had developed within a monsoonal trough of low pressure over the Cape York Peninsula, before moving into the Gulf of Carpentaria. After eventually moving into TCWC Perth's area of responsibility by 9 January, the low was designated as 10U as it was moving over land. After moving southward over Western Australia, TCWC Perth issued its final bulletin on 12 January.
Tropical Low 11U
On 7 January, the BoM noted that a tropical low had formed, and was called 11U. It started to intensify slowly until it reached its peak intensity at 1000 mbar. The peak was short-lived as it started to weaken gradually and was last noted on 8 January.
Tropical Low 14U
On 23 January, a tropical low developed over in the western area of the Gulf of Carpentaria. After moving west-southwestward over land, the low gradually developed and was designated as 14U during 26 January. During the next day, the JTWC began issuing advisories, classifying it as 03S as it moved over water. Slowly intensifying, 14U reached peak intensity with winds of and a minimum pressure of 988 hPa (mbar; 29.17 inHg), though the system was never classified as a tropical cyclone by BoM due to its asymmetry. Thereafter, 14U moved over cooler waters causing deep convection to dissipate, and both the JTWC and BoM issued their final advisories on 28 January.
Tropical Low 15U
A tropical low formed off the Pilbara coastline near Broome on 7 February and slowly strengthened while moving westwards. The system made landfall as a low during 8 February near Karratha. The system dropped of rainfall on at Karratha Airport, giving it its wettest February day on record and its second-wettest day overall. The low progressively moved southwestwards over the western Pilbara and Gascoyne region before moving back offshore between Carnarvon and Shark Bay.
During the night of 9 February the low linked up with a trough lying over the southwest of the country, resulting in both abnormally low temperatures and heavy rainfall across the region, with the area within 100 km of a line from Perth to Esperance the hardest hit. The Perth metro station received in the 24 hours leading up to 9:00 a.m. AWST (01:00 UTC) on 10 February, the second highest 24-hour total on record for the city and over ten times its monthly average of . Widespread flooding resulted in access to towns such as Wagin and Gnowangerup being cut off while the South Coast Highway crossing the Phillips River was washed away, resulting in no access between Jerramungup and Ravensthorpe. The Avon River experienced major flooding around Northam resulting in evacuations. The main river system in Perth, the Swan, also had flood warnings issued for the second time in as many weeks. Two people were confirmed killed in the Esperance region due to driving into floodwaters.
Despite the tropical origins of the system, the thick cloud cover over the area also resulted in records for the coldest February maximum temperatures being broken. Perth achieved a maximum temperature of just on 9 February, over 14 °C below the monthly average, beating its previous record of set in 1914. These temperatures were in stark contrast to the eastern states of Australia, which were experiencing a major heatwave during the same time.
Tropical Low 16U
Tropical Low 17U
Tropical Cyclone Alfred
On the night of 15 February, a tropical low had formed near Borroloola. The tropical low remained slow-moving near the southern Gulf of Carpentaria coast for a number of days before moving over open waters on 19 February. The tropical low gradually intensified while moving north towards Groote Eylandt before turning back towards the southeast. The low intensified into a Category 1 tropical cyclone on the Australian cyclone intensity scale on the morning of 20 February, and was named Alfred. Alfred remained a Category 1 tropical cyclone for almost 24 hours before weakening below cyclone strength, just before crossing the coast of the Gulf of Carpentaria, in the early afternoon of 21 February. The system dissipated on the next day. Alfred was the first tropical cyclone to hit the Northern Territory since Cyclone Nathan in 2015.
Tropical Cyclone Blanche
Early on 2 March, TCWC Darwin noted a developing tropical low in the north Arafura Sea, followed promptly by the JTWC that afternoon. TCWC Darwin began issuing advisories on the tropical low at 00:00 UTC on 4 March. Embedded within a moderate to high wind shear regime, the system was expected to track south or southwest into a more favourable environment over subsequent days. By 00:00 UTC on 5 March, the low had moved underneath an anticyclone, providing excellent outflow which offset the negative effects from continued wind shear. In accordance with satellite intensity estimates, the TCWC Darwin upgraded the low to Tropical Cyclone Blanche.