Weekly update - 31 March 2022

For the week ending 30 March 2022, low-pressure troughs across northern and eastern Australia resulted in heavy rainfall in the east and parts of the far north. Ex-tropical cyclone Charlotte, and associated low-pressure troughs brought heavy rainfall to large parts of Western Australia. High-pressure systems in the south resulted in clear, dry conditions for large areas of southern Australia.

Rainfall totals of between 10 and 100 millimetres were recorded across eastern and north-eastern parts of New South Wales, south-eastern to north-western and far northern Queensland, western and northern parts of Western Australia, as well as parts of the north and centre of the Northern Territory. Rainfall totals in excess of 100 millimetres were recorded across coastal areas of New South Wales and, south-east and northern Queensland. Remaining parts of Australia received little to no rainfall.

In cropping regions, rainfall totals of between 10 and 100 millimetres were recorded across northern New South Wales, much of Queensland and Western Australia. Rainfall in excess of 100 millimetres was recorded in isolated parts of cropping regions in north-eastern New South Wales and south-eastern Queensland. Little to no rainfall was recorded across cropping regions in southern New South Wales, Victoria and South Australia.

The heavy rainfalls across cropping regions in northern New South Wales and southern Queensland will have prevented field access for harvesting of what remains of early sown summer crops. The wet conditions will also have prevented the harvesting of early sown summer crops with long growth periods, such as cotton, in northern Queensland, and increased the risk of quality downgrades. On the other hand, the rainfall will have supported vegetative growth of late sown summer crops in Central Queensland, as well as boosting soil moisture levels across eastern and western cropping regions, as the planting window for winter crops approaches.

Rainfall for the week ending 30 March 2022

In southern Australia, the timing of the autumn break is an important ingredient for a successful In southern Australia, the timing of the autumn break is an important ingredient for a successful pasture and crop production season. The autumn break is the first significant rainfall of the winter growing season and provides enough moisture to initiate crop and pasture germination and support early plant growth. The 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 likely to be influenced by the autumn break

An early autumn break can increase the length of the growing season, potentially improving production and yield. 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.

It is important to remember that while the timing of the rain is important, as to whether it constitutes a break or not, it is the weather following this early break that will determine whether this is a ‘false’ break or a true early break. For example, a 30mm rainfall event in March followed by warm, dry weather may not constitute the break. However, if a similar rainfall event were to occur during April, it will likely be the break that many southern farmers have been waiting for. Furthermore, an early autumn break, in and of itself, does not guarantee a successful growing season; sufficient winter and spring rainfall is still required, particularly in areas with little to no stored soil moisture, to deliver a successful crop and pasture production season.

Southern pasture and cropping areas that have achieved 30 millimetres in any 7‐day period from 1 March to 30 March 2022

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 autumn break has been achieved across cropping regions of northern, eastern and southern New South Wales, southern Queensland, parts of central and eastern Victoria and large areas of northern Western Australia.

Typically, the autumn break is driven by westerly fronts moving across southern Australia and cut-off low pressure systems. This uncharacteristic early autumn break in south-eastern Australia has been driven by series of east coast lows pulling in moist tropical air from Coral Sea resulting in substantial rainfall. While in Western Australia the early autumn break has been the result of the break down and movement of Ex-tropical cyclone Charlotte as it tracks south down the Western Australian coast.

Over the 8-days to 7 April 2022, low-pressure systems drawing down moisture laden air are expected to bring rainfall to parts of south-eastern and western Australia. Meanwhile, high pressure systems are expected to bring mostly dry conditions to central and southern Australia.

Rainfall totals of between 10 and 50 millimetres are forecast for eastern New South Wales and Victoria, as well as parts of south-eastern and northern Queensland, western parts of Western Australia, the far north of the Northern Territory and north-east Tasmania. Rainfall in excess of 50 millimetres is expected for south-eastern New South Wales, eastern Victoria and the far west of Western Australia.

In Australian cropping regions, rainfall totals of between 10 and 50 millimetres are expected in parts of north-eastern New South Wales and south-eastern Queensland, as well as across Western Australia. Little to no rainfall is forecast for all remaining cropping regions during the next 8-days.

The dry conditions across northern cropping regions will be a welcome break from heavy rainfalls in the past month. Soil moisture levels are well above average for parts of southern Queensland and much of New South Wales, delaying the harvesting of summer crops and planting of long season winter crops. The forecast dry conditions will allow soil profiles to drain and mature crops to dry out. There are reports of yield losses for early sown sorghum crops due to grain shattering, as well as a high risk of quality downgrades for mung bean crops in southern Queensland and northern New South Wales due to recent rainfall. If dry conditions persist, planting of winter crops is likely to get underway in the coming weeks, with plentiful plant available water to support germination and establishment.

Total forecast rainfall (mm) for the period 31 March to 7 April 2022