Ag Weather Forum

Improved Rain for Australia Wheat

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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Eastern and southern Australia crop areas have had generous rain to begin the crop season. New South Wales has seen the largest increase. (Australia Bureau of Meteorology graphic)

After two years of exhausting and damaging drought, the wheat crop in Australia is looking set to rebound in a big way. The latest estimate from the Australia agriculture department, ABARES, calls for wheat production to increase by 76% compared to 2019-20 to 26.7 million metric tons in 2020-21. That figure is also 13% above the 10-year average to 2019-20. The 2019-20 wheat crop amounted to 15.2 mmt.

Improved rainfall is a big reason for this projection. The department's June crop report noted: "The opening to the winter cropping season in 2020-21 was generally very favourable, especially in the eastern states and South Australia. Total rainfall between February and April was above average in most cropping regions in eastern states and South Australia and was average in Western Australia. The start of the winter cropping season was significantly better in New South Wales and southern Queensland than the last two years. Rainfall during May was average in most cropping regions and timely in others to facilitate crop planting and germinate early sown crops."

There are some drier areas, but the extent is not nearly as large as in the past two seasons. "However, some cropping regions in Queensland and Western Australia did not receive sufficient rainfall in May to fully realise planting intentions," the agency said.

Weatherwise, two large-scale ocean features are combining for this optimistic crop projection; a developing La Nina in the equatorial Pacific Ocean and an Indian Ocean barometric pressure feature called the Indian Ocean Dipole, which is expected to be negative during the next six months. The Australia Bureau of Meteorology (BOM) posted this summary of the two features in early June.

"Both the El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) remain neutral. While neutral ENSO is forecast for the Southern Hemisphere winter, some models suggest a La Nina-like pattern could develop in spring. Similarly, four of six models suggest the possibility of a negative IOD developing in the Indian Ocean from mid-winter.

Key indicators of ENSO, such as the Southern Oscillation Index (SOI), trade winds, cloudiness near the Date Line, and sea surface temperatures in the tropical Pacific Ocean, are generally at levels consistent with a neutral ENSO state. However, sea surface temperatures across the tropical Pacific Ocean have cooled over the past two months, and sub-surface temperatures in the tropical Pacific Ocean are also cooler than average.

International climate models surveyed by the Bureau forecast further cooling in the central tropical Pacific but remain ENSO-neutral through the Southern Hemisphere winter. During spring, two out of the eight models exceed La Nina levels, with another two briefly touching thresholds. It is worth noting that ENSO predictions made in autumn or early winter have lower skill than those made later in the year.

The Bureau's ENSO Outlook is currently INACTIVE. However, if further cooling is observed in coming weeks, and any additional models suggest La Nina development, the ENSO Outlook will be raised to La Nina WATCH.

The IOD is currently neutral. Four of the six international climate models surveyed by the Bureau suggest the development of a negative IOD from the middle of the Southern Hemisphere winter, with other models remaining neutral. However, each model shows a broad spread of likely scenarios between the neutral and negative IOD range, and the most up-to-date model outlooks have shown a lower likelihood of negative IOD. A negative IOD typically brings above average winter-spring rainfall to southern Australia."

The presence of La Nina is a promising feature for Australia rainfall. It is the opposite of La Nina effects in the interior U.S., where dry conditions are largely in effect. When La Nina sets in, rain is a notable feature in the Australia crop weather scene -- especially in the eastern Australia crop areas.

Bryce Anderson can be reached at

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