Weekly Australian Climate, Water and Agricultural Update, 28 November 2024

For the week ending 27 November 2024, low-pressure systems and troughs brought rainfall much of Australia. A trough extending from the northwest to southeast brought rainfall totals of up to 100 millimetres in northern Western Australia, the Northern Territory, central and south-eastern South Australia, much of Victoria and isolated parts of southern New South Wales. Up to 150 millimetres of rainfall was recorded in some parts of the northern tropics in Queensland and the Northern Territory. In Western Australia, up to 50 millimetres of rainfall was recorded in central areas, and 5 and 25 millimetres in the southwest. In contrast, high-pressure systems kept much of northern New South Wales, southern Queensland and Tasmania relatively dry.

Across cropping regions, rainfall outcomes were mixed. Much of northern New South Wales, western South Australia, Queensland, and Western Australia saw little or no rainfall, with totals in these areas generally less than 10 millimetres. Rainfall totals were higher in the southeast, with between 10 and 50 millimetres recorded in southern New South Wales, Victoria, and eastern South Australia, with isolated areas seeing as much as 100 millimetres. For those south-eastern areas that recorded significant rainfall this week, this has likely delayed the harvest of remaining winter crops.

Rainfall for the week ending 27 November 2024

Over the 8 days to 5 December 2024, significant rainfall and storms are expected across the north and east of Australia. Falls of between 10 and 100 millimetres are forecast for much of the Northern Territory, Queensland, New South Wales, Victoria, South Australia, Tasmania and the east and north-east of Western Australia. High pressure systems are expected to keep central and western areas comparatively dry, with much of the remainder of Western Australia forecast to receive between 5 and 10 millimetres of rainfall, and much of South Australia forecast to receive between 10 and 25 millimetres.

Across cropping regions, rainfall is forecast to be relatively low in the west, with much of Western Australia expected to receive between 5 and 10 millimetres. In the east, rainfall totals of between 15 and 100 millimetres are forecast for New South Wales, Queensland and much of Victoria. In South Australian cropping regions, between 10 and 25 millimetres is forecast.

If realised, rainfall across eastern cropping regions will likely interrupt the harvest of remaining winter crops. Rainfall forecast for summer cropping regions in northern New South Wales and Queensland will likely provide a boost for soil moisture levels and support the germination and growth of crops already in the ground.

Total forecast rainfall for the period 28 November to 5 December 2024

The El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) climate drivers are currently neutral and having minimal influence on Australian rainfall. The Southern Annular Mode (SAM) is currently neutral and has a high chance to become positive in December. A positive SAM contributes to an increased chance of summer rain in south-eastern Australia.

The most recent rainfall outlook for December 2024 provided by the Bureau of Meteorology indicates that much of eastern Australia, including eastern Queensland, New South Wales, Victoria and Tasmania, as well as parts of Western Australia are likely to see above median rainfall. For the remaining regions, rainfall is likely to be similar to average.

According to the Bureau of Meteorology’s climate model, for December 2024, there is a 75% chance of rainfall between 25 and 100 millimetres across much of eastern Queensland, New South Wales and Victoria. Rainfall totals are likely to be higher in the north, with the northern tropics likely to receive between 100 and 200 millimetres of rainfall over the period, with isolated areas in the far-north of the Northern Territory and Queensland seeing as much as 300 millimetres. Tasmania is forecast to receive between 50 and 200 millimetres of rain in December. In contrast, much of western and central Australia is likely to receive between 5 and 50 millimetres.

Across cropping regions, there is a 75% chance of receiving between 25 and 100 millimetres of rainfall across much of Queensland and New South Wales in December 2024, with higher rainfall totals generally expected in eastern regions of these states. In South Australia, Victoria and eastern Western Australia, rainfall totals are expected to be between 10 and 25 millimetres. These relatively low expected rainfall totals across much of southern Australia continue to represent a significant downside risk for pasture growth over summer. However, if forecast rainfall totals are realised across much of New South Wales and Queensland, these falls are likely to be sufficient to support above average yield prospects for summer crops and average or better levels of pasture production in these regions.

Rainfall totals that have a 75% chance of occurring in December 2024

The rainfall outlook for December 2024 to February 2025 indicates an increased probability of above median rainfall across many eastern and western areas of Australia. In contrast, below median rainfall is slightly more likely across isolated areas of the Northern Territory. Much of the remainder of the country is showing an equal probability of above or below median rainfall.

Across cropping regions, the chance of receiving above median rainfall is between 60% and 80% across much of Queensland, New South Wales, Victoria and Western Australia. In South Australia, there are approximately equal chances of receiving above or below median rainfall.

Chance of exceeding the median rainfall December 2024 to February 2025

The outlook for December to February suggests a 75% chance of receiving rainfall totals of between 50 and 300 millimetres across much of Queensland, New South Wales, Victoria, Tasmania, and the Northern Territory. Rainfall totals in excess of 300 millimetres are forecast for the tropical north of Western Australia, the Northern Territory, and Queensland, as well as coastal areas of Queensland and New South Wales, and western Tasmania. Western Australia is likely to see between 25 and 200 millimetres, with rainfall totals generally higher in the north.

In summer cropping regions, there is a 75% chance of receiving between 100 and 300 millimetres of rainfall between December 2024 and February 2025. If realised, this will boost soil moisture profiles and would likely generate above average yield expectations for summer crops in Queensland and northern New South Wales. In winter cropping regions, rainfall totals from December 2024 to February 2025 are expected to be lower, with between 10 and 50 millimetres of rainfall likely across much of Western Australia and South Australia, and between 25 and 100 millimetres in Victoria.

Rainfall totals that have a 75% chance of occurring December 2024 to February 2025