Drought

Above average rainfall for parts of the southeast, but a very dry month for the west of Australia

May rainfall was below to very much below average across most of Western Australia, with a large number of stations, mostly in the west of the State, observing their driest May on record. Rainfall deficiencies have increased in extent and severity at each of the 5-, 8- and 14-month timescales across the South West Land Division and Southeast Coastal District in Western Australia.

Rainfall for the month was also below average across parts of the eastern mainland taking in coastal New South Wales, eastern Queensland as far north as the Central Coast, and parts of central Queensland.

Conversely, the passage of surface pressure troughs and cold fronts throughout the month brought above average May rainfall for some parts of southern South Australia, much of Victoria, and inland southern New South Wales. Rainfall for the month was also above average for most of the northern half of the Northern Territory, the far northeastern Kimberley, northern Cape York Peninsula and far southwest in Queensland, and an area of Central Australia. That said, average May rainfall tends to be fairly low for northern Australia away from east coast Queensland, so these totals do not much affect longer term deficiencies.

While above average May rainfall has been sufficient to lift large areas of Victoria and southern South Australia out of serious rainfall deficiency at the 5- and 8-month timescales (rainfall in the lowest 10% of historical totals for similar periods), above average rainfall over a prolonged period is typically required to bring sustained relief from drought. Drought takes many forms, and an easing of rainfall deficiencies does not automatically mean an end to agricultural, hydrological, or societal drought.

Meteorologists typically look for the following as an indication of significant relief from serious rainfall deficiencies over periods which have lasted up to around one year in duration:

• Total rainfall during the past month already in decile 3 or above for the three-month period commencing that month, or
• Rainfall for the past three months has been in decile 7 or above for that three-month period.

Neither of these conditions have yet been met over southeastern Australia, and rainfall for both the 5-month and 8-month period remains below average (in the lowest 30% of historical records for similar periods). Anomalies are broadly on the order of 50 mm to 100 mm below average rainfall for both periods, rising to 100 mm to 200 mm over central to northeastern Victoria and West Gippsland, and in excess of 150 mm over western Tasmania for the 8-month period.

Whilst the Drought Statement focuses on rainfall deficiencies for periods up to two years duration, the Bureau of Meteorology monitors rainfall deficiencies and impacts on water resources on longer timescales such as the current severe multi-year drought affecting large parts of eastern Australia. We have special climate statements on this long-term drought and recently the drought and its impact on water resources where we explore this current drought more deeply, we will update these statements as the situation continues.

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. Many of the areas which are affected by rainfall deficiencies as discussed in the current Drought Statement are also affected by these clear declining long-term rainfall trends. For large areas of both southeastern and southwestern Australia, rainfall for the past 20 years (June 1999 to May 2019) has been in the lowest 10% of historical records, and in some areas has been record low.

The role of climate change in rainfall reduction over southern Australia is further discussed in State of the Climate 2018.

The Climate Outlook for winter (June to August) indicates a low chance (less than 35%) of exceeding median winter rainfall over most of eastern Australia and southern South Australia, and a strong probability of warmer than average temperatures over nearly all of Australia. While there is a roughly equal chance of above or below media rainfall for winter overall across southwestern and southern Western Australia, there is a lower than average chance of exceeding median winter rainfall directly along the coastline in the southwest and south, and for July across South West Western Australia more broadly.

5-month rainfall deficiencies

Above average May rainfall has significantly reduced rainfall deficiencies across much of Victoria, southern South Australia, and border regions of southern New South Wales that had emerged following a very dry first four months of 2019 for much of mainland southeastern Australia. Conversely, the past month was quite dry for the west of the country, resulting in a marked increase in rainfall deficiencies across western and south coast Western Australia.

For the 5-month period (January–May 2019), serious to severe rainfall deficiencies are evident across the South West Land Division, extending into the southwest Gascoyne, Southeast Coastal, and southern Goldfields districts in Western Australia. Along part of the west coast rainfall was the lowest on record for the period.

Serious or severe rainfall deficiencies were also evident across much of the interior of Western Australia, extending in the north through much of the Northern Territory away from the east and the Top End, and in the south through the Nullarbor Plain and western and central pastoral districts of South Australia. Deficiencies also affect pockets around the Eyre Peninsula and Mid North; pockets of the coastal Kimberley in Western Australia; along the border of South Australia and Victoria; an area spanning Victoria's Central District and West Gippsland; the east coast of Tasmania; and northeastern New South Wales and southeastern Queensland.

8-month rainfall deficiencies

A dry month for the west of Australia has increased rainfall deficiencies over large areas, with serious or severe deficiencies emerging across much of the South West Land Division in Western Australia, as well as deficiencies in the north of the State increasing.

Conversely, above average May rainfall has decreased deficiencies in much of Victoria, southeastern South Australia, and western Tasmania.

For the 8-month period from October 2018 to May 2019, serious to severe rainfall deficiencies are evident in large parts of the northern half of Western Australia, particularly the northern Kimberley and northern Interior District, and across much of the South West Land Division. Serious to severe rainfall deficiencies were also present across much of northeast of New South Wales except parts of the coast, adjacent southern border regions of Queensland from the southern Maranoa to the eastern Darling Downs, an area of the southern Central Highlands, and parts of the Capricornia and Wide Bay coasts in Queensland. Deficiencies are also in place across a very large area of the central Northern Territory and parts of the west coast of the Top End; parts of South Australia's western to central pastoral areas, and pockets of some agricultural areas in the south and eastern border region; much of West and South Gippsland in Victoria, and pockets of the southwest coast and far western Mallee; and in southern Tasmania.

Northern Australia receives the bulk of its rainfall between October and April (the northern wet season), so rainfall deficiencies during this period are particularly significant, and will not usually be removed before the following wet season. It is therefore likely the rainfall deficiencies over the north of Western Australia and the Northern Territory will persist until at least the start of the next wet season later this year.

14-month rainfall deficiencies

May rainfall has reduced deficiencies across central and western Victoria, and southern New South Wales, but to a lesser extent than the reduction in rainfall deficiencies seen at the shorter 5- and 8-month periods.

Conversely, rainfall deficits have increased in northern New South Wales and the southeastern quarter of Queensland, and across the South West Land Division in Western Australia.

Serious or severe rainfall deficiencies are in place for the 14-month period from April 2018 to May 2019 across most of the northeastern quarter of Western Australia, except parts of the inland Kimberley, extending into the far northeastern Gascoyne and western Pilbara, and are also present in parts of the western Pilbara and across the South West Land Division. Rainfall deficiencies also affect most of the Northern Territory away from the Top End and eastern border regions; most of central and eastern South Australia, away from the far northeast and far southeast; most of the Warrego and Maranoa, Darling Downs, Central Highlands and Capricornia districts in Queensland; large areas of western, central southern, and northeastern New South Wales, extending inland through the Central West Slopes and Plains and part of the South West Slopes, and a pocket around the Illawarra; areas of Victoria in the Mallee, Northern Country, Central, and West and South Gippsland districts; and in parts of Tasmania's east coast.

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Soil moisture

May saw an increase in relative lower-layer soil moisture (from 10 cm to 100 cm deep) across western New South Wales, and much of Victoria and southern South Australia, and Central Australia. Soil moisture has however decreased across eastern New South Wales, southeastern Queensland, eastern Tasmania, and the west of Western Australia.

Soil moisture for May was below average for most of eastern New South Wales; across the greater southeast of Queensland, extending into the Capricornia District; West and South Gippsland in Victoria, extending into neighbouring districts; most of the eastern half of Tasmania; pockets along the western border of Victoria, Queensland's Gulf Country, and central western South Australia; and in large areas circling around the west of Australia from the southern Top End in the Northern Territory, through the Kimberley and northwest Western Australia, to cover most of the southwestern quarter of Western Australia, extending into the south of the Goldfields District.

Lower-layer soil moisture was above average across much of the southern two-thirds of Queensland inland of the Capricornia and Maranoa and Warrego Districts, extending into northeastern South Australia and the southeast of the Northern Territory; across most of the western half of New South Wales, extending into central western and far northeastern Victoria; along the coast of South Australia from the Eyre Peninsula west to the Nullarbor Plain in Western Australia; pockets of coastal northern Australia from Cape York Peninsula, across the Top End, to the northern Kimberley; and other small areas including western Tasmania, Kangaroo Island and about Port Augusta, and pockets of Central Australia and Western Australia's southern Interior District.

The low soil moisture during May extends the run of dry months this year, making the average soil moisture for January–May 2019 very much below average over most of Australia except Queensland's central to far northern east coast, a large area of central to western Queensland, the northeastern tip of the Top End, and an area of Western Australia's southern Interior District.

• Following above average May rainfall over parts of coastal South Australia, Victoria, and inland southern New South Wales, deficiencies at the 5- and 8-month timescales have reduced in these areas
• May rainfall was below to very much below average for most of Western Australia and along the east coast in New South Wales and Queensland, extending into parts of central Queensland, increasing rainfall deficiencies, particularly in the west and south of Western Australia
• Lower-level soil moisture below average for May across much of Western Australia, the southern Top End in the Northern Territory, eastern New South Wales and southeast Queensland, West and South Gippsland in Victoria, eastern Tasmania; above average for much of Queensland away from the southeast, western New South Wales, and South Australia's West Coast District
• Severe multi-year drought affecting large parts of eastern Australia, as well as shorter-term rainfall deficiencies
• Warmer than average May across much of eastern Australia continues to add to moisture stress