Weekly update - 10 December 2020

Weekly Australian Climate,
Water and Agricultural Update

Key issues

  • During the week ending 9  December troughs and cold fronts generated showers and thunderstorm activity across parts of northern, central and eastern Australia.
  • Rainfall this week across some eastern Australian cropping regions is likely to have slowed the progress of the winter crop harvest. Meanwhile, in summer cropping regions these falls are likely to benefit the production potential of earlier sown crops and assist the germination and establishment of dryland crops sown on variable soil moisture.
  • A La Niña event is ongoing in the tropical Pacific. The enhanced probabilities of a wetter than average summer rainfall will likely benefit pasture growth across eastern and northern Australia, summer crop production and an early northern rainfall onset.
  • There is a high chance that rainfall between December 2020 to February 2021 will be sufficient to sustain average crop and pasture production through the summer period. These highly probable rainfall totals – if realised – represent favourable growing conditions for the 2020–21 summer cropping season and wet season across northern Australia. With low soil moisture across most summer cropping regions, the development and production potential of dryland summer crops will be highly dependent on in-season rainfall.
  • Over the next eight days, troughs and cold fronts are expected to generate showers and storms over northern, western and eastern Australia. Across cropping regions, rainfall of between 10 and 50 millimetres is expected across parts of eastern and northern New South Wales, and south-eastern Queensland. Rainfall of between 5 and 10 millimetres is expected in cropping regions across parts of northern and western Queensland, central and western New South Wales, and central South Australia.
  • Water storage levels in the Murray-Darling Basin (MDB) decreased by 192 gigalitres (GL) between 2 December 2020 and 9 December 2020. The current volume of water held in storage is 14,892 GL, which represents 59% of total capacity.
  • Allocation prices in the Victorian Murray below the Barmah Choke increased from $210 per ML to $215 per ML between 3 December 2020 and 10 December 2020. Prices are lower in the Goulburn-Broken, Murrumbidgee and regions above the Barmah Choke, due to binding of the Goulburn intervalley trade and Murrumbidgee export limits, and the Barmah Choke trade constraint.

Climate

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Rainfall this week

During the week ending 9  December 2020 troughs and cold fronts generated showers and thunderstorm activity across parts of northern, central and eastern Australia.

Rainfall totals of between 10 and 50 millimetres were recorded across, northern Western Australia and the north and south of the Northern Territory, and across scattered areas of central and eastern New South Wales, southern Victoria, northern and eastern Queensland, and south-eastern South Australia. Rainfall totals in excess of 50 millimetres was recorded across parts of northern Western Australia and isolated parts of the Northern Territory and eastern Australia.

In Australia’s cropping regions, rainfall totals of between 5 and 25 millimetres were recorded across New South Wales, and across isolated parts of Queensland, Victoria and South Australia. Little to no rainfall was recorded across remaining cropping regions during the week ending 9  December 2020.

Rainfall across some eastern Australian cropping regions during the week ending 9 December 2020 has likely slowed the progress of the winter crop harvest, as harvest activities wrap up in southern Queensland and northern New South Wales and are well underway across southern Australia. Meanwhile, in summer cropping regions that received rainfall totals in excess of 15 millimetres, these falls are likely to benefit the production potential of earlier sown crops and assist the germination and establishment of dryland crops sown on variable soil moisture.

Rainfall for the week ending 9 December 2020

Map showing weekly rainfall totals in Australia. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

©Commonwealth of Australia 2020, Australian Bureau of Meteorology - Issued: 9/12/2020

Note: The rainfall analyses and associated maps utilise data contained in the Bureau of Meteorology climate database, the Australian Data Archive for Meteorology (ADAM). The analyses are initially produced automatically from real-time data with limited quality control. They are intended to provide a general overview of rainfall across Australia as quickly as possible after the observations are received. For further information go to http://www.bom.gov.au/climate/rainfall/

Climate Drivers

As the generally favourable winter cropping season wraps up, interest moves to the prospects of the summer cropping and pasture production seasons. To gain some insight it is important to look at the major climate drivers—the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD)—that influence spring and summer rainfall across southern Australia.

A La Niña is ongoing in the tropical Pacific. A La Niña during summer is likely to generate the favourable growing conditions for summer crop and pasture production that were central in developing ABARES summer crop and livestock production forecasts embodied in the ABARES December 2020 editions of the Australian crop report and Agricultural commodities. The enhanced probabilities of a wetter than average summer rainfall will likely benefit pasture growth across eastern and northern Australia, summer crop production and an early northern rainfall onset.

The IOD is neutral and expected to remain neutral for the remainder of December. IOD events do not form in summer due to the arrival of the Australian monsoon.

Cool anomalies in the central and eastern Pacific Ocean remain a similar strength to the past fortnight. The international climate models surveyed suggest the La Niña will peak at moderate to strong levels in December 2020 or January 2021. Seven out of the eight surveyed climate models suggest the La Niña will persist until at least through February 2021. Five of the models are forecasting sea surface temperatures to continue to exceed La Niña thresholds through March 2021.

Difference from average sea surface temperature observations 30 November to 6 December 2020

Map showing the global sea surface temperature observations difference from average during the previous week. The climatology baseline used is 1961 to 1990. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.
 

International climate model outlooks for the NINO 3.4 region in February 2021

Graph showing the average forecast value of NINO 3.4 for each international model surveyed by the Bureau of Meteorology for February 2021. Please refer to accompanying text for a more detailed description.

©Commonwealth of Australia 2020, Australian Bureau of Meteorology - Issued: 8/12/2020

Atmospheric indicators are generally consistent with a La Niña event, with stronger than average trade winds and decreased cloudiness near the Date Line. The Southern Oscillation Index (SOI) has returned to values consistent with a La Niña event. For the period ending 6 December the 30-day SOI value was 10.4 and the 90-day value was 7.9.

30-day Southern Oscillation Index (SOI) values ending 7 December 2020

Graph showing the 30-day Southern Oscillation Index (SOI) values for the past two years. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

The Southern Annular Mode (SAM) is currently positive and expected to be generally positive until at least early 2021. The SAM refers to the north-south shift of the band of rain-bearing westerly winds and weather systems in the Southern Ocean compared to the usual position. When SAM is positive during spring and summer, this band of westerly winds is further south than normal. This allows for increased moist onshore flow from the Tasman and Coral seas and more rainfall across eastern Australia and a reduced chance of extreme heat. A positive SAM is common in spring and summer during La Niña events and can enhance the wetter than average influence La Niña has on eastern Australia.

Southern Annular Mode (SAM) daily index

sam_index-daily-20201210.png

National Climate Outlook

These climate outlooks are generated by ACCESS–S (Australian Community Climate Earth-System Simulator–Seasonal). ACCESS–S is the Bureau of Meteorology's dynamical (physics-based) weather and climate model used for monthly, seasonal and longer-lead climate outlooks.

For further information, go to http://www.bom.gov.au/climate/ahead/about/

The latest rainfall outlook released by the Bureau of Meteorology suggests above average rainfall is more likely for much of Australia during December 2020. There is greater than 70% chance of above average rainfall across much of western and northern Australia.

The rainfall outlook for December 2020 to February 2021 suggests that wetter than average conditions are likely for most of mainland Australia and north-eastern Tasmania. There is no strong tendency of drier or wetter than average conditions for the remainder of Tasmania. There is greater than 70% chance of above average rainfall much of western and northern Australia, and parts of eastern Australia (Bureau of Meteorology ‘National Climate Outlook’, 3 December 2020). Bureau of Meteorology rainfall outlooks for December to February have greater than 55% past accuracy across large parts of Western Australia and parts of the north and east of Australia. There is lower accuracy, less than 55%, across much of the remainder of Australia, with less than 45% past accuracy across large parts of central Australia and parts of the east of Australia.

Chance of exceeding the median rainfall December 2020 to February 2021

Map showing the chance of exceeding median rainfall between December 2020 to February 2021 in Australia. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

©Commonwealth of Australia 2020, Australian Bureau of Meteorology Issued: 2/12/2020

The outlook for December 2020 suggests that there is a 75% chance of rainfall totals between 25 and 100 millimetres across much of northern Australia, and parts of eastern Australia. There is a 75% chance of rainfall totals between 1 and 25 millimetres across much of southern and south-western Australia. Rainfall totals in excess of 100 millimetres are likely across parts of northern Australia and isolated parts of eastern Australia and western Tasmania.

There is a high chance of recording close to average December rainfall totals across most agricultural regions. If realised, these totals are likely to support the growth of summer crops across New South Wales and Queensland and average pasture growth potentials across much of eastern New South Wales, Queensland, the tropical north of Australia and parts of Victoria.

In cropping regions there is a 75% chance of rainfall totals between 25 and 100 millimetres across much of New South Wales and Queensland. There is a 75% chance of rainfall totals between 10 and 25 for much of Victoria and South Australia and parts of south-western New South Wales and the eastern Western Australia wheat belt, with rainfall totals between 1 and 10 millimetres across the remainder of the Western Australia wheat belt for December 2020.

Rainfall totals that have a 75% chance of occurring December 2020

Map showing the rainfall totals that have a 75% chance of occurring during December 2020 in Australia. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

©Commonwealth of Australia 2020, Australian Bureau of Meteorology Issued: 3/12/2020

The outlook for December 2020 to February 2021 suggests that there is a 75% chance of rainfall totals between 25 and 200 millimetres across much of the southern two thirds of Australia. Lower rainfall totals between 10 and 25 millimetres are likely across parts of the central-south and south-west of Australia. Rainfall totals in excess of 300 millimetres are likely across parts of eastern New South Wales, eastern Queensland, western Tasmania and the tropical north of Australia.

There is a high chance of recording December to February rainfall totals sufficient to sustain close to average crop and pasture production through the summer period. With extremely low levels of upper layer soil moisture and variable levels of root zone soil moisture, the development and production potential of dryland summer crops will depend on in-season rainfall.

Across summer cropping regions, there is a 75% chance of receiving between 100 and 300 millimetres across most of New South Wales and Queensland, with totals up to 400 millimetres across cropping regions in northern Queensland between December 2020 and February 2021.

These high chance rainfall totals are almost equivalent to the seasonal median (between 1990 and 2012) and if realised represent favourable growing conditions for the 2020–21 summer cropping season in eastern Australia and wet season across northern Australia. 

Rainfall totals that have a 75% chance of occurring December 2020 to February 2021

Map showing the rainfall totals that have a 75% chance of occurring during the next three months in Australia. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

©Commonwealth of Australia 2020, Australian Bureau of Meteorology Issued: 3/12/2020

The temperature outlook for December 2020 to February 2021 indicates that night-time temperatures are likely to be between 0°C to 2°C above the 1990-2012 average across most of Australia. Day-time temperatures are likely to be close to the 1990-2012 average (- 1°C to 1°C) across most of Australia (Bureau of Meteorology ‘National Climate Outlook’, 3 December 2020).

Predicted maximum temperature anomaly for December 2020 to February 2021

Map showing the predicted maximum temperature anomaly for the next three months in Australia. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

Predicted minimum temperature anomaly for December 2020 to February 2021

Map showing the predicted minimum temperature anomaly for the next three months in Australia. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

Rainfall forecast for the next 8 days

Troughs and cold fronts are expected to generate showers and storms over northern, western and eastern Australia during the next eight days. Rainfall totals of between 10 and 50 millimetres are forecast for parts of eastern New South Wales, northern and eastern Queensland, southern Victoria, the north of Western Australia, the north of the Northern Territory and much of Tasmania. Rainfall totals in excess of 50 millimetres is expected across parts of northern Western Australia, the tropical north, far south-eastern Queensland and north-eastern New South Wales.

In cropping regions, rainfall of between 10 and 50 millimetres is expected across parts of eastern and northern New South Wales, and south-eastern Queensland. Rainfall of between 5 and 10 millimetres is expected in cropping regions across parts of northern and western Queensland, central and western New South Wales, and central South Australia. Little to no rainfall is expected across remaining cropping regions during the next eight days.

Total forecast rainfall (mm) for the period 10 December to 17 December 2020

Map of the total forecast rainfall for the next 8 days. Image provided by the Bureau of Meteorology. Please refer to accompanying text for a more detailed description.

©Commonwealth of Australia 2020, Australian Bureau of Meteorology - Issued: 10/12/2020

Note: This rainfall forecast is produced from computer models. As the model outputs are not altered by weather forecasters, it is important to check local forecasts and warnings issued by the Bureau of Meteorology.

Commodities

Information on weekly price changes in agricultural commodities is now available at the Weekly commodity price update.

Water

Water storages, water markets and water allocations - current week

The Tableau dashboard may not meet accessibility requirements. For information about the contents of these dashboards contact ABARES.

 
Last reviewed: 13 January 2021
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