Weekly update - 29 April 2021

During the week ending 28 April 2021, blocking high pressure systems resulted in little rainfall being recorded across much of Australia. In contrast, low pressure troughs and cold fronts generated rainfall across parts of north-eastern and far southern Australia.

Rainfall totals of between 5 and 25 millimetres were recorded across parts of central Queensland, southern Victoria, south-eastern South Australia and the north of the Northern Territory. Rainfall totals of between 25 and 100 millimetres were recorded across parts of north-eastern Queensland, the north of the Northern Territory and western Tasmania. Rainfall in excess of 100 millimetres was recorded across isolated parts of northern Queensland.

In cropping regions, rainfall of between 5 and 25 millimetres was recorded across parts of northern Queensland. Little to no rainfall was recorded across cropping regions in New South Wales, Victoria, South Australia, Western Australia and remaining cropping regions in Queensland.

The rainfall across cropping regions in northern Queensland has likely been beneficial for early sown winter crops. The dry conditions in northern cropping regions of New South Wales and central and southern Queensland have been ideal for late summer crop harvesting, as well as field preparation and sowing of winter crops. As most cropping regions in Victoria and South Australia received low rainfall totals during March and April and have low soil moisture levels, these regions will rely on May rainfall to support winter crop germination and establishment.

Rainfall for the week ending 28 April 2021

©Commonwealth of Australia 2021, Australian Bureau of Meteorology - Issued: 28/04/2021
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 definition of the autumn break in southern Australia varies. Pook et al. (2009) suggested an ideal break for north-western Victoria occurs during March–June when a mean fall of 25 millimetres or more is recorded over a period of 3 days or less, or when a mean fall of 30 millimetres or more is recorded over a period of 7 days or less.

ABARES has adapted the Pook et al. (2009) autumn break definition of falls of 30 millimetres or more recorded within any 7-day period from 1 March to identify where the autumn break threshold has been achieved across southern Australia. ABARES analysis of daily rainfall data sourced from the Bureau of Meteorology indicates that the early autumn break (during March 2021) had been achieved across much of New South Wales, Western Australia and parts of southern Queensland, central Victoria and northern and eastern Tasmania.

Areas that have achieved 30 millimetres in any 7‐day period from 1 to 31 March 2021

Source: Bureau of Meteorology, ABARES
Note: The autumn break generally applies to the southern pasture and cropping areas mainly in New South Wales, Victoria, South Australia, Western Australia and Tasmania — and occasionally parts of southern Queensland. Areas that are not typically influenced by the autumn break have been shaded out.

Rainfall during April has consolidated the early autumn break recorded across isolated parts of north-eastern New South Wales, southern Victoria, Western Australia and northern and eastern Tasmania. These falls have continued to improve soil moisture profiles and allowed for an ideal start to winter crop planting and autumn pasture growth in these areas. A consolidated early autumn break can increase the length of the growing season, potentially improving production and yield.

The early autumn break was not consolidated during April for large areas of New South Wales, Victoria, Western Australia and Tasmania. This dry period following the early autumn break increases the risk of plants experiencing moisture stress after germination, with a disconnect emerging between upper- and lower-layer soil moisture.

Areas that have received at least 25 millimetres of follow-up rainfall from 1 April to 27 April 2021

Source: Bureau of Meteorology, ABARES
Note: The autumn break generally applies to the southern pasture and cropping areas mainly in New South Wales, Victoria, South Australia, Western Australia and Tasmania — and occasionally parts of southern Queensland. Areas that are not typically influenced by the autumn break have been shaded out.

Troughs, cold fronts and onshore winds are likely to bring showers and storms to parts of southern and eastern Australia during the 8 days to 29 April 2021, while high pressure systems are expected to keep the remainder of Australia dry.

Rainfall totals of between 10 and 50 millimetres are forecast for much of New South Wales, Victoria, south-western Western Australia, Tasmania and parts of eastern Queensland and south-eastern South Australia. Rainfall totals in excess of 50 millimetres are forecast for isolated parts of far south-eastern and south-western Australia, and the eastern coast of Queensland.

In Australia’s cropping regions, rainfall totals of between 10 and 50 millimetres are expected across much of New South Wales, Victoria and Western Australia. Rainfall totals of between 5 and 10 millimetres are expected across the remainder of New South Wales cropping regions and cropping regions in parts of southern Queensland and central and eastern South Australia. Little to no rainfall is expected across remaining cropping regions in South Australia and Queensland. The rainfall across cropping regions in New South Wales and Victoria will boost soil moisture levels and benefit early sown winter crops following a dry April 2021.

Total forecast rainfall (mm) for the period 29 April to 6 May 2021

©Commonwealth of Australia 2021, Australian Bureau of Meteorology - Issued: 29/04/2021
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.