THE CLIMATE KELPIE BLOG: Whats predicted in September

Posted by BCG on 4th September 2019

The positive Indian Ocean Dipole (IOD) looks set to remain as the dominant climate driver for Australia over the coming months. So what does this mean for Spring? A positive IOD typically brings ‘Below Average’ rainfall as well as warmer than average days to much of central and southern Australia. There is also an increased risk of frost and fire for the south east of Australia.

Rainfall Roundup

In August, very dry conditions again persisted across large parts of Southern and central Australia, particularly in the Murray Darling Basin. Timely rain only fell in parts of Western Australia (WA) and in the south east of Australia (Fig. 1). Winter was one of the driest on record with only parts of Southern Victoria and Tasmania benefiting from ‘Above Average’ rainfall delivered by winter cold fronts (Fig. 2).

Figure 1. Rainfall deciles for August 2019.
Figure 2. Rainfall deciles for June to August 2019.

Rainfall Forecast

The BoM’s ACCESS model suggests ‘Very Much Below Average’ rainfall is likely over Spring for large parts of Australia including much of eastern, central and northern Australia (Fig. 3).

For the month of September, it is likely to be drier over most of Australia expect for western Tasmania and southwest WA where a wetter than average September is likely (Fig. 3).

At this time of year accuracy for the three-month forecast is moderate to high, except for parts of WA which are moderate.

Figure 3. Australian outlook for September to November.

Temperature Roundup

In August, maximum temperatures remained ‘Above Average’ for much of WA and the east coast regions of Australia, but parts of Victoria and central Australia experienced ‘Average’ to ‘Below Average’ daytime temperatures (Fig. 4). Minimum temperatures were ‘Very Much Below Average’ to ‘Average’ across large parts of Australia but parts of WA and QLD were ‘Above Average’ (Fig. 5).

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

Temperature Forecast

The BoM’s ACCESS model forecast suggests ‘Above Average’ maximum temperatures are likely across most of Australia over the next three months, with the expectation of Tasmania which is more likely to be ‘Average’ to ‘Below Average’ (Fig. 6).  

Minimum temperatures are likely to be “Above Average” in the north and west of Australia for Spring (Fig. 7). However, in September cooler than average temperatures are expected in the tropics (Fig. 7). 

With below average rainfall forecast and therefore clearer skies, nights are likely to be cooler than average in parts of the south east and therefore increased risk of frost in susceptible areas (Fig. 7).

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

Figure 6. September to November temperatures outlook.
Figure 7. September to November 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.