Wednesday 3 January 2007

A.C.T.  MONTHLY CLIMATE SUMMARY

Hot/dry start and a Cool/wet finish to December in Canberra

December 2006 - Main Points:

• Hot/dry start and a Cool/wet finish to December in Canberra.
• Average maximum temperature (27.7°C) was well above average.

December 2006

Rainfall:    The monthly rainfall total of  16.8 mm was well below the historic December average of 52.0 mm and the lowest since 2001 when 15.2 mm was recorded (the driest December was 2.0 mm in 1994). There were 5 rain days, just below the average of  8 rain days.  A.C.T. rainfall totals ranged from 46.6 mm at the Botanical Gardens to 8.0 mm at Tuggeranong.

Temperatures:    December had a hot start and cool finish, the average daily temperature (the average of daytime and night-time temperatures) of  20.1°C was well above the average of 18.6°C  (the record is 21.5°C  in 1997). The average maximum temperature at Canberra Airport was a very warm 27.7 °C, well above the historic average of 25.9°C. There were 10 days with a maximum temperature of 30.0°C or greater which is just above the average of  7 days.

Nights were slightly warmer at Canberra Airport, the average minimum temperature of 12.5°C was 1.2°C above the historic average of 11.3°C.   The highest temperature at Canberra Airport during December was 35.6°C on the 10th while the lowest was  4.8°C on the 26th.

Other phenomena:    There were 4 thunderstorms during the month with severe storms on  the afternoon of the 29th (3cm hail in northern suburbs and Queanbeyan, with significant amounts of damage to the National Museum of Australia).  On the 30th golf ball sized hail was reported at Cook.  The most severe thunderstorm was on the evening of the 31st when there was widespread flash flooding and very heavy hail (in some places it had accumulated up to half a metre deep) damaging hundreds of houses through southern and northwestern suburbs of Canberra. Tuggeranong recorded 38 mm (24 hours to 9am 1st) with unofficial falls of up to 90 mm in some southern suburbs. South of Canberra there were stock losses and fences washed away around Williamsdale and Lanyon.

Canberra recorded slightly below average sunshine during December with an average of  9.0 hours per day compared to the historic average of  9.4 hours per day. There was 1 hail day at Canberra Airport (average 0), 0 frosts (average 0 ), no fogs (average 1).  It was slightly windier than usual with an average wind run of 219 km per day (long term average 215 km/day) with 3 strong wind days (average 2).  Air pressure was well above average at 1016.5 hPa (historic average 1011.3 hPa), indicative of the persistence of high pressure systems over the region during December. Evaporation for the month was 271.0 mm well above the average of 250.8 mm.

Canberra Airport  (Elev 578 m)

December

2006

Historic average

2005

 27.7

25.9

 28.8

 12.5

11.3

 12.2

 20.1

18.6

 20.5

16.8

52.3#

 19.8

5

7

 2

9.0

9.4

 11.4

Average relative humidity at 3pm (%)

31

 36

 27

Number of thunderstorms

4

4

 3

Number of windy days

3

 2

 5

  Canberra Airport   (Elev (578 m)

   Tuggeranong    (Elev 587 m)

December 2006

Historic average

December 2006

Historic average#

 27.7

 25.9

 27.7

 27.4

 12.4

 11.3

 12.6

 11.9

 20.1

 18.6

 20.1

 19.7

 16.8

 52.3

 8.0

# 45.3

 5

 7

 2

# 7

Canberra Airport

Tuggeranong

December 2006

All years

December 2006

All years

Highest temperature (°C) and date
Warmest day

35.6
(10th)

39.2   (1994)

  36.1
   (10th)

38.3
(2005)

Lowest temperature (°C) and date
Coldest night

4.8
(26th)

1.1
  (1964)

2.8
 (26th)

1.2
(2001)

Lowest maximum temperature (°C) and date
Coldest day

17.3  (12th)

10.9
(1952)

17.8
(12th)

16.1
(2005)

Wettest day (mm) and date

10.6
(30th)

86.6
  (1948)

 6.8
(24th)

56.0
(1999)

Maximum wind gust (km/h) and date

 ENE
@ 74   (29th)*

NW
@ 105  (1957)

  NE 
@ 65 (29th)

NNW
@ 70
(2005)

This statement has been prepared based on information available at 4pm on 02/01/07. Although every effort has been made to check them, it is possible that results in December and Annual may change as new information becomes available.

A note about deciles: Deciles are used to give an element (in this case rainfall or temperature) a ranking. Deciles are calculated by arranging the totals in ascending order (from lowest to highest) then splitting them into 10 equal groups (thus the groups are called deciles). The first group would be in decile range one, the second group in decile range two, etc up to the highest annual totals (highest 10 per cent) being in decile range 10.

Averages: Historic average temperatures are based on the period 1961 to 1990 which is a convention of the World Meteorological Organisation. Historic rainfall averages and extremes based on the period 1939 to 2005.

Further information: Contact: Owen Offler on 02 62470411 or email: climate.act@bom.gov.au

A directory of Bureau services is available on poll fax: 1800 630 100

The latest rainfall and temperature maps are available here
Climate averages for New South Wales localities are available here
Daily Weather Observations for selected Australian Capital Territory localities are available here