Weekly update - 8 June 2023

For the week ending 7 June 2023, a low-pressure trough and a series of cold fronts brought rainfall up to 100 millimetres over western New South Wales, central and western Victoria, eastern South Australia, south-western Western Australia, northern and western Tasmania, parts of southern Northern Territory and scattered areas along eastern coast. High-pressure systems kept the remainder of the country dry.

Across cropping regions, rainfall totals up to 25 millimetres was recorded in southern New South Wales, across Victoria and eastern South Australia. Rainfall totals up to 100 millimetres were recorded in Western Australia cropping regions. Little to no rainfall was recorded in northern New South Wales, Queensland and western South Australia. This rainfall will have brought some very welcome relief from dry conditions that were seen during May. These falls should be sufficient to allow for the germination and establishment of dry sown crops.

Rainfall for the week ending 7 June 2023

Pasture growth during the March to May period affects the availability of fodder to support livestock production across northern Australia as it enters a seasonally low growth period. Across southern Australia, autumn pasture growth influences the standing biomass available to support livestock production over winter and the reliance on hay and grain during this period.

For the 3 months to May 2023, variable rainfall resulted in mixed pasture growth for this time of year across Australia. Pasture growth was average to extremely high across much of southern New South Wales, northern and eastern Victoria, southern and western Queensland, central Western Australia, central and southern Northern Territory and isolated parts of South Australia. Average to extremely high pasture production across grazing regions will likely enable farmers to continue to maintain current stock numbers and provide opportunities to build standing dry matter availability.

In contrast, extremely low to below average pasture growth rates were recorded across parts of southern and northern Western Australia, southern Victoria, large areas of northern and eastern New South Wales, parts of southern and northern Queensland, and the north of the Northern Territory, consistent with above average temperatures and/or below average rainfall. Across northern Australia, below average pasture growth over the past 3 months will likely result in graziers not being able to maintain current stocking rate leading to increased turnoff. Across southern Australia, graziers will be more reliant on the supplementary feed to maintain current stocking rate and production.

Relative pasture growth for 3-months ending May 2023 (1 March 2023 to 31 May 2023)

The climate drivers with the largest potential impact on Australia’s climate patterns are the El Niño–Southern Oscillation (ENSO), Madden-Julian Oscillation (MJO), Indian Ocean Dipole (IOD) and Southern Annular Mode (SAM). These climate drivers are likely to influence harvest progress of later planted summer crops in northern growing regions, pasture growth across both northern and southern Australia, and planting opportunities and the establishment and growth for winter crops.

The Madden–Julian Oscillation (MJO) pulse is currently over the Western Pacific and is forecast to become indiscernible in the coming days. At this time of the year MJO has little influence on northern Australia rainfall.

The Bureau of Meteorology’s ENSO outlook has shifted to El Niño ALERT, indicating that there is a 70% chance of an El Niño developing in 2023. Oceanic indicators are measured in terms of the sea surface temperature (SST) anomalies, which have warmed to El Niño thresholds. For the week ending 4 June, the SST were warmer than average over the eastern equatorial Pacific Ocean, with anomalies over 4°C in the far east. Compared to two weeks ago, the warm anomalies have remained similar in strength but extended spatially reaching further westwards. All models surveyed by the Bureau of Meteorology indicate the likelihood of further warming and the warm SSTs will remain above El Niño thresholds at least into the southern hemisphere spring.

Atmospheric indicators are measured in terms of the surface air pressure difference between Tahiti and Darwin, called Southern Oscillation Index (SOI), the direction and strength of the trade winds and cloudiness at the date line. Some atmospheric indicators such as the SOI have shifted towards El Niño thresholds. For the period ending 4 June 2023, the 30-day SOI was -20.5, the 60-day SOI was -10.6, and the 90-day SOI was -7.1. The gradual decrease in both the 30-day and 90-day SOI have entered the El-Niño threshold. However, winds, clouds and broadscale pressure patterns indicate that the ocean and atmosphere are yet to reinforce each other, as occurs during El Niño events.

Difference from average sea surface temperature observations 29 May to 4 June 2023

30-day Southern Oscillation Index (SOI) values ending 4 June 2023

All but one international climate model surveyed by the Australian Bureau of Meteorology suggest sea-surface temperatures in the tropical Pacific will exceed El Niño thresholds in June.

International climate model outlooks for the ENSO in NINO 3.4 region

The Indian Ocean Dipole (IOD) is currently neutral with index value of +0.32°C. All international climate models surveyed by the Bureau of Meteorology suggest a positive IOD event thresholds maybe reached this winter. A positive IOD can supress winter and spring rainfall over much of central and south-eastern Australia, potentially exacerbating the drying effect of El Niño.

International climate model outlook for the Indian Ocean Dipole

The Southern Annular Mode (SAM) index is currently neutral and is forecast to reach positive SAM thresholds in the coming days. During winter, a positive SAM often has a drying influence for parts of south-west and south-east Australia.

Southern Annular Mode (SAM) daily index

These climate outlooks are generated by ACCESS–S (Australian Community Climate Earth-System Simulator–Seasonal). ACCESS–S is the Bureau of Meteorology's dynamic (physics-based) weather and climate model used for monthly, seasonal, and longer-lead climate outlooks. For further information, go to http://www.bom.gov.au/climate/ahead/about/.

The Bureau of Meteorology’s latest rainfall outlook for July 2023 indicates drier than average conditions are expected across much of Australia.

The ACCESS-S climate model suggests that there is a 75% chance of rainfall totals between 10 and 50 millimetres across eastern New South Wales, scattered areas of coastal Queensland, Victoria, southern South Australia, much of Tasmania, and the southwest of Western Australia. Rainfall totals in excess of 100 millimetres are expected across western Tasmania and far southwest Western Australia.

Across cropping regions, there is a 75% chance of rainfall totals of between 10 and 25 millimetres across southern New South Wales and much of Victoria, and between 25 and 50 millimetres in South Australia and Western Australia. July rainfall totals are expected to be below 10 millimetres in the remaining cropping regions. Given the very dry conditions during May and the start of June, these probable low one-month rainfall totals are unlikely to be sufficient to sustain average levels of crop production, particularly in northern New South Wales and northern Queensland growing regions.

Rainfall totals that have a 75% chance of occurring in July 2023

The rainfall outlook for July to September 2023 suggests that below median rainfall is likely to very likely (60% to greater than 80% chance) for much of Australia. However, there is close to equal chances of above or below median rainfall for parts of Western Australia, tropical Queensland and coastal New South Wales, as well as in the southern Tasmania.

Bureau of Meteorology rainfall outlooks for July to September have greater than 55% past accuracy across most of Australia. Outlook accuracy is greater than 65% across large areas of eastern Australia. However, there is low past accuracy for scattered areas of central and southwestern Australia.

Chance of exceeding the median rainfall July to September 2023

The outlook for July to September 2023 suggests there is a 75% chance of rainfall totals between 25 and 200 millimetres across central and eastern New South Wales, parts of south-eastern and coastal Queensland, southern parts of South Australia and Western Australia, and much of Victoria and Tasmania. Rainfall totals in excess of 200 millimetres are forecast for alpine regions of Victoria and New South Wales, part of coastal northeast Queensland, far southwest of Western Australia and western Tasmania.

In the cropping regions, there is a 75% chance of receiving between 25 and 100 millimetres New South Wales, Victoria, South Australia, south-eastern Queensland, and Western Australia between July and September 2023. In those areas that have benefited from soaking rainfall during early June, these falls are likely to be sufficient to support close to average plant growth. However, in areas with low soil moisture these probable low three-month rainfall totals are unlikely to be sufficient to sustain average levels of crop production.

Rainfall totals that have a 75% chance of occurring July to September 2023

The temperature outlook for July to September 2023 indicates that maximum temperatures across the northern Australia, coastal east and Tasmania are likely to be close to the 1990-2012 average (-1°C to +1°C) while warmer (above +1°C) across much of southern and central Australia. The daytime temperatures in parts of Western Australia are likely to be even warmer (above +2°C). The minimum temperatures across most of Australia are expected to be close to the 1990-2012 average (-1°C to +1°C). The night-time temperatures in western parts of Western Australia are likely to be warmer that average (above +1°C).

Predicted maximum temperature anomaly for July to September 2023

Predicted minimum temperature anomaly for July to September 2023

Over the 8-days to 15 June 2023, an intense low, cold fronts and trough will generate showers up to 100 millimetres over parts of southern and central New South Wales, Victoria, far southwest Western Australia, parts of southern South Australia, and across Tasmania. A high-pressure system will keep the remainder of the country dry.

Rainfall totals of between 10 and 50 millimetres are expected across central and southern New South Wales, southern Victoria and parts of central and western South Australia. Little to no rainfall is expected across remaining cropping regions. This rainfall should be sufficient to allow for the germination and establishment of dry sown crops, and benefit soil moisture levels and the growth of earlier sown crops.

Total forecast rainfall for the period 8 June 2023 to 15 June 2023