Australia in December 2017

In brief

  • An exceptionally warm month for Australia as a whole, fifth-warmest December on record
  • Amongst the ten warmest Decembers on record for Queensland, New South Wales, Tasmania and the Northern Territory
  • Mean maximum temperature above average for most of eastern Australia and the Northern Territory, also for parts of coastal Western Australia, northeast and southwest South Australia
  • Mean minimum temperature above average for much of eastern Australia, except parts of northern and eastern Queensland; also above average for eastern South Australia, southeast Northern Territory and much of western to central Western Australia
  • December minima warmest on record for Tasmania and mainland east coast between Port Phillip in Victoria and the southern Hunter District in New South Wales
  • December rainfall above to very much above average for eastern and northern Victoria, southern New South Wales, eastern Tasmania, much of southern South Australia, the west coast of Western Australia and from the western Kimberley to central Western Australia
  • Rainfall below average for much of the Northern Territory and Queensland

Temperatures

December was an exceptionally warm month for Australia as a whole; the monthly mean temperature anomaly was the fifth-warmest on record for December, while mean maximum temperature was sixth-warmest and mean minimum temperature the equal fifth-warmest.

The mean maximum temperature was the fifth-warmest on record for December for Queensland, the sixth-warmest on record for Tasmania, and the tenth-warmest on record for the Northern Territory. The December mean minimum temperature was the warmest on record for Tasmania, the second-warmest on record for New South Wales, eighth-warmest for Victoria, and equal eighth-warmest for Queensland.

After a much cooler than average start to the month for most of the country, widespread hot weather affected all States and Territories from the 12th as a strong blocking high pressure system over the Tasman Sea and low pressure surface trough over northern Australia maintained a northerly airflow over the east of the country, which persisted throughout most of the rest of the month. Multiple sites in New South Wales and South Australia set new daily high temperature records for December on the 14th or between the 18th and 24th. Record warm minimum temperatures were also observed at a number of sites, mostly in New South Wales on the 19th or 20th.

Maximum temperatures were above average across most of eastern Australia and the Northern Territory, but near average for an area of Queensland’s central east coast, northwestern Victoria and parts of southern New South Wales inland of the ranges, and the south of the Victoria River District in the Northern Territory. Maxima were in the warmest 10% of historical observations (decile 10) for December across nearly all of Tasmania, western Queensland and the Cape York Peninsula, most of the Top End, and eastern border regions of the Northern Territory.

Maxima were also above average for coastal southwestern South Australia and southeastern Western Australia, and areas around the perimeter of Western Australia in the southwest, coastal Gascoyne to inland Pilbara, and the coastal Kimberley.

Maxima were below average for an area of the Interior District in Western Australia, associated with the passage of ex-tropical cyclone Hilda late in the month.

Minimum temperatures for the month were above to very much above average across Tasmania, Victoria, New South Wales, western and southern Queensland, much of eastern South Australia, and the southeast of the Northern Territory. Mean monthly minima were the warmest on record for December across Tasmania and along the east coast from Western Port, east of Melbourne, across Gippsland, and coastal southern to central New South Wales reaching as far inland as the Australian Capital Territory and Mudgee and Scone in New South Wales. December mean daily minimum temperature records were set at many sites in Tasmania, Victoria, and New South Wales.

Minima were also above average for parts of the coast of the Top End and Cape York Peninsula, and most of Western Australia except for near-average values across most of the south coast, the eastern Kimberley, and the northeast and southwest of the Interior District.

Minima were below average for a few pockets of northern Australia, the largest being in an area of the southern Top End and Roper-McArthur District in the Northern Territory.


Areal average temperatures
Maximum Temperature Minimum Temperature Mean Temperature
Rank
(of 108)
Anomaly
(°C)
Comment Rank
(of 108)
Anomaly
(°C)
Comment Rank
(of 108)
Anomaly
(°C)
Comment
Australia 103 +1.17 6th highest = 103 +1.03 equal 5th highest 104 +1.10 5th highest; highest since 1990
Queensland 104 +1.86 5th highest; highest since 2005 = 100 +1.24 equal 8th highest 106 +1.55 3rd highest (record +2.20 °C in 2005)
New South Wales 90 +1.80 107 +2.20 2nd highest (record +2.55 °C in 1914) 102 +2.00 7th highest
Victoria 81 +1.26 101 +1.70 8th highest = 97 +1.48
Tasmania 103 +1.68 6th highest 108 +1.78 highest (was +1.58 °C in 1985) 107 +1.73 2nd highest (record +2.17 °C in 2015)
South Australia 78 +0.99 85 +0.95 85 +0.97
Western Australia 91 +0.62 96 +0.64 94 +0.63
Northern Territory 99 +1.03 10th highest; highest since 2002 92 +0.66 102 +0.85 7th highest; highest since 1990

Rank ranges from 1 (lowest) to 108 (highest). A rank marked with ’=‘ indicates the value is tied for that rank. Anomaly is the departure from the long-term (1961–1990) average.


Temperature maps
MeanAnomalyDeciles
Mean
daily
maximum
temperatures
Map of mean daily maximum temperature Map of mean daily maximum temperature anomalies Map of mean daily maximum temperature deciles
Mean
daily
minimum
temperatures
Map of mean daily minimum temperature Map of mean daily minimum temperature anomalies Map of mean daily minimum temperature deciles
Mean
daily
temperatures
Map of mean daily temperature Map of mean daily temperature anomalies Map of mean daily temperature deciles

Rainfall

Rainfall for Australia as a whole was below average for December. Totals for the month were below to very much below average for most of the Northern Territory and Queensland, but near average for parts of the Alice Springs District and parts of southern Queensland. Monthly rainfall was also below average for scattered areas in northeastern New South Wales, northwestern New South Wales and northeastern South Australia, and areas of Western Australia, mostly in the southeastern Pilbara and the Goldfields district.

Rainfall for December was above average along the west coast of Western Australia and along the path of tropical cyclone Hilda, extending from the western Kimberley through the northeastern side of the Interior District to about Wiluna. Hilda produced daily rainfall totals in the range of 100 mm to 300 mm in the west Kimberley from the 27th to 29th, breaking December daily rainfall records at a number of sites; however, structural damage was fairly limited.

Monthly rainfall was also above average for the coastal southeast of Western Australia; large parts of southern to central western South Australia; for southern New South Wales, the eastern half and northern border regions of Victoria; and eastern Tasmania.

Above average rainfall in southeastern Australia resulted from a few separate significant rainfall events.

In the first days of December a blocking high over the Tasman Sea drew moist tropical air into southeastern Australia, resulting in multi-day totals exceeding 100 mm for 1 to 3 December across parts of central to northeastern Victoria, extending to the Australian Capital Territory. Flooding occurred in several northern towns while flash flooding was reported in parts of Melbourne.

Many sites in Victoria, southern New South Wales, and northern Tasmania had their wettest December day on record. Some sites in northern Victoria had their wettest day on record for any month of the year, including Echuca Aerodrome, Euroa, Lake Eildon and Strathbogie, all of which have more than 100 years of observations. In Tasmania the event brought snowfall to levels as low as 900 m on the 2nd.

As well as the record rainfall at the start of the month severe thunderstorms extended eastwards across most of central and eastern Victoria during the afternoon and evening of the 19th as a hot, humid and unstable air-mass moved through ahead of a cold front and low pressure trough. Flash flooding and large hail was reported in parts of Melbourne city and a number of the surrounding suburbs, most notably on the eastern side of the city and in northeastern Victoria.

Stormy days brought heavy rainfall across Melbourne on the evening and night of the 7th, with flash flooding reported in some eastern and southeastern suburbs, and to eastern Victoria and southeastern New South Wales around the 29th, although the effects of both events were generally minor.


Area-average rainfall
Rank
(of 118)
Average
(mm)
Departure
from mean
Comment
Australia 43 45.7 −13%
Queensland 12 35.4 −57%
New South Wales 78 66.3 +23%
Victoria 107 80.2 +69%
Tasmania 77 112.1 +7%
South Australia 82 23.4 +28%
Western Australia 86 48.6 +53%
Northern Territory 25 48.6 −35%
Murray-Darling Basin 82 59.6 +23%

Rank ranges from 1 (lowest) to 118 (highest). A rank marked with ’=‘ indicates the value is tied for that rank. Departure from mean is relative to the long-term (1961–1990) average.


Rainfall maps
TotalsPercentagesDeciles
Total
rainfall
Map of total rainfall Map of percentage of normal rain Map of rainfall deciles


Australian weather extremes during December 2017
Hottest day 47.4 °C    Birdsville Airport (Qld) on the 29th
Coldest day 2.3 °C    at kunanyi (Mount Wellington Pinnacle) (Tas.) on the 3rd
Coldest night −2.3 °C    at Liawenee (Tas.) on the 17th
Warmest night 33.5 °C    at Windorah Airport (Qld.) on the 25th and Tibooburra Airport (NSW) on the 19th
Wettest day 291.5 mm at Cygnet Bay (WA) on the 27th


Notes

The Monthly Climate Summary is prepared to list the main features of the weather in Australia using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

Climate Summaries are usually published on the first working day of each month.

This statement has been prepared based on information available at 1 pm EST on Monday 8 January 2018. Some checks have been made on the data, but it is possible that results will change as new information becomes available, especially for rainfall where much more data becomes available as returns are received from volunteers.

Long-term averages in this statement and associated tables are for the period 1961 to 1990 unless otherwise specified.

The system used for calculating areal averages of rainfall was changed in December 2009; the main effect was that current and historical values for Tasmania were increased. Since December 2012, ACORN-SAT has been used for calculating areal averages of temperature; the major change from earlier datasets is that the ACORN-SAT dataset commences in 1910, and hence rankings are calculated using a larger set of years.


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