THE CLIMATE KELPIE BLOG: What’s predicted in August?

Posted by BCG on 10th August 2021

The Indian Ocean Dipole (IOD) has finally hit the negative threshold and is forecast to remain negative throughout spring. A negative IOD greatly increases the chances of ‘Above Average’ rainfall across southern and eastern Australia.

In terms of the El Niño–Southern Oscillation (ENSO), this climate driver remains neutral however ocean temperatures in the tropical Pacific Ocean are cooling with some models hinting at a La Niña forming later in the year. Whether this unfolds, only time will tell but regardless, this cooling is favourable for increasing the chances of ‘Above Average’ rainfall in eastern and northern parts of Australia.

Our shorter-term climate driver, the Southern Annular Mode (SAM) is currently neutral and thus having little influence on our climate now. Likewise, the Madden-Julian Oscillation (MJO) is also not having an influence on Australia’s climate at the moment.

The overall outlook for August to October is for rainfall to be ‘Above Average’ for much of Australia, however western parts of Western Australia are likely to be ‘Below Average’. In terms of temperatures, minimums are likely to be ‘Above Average’ across much of Australia except for south west Western Australia where ‘Below Average’ minimums are likely. Maximum temperatures are forecast to be ‘Above Average’ for northern Australia, much of Victoria and Tasmania and ‘Below Average’ maximums are likely for southern parts of mainland Australia.

Rainfall Roundup

In July, rainfall was ‘Above Average’ for much of the east coast of Australia, north west Tasmania, south east South Australia and south west Western Australia (Fig. 1). There were however areas that missed out on rain in July, notably eastern Tasmania, Gippsland in Victoria, the south east coastline of New South Wales and parts of central Australia (Fig. 1).

Over the last three months south west Western Australia and parts of south east Australia have received ‘Above Average’ rainfall with the rest of the country recording ‘Average’ rainfall conditions. However, south west Tasmania, the northern coastline of New South Wales, parts of central Australia as well as the northern coastline of Australia have all experienced ‘Below Average’ rainfall over the last three months (Fig. 2).

Figure 1. Rainfall deciles for July 2021.
Figure 2. Rainfall deciles for May 2021 to July 2021.

Rainfall Forecast

The BoM’s ACCESS model predicts that rainfall in August is likely to be ‘Above Average’ for much of Australia, except for western parts of Western Australia which are likely to be ‘Below Average’, as well as northern Queensland and coastal areas in southern Australia, which have equal chances of ‘Above’ or ‘Below Average’ rainfall (Fig. 3).

For the three-month forecast, August to October, the rainfall forecast again resembles the outlook for August with much of the eastern two-thirds of Australia likely to receive ‘Above Average’ rainfall (Fig. 3). At this time of year accuracy for the three-month forecast is moderate to high for most of Australia except for small parts of Western Australia, south east New South Wales and East Gippsland in Victoria (Fig. 3). 

Figure 3. Australian rainfall outlook for August to October 2021.

Temperature Roundup

Maximum temperatures in July were ‘Above Average’ for much of northern and central Australia as well as Tasmania and the coastlines of Victoria and New South Wales (Fig. 4). The remaining parts of the country were ‘Average’ except for a very small pocket in south east Queensland which was ‘Below Average’ (Fig. 4). Minimum temperatures were mainly ‘Above Average’ across much of Australia with a few of areas in the Northern Territory and a pocket in northern New South Wales and northern Western Australia which were ‘Below Average’ (Fig. 5).

Figure 4. Maximum temperature deciles for July 2021.
Figure 5. Minimum temperature deciles for July 2021.

Temperature Forecast

The BoM’s ACCESS model forecast predicts that over the next three months maximum temperatures are likely to be ‘Above Average’ for northern Australia as well as all of Tasmania and parts of Victoria and New South Wales (Fig. 6). For a large area stretching from Western Australia, to New South Wales and up into southern Queensland there is an increased chance of ‘Below Average’ maximum temperatures (Fig. 6).

For minimum temperatures, much of Australia is likely to be ‘Above Average’ for the next three months, except for south west Western Australia where they are likely to be ‘Below Average’ (Fig. 7).

At this time of year accuracy for the three-month maximum temperature forecast is moderate to high for much of Australia, except for a small pocket in the Northern Territory where accuracy is low (Fig. 6). For minimum temperatures, accuracy is high for much of Australia excluding south west Western Australia and the Eyre Peninsula in South Australia where accuracy is low (Fig. 7). 

Figure 6. August to October 2021 maximum temperature outlook.
Figure 7. August to October 2021 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.

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