Weekly update - 10 September 2020
During the week ending 9 September 2020, cold fronts moved over southern Australia and moist onshore flow developed on the north-eastern coast, bringing moderate rainfall to isolated areas. Moderate falls in parts of the south-west Western Australian wheat belt are likely to support average yields and boost soil moisture as the winter cropping season begins to wrap up.
It is expected that cooling in the central Pacific Ocean will continue and a La Niña event is likely to eventuate in spring. Similarly, large parts of the Indian Ocean are warmer than average and half of models surveyed are expected to exceed negative IOD in October. The development of these major climate drivers are potentially contributing to the above average spring rainfall outlook for parts of Australia.
There is a high chance that rainfall between October and December will be sufficient to sustain above average crop and pasture production through the remainder of spring in areas where soil moisture is close to average or above average. With the exception of parts of Western Australia, these highly probable rainfall totals – if realised - represent an excellent finish to the 2020 winter growing season across southern Australia and start to the 2020-21 summer cropping season and wet season across northern Australia.
Over the next eight days, cold fronts, troughs and onshore flow are expected to bring rainfall to parts of south-eastern and eastern Australia, with high-pressure systems expected to prevent rain bearing systems from moving further over Australia during the week. Across cropping regions, rainfall of between 5 and 25 millimetres is expected across Victoria and South Australia, and isolated parts of north-eastern and far southern New South Wales, and the eastern Western Australian wheat belt.
Water storage levels in the Murray-Darling Basin (MDB) increased between 2 September 2020 and 9 September 2020 by 133 gigalitres (GL). The current volume of water held in storage is 14,014 GL which represents 55 per cent of total capacity.
Allocation prices in the Victorian Murray below the Barmah Choke increased from $235 per ML from 3 September 2020 to $310 per ML 10 September 2020. Prices are lower in the Goulburn-Broken, Murrumbidgee and regions above the Barmah Choke, due to binding of the Goulburn intervalley trade and Murrumbidgee export limits, and the Barmah Choke trade constraint.
During the week ending 9 September 2020 cold fronts moved over southern Australia and moist onshore flow developed on the north-eastern coast, bringing moderate rainfall to isolated areas. Rainfall totals of between 10 and 50 millimetres were recorded across parts south-eastern Western Australia and northern and western Tasmania, as well as isolated parts of eastern New South Wales, eastern Queensland and far southern Victoria and south-eastern South Australia. Rainfall in excess of 50 millimetres was recorded across isolated parts of south-western Western Australia and western Tasmania.
In Australia's cropping regions, rainfall totals of between 5 and 10 millimetres were recorded across parts of the western and central Western Australian wheat belt and isolated parts of eastern New South Wales and south-western Victoria. Little to no rainfall was recorded across remaining cropping regions during the week ending 9 September 2020.
These moderate falls in parts of the south-west Western Australia wheat belt are likely to support average yields and boost soil moisture. The drier conditions across parts of New South Wales and Victoria which recorded substantial winter rainfall are likely to benefit production and alleviate water logging. In contrast, in regions that recorded below average rainfall during winter and have low soil moisture reserves these dry conditions are likely to be a concern for yield prospect and pasture production.
Rainfall for the week ending 9 September 2020
Understanding rainfall deficiencies
Long term rainfall deficiencies are monitored to help determine whether rainfall conditions have been favourable or unfavourable for catchment hydrology and what this means for irrigated agricultural production. If below-average rainfall continues over months and years, water storages are depleted. Dam and reservoir levels drop, river and groundwater levels fall (some may dry up completely).
Longer-term rainfall deficiencies during a growing season can also give an early indication of drought for dryland agriculture. However, analysis of previous production years is not usually the best indicator that a drought has finished and more normal production conditions have commenced. This is because seasonal conditions in past growing seasons can have little effect on conditions for agriculture in future growing seasons. For most of Australia's agriculture regions measures of soil moisture and pasture biomass provide a much more accurate assessment of conditions coming into a new growing season.
A comparison of long term deficiencies, soil moisture and pasture growth at the end of March 2020 in New South Wales can be used to highlight this point. While serious or severe rainfall deficiencies were evident across much of New South Wales as a result of very low rainfall during the previous (2019) growing season across southern Australia, relative root zone soil moisture and relative pasture growth was average to well above average for the start of the current (2020) growing season.
Rainfall deciles for the 12-month period 1 April 2019 to 31 March 2020
Relative root zone soil moisture for March 2020
Relative pasture growth percentiles for March 2020
For agriculture in southern Australia, each new growing season starts in autumn and finishes in early summer. In northern Australia the growing season extends from October to March. Key success factors include stored soil moisture for cropping systems in regions with suitable soils, combined with standing biomass in grazing regions.
Within season rainfall deficiencies provide some indication of what is likely to happen to soil moisture and crop and pasture production, but usually only some weeks or months after conditions have started to change. Short term deficiencies can be offset by stored soil moisture or alleviated by one or two substantial rainfall events, and so are not always a reliable indicator of a protracted downturn in crop and pasture production.
Much more direct estimates of soil moisture and pasture growth are available to track conditions leading into a growing season. These latter measures can also be combined with seasonal climate forecasts to anticipate conditions 3 months into the future.
Above average rainfall across large areas of Australia during August 2020 decreased short term deficiencies across south-western and central-eastern Australia. Reflecting this above average rainfall, root-zone soil moisture improved in August to average or better across large areas of central and southern Australia.
Serious or severe rainfall deficiencies for the 5-month period April to August 2020 are evident in Western Australia across most of the south-western half of the State, excluding parts of the Gascoyne, south coast and Central West District. Serious rainfall deficiencies are also affecting parts of south-east Queensland.
Across southern Western Australia the most severe short-term deficiencies remain in areas largely outside of the major agricultural regions and have had little impact on current crop development. While, rainfall totals for the growing season-to-date (1 April to 9 September) have been sufficient to maintain average crop yield potential, they have not been sufficient to build any meaningfully soil water store. As temperatures continue to increase into spring this lack of stored soil moisture is likely to impact final yield potential if timely and sufficient rainfall does not eventuate during the remainder of September.
Rainfall deficiencies for the 5-month period 1 April 2020 to 31 August 2020
Rainfall total for the southern wet season to date 1 April 2020 to 9 September 2020
Following a generally favourable winter cropping season-to-date in Australia, there is interest in how the remainder of the growing season may pan out. To gain some insight it is important to look at the major climate drivers—the Indian Ocean Dipole (IOD) and the El Nino Southern Oscillation (ENSO)—that influence spring rainfall across southern Australia. If La Niña and negative IOD conditions were to eventuate as forecast by a range of international climate models, these key climate drivers would become the major influencing factor for the spring and early summer rainfall outlook across eastern Australia.
If a La Niña and negative IOD conditions were to eventuate during spring, they are likely to create more favourable seasonal conditions for winter crop production than those embodied in the ABARES June 2020 edition of Agricultural commodities. This change in the status of major climate drivers and the resultant favourable seasonal conditions were central in developing ABARES winter and summer crop production forecasts embodied in the September 2020 edition of the Australian crop report. The enhanced probabilities of a wetter than average spring rainfall would also benefit spring pasture growth across eastern and northern Australia, summer crop production and an early northern rainfall onset.
The Bureau of Meteorology's ENSO Outlook remains at La Niña ALERT. This means that while the El Niño-Southern Oscillation is currently neutral, the chance of a La Niña forming during the southern hemisphere spring has increased to around 70% - roughly three times the normal likelihood.
A La Niña ALERT is not a guarantee that a La Niña will occur; it is an indication that some of the typical precursors of an event are in place. The potential impact of a La Niña event on agricultural production across southern Australia decreases if the event forms during spring or summer, as it has a shorter time to strengthen and will persist for a shorter time before it decays in late summer.
Cooling in the central and eastern Pacific Ocean has continued and has extended along the tropical coastline of South America. Six of the eight surveyed climate models suggest the cooling will exceed La Niña thresholds in spring.
Difference from average sea surface temperature observations 10 August to 16 August 2020
Atmospheric indicators are consistent with the early stages of La Niña development, with stronger than average trade winds, decreased cloudiness near the Date and the Southern Oscillation Index (SOI) has recently exceeded the threshold into La Niña values. Sustained SOI values above 7 typically indicate La Niña and the latest 30-day SOI value was 9.1 and the latest 90-day value was 2.3.
30-day Southern Oscillation Index (SOI) values ending 30 August 2020
The El Niño–Southern Oscillation (ENSO) is currently neutral and likely to remain neutral during early spring. It is expected that further cooling in the central tropical Pacific Ocean will occur and a La Niña event is likely to eventuate, with five of the eight surveyed models exceeding La Niña thresholds in October and six in November and December, potentially contributing to the above average spring rainfall outlook for parts of Australia.
Large parts of the Indian Ocean are warmer than average, however the Indian Ocean Dipole (IOD) has returned to neutral values after having surpassed the negative threshold for three consecutive weeks. IOD values at or below -0.4 must be sustained for eight weeks for this to be considered a negative IOD event. Half of the surveyed models are expected to exceed negative IOD thresholds during September, with the Bureau's model reaching negative IOD thresholds during October to December. These models suggest current negative IOD values are likely to be sustained during spring. A negative IOD typically brings above average rainfall to south-eastern Australia, and the Northern Territory and Queensland during spring and is associated with an early northern rainfall onset.
The Southern Annular Mode (SAM) is currently neutral and expected to become weakly positive neutral for the remainder of September. The SAM refers to the north-south shift of the band of rain-bearing westerly winds and weather systems in the Southern Ocean compared to the usual position. When SAM is positive during spring, this band of westerly winds is further south than normal. This allows for increased moist onshore flow from the Tasman and Coral seas and more rainfall across eastern Australia and a reduced chance of extreme heat.
The latest rainfall outlook released by the Bureau of Meteorology suggests above average rainfall is much more likely for central and eastern Australia, and drier than average rainfall is likely for isolated parts of north-western Australia and south-western Tasmania during September.
The rainfall outlook for October to December 2020 suggests that wetter than average conditions are likely for much of central and eastern Australia and drier than average rainfall is more likely for isolated parts of central Western Australia and western Tasmania. There are roughly equal chances of a wetter or drier than average three months across the remainder of the country (Bureau of Meteorology 'National Climate Outlook', 10 September 2019). Bureau of Meteorology rainfall outlooks for October to December have greater than 65% past accuracy across much of the eastern half of Australia and lower accuracy, less than 55%, across parts of south-western Queensland, central and southern Western Australia and south of the Northern Territory.
Chance of exceeding the median rainfall October to December 2020
©Commonwealth of Australia 2020, Australian Bureau of Meteorology Issued: 10/09/2020
The outlook for October 2020 suggests that there is a 75% chance of rainfall totals between 10 and 50 millimetres across much of eastern Australia and parts of central, northern and far southern Australia. Rainfall totals in excess of 50 millimetres are likely across parts of south-eastern Australia and much of Tasmania.
There is a high chance of recording close to average October rainfall totals across most agricultural regions, with the exception of south-western Australia. These totals are likely to support above average crop yield potentials across New South Wales and Victoria, and parts of South Australia.
In cropping regions there is a 75% chance of rainfall totals between 10 and 50 millimetres across much of New South Wales, Queensland, Victoria and South Australia. In Western Australian cropping regions there is a 75% chance of rainfall totals between 5 and 25 millimetres across most cropping regions, with rainfall totals up to 50 millimetres across isolated parts of the far south for October 2020.
Rainfall totals that have a 75% chance of occurring October 2020
The outlook for October to December 2020 suggests that there is a 75% chance of rainfall totals between 50 and 200 millimetres across much of eastern and northern Australia and parts of central and far southern Australia. Lower rainfall totals between 25 and 50 millimetres are likely across the much of inland Western Australia and the remainder of central Australia. Rainfall totals in excess of 200 millimetres are likely across parts of eastern New South Wales, eastern and northern Queensland, eastern Victoria, north of the Northern Territory and western Tasmania.
These totals indicate that the northern rainfall onset may occur across much of northern Australia during October to December. 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.
In many areas where soil moisture is close to average to above average for this time of year, there is a high chance of recording October to December rainfall totals sufficient to sustain above average crop and pasture production through the remainder of spring.
In cropping regions, there is a 75% chance of receiving between 100 and 200 millimetres across most of New South Wales, Queensland and parts of southern Victoria and central South Australia. Rainfall totals greater than 200 millimetres are likely across cropping regions in parts of central and south-eastern Queensland and north-eastern New South Wales. Rainfall totals between 25 and 100 millimetres are likely across cropping regions in northern and western Victoria, much of South Australia and the central and southern Western Australian wheat belt between October and December 2020.
With the exception of parts of Western Australia these high chance expected rainfall totals are equivalent to the seasonal median between (1990 and 2012) and represent an excellent finish to the 2020 winter growing season across southern Australia and start to the 2020-21 summer cropping season and wet season across northern Australia.
Rainfall totals that have a 75% chance of occurring October to December 2020
The temperature outlook for October to December 2020 indicates that temperatures are likely to be between 1°C to 2°C above the 1990-2012 average across parts of northern Australia during the night-time. Average (- 1°C to 1°C) daytime and night-time temperatures are likely for the remainder of the country (Bureau of Meteorology 'National Climate Outlook', 10 September 2020).
Predicted maximum temperature anomaly for October to December 2020
Predicted minimum temperature anomaly for October to December 2020
Cold fronts, troughs and onshore flow are expected to bring rainfall to parts of south-eastern and eastern Australia, with high-pressure systems expected to prevent rain bearing systems from moving further over Australia during the week. Rainfall totals of between 10 and 25 millimetres are forecast for parts of north-eastern New South Wales, eastern Queensland, Victoria, south-eastern South Australia and eastern Tasmania. Rainfall in excess of 25 millimetres is expected across western Tasmania and isolated parts of eastern Queensland.
In cropping regions, rainfall of between 5 and 25 millimetres is expected across Victoria and South Australia, and isolated parts of north-eastern and far southern New South Wales, and the eastern Western Australian wheat belt. Little to no rainfall is expected across cropping regions in Queensland and remaining cropping regions in New South Wales and Western Australia during the next eight days.
Total forecast rainfall (mm) for the period 10 September 2020 to 17 September 2020
Current indicators – 10 September 2020
AUD/USD Exchange rate 09-Sep US$/A$ 0.73 0.73 -1% 0.68 6% chart
Wheat – US no. 2 hard red winter wheat, fob Gulf 09-Sep US$/t 242 243 -1% 205 18% chart
Coarse Grains – US no. 2 yellow corn, fob Gulf 19-Aug US$/t 150 145 3% 157 -4% chart
Canola – Rapeseed, Canada, fob Vancouver 09-Sep US$/t 413 411 0% 363 14% chart
Cotton – Cotlook 'A' Index 09-Sep USc/lb 71 71 0% 73 -3% chart
Sugar – Intercontinental Exchange, nearby futures, no.11 contract 09-Sep USc/lb 12 12 -4% 11 11% chart
Wool – Eastern Market Indicator 09-Sep Ac/kg clean 890 858 4% 1,754 -49% chart
Wool – Western Market Indicator 09-Sep Ac/kg clean 922 895 3% 1,995 -54% chart
Milling Wheat – APW, Port Adelaide, SA 09-Sep A$/t 328 324 1% 366 -10% chart
Feed Wheat – ASW, Port Adelaide, SA 09-Sep A$/t 312 309 1% 354 -12% chart
Feed Barley – Port Adelaide, SA 09-Sep A$/t 264 263 0% 328 -20% chart
Canola – Kwinana, WA 09-Sep A$/t 642 637 1% 656 -2% chart
Grain Sorghum – Brisbane, QLD 09-Sep A$/t 356 360 -1% 424 -16% chart
Beef – Eastern Young Cattle Indicator 02-Sep Ac/kg cwt 778 786 -1% 483 61% chart
Mutton – Mutton indicator (18–24 kg fat score 2–3), Vic 02-Sep Ac/kg cwt 549 589 -7% 611 -10% chart
Lamb – Eastern States Trade Lamb Indicator 02-Sep Ac/kg cwt 681 669 2% 789 -14% chart
Pig – Eastern Seaboard (60.1–75 kg), average of buyers & sellers 26-Aug Ac/kg cwt 318 309 3% 354 -10% chart
Goat – Eastern States (12.1–16 kg) 02-Sep Ac/kg cwt 843 773 9% 902 -7% chart
Live cattle – Light steers ex Darwin to Indonesia 02-Sep Ac/kg lwt 355 355 0% 310 15% chart
Dairy – Whole milk powder 02-Sep US$/t 2,884 2,936 -2% 2,973 -3% chart
Dairy – Skim milk powder 02-Sep US$/t 2,663 2,608 2% 1,959 36% chart
Dairy – Cheddar cheese 02-Sep US$/t 3,428 3,442 0% 3,596 -5% chart
Dairy – Anhydrous milk fat 02-Sep US$/t 3,852 3,873 -1% 5,629 -32% chart