THE CLIMATE KELPIE BLOG: What’s predicted in August

Posted by BCG on 2nd August 2019

During the next three months the dominant climate driver for Australia is likely to be the positive Indian Ocean Dipole (IOD) as the ENSO is expected to remain neutral for the remainder of 2019. So what does this mean for August to October? A positive IOD typically brings ‘Below Average’ rainfall to much of central and southern Australia during winter-spring. It can also indicate an early start to the southern bushfire season.

Rainfall Roundup

The first half of this year was very dry which has prolonged the drought in several areas particularly in the northern Murray Darling Basin. In July, very dry conditions have again persisted across large parts of Southern Australia (Fig 1). Timely rain did fall in parts of Western Australia (WA) and in the south east of Australia, in particularly ‘Above Average’ rainfall was recorded in western Tasmania (Fig 1). These rainfall events have helped increase the overall three-month decile for those regions however, many areas are still ‘Below Average’ to ‘Very Much Below Average’ across Australia (Fig. 2).

Figure 1. Rainfall deciles for July 2019
Figure 2. Rainfall deciles for May to July 2019

Rainfall Forecast

The BoM’s ACCESS model suggests ‘Average’ to ‘Below Average’ rainfall is likely over the next three months for large parts of Australia including much of eastern and northern Australia and parts of southwest WA and southern SA (Fig. 3).

For the month of August, it is likely to be drier over the tropical north (typically of this time of year) and extending down into eastern Queensland, NSW and northern Victoria (Fig. 3). In contrast, southeast WA is likely to be wetter than ‘Average’.

The skill of this model is moderate to high for most of the country in August to October providing improved certainty coming into Spring, except for parts of southeast and southwest Australia which have low accuracy at this time (Fig.3).  

Figure 3. Australian outlook for August to October 2019.

Temperature Roundup

For the coldest month of the year, July maximum temperatures remained ‘Above Average’ for most areas of Australia (Fig 4). Minimum temperatures were ‘Below Average’ to ‘Average’ in inland central Australia, parts of Western Australia and across the top end (Fig 5). In contrast, south eastern Australia was ‘Above Average’ overall but some nights still brought fog and frost.

Figure 4. Maximum temperature deciles for July 2019.
Figure 5. Minimum temperature deciles for July 2019.

Temperature Forecast

The BoM’s ACCESS model forecast suggests ‘Above Average’ maximum temperatures are more likely across most of Australia during August to October, with very high chances for the northern two-thirds of the country (Fig. 6). Northeast Queensland, southern Victoria and western Tasmania have roughly equal chances of warmer or cooler maximum temperatures.

Minimum temperatures are likely to be “Above Average” for much of Australia (Fig. 7). However, parts of southern Australia and northeast Queensland have roughly equal chances of warmer or cooler minimum temperatures.

Areas with dry soils and the forecast of drier than average conditions mean more cloud-free days and nights are expected which is likely to increase the risk of frost in susceptible areas.

At this time of year accuracy for the three-month forecast is moderate to high (except for parts of the Pilbara and south coastal WA) for the maximum temperatures and moderate across most of Australia for the minimum temperatures.  

Figure 6. August to October maximum temperature outlook.
Figure 7. August to October minimum temperature outlook.

Climate and Water Outlook Videos

The Bureau of Meteorology releases regular outlook videos, covering all this information. Watch the most recent video below.

https://youtu.be/lgFXwjDmANEI4jvzE