A very dry month for the southeastern mainland increases rainfall deficiencies
April rainfall was below to very much below average for much mainland southeastern Australia, including Victoria, most of the southeastern quarter of South Australia, the eastern half of New South Wales and border regions of the west and south of that State. Below average rainfall extended into the inland southeast of Queensland, and affected eastern Tasmania, northern South Australia, most of the southern two thirds of the Northern Territory, and parts of western Queensland.
The persistence of strong high pressure systems over the southern Tasman Sea continued during April; this pattern has been a dominant feature for many months and again impeded the passage of cold fronts and intrusion of moist tropical air over the southeast of the continent. For the year to date (January–April), rainfall has been below to very much below average over much of Australia, and rainfall deficiencies have increased in extent and severity at each of the 4-, 7- and 13-month timescales across much of Victoria and southern South Australia.
In addition to a very dry start to the year for much of the country, it has also been the warmest January to April period on record for Australia.
The Climate Outlook for May indicates a lower than average chance of exceeding median rainfall across most of eastern Australia, and a strong probability of warmer than average temperatures. Over the longer period (May–July), the outlook is more neutral over eastern and southern Australia, meaning there is no strong tendency towards above or below average rainfall indicated during that time.
Despite above average April rainfall in parts of the west and north of the country, and in a band extending from Queensland's Central Coast, through parts of central and southern Queensland and into northwestern New South Wales, rainfall deficiencies persist.
The unusual length and severity of the current drought was discussed in a Special Climate Statement released last month.
Rainfall has been below average over very large areas for a prolonged period, extending beyond the 2-year timeframe that the Drought Statement traditionally encompasses. While the 25-month period has been removed from formal monitoring within the Drought Statement, Bureau climatologists will continue to track this long dry.
4-month rainfall deficiencies
The first four months of 2019 have brought a very dry start to the year, with April particularly dry for much of the mainland southeast, and a resulting increase in rainfall deficiencies.
Compared to last month, rainfall deficiencies have increased through most of Victoria, southern and western South Australia, much of the central to western Northern Territory south of the Top End, and along the eastern border of inland Western Australia.
Serious or severe rainfall deficiencies affect most of Victoria except the far northeast and far east of Gippsland; most of southern and central to western South Australia; most of the Northern Territory away from the Top End and the eastern border; the east of Western Australia's Interior District and the far southeast of that State, as well as pockets in the Southeast Coastal, Central West, and northern Kimberley districts; across northeastern New South Wales and southeastern Queensland; and along eastern and northeastern Tasmania.
Many farmers in southern Australia look to the autumn break—generally defined as the first significant rain event after summer—as the marker for the start of the crop and pasture growing season. In much of southern Australia that rain event has not yet come, although rainfall forecast for the first week of May might see some regions receive this much-anticipated rainfall.
7-month rainfall deficiencies
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. With little rain over areas affected by rainfall deficits during April, it is now likely these rainfall deficiencies will persist until next spring.
However, rainfall during the month decreased deficiencies in the Gascyone in Western Australia, and in Queensland's Central Highlands.
A dry month for much of the southeastern mainland has resulted in an increase in 7-month rainfall deficiencies in this part of the country, compared to last month.
Serious or severe rainfall deficiencies for the seven-month period starting October 2018 are apparent in the northern Kimberley, the north of the Interior District, and pockets of the western Pilbara and to the north of Perth in Western Australia; a very large area in the central Northern Territory and pockets of the western Top End coast; along the border of New South Wales and Queensland, and a pocket of the southern Central Highlands in Queensland; parts of the eastern half of South Australia, including the Eyre, Fleurieu, and Yorke peninsulas; most of the southern half of Victoria; and in the west and south of Tasmania.
13-month rainfall deficiencies
Rainfall during April has reduced deficiencies in parts of Western Australia's Gascoyne, southwestern Queensland and northwestern New South Wales. Conversely, rainfall deficits have increased in Victoria and southeastern South Australia, and generally continue with little change elsewhere.
Serious or severe rainfall deficiencies are in place across central to eastern South Australia except parts of the far northeast and far southeast; across much of northern, central southern and eastern Victoria; across much of the Riverina in New South Wales as well as much of the west and northeast of that State; along the southern border of Queensland, extending across the greater southeast to around Taroom and Rockhampton; much of the Northern Territory away from the eastern border and much of the Top End; and across much of the Kimberley, northern half of the Interior District, and adjacent eastern Pilbara in Western Australia, as well as areas in the Central West, South Coast, and Southeast Coastal districts.
Compared to March, there has been an increase in relative lower-layer soil moisture (from 10 cm to 100 cm deep) across parts of northern Australia, particularly about the coastal Pilbara, the southern and eastern Gulf of Carpentaria coast and Cape York, and across central Queensland to the east of the Northern Territory. Soil moisture has however decreased across the base of Cape York Peninsula, much of the Top End and the Kimberley, inland Western Australia, and the south of the Northern Territory and west of South Australia.
Soil moisture for April was below average for most of Victoria, South Australia away from the northeast, southeast Western Australia, much of the Northern Territory away from the Top End and the east of the Territory, the eastern half of the Kimberley, and the northeast of New South Wales.
Lower-layer soil moisture was raised to above average levels over much of Queensland following rain during April, soil moisture for the month also above average for pockets of New South Wales inland of the ranges and north of the Riverina, for northeastern South Australia, much of the eastern half of the Northern Territory, and areas along the coast of Western Australia between the western Kimberley and the northwestern Gascoyne, as well as along the inland edge of the South West Land Division and an area of the southern Interior District.
The low soil moisture during April extends the run of dry months this year, making the average soil moisture for January–April 2019 very much below average in many of these areas.
- April rainfall below to very much below average for much of mainland southeastern Australia, but above average for Western Australia's Gascoyne, areas around the northern coast of Australia, and in a band between Central Coast Queensland and northwestern New South Wales
- Above average rainfall in Queensland, but mostly over areas not experiencing serious or severe rainfall deficiencies, thus having little effect on rainfall deficits
- Rainfall deficiencies have increased across much of Victoria and southern South Australia
- Lower-level soil moisture below average for April across most of Victoria, South Australia, and the west of the Northern Territory; above average for much of Queensland, extending into adjacent areas
- Equal-seventh-warmest April on record for Australia continues a run of warm months, adding to moisture stress
Product code: IDCKGD0AR0
Soil moisture details are reported when there are periods of significant rainfall deficits.
Soil moisture data is from the Bureau's Australian Water Resources Assessment Landscape (AWRA-L) model, developed through the Water Information Research and Development Alliance between the Bureau and CSIRO.
See: Australian Landscape Water Balance.
What is drought?
Drought is a prolonged, abnormally dry period when the amount of available water is insufficient to meet our normal use. Drought is not simply low rainfall; if it was, much of inland Australia would be in almost perpetual drought. Because people use water in so many different ways, there is no universal definition of drought. Meteorologists monitor the extent and severity of drought in terms of rainfall deficiencies. Agriculturalists rate the impact on primary industries, hydrologists compare ground water levels, and sociologists define it by social expectations and perceptions.
It is generally difficult to compare one drought to another, since each drought differs in the seasonality, location, spatial extent and duration of the associated rainfall deficiencies. Additionally, each drought is accompanied by varying temperatures and soil moisture deficits.
Rainfall averages, variability and trends
- Average rainfall: How much rain do you expect?
- Rainfall variability: How consistent is rainfall in your area?
- Rainfall history: Check tables, graphs and data from your local weather station.
- Rainfall trends: Has your rainfall changed?
Lowest on record - lowest since at least 1900 when the data analysed begin.
Severe deficiency - rainfalls in the lowest 5% of historical totals.
Serious deficiency - rainfalls in the lowest 10% of historical totals, but not in the lowest 5%.
Very much below average - rainfalls in the lowest 10% of historical totals.
Below average - rainfalls in the lowest 30% of historical totals, but not in the lowest 10%.
Average - rainfalls in the middle 40% of historical totals.
Above average - rainfalls in the highest 30% of historical totals, but not in the highest 10%.
Very much above average - rainfalls in the highest 10% of historical totals.
For the week to 21 May 2019, rainfall was recorded in the south of Western Australia; the eastern half of the Top End and the southern half of the Northern Territory; the far north and coastal South Australia; southwestern and central Victoria; western and northern Tasmania; far northeastern New South Wales and along the east coast and northern interior of Queensland.
At the start of the week, ex-tropical cyclone Ann was located northeast of Cairns, and tracked west towards Queensland's north tropical coast. The system crossed the coast near Lockhart River, and brought showers and rain with heavy falls to the Cape York Peninsula and North Tropical Coast districts. Light falls were recorded across parts of the northern interior and central Queensland due to a surface trough that extended south from the tropical low through inland Queensland. The system moved into the Gulf of Carpentaria and brought showers and thunderstorms to Arnhem Land in the Northern Territory from early in the week.
Onshore flow brought light falls to southeastern Queensland and northeastern New South Wales throughout the week.
In the west, a cold front and pre-frontal trough generated an extensive cloudband that tracked across southwest Western Australia, generating light to moderate falls in the South West Land Division and southern parts of the State during the first part of the week.
By the middle of the week, the cloudband continued to track eastwards, with a surface trough extending north into Central Australia and generating thunderstorms and moderate falls in the southern half of the Northern Territory and northern South Australia. The cloudband also spiralled south into a low pressure centre over the Great Australian Bight. Widespread thunderstorm activity associated with the passage of the surface trough brought moderate falls to parts of the West Coast District, the Eyre and Yorke peninsulas, Kangaroo Island, and the southeast of South Australia. Light falls were reported in southwestern Victoria, while showers and thunderstorms produced moderate falls in western and northern Tasmania at the end of the week.
Rainfall totals in excess of 100 mm were recorded in far northeastern Queensland, including the highest weekly total of 164 mm at Tully Sugar Mill.
Rainfall totals in excess of 50 mm were recorded in small areas of the Upper North Coast in New South Wales, and in areas along the northeast coast of Queensland from the northern Cape York Peninsula south to around Innisfail.
Rainfall totals between 10 mm and 50 mm were recorded in southwest and southern Western Australia, in the eastern half of the Top End and southern half of the Northern Territory, in northern and coastal South Australia, western Tasmania, northeastern New South Wales and along the east coast and northern interior of Queensland. Scattered locations in Victoria also observed weekly totals in excess of 10 mm.
Little or no rainfall was recorded in remaining parts of Western Australia, the Northern Territory and South Australia; northwest and eastern Victoria; east coast and southeastern Tasmania; most of New South Wales except about the northeast coast; and Queensland away from the east coast and northern interior of the State.
Impact of recent rainfall on deficits
The Drought Statement, issued on 3 May 2019, discusses rainfall deficits over Australia for the 4-month (January 2019–April 2019), 7-month (October 2018–April 2019) and 13-month (April 2018– April 2019) periods. Rainfall deficit maps are available for these periods as well as for standard periods.
The maps below show the percentage of mean rainfall that has been received for the rainfall deficit period for the 4-month, 7-month and 13-month periods ending 21 May 2019.
Rainfall for the period 1 January 2019 to 21 May 2019
For the 4-month period, serious to severe rainfall deficiencies are evident across most of Victoria except the far northeast and east Gippsland; most of southern and central to western South Australia; the Northern Territory away from the Top End and eastern border; the east of the Western Australian Interior District and the far southeast and pockets of the Southeast Coastal, Central West and the far southeast of Western Australia; northeastern New South Wales and southeastern Queensland, and eastern and northeastern Tasmania.
Rainfall in the last week eased deficiencies is small areas of Central Australia and some parts of coastal South Australia, but had little impact on deficiencies at this time scale elsewhere.
Affected areas have received less than 50% of their average rainfall for the period, with most of the affected areas in the Northern Territory and northwestern South Australia receiving less than 20% of average, except a small area along the border of South Australia and the Northern Territory. Areas around the border of Victoria and South Australia have generally received less than 40% of average rainfall for the period.
Rainfall for the period 1 October 2018 to 21 May 2019
For the 7-month period, serious to severe rainfall deficiencies are evident in the northern Kimberley, the north of the Interior District, pockets of the western Pilbara and to the north of Perth in Western Australia; central areas of the Northern Territory and coastal pockets of the western Top End; along the border of New South Wales and Queensland, and an area of the southern Central Highlands in Queensland; parts of the eastern half of South Australia, most of the southern half of Victoria, and in the west and south of Tasmania.
The rain that fell in the last week eased deficiencies ever so slightly in central parts of the Northern Territory, but had very little impact on deficiencies in affected areas.
Affected areas in Tasmania, Victoria, southern South Australia, the northern Kimberley, and about the border of New South Wales and Queensland have generally received less than 70% of their average rainfall for the period. Areas of the central Northern Territory, central to northeastern South Australia, and remaining affected areas of Western Australia have generally received less than 40% of average rainfall for the period.
Rainfall for the period 1 April 2018 to 21 May 2019
Serious or severe rainfall deficiencies are in place at the 13-month period across central to eastern South Australia away from the far northeast and far southeast; across much of central southern and eastern Victoria, and along the border in the central north and northwest of that State; across much of the Riverina in New South Wales as well as much of the west and north of that State; most of southern Queensland, extending north to around Taroom and Rockhampton; much of the Northern Territory except parts of the southwest, east, and Top End; and across much of the Kimberley, northern half of the Interior District, and adjacent eastern Pilbara in Western Australia, as well as areas in the Gascoyne, and much of the South Coast and Southeast Coastal districts.
Rainfall in the last week has generally had very little impact.
Affected areas across inland areas of Western Australia, the Northern Territory, South Australia, and western New South Wales have generally received less than 40% of average rainfall for the period, while remaining areas closer to the coast and along the border of New South Wales and Victoria have generally received less than 70% of average rainfall for the period.
Product code: IDCKGRWAR0