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High temperatures, bushfires may return to Australia from next week

Vinson Kurian January 23 | Updated on January 23, 2020

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The monsoon is yet to make landfall over Australia; ongoing rains do not bear the typical monsoon signature

 

The Bushfires may in South and East Australia may have abated following recent spells of heavy rain/hailstorms, but dryness and high temperatures will return to the region during the next two weeks, say the Global Forecast System (GFS) of the US National Weather Service and the Coupled Forecast System (CFS) of the US National Centres for Environmental Prediction.

Higher temperatures to return

The second of the two weeks (January 29 to February 4) are forecast to have well-above-average temperatures and these expected to expand and include much of South Australia, Victoria, New South Wales, and South Queensland.

A European Centre for Medium-Range Weather Forecast assessment also indicates that daily maximum temperatures have a near 60 percent chance of exceeding the 85th percentile of the climatological distribution in these areas at the end of January into the beginning of February. This is despite the ongoing week (January 22 to 28) likely witnessing above-average rainfall over the Northern Territory and parts of Queensland. The deterministic GFS model indicates local amounts exceeding 20 cm within the week across the Northern Territory and Queensland.

Primed for bushfires, heatwaves

The Australian Bureau of Meteorology said that the effects of the strong positive Indian Ocean Dipole (IOD) event in the second half of 2019 and the delayed withdrawal of the Indian monsoon persist, with the Australian landscape primed for bushfire weather and heatwaves this summer. The combined effect has delayed the onset of the monsoon, due in December, Down Under.

The ongoing rains do not bear the typical monsoon signature. Widespread rainfall is forecast for North Australia this week (starting January 21), the Bureau said. Weather models indicate the region could see rainfall of between 2.5-10 cm, with some parts far to the North-West likely to see rainfall totals in excess of 15 cm.

The predicted rainfall is associated with humid, deep-layer westerly winds over the North of the continent. This wind flow and humidity is likely to combine with surface troughs over the continent to generate significant rainfall, extending from the Kimberley region of West Australia, across nearly all of the Northern Territory and throughout Queensland.

Rainy, but not monsoon-like yet

The current conditions across northern Australia are monsoon-like, based on the humidity and westerly wind flow. However, some characteristics of this environment differ from a typical monsoon, in particular the lack of a well-defined monsoon trough, the Bureau explained.

In addition to widespread rainfall across North Australia in the coming week, some models predict a low-pressure system may develop over the inland Northern Territory or East Kimberly region; this could potentially generate locally heavy falls well in excess of 10 cm.

The Bureau suspected that if the technical definition of a monsoon is not met during the current weather situation over North Australia, it is likely that 2019–20 will observe the latest on-record monsoon onset — the biggest delay since records commenced in 1957–58 was 25 January, 1972. Australia’s monsoon onset takes place over Darwin.

Strong MJO wave over Pacific Ocean

A factor that might reduce the chance of a true monsoon developing over North Australia is the location of a strong pulse of the Madden–Julian Oscillation (MJO), a weather-creating low-pressure wave that passes across the Indian Ocean periodically, with major influence on monsoon onsets and storm genesis.

The MJO wave has moved well past Australia to the East and is approaching the tropical Central Pacific Ocean. While the presence of an active MJO is not a necessary component of monsoon development, as the MJO pulse moves further away, the environment over Australia becomes less favourable for widespread cloudiness and rainfall.

At this time of the year, an MJO pulse over the central Pacific typically enhances rainfall to a moderate degree over North Queensland, but has no significant influence on rainfall patterns across the remainder of North Australia. If the MJO pulse tracks further East over the tropical East Pacific Ocean, then North Australia and the Maritime Continent (South-East Asian region covering Indonesia, the Philippines and Papua New Guinea) would typically enter a period of suppressed cloudiness and rainfall. However, the MJO pulse is forecast to weaken steadily before this happens and become indiscernible in about a week, the Bureau said.

Published on January 23, 2020

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