Large areas of southern Australia have just experienced the driest June on record, with rainfall deficiencies impacting key winter cropping areas in WA, SA and Victoria.
June rainfall was below average for most of Australia, and lowest on record for much of inland northern and northeastern Victoria, adjacent inland southern New South Wales, southwest and western Western Australia, and eastern Tasmania. Rainfall was also below average for seasonally dry areas of northern Western Australia, the Northern Territory, and Queensland, and also below average for some areas of east coast Queensland which typically do receive rainfall during June.
Nationally, the area-averaged June rainfall was 62% below the long-term mean, coming in as the second-driest June on record. Across the country over 100 stations with more than 50 years of observations have reported their lowest June rainfall total on record. This very dry June was largely due to very much higher than average mean sea level pressure (MSLP) across southern Australia, associated with a positive phase of the Southern Annular Mode (SAM).
As a consequence of June’s exceptional dryness, large areas of inland New South Wales and Queensland are experiencing significant deficiencies at the shorter 3-month timescale, which are masked at the 4-month timescale due to above average rainfall during March along the eastern seaboard.
4-month rainfall deficiencies
Compared to the 3-month period ending May 2017, rainfall deficiencies have increased in both areal extent and severity along the west coast of Western Australia, with a large area around the Gascoyne coast, and smaller areas in the Central West and South West districts, observing lowest on record rainfall for similar March to June periods.
Rainfall deficiencies have also worsened on the Eyre Peninsula in South Australia, and have emerged on the Yorke and Fleurieu peninsulas, parts of the Adelaide region and the mid-North, and on Kangaroo Island; have emerged in West Gippsland and adjacent parts of northeastern Victoria; and have increased in Tasmania, now also affecting the west more broadly and the south of Tasmania.
Soil moisture in the lower layer (from 10 cm to 100 cm deep) decreased for June compared to May across most of Australia. The only areas to observe significant increases in lower layer soil moisture during the month were across the base of Cape York Peninsula, as rainfall received during May infiltrated the deeper soil.
Soil moisture for June was below average for the west and south of Western Australia; most of southern South Australia, except the far southeast; areas of western and southern Tasmania; eastern Victoria; areas of inland eastern and northern New South Wales; most of Queensland away from the east coast and Cape York Peninsula; the southern half of the Northern Territory and adjacent far northern South Australia.
Soil moisture for the month was above average for the Top End of the Northern Territory; the south of the Cape York Peninsula and Central Coast in Queensland; an area in northeastern New South Wales; scattered areas in inland Western Australia, near Derby in the Kimberley, and in central South Australia; and parts of far southeastern South Australia, the western half of Victoria, and adjacent parts of southwestern New South Wales.