Weekly Tropical Climate Note

Heavy rainfall across Maritime Continent and northern Australia

Monsoonal conditions continued over the Maritime Continent and northern Australia last week. Many locations in the Kimberley region of Western Australia and the western part of the Northern Territory’s Top End observed weekly rainfall totals in excess of 200 mm. Heavy rainfall generated landslides and led to multiple fatalities in Bali, Indonesia. Further east, widespread rains generated floods in the South Pacific affecting an area which extended from the Papua New Guinea to Samoa, including the Solomon Islands, Fiji and Tonga.

Climate influences which contributed to the rainfall included an unusually strong westerly wind-flow across the Maritime Continent and a moderate to strong Madden–Julian Oscillation (MJO) which moved over the Western and central Pacific regions during the period. Cloudiness and rainfall over the western South Pacific Ocean was significantly more active than normal.

Madden–Julian Oscillation to maintain strength

International climate models indicate the Madden–Julian Oscillation (MJO) will maintain its strength as it continues east over the central Pacific Ocean and towards the Americas this coming week. Typically, rainfall over most of the Australian tropics is not enhanced significantly when the MJO signal is over the central Pacific Ocean; however, far eastern parts of the Maritime Continent and Cape York Peninsula can observe above-average rainfall. Suppressed rainfall and cloudiness is typically experienced over Australian longitudes when the MJO signal reaches the eastern Pacific region; however, smaller-scale weather systems can dominate the influence of the MJO and produce significant, localised rainfall. While no tropical cyclones have yet formed in the south Pacific region during the 2016-17 season, there is currently an enhanced risk with the MJO in the region.

For more information on the MJO, see the Bureau's current MJO monitoring information.

El Niño–Southern Oscillation remains neutral

The El Niño–Southern Oscillation (ENSO) remains neutral, with virtually all indicators close to their average values. In recent weeks, the central and eastern tropical Pacific Ocean has shown surface warming, and most climate models suggest this warming is likely to continue during the southern autumn.

However, as this is the time of year when both ENSO and climate models have greatest variability, some caution must be taken when extrapolating the recent Pacific warming to later in 2017. Hence, either neutral or El Niño is considered the most likely ENSO state for the southern winter/spring.  

See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and Indian Ocean Dipole information.

Product code: IDCKGEW000

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