Tuesday, 3 January 2012 - Monthly Climate Summary for ACT Monthly Summary - Product code IDCKGC25R0

Canberra in December 2011: Coldest December since 1986

  • Coldest mean temperatures since 1986, equal 6th coldest on record
  • 5th coldest maximum temperatures on record for Canberra, coldest since 1966
  • Well below average minimum temperatures
  • Above average rainfall
  • Equal 4th highest number of rain days on record

Extremes Records Summaries Important notes the top

Rainfall

Canberra Airport recorded 72.2 mm of rain during December, above the historical average of 53.8 mm, although it is the driest December since 2006. The rain fell over 14 days, above the December average of 8 rain days and the equal 4th highest on record for December. The wettest days reached 15.6 mm at the Airport, associated with a thunderstorm on the 12th and a low pressure trough on the 21st, with 13.8 mm recorded on the 1st during a thunderstorm. Rainfall was heavier at Mt Ginini and Tuggeranong, including a maximum daily fall of 44.8 mm at Tuggeranong during the thunderstorm on the 12th, of which 32.8 mm fell over 30 minutes between 12:30 and 13:00, with some flash flooding reported. Thunderstorms also brought falls of up to 38.4 mm at Tharwa on the 26th, although almost no rain fell at Canberra Airport.

Temperature

Canberra Airport experienced its coldest December since 1966 and its equal 5th coldest on record, with an average maximum temperature of just 23.6 °C, 2.5 °C below the historical average. The cool average was associated with a lack of hot days during the month, with only seven days reaching 25 °C during December, well below the previous record of 9 days in December 1947. The warmest day was Christmas Day, reaching 28.8 °C; the only other December with no days above 30 °C was in 1992, when the warmest day reached 28.9 °C. In comparison, Canberra typically experiences 18 days above 25 °C and 7 days above 30 °C during December. However, no days were cooler than 18 °C (average 1.4 days).

Minimum temperatures were also below average during December at 10.3 °C, the coolest since 10.1 °C in December 1995. There were ten nights below 10 °C during the month, average for December, including the coldest December night since 2002 on the 5th falling to 3.3 °C. Nights were warmer later in the month, with the warmest night, 14.6 °C, occurring on the 19th. However, no nights exceeded 15 °C (average 4 nights) for the first time since 1984.

The lack of warm days and nights was associated primarily with a lack of warm westerly winds during the month, with above average cloud cover and rain particularly affecting daytime temperatures. The mean temperature at Canberra Airport was consequently 1.7 °C below average at 17 °C, the coldest December since 1986 and the equal 6th coolest on record.

Wind

The prevailing winds at Canberra Airport during December were S-E at 9am, 52% of observations, which is above average for December. 3pm winds were also less westerly than usual, with only 39% between N and W (average 65%). The strongest wind gust at Canberra Airport was 57 km/hr on the 24th, with the strongest winds anywhere in the ACT reaching 67 km/hr at Mt Ginini on the 19th.

Other phenomena

There were 9 thunderstorms in the ACT during December, with hail reported during a storm on the 11th. There were only 4 clear days during the month (average 8 days), with an average of 5 oktas of cloud at both 9am and 3pm, above average for December.

Further information

Climate Officer
NSW Climate Services Centre
NSW Regional Office
Bureau of Meteorology
Phone (02) 9296 1555
Email climate.nsw@bom.gov.au
Extremes in December 2011
Hottest day 29.2 °C at Tuggeranong (Isabella Plains) AWS on the 24th
Warmest days on average 23.6 °C at Canberra Airport
Coolest days on average 14.8 °C at Mount Ginini AWS
Coldest day 9.3 °C at Mount Ginini AWS on the 5th
Coldest night -3.0 °C at Mount Ginini AWS on the 5th
Coolest nights on average 5.1 °C at Mount Ginini AWS
Warmest nights on average 11.3 °C at Tuggeranong (Isabella Plains) AWS
Warmest night 15.1 °C at Tuggeranong (Isabella Plains) AWS on the 26th
Warmest on average overall 17.3 °C at Tuggeranong (Isabella Plains) AWS
Coolest on average overall 9.9 °C at Mount Ginini AWS
Wettest overall 172.8 mm at Mount Ginini AWS
Wettest day 44.8 mm at Tuggeranong (Isabella Plains) AWS on the 12th
Highest wind gust 67 km/h at Mount Ginini AWS on the 19th

Extremes Records Summaries Important notes the top

Summary statistics for December 2011
Maximum temperatures
for December
(°C)		 Minimum temperatures
for December
(°C)		 Rainfall
for December
(millimetres)
Mean for
December
2011		 Diff
from
average		 Highest for
December
2011		 Mean for
December
2011		 Diff
from
average		 Lowest for
December
2011		 Total for
December
2011		 Average
for
December		 Rank of
December
2011		 Fraction of
December
average
Canberra Airport 23.6 -2.5 28.8 25th 10.3 -1.1 3.3 5th 72.2 53.8 high 134%
Mount Ginini AWS 14.8   20.7 25th 5.1   -3.0 5th 172.8
Tidbinbilla Nature Reserve 22.1 -2.9 27.5 25th 9.9 -0.9 3.2 1st 94.4 65.3 high 145%
Tuggeranong (Isabella Plains) AWS 23.4   29.2 24th 11.3   4.6 1st 140.6

Extremes Records Summaries Important notes the top

Notes

As of March 2010, the official station for Canberra is 70351 'Canberra Airport'. Averages from the previous site, 70014 Canberra Airport Comparison, are used for comparisons (all years of record).

A Monthly Climate Summary is prepared to list the main features of the weather in ACT Monthly Summary 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.

This statement has been prepared based on information available at 8 am 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.

Averages are long-term means based on observations from all available years of record, which vary widely from site to site. They are not shown for sites with less than 20 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site, based on the decile ranking (very low rainfall is in decile 1, low in decile 2 or 3, average in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

Climate Officer
NSW Climate Services Centre
NSW Regional Office
Bureau of Meteorology
Phone (02) 9296 1555
Email climate.nsw@bom.gov.au