Dry with warm days
The 2019–20 financial year (July 2019 to June 2020) was drier than average over much of Australia. After a very dry end to 2019, rainfall returned to eastern Australia in the first half of 2020. Rainfall was above average across large areas of New South Wales and Victoria from January to April, but the 12 months ended with Australia's fourth-driest June on record. Daytime temperatures were warmer than average across most of the country, including large areas of the west and east that had their highest mean maximum temperature on record for the year ending 30 June. Night-time temperatures tended to be closer to average but were still highest on record over parts of Western Australia.
Sixth-driest on recordAustralian total rainfall for 2019–20 was 24% below average, the sixth-driest on record and driest since last financial year (see Figure 1, Figure 2, and Table 1). The consecutive dry years resulted in Australia's second-driest 24-month period, ending June, on record.
The second half of 2019 was very dry in most areas of the country, including Australia's driest December on record. Rain returned to eastern Australia in early 2020, with above average rainfall from January to April across much of the Murray–Darling Basin. However, high pressure systems dominated over central and southeastern Australia in May and June and the financial year ended with the country's fourth-driest June on record.
Rainfall totals for the financial year were below average across large areas of the country. That included areas of very much below average rainfall in:
- western and southern Western Australia;
- much of South Australia away from the southeast;
- southern Northern Territory and parts of the Top End;
- southeastern Queensland;
- far western New South Wales; and
- far eastern Victoria into neighbouring parts of southern coastal New South Wales.
Rainfall totals were above average in western Tasmania, an area east of Melbourne into West Gippsland, and in isolated patches across northern and central Western Australia and in the Northern Territory.
In July 2019, root-zone soil moisture was already below to very much below average over large areas of the country, perhaps most notably in the northern Murray–Darling Basin (see Figure 3). A very dry end to 2019 exacerbated conditions. By December 2019, root-zone soil moisture was lowest on record in many areas, including along parts of the Eastern Seaboard, southeast Queensland, scattered parts of southwest Western Australia, and in the Top End of the Northern Territory after a late start to the monsoon.
In early 2020, rainfall returned to large parts of eastern Australia and by April, root-zone soil moisture was above average over much of the Murray–Darling Basin, Tasmania, and South Australia. However, Australia's dry June again saw soils drying out and by the end of the financial year there were large areas of near-average to below average soil moisture across the country.
Third-warmest on record
Australia experienced its third-warmest financial year on record, behind only 2015–2016 and 2018–19 (see Figure 4 and Figure 5). The consecutive very warm years resulted in Australia's warmest 24- and 36-month periods on record, ending June. Daytime temperatures were especially warm during the past 12 months, with Australia's mean maximum temperature 1.67 °C warmer than average, the second-highest on record behind 2018–19 (+1.70 °C; see Table 2). Night-time temperatures were cooler than average over large areas at times during the past 12 months, resulting in a less extreme mean minimum temperature for the country as a whole, but still 0.80 °C above average and the eighth-highest on record.
Mean temperatures were above to very much above average across most of Australia, including areas of highest on record across much of southern Western Australia, neighbouring parts of South Australia and the Northern Territory, and southeast Queensland into northeast New South Wales. The above average mean temperatures were largely driven by the warmer than average days, with night-time temperatures closer to average or even cooler than average in some areas of southeastern Australia and parts of the north. However, minimum temperatures were still very much above average to highest on record for much of Western Australia. Some long-term sites in Western Australia had their warmest days and warmest nights on record for the financial year, including Kalgoorlie-Boulder, Meekatharra, and Onslow airports.
Humidity was below average for the 12 months, particularly across northern Australia, with mean 3pm vapour pressure more than 3 hPa below average across large areas of the Northern Territory, northern Western Australia, and isolated patches of Queensland.
High pressure systems dominated Australia's skies during the past 12 months, with the mean sea level pressure for the financial year more than 3 hPa above average over much of central Australia, some of the largest positive differences from average on the globe in 2019–20.
The continued hot and dry conditions across much of Australia during July to December 2019 affected water resources in all states, resulting in reduced water in the soil, storages, rivers, and groundwater. Higher rainfall since January 2020, particularly over southeastern Australia, resulted in some recovery in these resources.
Mostly below average streamflows
Poor rainfall and dry soils over much of Australia during the latter half of 2019 contributed to generally below-average streamflow across the whole country in 2019–20, particularly throughout southeastern Australia (Figure 6). In the Murray–Darling Basin (the Basin), most of the rivers had reached record low flows in December 2019. Very few rivers across the northern part of the Basin were flowing at all. Above-average rainfall across large areas of New South Wales and Victoria in the first half of 2020, particularly during February to April, resulted in some recovery, with flows occurring in all the major rivers within the Murray–Darling Basin. Streamflow in the lower Darling River reconnected with the Murray River in mid-April 2020 for the first time since January 2018. In February 2020, major flows from the Lower Balonne River into the Ramsar-listed Narran Lakes wetland system occurred for the first time in eight years.
The delayed onset of the monsoon period contributed to low flows in rivers across most of northern Australia, particularly in northern areas of Queensland (Figure 6). The streamflow in southwest Western Australia was also below average in 2019–20 due to very much below-average winter rainfall.
Increasing surface water availability
The dry conditions and below-average streamflows across southeastern Australia in 2019–20 meant that storage levels throughout most of the Murray–Darling Basin remained low, particularly in the northern part of the Basin (Figure 7). Figure 8 shows that although the storages remained low across the region, the storage volumes at the end of June 2020 were higher than at the same time last year. Storage volumes increased since February 2020 following higher rainfall across the region during February–April 2020; however, many areas of the Basin have experienced prolonged dry conditions and by the end of June 2020, significant follow-up rainfall was still needed to replenish these water storages. Figure 9 shows the storage level for the northern Basin in June 2020 compared with the previous ten years.
Storages in northwestern Australia were also very low in June 2020 (Figure 7). In Lake Argyle, the normal filling and spilling of the storage had not occurred for three consecutive years due to poor wet season rainfall. By the end of 2019–20, the storage was only 40% full, the lowest level in almost 30 years.
In Sydney, 400 mm of rain in one week during February 2020 produced enough runoff to almost double the amount of water stored in Sydney's urban storages. The accessible water in the Sydney storages increased from 42% on 8 February to 81% on 18 February (Figure 10). Sydney water storages had been declining since July 2016. Level 2 water restrictions were introduced in December 2019 and Sydney's desalination plant was operating at full capacity to reduce pressure on surface water supply. Water restrictions were lowered to Level 1 on 1 March 2020 following the high rainfall in February.
Low groundwater levels in key regions
The ongoing drought in the Murray–Darling Basin during the latter half of 2019 resulted in widespread decline in groundwater levels. An example bore in the Lower Lachlan shows that levels increased since February 2020 (Figure 11) following higher rainfall across the region during February–April 2020; however, groundwater levels at the end of 2019–20 were still below average.
A dried than wet season in the Top End of the Northern Territory resulted in almost no groundwater recharge in the Katherine region for the second consecutive year. By the end of June 2020, groundwater levels in the region's Tindall aquifer were at their lowest levels in more than 20 years (Figure 11).
In the Perth region, groundwater levels in the Gnangara Mound remained well below average, reflecting the decline in rainfall since the 1970s. However, the improved rainfall conditions over the last four years have led to an increase in water levels since 2016. This rising trend has also been influenced by efforts to reduce and redistribute groundwater extraction (Figure 11).
Major climate influences
The Indian Ocean exerted a strong influence on Australia's climate during much of 2019–20. The positive phase of the Indian Ocean Dipole (IOD) during spring 2019 contributed to the dry conditions that persisted over much of Australia during the second half of 2019. During spring 2019, the IOD index reached the highest weekly values observed in the Bureau's dataset, which extends from 2001. The index peaked at +2.15 °C for the week ending 13 October 2019, well above the previous record of +1.48 °C for the week ending 5 November 2006. Values remained above the previous record from mid-September to mid-November. Values from NOAA's monthly IOD dataset suggest the 2019 positive IOD event was amongst the strongest on record, comparable to the very strong events of 1961, 1994, and 1997.
Typically, IOD events break down in late spring or early summer as the monsoon trough moves into the southern hemisphere, changing broadscale wind patterns over the IOD region, and returning sea surface temperatures to near average. However, the retreat of the Southwest Indian Monsoon was very slow during 2019, six weeks later than average and the latest on record. The transition of the monsoon trough into the southern hemisphere was very late, and the positive IOD persisted into the first week of January 2020.
In early 2020, the IOD returned to neutral and warmer than average sea surface temperatures off the northwest coast of Australia saw tropical moisture make its way south across the continent, often interacting with cold fronts from the south, to produce good rainfall for many areas of eastern Australia.
The tropical Pacific Ocean had less impact, with a neutral phase of the El Niño–Southern Oscillation (ENSO) persisting through much of the financial year.
A sudden stratospheric warming (SSW), when the stratosphere high above the South Pole rapidly heated, began at the end of August 2019, and was the strongest since 2002. This induced a negative phase of the Southern Annular Mode (SAM) from late October to late December, shifting the belt of westerly winds over the Southern Ocean northwards from their normal position. The temperature and rainfall patterns of spring and early summer 2019 were consistent with that negative SAM, which is typically associated with a reduction in rainfall over parts of eastern Australia owing to decreased onshore flow, but wetter conditions for western Tasmania and other areas of the southern coastline that are exposed to the enhanced westerly winds. Negative SAM in spring is also typically associated with warmer than average temperatures and an increased chance of spring heatwaves across southern and eastern Australia.
Later in the financial year, the SAM was positive for much of May and June 2020; during winter, a positive SAM typically means less rainfall for southwest Western Australia, southern Victoria, and Tasmania. The dry conditions over much of southern Australia during June were consistent with a winter-time positive SAM.
In addition to the influence of natural drivers, Australia's climate is increasingly influenced by global warming. Australia has warmed by more than one degree since 1910, with most of the warming occurring since 1950. The ocean waters around Australia have also warmed over the past century, and have been very warm to record warm consistently across the past two decades. The background warming trend can only be explained by human influence on the global climate. There has also been a significant decline in autumn and winter rainfall observed over southeast and southwest Australia in recent decades. The drying trend is particularly strong for May to July over southwest Western Australia since 1970, and for April to October over the southeast of the continent since 1999.The role of climate change is further discussed in State of the Climate.
Australia's driest December in 2019 brought to an end the country's driest calendar year on record and exacerbated the drought conditions in eastern Australia, with much of New South Wales in serious to severe rainfall deficiency at periods of 5 to 36 months. More details about the very dry conditions and their impacts on water resources can be found in Special Climate Statement 70: Drought conditions in eastern Australia and impact on water resources in the Murray–Darling Basin.
In spring 2019, extremely dry conditions and very much above average temperatures led to increased fire risk across New South Wales and Queensland. Many large bushfires were burning across southeast Queensland and northeast New South Wales by the second week of September. More information about the associated climate and weather conditions can be found in Special Climate Statement 71: Severe fire weather conditions in southeast Queensland and northeast New South Wales in September 2019.
Dangerous fire weather continued throughout spring and new bushfires started in areas further south. Details on some of these fires, and the antecedent conditions, can be found in Special Climate Statement 72: Dangerous bushfire weather and heat in spring 2019.
Significant heat affected large parts of central and southern Australia from 12 December 2019 as a slow-moving high pressure system over the Great Australian Bight allowed heat to build over the continent. Temperatures in the mid to high 40s were observed across large areas. As the hot air moved eastward, large areas of Australia approached or exceeded December daily maximum temperature records. For a number of locations, records were set for the hottest day for any time of the year.
On 17 and 18 December 2019, records were set for Australia's hottest day on record. The national area-averaged maximum temperature on the 18th was 41.9 °C, a whole degree above the value for the 17th (40.9 °C). Both these values exceeded the previous record of 40.30 °C set on 7 January 2013. The extreme heat during December also led to Australia's warmest week (7 days ending 24 December) and warmest month on record in terms of national area-averaged maximum temperature. Further details about the extreme heat during summer can be found in Special Climate Statement 73: Extreme heat and fire weather in December 2019 and January 2020.
Sea surface temperatures (SSTs) on the Great Barrier Reef (GBR) during February 2020 were the warmest for any month since instrumental records began in 1900, with temperatures 1.2 °C warmer than the long-term February average (1961–1990). Sea surface temperatures were elevated across the whole reef and there was widespread coral bleaching. This event is the third marine heatwave in five years, coming soon after the consecutive events of 2015–16 and 2016–17. There have now been three mass coral bleaching events on the GBR in the past five years. Further information about the high sea surface temperatures can be found in 2020 marine heatwave on the Great Barrier Reef.
The 2019–20 tropical cyclone season for the Australian region saw eight tropical cyclones compared to an average of eleven. The first tropical cyclone of the season was TC Blake, which formed on 4 January 2020, making it the second-latest start to the tropical cyclone season on record, behind 1986–87. It was also a late end to the season, with TC Mangga named on 21 May 2020 by the Tropical Cyclone Warning Centre (TCWC) Jakarta before the system moved southeast into the Australian region. The remnants of Mangga combined with a cold front to bring damaging winds, high tides, raised dust, and heavy rain to southwest Western Australia.
Coastal inundation was reported at low-lying locations around
Australia – minor inundation occurred during king tide events at Brisbane
Arguably the most significant coastal flood events, at least in terms of their rarity, were those produced by ex-Tropical Cyclone Mangga in Western Australia on 25 May 2020. This event included the second-highest hourly sea level observation recorded at Hillarys (near Perth) since the tide gauge was installed in November 1990, and fourth-highest sea level on record in 120 years of near-continuous observations at Fremantle. The high sea levels and large waves also caused significant erosion along the west coast of Western Australia; at one location near Bunbury, a beach lost sufficient sand to drop 3m vertically, rendering it inaccessible.
Between July 2019 and June 2020, total sea-ice cover around the Antarctic continent was mostly below the average of the 40-year satellite-based record. In October 2019, sea-ice concentration recovered to close-to average conditions for that time of the year before declining rapidly during November in the western part of the Australian Antarctic Territory (AAT) and to below average in the eastern part of the AAT. Further, the eastern Weddell Sea and the Ross Sea experienced a shortened sea-ice season (number of days with sea-ice cover in a given area). Only small regions of the offshore Bellingshausen Sea, eastern Amundsen Sea and the northern part of western Weddell Sea showed a slightly longer sea-ice season.
The annual maximum sea-ice extent was recorded on 30 September 2019 at 18.46 million square kilometres, the tenth-lowest in 40 years of record. The annual maximum sea-ice area was observed on 3 September 2019 at 14.78 million square kilometres, a value in the lower third of the 40-year record. On 19 February 2020, the pan-Antarctic sea-ice extent reached its annual minimum at 2.66 million square kilometres and the annual sea-ice area minimum was 1.65 million square kilometres on the same day.
In late September 2019, a large tabular iceberg calved off the Amery Ice Shelf, which is located between the Davis and Mawson stations and is one of the three largest ice shelves around the continent. The large iceberg was 1,636 square kilometres (about the size of Bathurst Island, Northern Territory) when it broke off. The Bureau of Meteorology continues to monitor the drift of the iceberg due to the threat it poses to shipping channels. As of June 2020, the iceberg is 130 km northeast of Mawson Station and drifting westward.
Both the mean maximum and mean minimum temperatures were warmer than average at Davis and Mawson stations, with a cooler than average March offset by several warmer than average months. Further east at Casey Station, despite April being much warmer than average, several cooler months saw mean temperatures for the financial year as a whole being slightly cooler than average.
At Macquarie Island, most months were warmer than average and the overall mean daytime and night-time temperatures for the financial year were about half a degree warmer than average. Total precipitation at Macquarie Island was 14% above average for the financial year after generally being close-to or above average during most months.
For more information, find area average data and time series for the financial year period, with maps for the 12-months periods ending June available from recent conditions. This current and historical climate information allows for comparison of climate impacts from one year to the next, and aligns with other reporting processes that occur over financial year periods.
This summary has been prepared using the homogenised Australian temperature dataset (ACORN-SAT version 2.0) for area-averaged temperature values and the observational dataset (AWAP) for area-averaged rainfall values and mapped analyses for both temperature and rainfall.
Australian weather extremes during the 2019–20 financial year
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