Tropical Climate Update

Wrap up of the 2021–22 Australian tropical cyclone season

The Australian Region tropical cyclone season for 2021-22 officially concluded on 30 April. There were 8 tropical cyclones in the Australian Region this season. Among them, 2 cyclones reached severe strength (at least category 3 ): Vernon reached category 4 in the Indian Ocean within the Western Region to the west of the Cocos Islands during February; Charlotte reached category 4 strength in the Western Region during March, remaining well off Western Australia's north-west coast.

Two tropical cyclones made landfall on mainland Australia: in late December, Tiffany developed in the Coral Sea and weakened after making landfall over northern Queensland, before it restrengthened in the Gulf of Carpentaria and made another landfall over the Northern Territory in January; Annika developed in the Timor Sea and crossed Western Australia's north Kimberley coast at category 2 intensity in late February then made a second landfall as a category 1 system over the far west Kimberley coast in early March.

In addition to 8 tropical cyclones, there were around twenty observed tropical lows in the Australia Region in the 2021-22 season, one of which brought significant rainfall to north-western Australia at the end of January and beginning of February. The number of tropical cyclone in the 2021-22 season was below the long-term average of 11 in the Australian Region.

Madden–Julian Oscillation could develop over Western Pacific

The Madden–Julian Oscillation (MJO) has recently been weak and is expected to remain mostly weak for the coming fortnight. Some climate model outlooks show the MJO could develop over the Western Pacific next week, but this scenario would not typically cause strong impacts on northern Australia at this time of year. As such, the MJO is unlikely to exert a significant influence on rainfall patterns across northern Australia this coming fortnight.

Read more about the Madden–Julian Oscillation (MJO)

La Niña and Indian Ocean Dipole update

The 2021–22 La Niña event continues but is gradually weakening. Climate outlooks indicate a return to a neutral El Niño–Southern Oscillation (ENSO) phase—neither La Niña nor El Niño—by the southern hemisphere early winter. Only one of the seven models surveyed hints at a third consecutive La Niña in 2022–23. Even as La Niña weakens, it may continue to influence global weather and climate.

The Indian Ocean Dipole (IOD) is neutral. International climate model outlooks indicate a negative IOD potentially developing from late autumn. IOD outlooks have low accuracy at this time of year while the Indian and Pacific Oceans are in transition, though there is consistency across the international climate model outlooks. A negative IOD increases the chances of above average winter–spring rainfall for much of Australia. It also increases the chances of warmer days and nights for northern Australia. Typically, the IOD has little to no influence on Australian climate between the months of December to April.

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