THE CLIMATE KELPIE BLOG: What is predicted in May?

Posted by BCG on 7th May 2021

Many of Australia’s main climate drivers remain in the neutral position and are predicted to stay this way for the remainder of autumn and into early winter. This include the El Niño–Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and our shorter-term climate driver the Southern Annular Mode (SAM). There is however some activity in the Indian Ocean with ‘Above Average’ sea surface temperatures outside of the IOD region which may lead to more favourable conditions for rainfall across some parts of Australia.

The Madden-Julian Oscillation (MJO) is currently over tropical America and is forecast to move towards Africa. When the MJO is in this position ‘Below Average’ rainfall is likely over northern Australia. Note that the MJO is now starting to have less of an influence on Australia’s conditions and more of an impact in the northern hemisphere.

As a result, the overall outlook for May to July is for much of the southern half of mainland Australia to have an increased chance of rainfall being ‘Above Average’ with ‘Below Average’ rainfall likely for western Tasmania, small pockets in south west Western Australia and across northern Australia. In terms of temperatures, minimums are likely to be ‘Above Average’ across Australia and maximums are likely to be ‘Above Average’ for much of Australia, except for parts of Western Australia, South Australia and small pockets in Queensland where there are equal chances of maximum temperatures being ‘Above’ or ‘Below Average’.

Rainfall Roundup

In April, rainfall was ‘Below Average’ for most of Australia except for northern Queensland and along the Western Australia coastline where ‘Above Average’ rainfall was recorded (Fig. 1). Despite this, rainfall totals over the last 3 months have been ‘Above Average’ for much of New South Wales, central Australia, parts of Tasmania, the Western Australia coastline and areas in Queensland and the Northern Territory. However, ‘Below Average’ rainfall conditions remain for some regions most notably in south eastern parts of mainland Australia (Fig. 2).

Figure 1. Rainfall deciles for April 2021.
Figure 2. Rainfall deciles for February 2021 to April 2021.

Rainfall Forecast

The BoM’s ACCESS model predicts that rainfall in May is likely to be ‘Below Average’, for northern Australia, western Tasmania and pockets in Victoria and south west Western Australia (Fig. 3). The rest of the country has equal chances of rainfall being ‘Above’ or ‘Below Average’ with a slight increased chance of rainfall being ‘Above Average’ for central Western Australia into South Australia as well as along the New South Wales and Victorian coastline (Fig. 3).

For the three-month forecast, May to July, much of the southern half of mainland Australia has an increased chance of rainfall being ‘Above Average’ (Fig. 3).  However, western Tasmania, small pockets in south west Western Australia and across northern Australia are likely to experience ‘Below 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 areas of South Australia, small pockets in Victoria and Tasmania as well as along the New South Wales coastline and parts of Queensland where accuracy is low (Fig. 3).

Figure 3. Australian rainfall outlook for May to July 2021.

Temperature Roundup

Maximum temperatures in April were ‘Above Average’ for much of Western Australia, the southern half of South Australia, north east Tasmania and across northern Australia (Fig. 4). The rest of Australia was ‘Average’ except for an area on the New South Wales and Queensland border and small pockets in northern Queensland, the Northern Territory and Western Australia where maximum temperatures were ‘Below Average’ (Fig. 4).

Minimum temperatures on the other hand were ‘Below Average’ across northern Western Australia into central Australia as well as much of south east Australia, particularly New South Wales (Fig. 5). All other regions of Australia were ‘Average’ to ‘Above Average’ for minimum temperatures (Fig. 5).

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

Temperature Forecast

The BoM’s ACCESS model forecast suggests that over the next three months maximum temperatures are likely to be ‘Above Average’ for much of Australia, except for parts of Western Australia, South Australia and small pockets in Queensland where there are equal chances of maximum temperatures being ‘Above’ or ‘Below Average’ (Fig. 6). For minimum temperatures, all of Australia is likely to be ‘Above Average’ for the next three months (Fig. 7).

At this time of year accuracy for the three-month maximum temperature forecast is moderate to high for much of Australia, except along the New South Wales coastline and a band through the Northern Territory where accuracy is low (Fig. 6). For minimum temperatures, accuracy is low for much of south east Australia and the far south west of Western Australia with the rest of Australia having moderate to high accuracy (Fig. 7).

Figure 6. May to July 2021 maximum temperature outlook.
Figure 7. May to July 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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