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

Posted by BCG on 6th December 2019

Both the positive Indian Ocean Dipole (IOD) and negative Southern Annular Mode (SAM) are looking likely to continue into December contributing to the hot and dry conditions forecast for much of Australia. However, towards the middle of summer the positive IOD and negative SAM are likely to break down, easing the switch off the dry signal. The northern wet season is likely to arrive later than previous years as the monsoon trough is yet to reach the southern hemisphere after a record late retreat from India. The outlook therefore for summer is for likely hotter and drier conditions for most of Australia with “Below Average” rainfall and an increased risk of heatwaves and bushfires.

Rainfall Roundup

In November, large parts of Australia continued to remain very dry (Fig. 1) but there were areas of eastern Australia that received “Average” to “Above Average” rainfall for example, western Tasmania, northern NSW and along the north west coast of WA.

Spring overall has been one of the driest on record for Australia (Fig 2). With the exception of southern QLD and northwest NSW who received good rainfall totals at the end of October and parts of WA, the rest of Australia was “Very Much Below Average” (Fig 2).

Figure 1. Rainfall deciles for November 2019.
Figure 2. Rainfall deciles for September to November 2019.

Rainfall Forecast

The BoM’s ACCESS model suggests that December is likely to be drier than usual for most of Australia, particularly for eastern Australia (Fig. 3). However, parts of WA are likely to receive “Above Average” rainfall.

At this time of year accuracy for the three-month forecast is moderate, except for parts of QLD, NSW, SA, WA and much of the NT which have low accuracy at this time of year (Fig. 3).

Figure 3. Australian outlook for December to February 2019.

Temperature Roundup

In November, Australia was very warm with “Very Much Above Average” maximum temperatures recorded across WA, NT, QLD and the east coast of Australia with several regions experiencing there hottest November days on record (Fig. 4). The other states however, recorded “Average” maximum temperatures.

Minimum temperatures were “Below Average” through central Australia and “Average” across most of the other regions expect for WA and a few other pockets across the country which were “Above Average” (Fig. 5).

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

Temperature Forecast

The BoM’s ACCESS model forecast suggests “Above Average” maximum temperatures are likely across most of southern and eastern Australia over the next three months (Fig. 6).

Minimum temperatures are also likely to be “Above Average” for large parts of the country except for parts of Vic and Tas which are likely to be “Average” to “Below Average” (Fig. 7).

At this time of year accuracy for the three-month forecast is moderate to high for the maximum temperatures (except for a pocket in the NT/QLD which has low accuracy). Accuracy is moderate across most of Australia for the minimum temperatures (except for parts of QLD, NT and WA which have low accuracy).  

Figure 6. December to February maximum temperature outlook.
Figure 7. December to February 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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