Weekly update - 29 October 2020

During the week ending 28 October 2020 low pressure systems and troughs generated thunderstorm activity and showers across parts of northern, eastern and southern Australia.

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

In Australia’s cropping regions, rainfall totals of between 10 and 50 millimetres were recorded across much of New South Wales, Queensland, eastern and northern Victoria and parts of western and northern South Australia. Rainfall totals in excess of 50 millimetres were recorded in cropping regions across large parts of eastern New South Wales and eastern Queensland. Little to no rainfall was recorded across cropping regions in Western Australia during the week ending 28 October 2020.

The substantial but patchy falls in eastern cropping regions may have adversely impacted the quality of winter crops in the final stages of growth. While, isolated hail storms in northern New South Wales and southern Queensland are likely to have resulted in significant crop losses on some farms but are unlikely to result in significant production downturn at the state or national level. The full extent of damage and any quality downgrades will be revealed in the coming days as harvest recommences.

In Queensland where many growers are likely to only produced modest winter crops due to the dry season, are now looking to sow a substantial summer crop. In many areas these falls should be sufficient stimulate summer crop planting, while not delaying the winter crop harvest for too long.

Rainfall for the week ending 28 October 2020

©Commonwealth of Australia 2020, Australian Bureau of Meteorology - Issued: 28/10/2020

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/

The northern rainfall onset occurs when the total rainfall after 1 September reaches 50 millimetres. This is considered approximately the amount of rainfall required to stimulate plant growth. The northern rainfall onset has occurred in parts of eastern and central Queensland, the far north of Western Australia and the south and north of the Northern Territory that have recorded rainfall totals between 50 to 200 millimetres from 1 September to 27 October 2020.

The ongoing La Niña event has enhanced probabilities of a wetter than average late spring and early summer rainfall, and an early northern rainfall onset across most of northern Australia.

Median Northern Rainfall Onset in La Niña Years

Northern Rainfall Totals since 1 September to 27 October 2020

Tropical cyclones and tropical lows can cause damaging winds, widespread rainfall and flooding in northern Australia and their impacts can also extend into southern Australia. Increased rainfall, soil moisture and water storage in northern Australia may benefit pasture and summer crop development, however widespread flooding and severe weather can also adversely impact crop and livestock development.

The tropical cyclone season in the Australian region extends from 1 November to 30 April and the influence of climate drivers cause large variability in tropical cyclone activity each season. This outlook was developed by the Bureau of Meteorology using the July, August and September Southern Oscillation Index (SOI) and NINO3.4 values. Since 2000, the average number of tropical cyclones each season in the Australian region has been 9 and four of these typically cross the coast of Australia. The long term average number of tropical cyclones each season is 11 (since 1969‑70) and there has been a decline in the average number of tropical cyclones forming in the Australian region during recent decades which is consistent with the expected impacts of climate change.

The 2020‑21 tropical cyclone outlook is influenced by the current La Niña event and associated ocean temperatures that are expected to persist until early 2021. It is expected that there will be an average to slightly above average number of tropical cyclones and tropical lows during the 2020–21 season. There is a 66% chance of more than 11 tropical cyclones developing in the Australian region. During La Niña years the first tropical cyclone to develop in the Australia region typically occurs in mid-December.

Chance of more tropical cyclones than average during the 2020–21 season

© Australian Bureau of Meteorology
Note: This map shows the average number of tropical cyclones in the Australian region and the chance (as a percentage) of a higher than average number of tropical during the 2020–21 season using data based on a 48 year period from 1969 70 to 2019 20 tropical cyclone season and is based on the status of the El Niño–Southern Oscillation (ENSO) over the preceding July to September.

Troughs over western and eastern Australia are expected to generate thunderstorms and showers during the next eight days. Rainfall totals of between 10 and 50 millimetres are forecast for large parts of southern and eastern New South Wales and Victoria and isolated parts of south-eastern Queensland, south-eastern South Australia, southern Western Australia and Tasmania. Rainfall in excess of 50 millimetres is expected across an isolated part of south-eastern New South Wales.

In cropping regions, rainfall of between 10 and 25 millimetres is expected across parts of southern New South Wales, south-eastern Queensland, Victoria, eastern South Australia and the southern Western Australia wheat belt. Little to no rainfall is expected across remaining cropping regions during the next eight days.

Total forecast rainfall (mm) for the period 29 October 2020 to 5 November 2020

©Commonwealth of Australia 2020, Australian Bureau of Meteorology - Issued: 29/10/2020

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.

^a Global Dairy Trade prices are updated twice monthly on the first and third Tuesday of each month.

Selected world indicator prices
Selected domestic crop indicator prices
Selected domestic livestock indicator prices
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Movements in selected fruit and vegetable prices
Data attribution