Weekly update - 29 July 2021

During the week ending 28 July 2021, cold fronts and troughs brought rainfall to much of southern Australia early in the week. High-pressure systems resulted in clear conditions in the middle of the week across much of southern Australia, with cold fronts, troughs and rainfall returning toward the end of the week. Conditions remained dry across northern Australia throughout the week.

Rainfall totals of between 10 and 50 millimetres were recorded across parts of southern, central and north-eastern New South Wales, isolated areas of south-eastern Queensland, much of Victoria, the south of South Australia, the south-west of Western Australia and parts of Tasmania. Rainfall totals in excess of 50 millimetres were recorded in alpine regions of New South Wales and Victoria, western Tasmania and isolated parts of Western Australia.

In cropping regions, rainfall totals of between 10 and 50 millimetres were recorded in parts of eastern, central and northern New South Wales, Victoria, South Australia and northern and southern Western Australia, and isolated parts of south-east Queensland. Little to no rainfall was recorded across cropping regions in north-western New South Wales and most Queensland during the week ending 28 July 2021.

Soil moisture levels across most cropping regions continue to be favourable and likely supported on-going crop development, even in areas where little to no rainfall was recorded this week. The wet conditions in some parts, such as central New South Wales and southern Western Australia, have restricted on-farm access, limiting the ability to apply nitrogen and spray crops. Those previously dry areas of eastern South Australia and north-western Victoria received 10 to 25 millimetres over the past week providing some much-needed moisture. However, further rainfall will be required in these areas to support ongoing crop development and yield potential.

Rainfall for the week ending 28 July 2021

©Commonwealth of Australia 2021, Australian Bureau of Meteorology - Issued: 28/07/2021
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 outlook provides an indication of whether the first significant rains after the dry season are likely to be earlier or later than normal. The 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. Coastal parts of northern Australia usually accumulate 50 millimetres of rainfall by late October or early November, spreading to inland areas over subsequent weeks.

An early northern rainfall onset for 2021–22 season is more likely across most of northern Australia, according to the latest northern rainfall onset outlook released by the Bureau of Meteorology. The chance of an early rainfall onset is greater than 65% for most of Queensland, the Northern Territory, northern South Australia and parts of Western Australia. The La Niña event during spring-summer of 2020 also resulted in an early northern rainfall onset across much of northern Australia. In contrast, 2018 and 2019 had later than normal onsets, reducing the length of the dryland summer growing season and the recharge of water storages. An early onset of the 2021–22 northern wet season is likely to boost soil moisture and water storages, and benefit summer crop production and northern pasture growth.

Earlier than normal northern rainfall onset is associated with the possible emergence of a La Niña conditions in late spring, which some international climate models are predicting. In the Indian Ocean, negative Indian Ocean Dipole conditions are forecast out to November. This is also contributing to the higher likelihood of an earlier than normal northern rainfall onset.

Chance of early northern rainfall onset

Low pressure systems and cold fronts across southern Australia are likely to bring rainfall to parts of New South Wales, Victoria, South Australia, Western Australia and Tasmania over the next 8 days to 5 August 2021. High pressure systems are likely to prevent substantial rainfalls for northern and central parts of Australia.

Rainfall totals of between 10 and 50 millimetres are forecast for isolated parts of New South Wales, as well as much of Victoria, the far south of South Australia, south-west Western Australia and much of Tasmania.

In Australia’s cropping regions, rainfall totals of between 10 and 25 millimetres are forecast for southern Victoria, central and western South Australia and much of Western Australia.The forecast rainfall for cropping regions will continue to support the growth of early sown crops and establishment of later sown crops, as well as boosting soil moisture.

Soil moisture levels are average to above average across most eastern and western cropping regions, which will support ongoing crop growth and yield potential. The low rainfall expected for much of New South Wales will provide a reprieve from potential waterlogging, particularly in the central-west growing region. The forecast rainfall for parts of south-western Western Australia, on the other hand, may exacerbate waterlogging, negatively affecting crop growth. Some southern growing regions in Western Australia have already recorded rainfall totals double the July average leading to a complete saturation of the soil profile.

Total forecast rainfall (mm) for the period 29 July to 5 August 2021

©Commonwealth of Australia 2021, Australian Bureau of Meteorology - Issued: 29/07/2021