A rather wet December eases deficiencies in the southeast
Rainfall for December was below to very much below average for most of the Northern Territory and most of Queensland, and for most of the Goldfields region of Western Australia.
Monthly rainfall totals were above average along the west coast of Western Australia and along the path of tropical cyclone Hilda, extending from the western Kimberley through the northeastern side of the Interior District to about Wiluna, from southeast Western Australia through western and most of southern South Australia, southern New South Wales, the eastern half and northern border regions of Victoria, and eastern Tasmania
A heavy rainfall event in the first four days of December saw large areas of northern Victoria and southern New South Wales receive two to three times the average total December rainfall, with many sites in Victoria, southern New South Wales, and northern Tasmania observing their wettest December day on record. Storms also brought short-lived heavy rainfall to central and eastern Victoria and southeastern New South Wales at other times during the month.
December rainfall has eased deficiencies across the southeast of Australia at both the 7- and 10-month timescales, particularly in inland New South Wales and in Gippsland in Victoria.
7-month rainfall deficiencies
Serious to severe rainfall deficiencies persist in areas of the western to central Pilbara in Western Australia. Deficiencies are also present at a number of scattered locations across the south of Western Australia and near Port Augusta in South Australia, far eastern Victoria, and central to western Queensland. Larger pockets of deficiencies are present in central eastern New South Wales roughly between Tamworth and the Illawarra, and along the east coast of Tasmania.
Compared to the 6-month period ending November, deficiencies have eased in affected areas of southeastern Australia and South Australia.
10-month rainfall deficiencies
Rainfall deficiencies persist along the west coast of Western Australia between about Exmouth and just north of Perth, extending inland through part of the South West Land Division and just into the southwest of the Goldfields District. Deficiencies also persist in an area around Ceduna in coastal South Australia, and scattered pockets of western and central Queensland. Compared to deficiencies for the 9-month period ending November, deficiencies have increased in affected areas of Queensland.
Rainfall during the past month has largely cleared deficiencies at this timescale in Gippsland in Victoria and along the east coast of Tasmania, although small pockets of serious deficiencies persist in both regions.
Soil moisture in the lower layer (from 10 cm to 100 cm deep) for December increased across much of southern Australia, particularly the mainland southeast, while decreasing compared to values for November across Queensland and the coastal north of Australia.
Soil moisture was above average across much of southeastern Western Australia, most of South Australia, much of the Northern Territory, most of Victoria, most of New South Wales away from the central coast and northeast, and the coastal southeast of Queensland. Soil moisture was also above average along the west coast of Western Australia in the southern Pilbara and Gascoyne, and for scattered pockets of the Kimberley and Top End.
Lower-layer soil moisture was below average for areas of New South Wales between the central coast and Tablelands, reaching just into Queensland's Darling Downs, scattered small pockets of Queensland, along the west coast of Tasmania, and in areas of Western Australia mostly around the Goldfields District and inland Pilbara.
- December rainfall above to very much above average for eastern and northern Victoria, southern New South Wales, eastern Tasmania, much of southern South Australia, along the west coast of Western Australia and from the western Kimberley to central Western Australia
- Rainfall during December below average for much of the Northern Territory and Queensland
- Serious to severe rainfall deficiencies remain at the 7-month timescale in the Pilbara in Western Australia, and small areas of eastern Australia, particularly in central eastern New South Wales and the east coast of Tasmania
- Serious to severe rainfall deficiencies are evident at the 10-month timescale near the west coast of Western Australia, and areas of central and western Queensland
- Lower-layer soil moisture was below average for December in most of Queensland, the eastern Top End, parts of northeastern New South Wales, and much of Tasmania
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 16 January 2018, rainfall was recorded in most of Western Australia, the Northern Territory, northern and northwestern Queensland, the eastern half of New South Wales, Victoria and Tasmania.
At the start of the week, the monsoon trough over the Australian northwest coast and a developing tropical low near the west Kimberley in Western Australia produced extensive thunderstorms in the Top End of the Northern Territory and the Kimberley coast, with tropical moisture streaming southeast into South Australia. A surface trough and upper level disturbance in southwest Western Australia produced an active cloudband with isolated, embedded showers and thunderstorms. Moderate rainfall totals were recorded over southern Western Australia and western parts of South Australia. In the east, a surface trough moving across southeastern Australia produced thunderstorms with light to moderate fall in eastern New South Wales and Tasmania.
The tropical low developed into a tropical cyclone on 11 January, named tropical cyclone Joyce. The system tracked southwards and made landfall in the far west Kimberley coast near Wallal the next day. Tropical cyclone Joyce soon weakened to a tropical low and moved southwest through the Pilbara and northern Gascoyne. Heavy rainfall with localised very heavy falls was recorded along the system's passage about the western Kimberley, Pilbara and Gascoyne, with moderate falls recorded across much of northern Australia and central Australia, while a series of surface troughs delivered moderate falls across southern Western Australia and South Australia, also. Widespread light to moderate falls were also recorded in southeastern Australia, including Tasmania during the middle of the week.
From the latter part of the week, ex-tropical cyclone Joyce tracked south parallel to the west coast of Western Australia. The system brought widespread moderate to heavy falls from the northwest to the southwest of Western Australia Heavy rainfall with daily totals in excess of 100 mm around the Perth area saw some January daily rainfall records at the end of the week. An extensive surface trough across the tropical north also produced thunderstorms with moderate rainfall to the northern and central Western Australia, the western Top End in Northern Territory, and the Cape York and tropical north coast of Queensland.
Rainfall totals exceeding 100 mm were recorded in parts of the northwestern Top End in the Northern Territory, and along the Kimberley and Gascoyne coasts and adjacent inland districts; also in areas of the southwest coast of Western Australia. The highest weekly total was 310 mm at Wallal Downs in Western Australia.
Rainfall totals between 50 mm and 100 mm were recorded in areas of northern and eastern Queensland, in areas of eastern New South Wales, far eastern Victoria, and in the southwest and northwest of the Northern Territory. Similar totals were recorded in the Kimberley, Pilbara, parts of the Gascoyne, central interior, and along the southwest coast of Western Australia surrounding heavier falls.
Rainfall totals between 10 mm and 50 mm were recorded in northern, western and southwestern parts of Western Australia, southwest and northwest South Australia, central and eastern Victoria, much of the eastern half of New South Wales. Similar totals were recorded in southern, western and northwestern parts of the Northern Territory, and northwestern and northern Queensland.
Little or no rainfall was recorded in eastern inland parts of Western Australia, northeastern South Australia, northwestern Victoria, western New South Wales, southern Queensland and some eastern parts of the Northern Territory.
Impact of recent rainfall on deficits
The Drought Statement, issued on 9 January 2018, discusses rainfall deficits over Australia for the 7-month (June 2017–December 2017) and 10-month (March 2017–December 2017) periods. The rainfall deficit map is available for this period 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 7- and 10-month periods ending 16 January 2018.
Rainfall for the period 1 June 2017 to 16 January 2018
Serious to severe deficiencies persist at the 7-month period in areas of the western to central Pilbara in Western Australia. Deficiencies are also evident in central eastern New South Wales and along the east coast of Tasmania; and in scattered locations across the south of Western Australia and near Port Augusta in South Australia, far eastern Victoria, and central to western Queensland.
Rainfall in the last week has slightly eased deficiencies in the Pilbara, as affected areas have received less than 40% to 50% of the average for the period. Remaining affected areas have generally received between 40% and 60% of average.
Rainfall for the period 1 March to 16 January 2018
Serious to severe rainfall deficiencies persist at the 10-month period persist along the west coast of Western Australia between about Exmouth and north of Perth, extending inland east to parts of the South West Land Division and southwest of the Goldfields District. Deficiencies are also present in scattered parts of western and central Queensland, and near Ceduna in South Australia.
Rainfall in the last week has eased deficiencies in the Pilbara and areas along the west coast, south of the Gascoyne. Affected areas have received less than 50% to 70% of the average for the period.
Affected areas in far western Queensland received less than 30% of the average, while areas in central Queensland have received between 30% and 50% of the average for the period. Affected areas in South Australia, eastern Victoria and Tasmania received less than 70% to 80% of the average for the period.
Product code: IDCKGRWAR0