Welcome to the Climate and Water Outlook for July–September 2017. June has been very dry overall for much of Australia. Outlooks suggest dry and warm conditions are likely to extend into early spring. First, let's look at recent conditions.
For much of the past month, the Southern Hemisphere has been dominated by unusually high pressure. Large, slow-moving highs have reduced cloud cover over inland Australia and pushed cold fronts southwards.
[Mean sea level pressure maps of the Southern Hemisphere for 9– 17 June 2017 show large high-pressure systems circulating clockwise around Antarctica (from west to east) at mid-latitudes, and low pressure systems with associated cold fronts confined to southerly latitudes, i.e. close to Antarctica.]
This high pressure has resulted in one of Australia’s driest Junes on record. Areas that had a particularly dry autumn, such as western WA and parts of South Australia were also some of the driest regions in June. 
[Rainfall deciles map for 1–26 June 2017 shows rainfall totals well below average for the month in the southwest of Western Australia, most of South Australia, inland New South Wales, almost all of Victoria and Tasmania, and large parts of Queensland. Only part of the northern New South Wales coast had significantly above-average June rain.]
This means soil moisture is now below average in many regions. Western Victoria, though, has above-average soil moisture for the time of year—largely the result of April rains.
[Lower-layer soil moisture map for 1–24 June 2017 shows soil moistures very much below average for the time of year in the west and south of Western Australia and South Australia, the south of the Northern Territory, and central parts of Queensland and New South Wales. Soil moisture has been above average for June in some northern parts of the Northern Territory and Queensland.]
Overall, drying soils mean there were fewer high streamflows in May, compared with April.
[Observed streamflows map for May 2017 shows higher-than-average flows in the northwest of the country, and in a few locations elsewhere, but lower-than-average flows in most locations in southwest Western Australia, northern Queensland and Victoria.]
For parts of southern Australia, this means water storage inflows in this early part of the winter filling season have been lower than expected.
With more cloud-free skies than usual and fewer cold fronts, warm daytime temperatures have persisted into June. 
[Temperature deciles map for 1–25 June 2017 shows above-average maximum (daytime) temperatures for the time of year across most of the country, particularly the south of Western Australia.]
But clear nights, with no cloud to keep the heat in, have led to very low overnight temperatures, and fog has been abundant in many low-lying areas. 
So what is driving Australia’s climate towards drier and warmer conditions? The unusually high pressure over Australia is due in part to a climate driver called the Southern Annular Mode, or SAM.
When SAM is positive, the belt of high pressure around the globe expands, pushing cold fronts and moisture to the south, away from Australia.
[Southern Annular Mode (SAM) graphic shows the west-to-east flow of cold fronts moving further to the south of Australia as SAM turns positive.]
The Indian Ocean Dipole remains neutral, but around half the climate models suggest a positive phase later in the year. A positive IOD typically increases the chance of a drier-than-normal winter and spring for central and southeastern Australia.
[Sea surface temperature maps for May and June 2017 show waters on either side of the Indian Ocean near average for the time of year in recent weeks, but then expected to turn warmer than average near the Horn of Africa and cooler than average near Indonesia (a positive IOD) later in the year.]
In the Pacific, ocean waters near Peru were several degrees above normal during March and April, but cooled during May and June. 
[Sea surface temperature map for 20–26 March 2017 shows waters more than 5°C warmer than usual off the coast of Peru; but same map for 12–18 June 2017 shows waters in that area much closer to average temperatures for the time of year.]
This warmth could have spread and developed into an El Niño, but eased due to persistent trade winds. All eight models now predict El Niño is unlikely to develop this year. As a result, our ENSO Outlook has been downgraded from El Niño WATCH to inactive.
So what’s the rainfall outlook for July–September? While El Niño is now unlikely, below-average rainfall is still expected for parts of southern Australia.
[Rainfall outlook map for July–September 2017 shows less than 30 per cent chance of above-average rainfall for the period in the southwestern corner of Western Australia, central Victoria and over the border into southern parts of inland New South Wales. Odds of above or below average rainfall for the rest of the country are closer to 50:50.]
Turning to streamflows for June–August: Near-median flows are more likely in most places; but in southern and western Australia, where soils are drier, streamflows in several areas are likely to remain low.
[Streamflow forecast map for June–August 2017 shows higher-than-average flows likely at 22 locations, particularly in the northwest of the country; near-median flows expected at 58 locations, particularly in the southeast; and low flows at 41 locations, particularly in the southwestern corner of Western Australia.]
In terms of temperatures: Days and nights are likely to be generally warmer than average for much of Australia; but with less cloud cover, some nights may be very cold. Keep an eye on your local forecast for frost warnings. 
[Maximum temperature outlook map for July–September 2017 shows greater than 65 per cent chances of above-average daytime temperatures (averaged over the period) for most of the country, except the southeast of Western Australia and most of South Australia. Odds of above-average temperatures are 80 per cent or more in the southwest of Western Australia, the northern tips of Queensland and the Norther Territory, the southeast of New South Wales, central and eastern Victoria, and across Tasmania.]
In summary: El Niño is very unlikely for this year; but rainfall is likely to be below average for parts of southern Australia; streamflows are expected to be near-median to low in most places; and temperatures are likely to be warmer than average for much of the country.
For more details, visit our website at bom.gov.au/climate/ahead. You can also get updates via Facebook and Twitter.
Our next video will be released on Thursday 27 July. For the Bureau of Meteorology, I’m Paul Feikema.