Australia in December 2011

In Brief

December was cooler than normal across much of Australia for both daytime and overnight temperatures with the exception of the west coast and parts of southern Australia. Rainfall was average to above average across most of the country with the main exceptions of below average rainfall near the northwest coast of WA and most of Tasmania.


Temperatures

Daytime temperatures were below normal over most of the country, with a national area-averaged anomaly of −0.86 °C (13th coolest of 62 years). Most of NSW and southern Queensland experienced a very cool December with NSW and the Murray-Darling basin recording their third coldest December on record with an anomaly of −2.46 °C and −2.19 °C, respectively. Maximum temperatures were in excess of 3 °C below normal in northeastern NSW and southern Queensland, with smaller areas within this region more than 5 °C below normal. December maximum temperatures were the coldest on record over this area. Large parts of northern Queensland, the northern NT, southern WA also recorded below average daytime temperatures. Small areas in northern SA and the Gippsland region of Victoria also recorded below average maximum temperatures.

Above average maximum temperatures were recorded over most of Tasmania, western Victoria, parts of the SA coast, the western and northwestern coastlines in WA as well as the western coast of the NT. Temperatures were over 1 °C above normal in parts of southeast Australia and the western and northern coasts of WA. An area near Derby, in the western Kimberley, was more than 2 °C above normal with the December maximum temperatures ranking as the highest on record. The Pilbara region of WA experienced very hot daily temperatures in excess of 45 °C between the 20th and 27th of the month. The hottest daily December temperature record for WA was broken during this period, with 49.4 °C recorded on the 21st at Roebourne near Karratha in WA (previous record 48.8 °C, set at Mardie in 1986). This was also the second hottest daily temperature for Australia (record is 49.5 °C, set at Birdsville, Queensland in 1972). Several other locations recorded temperatures in excess of 48 °C. Victoria, Tasmania and SA all recorded above average statewide maximum temperatures.

Minimum temperatures averaged over Australia were 0.28 °C below normal, ranking equal 19th coolest of 62 years. An area stretching across the northeastern half of NSW through the southern, central and Carpentaria region of Queensland, the central NT, through to the interior of WA recorded below average minimum temperatures. Some areas within this band recorded minimum temperatures ranking in the coldest 10% of records. In contrast, parts of the tropical coast including most of the Cape York Peninsula in Queensland, the Gascoyne region of WA, the west and south coast of Australia and Tasmania recorded above average temperatures. Some of these coastal areas recorded overnight temperatures that ranked in the top 10% of all Decembers on record.


Areal average temperatures
  Maximum Temperature Minimum Temperature
Rank
(out of 62)
Anomaly*
(°C)
Comment Rank
(out of 62)
Anomaly*
(°C)
Comment
Australia 13 −0.91 19 −0.29
Queensland 6 −1.78 13 −0.75
New South Wales 3 −2.46 third lowest, record is −2.58 (1999) 17 −0.86
Victoria 32 +0.20 49 +0.69
Tasmania 54 +1.55 46 +0.46
South Australia 36 +0.35 32 +0.28
Western Australia 28 −0.40 45 +0.28
Northern Territory 16 −1.01 8 −1.06

*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

Rainfall

Rainfall averaged over Australia was 34% above normal, ranking as the 25th wettest of 112 years. Most states and territories recording average to above average falls during December, with the exception of Tasmania which recorded below normal falls (−46%), the lowest December total since 1994 (17 years). The rainfall pattern across Australia was somewhat patchy (see rainfall decile map below) however most areas in eastern Australia as well as southern and the northeast of WA recorded above average falls. An area in southwest WA, including parts of Perth, recorded its wettest December on record. The Katherine region of the NT experienced some very heavy falls on Boxing Day due to Tropical Cyclone Grant which crossed the NT coast east of Darwin early on Boxing Day before decaying to a tropical low by the end of the day. A low pressure system and associated trough triggered severe thunderstorms across the greater Melbourne area on Christmas Day with heavy rainfall, localised flooding, large hail, strong winds and a tornado reported on the day.

Below average rainfall was recorded only in small isolated areas across the country. Tasmania recorded below average rainfall with the west coast recording rainfall which ranks in the driest 10% of Decembers on record. Victoria was also slightly below average (8%) with the west coast recording below average falls in December.


Areal average rainfall
Rank
(out of 112)
Average
(mm)
Departure
from mean*
Comment
Australia 95 76.4 +46%
Queensland 100 127.0 +54%
New South Wales 83 71.1 +32%
Victoria 59 45.8 −4%
Tasmania 20 58.5 −44% lowest since 1994
South Australia 84 27.2 +49%
Western Australia 80 47.0 +48%
Northern Territory 86 112.2 +51%
Murray-Darling Basin 100 79.8 +65%

*The mean is calculated for the 1961-1990 reference period.


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


Australian weather extremes in December 2011
Hottest day 49.4 °C at Roebourne (WA) on the 21st
Coldest day 2.2 °C at Mount Baw Baw (Vic) on the 1st
Coldest night −5.4 °C at Mount Hotham (Vic) on the 5th
Warmest night 33.2 °C at Wittenoom (WA) on the 22nd
Wettest day 385.0 mm at Edith Falls Ridge (NT) 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.

This statement has been prepared based on information available at 2pm EST on Tuesday, 3 January 2012. 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.

In the tables, fractional ranks denote tied values.

A new area-averaging method was adopted for rainfall in May 2009. Current and historical totals for Tasmania are substantially higher than under the old scheme, but differences for other states, and nationally, are negligible. The rankings and departures from mean shown here use the new method.


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