Weekly Tropical Climate Note

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2015-16 southern hemisphere wet-season review

Large parts of northern Australia experienced drier-than-average and warmer-than-average conditions during the 2015-16 northern wet season, with several areas experiencing record dry and heat since the start of 2016. Tropical cyclone activity was significantly below average, with only three tropical cyclones observed in the Australian region – the lowest number of tropical cyclones to develop in the Australian region on record. Historically, wet seasons have often been hotter and drier, with fewer cyclones than normal, during El Niño. For more information on 2015-16 wet season rainfall and temperature, please see our climate update: Dry and hot in the northern tropics.

In the southern Indian Ocean, the October to April period was characterised by above-average cloudiness in the central southern Indian Ocean, but below-average tropical cyclone activity, with only nine named systems compared to the average of more than sixteen. The most significant system for the 2015-16 season was the category 5 tropical cyclone Fantala, which was one of the strongest cyclones ever recorded in the Indian Ocean basin.

The southern Pacific Ocean region had significantly above-average cloudiness and rainfall in the central Pacific, but very much below-average cloudiness in the southwest Pacific. The rainfall deficiencies in the southwest Pacific region caused major rainfall deficits in many countries, including parts of Papua New Guinea, Vanuatu and Fiji. Parts of South-East Asia have also been significantly affected by poor wet-season rainfall. This pattern is consistent with the impacts of El Niño across the tropical Pacific Ocean.

Tropical cyclone activity in the southern Pacific Ocean was near normal with eleven named systems (average is ten). Category 5 Winston, which severely impacted Fiji and other nearby islands, was the strongest tropical cyclone to develop in the period. Overall, 20 tropical cyclones were observed in the southern hemisphere during the 2015-16 tropical cyclone season, somewhat less than the average of 26.

Madden–Julian Oscillation strengthens in Indian Ocean

The Madden–Julian Oscillation (MJO) has recently strengthened and moved over the tropical Indian Ocean. Cloudiness in this region has increased in recent days as the MJO and other tropical waves have impacted the region. Most climate models forecast the MJO to strengthen further and move east over the next fortnight. If the MJO moves east into the Maritime Continent at moderate strength, cloudiness and rainfall across Australian longitudes would typically be enhanced. Climatologically, increased rainfall is unlikely to significantly affect northern Australia at this time of the year, apart from northern Queensland. However, increased rainfall is likely across parts of the Maritime Continent to the north of Australia.

See the Bureau's MJO Monitoring for current MJO information.

El Niño nearing its end

The current El Niño is now in its final stages, with the Pacific Ocean now at borderline El Niño-neutral levels. Model outlooks and current observations indicate there is now a 50% likelihood of La Niña developing in the second half of 2016 – about double the normal chance. La Niña is often, but not always, associated with above-average winter-spring rainfall over northern, central and eastern Australia.

Very warm sea surface temperatures continue across waters off the northern Australia coastline. Warmth from this region is expected to contribute to above-average temperatures across northern Australia in the coming months.

See the Bureau of Meteorology's ENSO Wrap-Up for official El Niño information.

Product code: IDCKGEW000

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