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

Posted by BCG on 6th July 2021

The Indian Ocean Dipole (IOD) is showing encouraging signs that a negative IOD event may occur in winter/spring. The IOD index has been below the negative threshold of six consecutive weeks now and requires only two more weeks before a negative IOD event can be declared. If this does come to fruition much of southern and eastern Australia has a high chance of receiving ‘Above Average’ winter-spring rainfall.

In terms of the El Niño–Southern Oscillation (ENSO), this climate driver remains neutral and forecast to stay this way at least until the end of spring. However, sea surface temperatures in the central and eastern Pacific Ocean are predicted to slowly cool over the coming months which may result in ‘Above Average’ rainfall for some parts of Australia.

Our shorter-term climate driver, the Southern Annular Mode (SAM) is currently positive and forecast to remain this way for the next fortnight. A positive SAM typical results in cold fronts shifting further south than usual thus parts of southern Australia may experience ‘Below Average’ rainfall however, this is competing with the wetter signals from the Indian Ocean.

The Madden-Julian Oscillation (MJO) is not having an influence on Australia’s climate at the moment.

The overall outlook for July to September is for rainfall to be ‘Above Average’ for much of Australia, however some parts Western Australia, south-east Australia and Tasmania have equal chances of rainfall being ‘Above’ or ‘Below Average’. In terms of temperatures, minimums are likely to be ‘Above Average’ across much of Australia. Maximums, however, are likely to be ‘Above Average’ for northern Australia and parts of south-west and south-east Australia and ‘Below Average’ across a broad area extending from South Australia across to western New South Wales and into Southern Queensland.

Rainfall Roundup

In June, rainfall was ‘Above Average’ for much of eastern Australia and the southern coastline of Western Australia and South Australia. Regions of northern Australia also recorded ‘Above Average’ rainfall but note that this region is now in the dry season and thus not much rainfall is required for it to be ‘Above Average’ (Fig. 1). There were however areas that missed out on rain in June, notably western Tasmania and south west Western Australia (Fig. 1).

Over the last three months much of Australia has experienced ‘Below Average’ rainfall conditions except for northern Queensland, the central and southern coastlines of Western Australia, eastern Victoria and small pockets of the Northern Territory and New South Wales which were ‘Above Average’ (Fig. 2).  

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

Rainfall Forecast

The BoM’s ACCESS model predicts that rainfall in July is likely to be ‘Above Average’ for much of Australia except for western parts of Western Australia, coastal areas of south-east Australia and western Tasmania where equal chances of ‘Above’ or ‘Below Average’ rainfall is likely (Fig. 3).

For the three-month forecast, July to September, the rainfall forecast again closely resembles the outlook for July (Fig. 3). At this time of year accuracy for the three-month forecast is moderate to high for most of Australia except for parts of coastal Western Australia and southern New South Wales into eastern Victoria (Fig. 3). 

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

Temperature Roundup

For much of Australia, maximum temperatures in June were ‘Average’ except for large parts of south-east Australia and northern Australia where maximum temperatures were ‘Above Average’ and large areas of Western Australia, plus small pockets of Queensland, South Australia and the Northern Territory which where ‘Below Average’ (Fig. 4). Minimum temperatures were mainly ‘Above Average’ across northern and southern parts of Australia with a couple of areas in Western Australia and the Northern Territory ‘Below Average’ (Fig. 5).

Figure 4. Maximum temperature deciles for June 2021
Figure 5. Minimum temperature deciles for June 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 the western coastline of Western Australia, all of Tasmania and parts of Victoria and New South Wales (Fig. 6). For a large area stretching from South Australia, across western New South Wales and 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 (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 an area around the Northern Territory and Queensland border where accuracy is low (Fig. 6). For minimum temperatures, accuracy is high for much of Australia unless you are in Western Australia, where much of central and southern parts have low accuracy (Fig. 7). 

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