A dry and warm twelve months
The 2018–19 financial year (July 2018 to June 2019) was drier than average over much of Australia, leading to an intensification of drought conditions over many parts of the country, especially in the northern half of the Murray-Darling Basin. Northwest Australia was also dry, with a delayed monsoon onset contributing to below average rainfall for the period as a whole. Extremely warm temperatures—it was the second-warmest financial year on record, with record-warm daytime temperatures—created additional water stress for many areas.
Dry in most areas, but wet in parts of Queensland
Australia's total rainfall during the 2018–19 financial year was 351.4 mm, 24% below average. It was the driest financial year since 1969–70 (see Figure 1, Figure 2, and Table 1) and the fifth-driest on record. Large areas of the country had very much below average rainfall (lowest 10 per cent) for the period and this saw an extension of the severe drought conditions in many parts of eastern Australia. For northwestern Australia, the drier than average wet season saw the Northern Territory experience its driest financial year since 1964.
The period began very dry for New South Wales and eastern parts of Western Australia. New South Wales had an especially dry July, with rainfall the fifth-lowest on record and the driest since the severe El Niño drought of 2002. These drier than average conditions exacerbated long-term drought conditions that had been in place since around April of 2017. September 2018 was the driest September on record for the country as a whole and the second-driest for Victoria. New South Wales saw a continuation of dry July to September periods, with 2018 the third-driest such period on record for the State, behind 2017, which was the second-driest. Such dry conditions during what is usually an important period for replenishing water resources in southern catchments added to the severity of drought conditions.
Rainfall was close to average across much of southern Australia during October to December. Exceptions were a large area southeastern Western Australia, which saw very much above average rainfall, and the western half of Tasmania, which had very much below average rainfall.
The northern wet season from October to April is when Northern Australia receives much of its rainfall. In 2018–19, northwest Australia had a delayed start to the monsoon, with an onset date at Darwin of 23 January—the equal third-latest since reliable records commenced in 1957. For the Northern Territory, it was the driest wet season since 1992–93, with total rainfall 34% below the long-term average.
Southern Australia continued dry into 2019. Tasmania had its second-driest January on record, though this was followed by above average rainfall in February, while Victoria had its driest April since 1997. In New South Wales and southern Queensland, it stayed largely drier than average with some average to above average rainfall in March, followed by a very much drier than average April in eastern New South Wales and southeastern Queensland. January and February were especially dry for northeastern New South Wales and southeastern Queensland. Large areas of these States had lowest on record rainfall for these two months. For Western Australia, it was a very dry second half of the financial year, with May the third-driest on record for the State. However, due largely to a very wet October and November 2018, parts of the Goldfields and Central Wheatbelt in Western Australia had a near-average or wetter than average twelve months.
Over the twelve-month period, central and northern Queensland were the only extensive areas of very much above average rainfall. This was partly due to record rainfall in late-January and February 2019 associated with an intense and very slow-moving monsoon low. March also saw above average rainfall in parts of western to central Queensland, as the remnants of ex-tropical cyclone Trevor tracked across the State.
Warmest mean maximum temperature on record
Australia experienced its second-warmest financial year on record (see Figure 3 and Figure 4). Daytime temperatures were especially warm, with Australia's mean daily maximum temperature 1.70 °C warmer than average, the highest on record (see Table 2).
Most of the country had very much above average maximum temperatures. Much of the Northern Territory, central and northern parts of Western Australia, northeastern New South Wales into southeastern Queensland, and central and southeastern Victoria saw record-warm daytime temperatures for the period. Minimum temperatures were also very warm. Much of southeastern Australia observed very much above average night-time temperatures for the 12-month period, with some areas of highest on record mean minimum temperatures in the Northern Territory and north central New South Wales into southern Queensland.
All individual months of the financial year were warmer than average for both mean temperatures and daytime temperatures. December and January were standout months, with the warmest on record mean maximum and minimum temperatures for Australia and several of the States and Territories. These two months saw widespread heatwaves across the country as detailed in Special Climate Statement 68: Widespread heatwaves during December 2018 and January 2019, with January 2019 being Australia's warmest month on record.
Record-warm temperatures in parts of eastern Australia exacerbated water stress and hence the intensity of drought conditions across the region.
The hot and dry conditions across much of Australia affected water resources in all States, resulting in reduced water in the soil, storages, rivers, and groundwater. The heavy rain in the latter part of the financial year in north-central Queensland and June rainfall in southwest Western Australia relieved some of the pressure on water resources in these areas.
Lowest soil moisture on record
Average soil moisture across Australia for the 2018–19 financial year was the lowest on record. The national average soil moisture in the top 100 cm was only 8.5%, lower than the previous record of 8.7% in 1914–15 and well below the long-term average of 12.0%.
The soil moisture deciles in Figure 5 indicate the moisture stress experienced by vegetation in the past twelve months and the severity of the agricultural drought across large areas of the country. Soil moisture across most of Australia was already drier than average in July 2018. As the year progressed into the summer, the soil continued to dry with areas of Queensland and New South Wales reaching lowest on record levels by February 2019. The recent autumn and early winter rainfall provided some relief to parts of southeastern Australia but in June 2019, soil moisture in large areas of New South Wales, Western Australia, and the Northern Territory remained very much below average. The very dry soil conditions resulted in limited runoff into rivers and storages with much of the rainfall that occurred being soaked up by the soil.
Mostly below average streamflows
Streamflow showed a stark contrast from the north to south of eastern Australia in 2018–19 (Figure 6). Northern Queensland saw highest on record annual flows (since 1975) in a number of rivers. Heavy rainfall in the second half of the financial year produced extensive flooding in Townsville, major flooding in the Burdekin River and significant flows into Lake Eyre (North) / Kati Thanda.
Through most of south eastern Australia, limited runoff due to low rainfall and dry soils resulted in very low streamflow. Lowest on record (since 1975) streamflow was recorded on both the east and west sides of the Great Dividing Range. In the Darling River system, streamflow remained low from the top reaches to the confluence with the Murray River and was the lowest on record (since 1975) at Bourke.
The below average monsoon rains and low groundwater levels contributed to low flows in rivers in northern areas of the Northern Territory and Western Australia. The streamflow in southwest Western Australia was around average in 2018–19 due to near-average winter rainfall.
Falling surface water availability
Total surface water storage volume for Australia at the end of June 2019 was down 12.5% compared to last year. Figure 7 highlights low storage levels in June throughout most of the Murray-Darling Basin and particularly low storage in the northern part of the basin due to the low rainfall, dry soils, and limited runoff. In contrast, a number of rural systems in northern Queensland had storage levels above 80% full, reflecting the heavy rainfall and flooding in the second half of the financial year.
For individual states, storage changes ranged from a decrease of 0.2% in South Australia to a 23.7% fall in Western Australia (Table 3).
In New South Wales, storage levels have steadily decreased over the past two years with little to no increase in the traditional winter-spring filling seasons. Despite near-to-average rainfall in the Sydney catchment area in June 2019, relatively dry antecedent soil moisture conditions resulted in little runoff. Sydney storage volumes fell to 51.6% by the end of June, down 16.8% from last year, prompting the introduction of water restrictions for Australia's largest city (Figure 8).
Storage levels in the northern Murray-Darling Basin dropped to less than 7% full by the end of June 2019, lower than any point during the Millennium Drought (Figure 9). While the storages in the northern Murray-Darling Basin are smaller than in the south, they crucially feed the Darling River system, which has consequently seen record low streamflow in the 2018–19 financial year.
Low groundwater levels in key regions
The ongoing drought in the Murray-Darling Basin resulted in widespread declines in groundwater levels (Figure 10). In 2018–19, annual peak groundwater levels in 83% of assessed bores in the Murray-Darling Basin were below average and, in 20% of bores, levels were the lowest on record and below the levels at the end of the Millennium Drought.
The failed monsoon season in the top end resulted in almost no groundwater recharge over 2018–19 in the Rural Darwin and Katherine regions with little recovery in groundwater levels in the wet season (Figure 11).
In contrast, groundwater levels in northeast Queensland remain high after several years of good rainfalls and recharge from recent floods. In the Perth region, groundwater levels in the Gnangara Mound remained well below the long-term average reflecting the decline in rainfall since the 1970s. However, the rate of groundwater level decline is slowing, with levels in some bores rising in 2018–19, driven by efforts to reduce and redistribute groundwater extraction and wet winter conditions (Figure 11).
Major climate influences
The Indian Ocean exerted a strong influence on Australia's climate at times during 2018–19. The positive phase of the Indian Ocean Dipole (IOD) during spring 2018 and again in late autumn to winter 2019 likely contributed to the dry conditions that persisted over much of Australia during the financial year. For much of the financial year, even when the IOD value was neutral, the gradient of sea surface temperatures across the broader Indian Ocean (warmer in the west, compared to average in the east) tended to shift rainfall patterns away from Australia.
The tropical Pacific Ocean had less impact, with a warm-neutral phase of the El Niño–Southern Oscillation (ENSO) persisting through much of the financial year. There were signs of a possible El Niño from late winter 2018, but the atmosphere and ocean had weak coupling at best, meaning a truly self-sustaining event didn't eventuate. However, El Niño-like weather patterns at times may have contributed to the drier than average wet season across northern Australia, where Darwin had its equal-third latest monsoon onset since 1957–58.
While the IOD exerted a drying influence during the year, a positive phase of the Southern Annular Mode (SAM) from late October 2018 to late December 2018 brought some rainfall relief to eastern mainland Australia during late spring and early summer as it directed more onshore conditions off the Tasman Sea and into eastern Australia.
In addition to the influence of natural drivers, Australia's climate is increasingly influenced by global warming. Australia has warmed by just over one degree since 1910, with most of the warming occurring since 1950. The ocean waters around Australia have also warmed significantly 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. The role of climate change is further discussed in State of the Climate 2018.
There has 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–July over southwest Western Australia since 1970, and for April–October over the southeast of the continent since 1999.
A major influence on this drying has been the strengthening and extension of the subtropical high pressure ridge during winter, shifting many potential rain-bearing weather systems south of the Australian continent. This southwards shift of frontal systems is an expected outcome of climate change.
Conversely, there has been an observed increase in rainfall over parts of northern Australia since the 1970s. This trend towards wetter years in the north is contributing to a slight increase in mean annual rainfall for Australia as a whole.
Below average rainfall and drought were constant companions during 2018–19. Australia's driest September on record exacerbated the abnormally dry conditions in eastern Australia and much of New South Wales was in serious to severe rainfall deficiency at periods of 6 to 18 months. Rainfall eased conditions in some areas during October and November, but a very dry first half of 2019 in many areas meant that impacts remained severe in much of eastern Australia and parts of the southwest.
The 2018–19 southern bushfire season was longer than average, with winter bushfires in southern areas of Australia in both 2018 and 2019. In August 2018, fires were reported in New South Wales, Victoria, and Queensland. One started near Marlo in Gippsland, Victoria, while another in the Bega Valley at Bemboka on the New South Wales south coast burnt 19 000 hectares. In June 2019, more than 2000 hectares were burnt in three separate fires in southwest Western Australia, the largest of which was near Jarrahwood.
Long-lived fires burnt for many weeks through large areas of Tasmania during the summer. Started by lightning strikes onto dry vegetation in mid-January, more than 178 000 hectares, or about 2.6% of Tasmania, was burnt by the end of the month. Fires also affected large areas of Victoria during summer, including more than 20 000 hectares burnt in steep terrain at Timbarra in Gippsland during January.
Severe thunderstorms affected central to southeast Queensland during October, with two reports of tornadoes, numerous reports of large hail, damaging winds, and heavy rainfall.
Starting in late November 2018, an extreme heatwave affected the tropical Queensland coast. Numerous fires started or flared during the heatwave event and by early December, over one million hectares had burnt in areas extending from just south of Cairns to the Gold Coast. Later in summer, an extended period of heatwaves over much of Australia began in early December 2018 and continued into January 2019. A persistence of stable and sunny conditions over much of the country, and a delayed onset of the Australian monsoon over northern Australia, created ideal conditions for heat build-up. The heatwave conditions contributed to summer 2018–19 being Australia's warmest on record.
On December 20, the eastern half of New South Wales saw widespread thunderstorms and hail that caused extensive property damage in Sydney, the Blue Mountains, and Central Coast regions. Insurance claims reached $1.271 billion, including almost 95 000 private and commercial motor vehicles damaged or destroyed.
The 2018–19 tropical cyclone season was the first since 2014–15 to feature at least six severe tropical cyclones in the Australian region. The strongest storms of the season were Veronica, Trevor, and Savannah, all of which developed in March 2019. Two tropical cyclones, Lili and Ann, developed during May, making for a later than average end to the season.
An active monsoon trough and slow-moving low pressure system produced heavy rainfall and flooding in tropical Queensland from late-January into early February 2019. Flooding affected Queensland's tropical coast between Daintree and Mackay, and was particularly extensive and long-lived in the Gulf Country. Western and central Queensland received further widespread moderate to locally heavy falls from ex-tropical cyclone Trevor in March, with floodwaters slowly making their way south to partially fill Lake Eyre (North) / Kati-Thanda.
A particularly widespread coastal inundation event affected many low-lying coastal areas of Queensland and New South Wales from 18–21 February, 2019. Salt-water inundation of roads, parks, walking paths, and other coastal assets near estuaries and tidal rivers was reported in numerous locations, especially around Brisbane and the Gold Coast. The highest sea level reported in Brisbane during the event was 2.78 m at 10am (local time) on the 20th. Analysis of the event indicates that this was a tidal inundation event, with flooding due primarily to the gravitational effects of the sun and moon on the Earth, superimposed on the trend of increasing mean sea level. This was despite the presence of tropical cyclone Oma offshore, which had negligible contribution to water levels in sheltered coasts such as bays, estuaries, ports, and tidal rivers where impacts were reported.
Between July 2018 and June 2019, sea ice extent and area around the Antarctic continent were both generally much below the average over the long-term satellite-based record. But those general observations mask varying basin-scale values. In the Australian Antarctic Territory (which covers much of the Indian Ocean Sector and the Western Pacific Ocean Sector), such varying anomalies showed up as below average extent and area between roughly 60°E and 100°E (with accompanying minimal sea-ice concentration/area) and slightly above average conditions further east and west.
The annual maximum sea ice extent was recorded in late September 2018 at 18.22 million square kilometres, marginally up from the 2017 value but still the fourth-lowest in 40 years of record. Maximum sea ice area also occurred in late September at 14.56 million square kilometres, the ninth-lowest on record. The annual minimum sea ice extent occurred in late February 2019 at 2.44 million square kilometres, the seventh-lowest on record, with the minimum sea ice area 1.62 million square kilometres and the eleventh-lowest on record.
Australia's Antarctic bases of Mawson and Davis were warmer than average overall, whilst Casey was a little cooler than average. August was exceptionally warm at Mawson and Davis, and the mean maximum temperature for the financial year at Mawson was 0.7 °C above average, the highest for the site since 1991–92.
It was a record warm financial year on sub-Antarctic Macquarie Island, with the mean maximum and mean minimum temperature 1.0 °C above average and 0.1 °C above the previous record from 2016. Total precipitation of 1134 mm made it Macquarie Island's eleventh-wettest financial year in 66 years of record. Precipitation has generally been increasing at Macquarie Island over the last few decades.
Why do we report over calendar years and financial years
The Bureau of Meteorology routinely reports on Australia's climate each month, each traditional season, and each calendar year. But the climate does not always follow those periods—seasonality in climate varies markedly across Australia and there is no single period that is universal for all regions and climate features. For example, the climate in Australia's north is more characterised by a "wet season" (typically October to April) and a "dry season", with the first of these occurring across two calendar years.
Drivers of Australia's climate such as El Niño can have a large impact on year-to-year rainfall variability. El Niño can impact Australia's climate from winter of one year to autumn of the following year, with the largest impact in the year that the event starts. Analysing Australia's climate over the financial year captures these important impacts rather than splitting them between two calendar year periods.
Reporting on climate over 12-month periods that do not match the calendar year is not new. The Bureau of Meteorology's water reports (National Water Account and water assessments) discuss the climate over the water year, also defined as the 12 months from July to June.
The July to June period cannot be universally applied, but reports such as this can capture many climate drivers and impacts that may occur over calendar year boundaries and be seamlessly integrated with our water reports.
Outlook for the rest of 2019
January to June 2019 has been Australia's second-warmest first six months of the year on record for mean temperature (behind January to June 2016). The climate outlook indicates that warmer than average days are likely for much of the country during winter and early spring. So, we already know that the 2019 calendar year is highly likely to be warmer than the long-term average and the outlook increases the likelihood that 2019 will be amongst Australia's warmest years on record.
Rainfall averaged over Australia has been very much below average for the first six months of the year (driest January to June period since 2005). A positive Indian Ocean Dipole (IOD) event is likely throughout winter and spring 2019, which would typically result in below average winter–spring rainfall over southern and central Australia. This makes it likely that 2019 will be a drier than average year for Australia as a whole.
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, released in December 2018) for area-averaged temperature values and the observational dataset (AWAP) for area-averaged rainfall values and mapped analyses for both temperature and rainfall.