Weekly Tropical Climate Note

Issued 21 April 2015

Northern Australia transitions into dry season

While the official end of the northern wet season is 30 April, recent weather patterns across tropical Australia are more reminiscent of the dry season. A strong high pressure system currently located over the Great Australian Bight has pushed a surge of dry southerly air northwards, reducing humidty across much of Australia's tropical north.

Recent rainfall over the Kimberley region and central Australia resulted from the development of a cloudband which transported moist, tropical air from the warm Indian Ocean over central parts of the continent over the weekend. Northwest cloudbands are usually a weather feature of late autumn and early winter.

The near-equatorial trough has now begun its steady annual northward migration and is not expected to impact on the Australian continent again this wet season. The onset of the South East Asian and Indian monsoons will be monitored over the coming months. India has already seen above average rainfall this year even before the onset of the Indian Monsoon.

A weak Madden-Julian Oscillation (MJO), currently located over the central Indian Ocean, is forecast to weaken further and remain weak for the coming fortnight. Hence, the MJO is unlikely to influence tropical convection in the coming weeks. See the Bureau's MJO Monitoring for more information.

At least 70% chance of El Niño in 2015

Recent warming of the tropical Pacific Ocean has primed the Pacific for El Niño. All international climate models monitored by the Bureau indicate the tropical Pacific will exceed El Niño thresholds by mid-year. However, the accuracy of model outlooks at this time of year is lower than outlooks made at other times of the year. The Bureau's ENSO Tracker indicates that the likelihood of El Niño developing in the coming months is at least 70%.

El Niño is often, but not always, associated with below average rainfall across eastern Australian during the second half of the year. Daytime temperatures tend to be above average over the southern half of Australia.

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

Next update expected by 28 April 2015 | Product Code IDCKGEW000

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