Friday, 1 May 2009 - Monthly Climate Summary for Canberra rainfall extremes - Product code IDCKGC15x0

Canberra has wettest April since 1990

  • Above average rainfall, the highest for April since 1990
  • Close to average maximum temperatures
  • Well above average minimum temperatures, highest for 11 years
  • Coldest consecutive 5 days in April since 1952

An archive of previous monthly summaries for Canberra rainfall extremes is also available, as are summaries for other states and many other climate summaries and diagnostics.

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Rainfall

Following very dry conditions in February and March, some welcome rain was recorded over the ACT during April. Canberra Airport recorded its wettest April since 1990 with a total of 71 mm, compared to the historic average1 of 46 mm. It is also the wettest Autumn month in Canberra since May 1995, which goes against a recent trend of dry Autumns in the ACT. Tuggeranong recorded considerably higher rainfall with a total of 99 mm for the month and Mount Ginini in the Brindabella Ranges recorded 140 mm. There were 10 rain days at Canberra Airport during the month compared to the historic average of 7 rain days. Active low pressure troughs on the 3rd, 14th and 26th were responsible for most of the rain.

Mount Ginini had the Territory's highest April total of 140 mm while Kingston recorded the lowest total of only 67 mm. The wettest day was 42.0 mm at Deakin West on the 14th caused by a low pressure trough.

Temperatures

Daytime temperatures were cool to mild in the ACT during April. Canberra Airport recorded an average maximum temperature of 19.6°C, which is 0.4°C below the historical average of 20.0°C. Daily maximum temperatures reached the low 20's for most of the month except during the last week when a cool change brought much colder weather. Canberra Airport recorded 5 consecutive days (25th to 29th) with a maximum temperature below 15°C, the longest cold spell for April since 1952.

The below average daytime temperatures were partly due to prevailing S-SE winds, especially during the mornings and the partly cloudy, showery weather.

Overnight temperatures were quite mild. The average minimum temperature at Canberra Airport was 8.4°C which is 1.8°C above the historic average. This is the highest average minimum temperature for April since 1998. The minimum temperature on the warmest night was 15.1°C both on the 1st and 2nd. The minimum temperature on the first 3 days of the month exceeded 14.5°C, which has not occurred over 3 consecutive days in April since 1989.

Temperature extremes at Canberra Airport ranged from a high of 28.6°C on the 3rd to an overnight low of 1.8°C on the 29th. The lowest temperature in the ACT was −5.0°C at Mount Ginini AWS on the 29th following a strong cold front.

Wind

S-SE winds prevailed over the ACT during April for 50% of the time during the mornings which is more than twice the normal frequency from this direction. There were 2 windy days recorded during the month associated with westerly winds. The highest wind gust was 96 km/h from NNW at Canberra Airport on the 24th associated with the passage of a cold front, the strongest winds in April since 1993. The more exposed mountains to the SW of the city recorded wind gusts of 100 km/h from the northwest at Mount Ginini AWS on the 25th.

Other phenomena

Cloudy days prevailed in the ACT during April. A total of 14 cloudy days exceeded the historic average of 9 cloudy days. Sunshine averaged 7.1 hours per day, a little below the historic April average of 7.3 hours per day. There were 3 thunderstorms reported at Canberra Airport during the month, on the 3rd, 11th and 14th. Widespread raised dust on the 15th reduced visibility to only 4 km over the ACT. The dust originated over western Victoria and southern NSW and was caused by the combination of strong westerly winds and persistent dry weather over southern inland NSW. At least 10 cm snow fell on the mountains to the SW of Canberra from 26th to the 28th following the passage of a cold front.

Further information

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

Extremes for the ACT

Hottest day
Highest temperature		 28.6°C at Canberra Airport on the 3rd
Warmest days on average
Highest mean daily maximum temperature		 19.6°C at Canberra Airport and Tuggeranong AWS
Coolest days on average
Lowest mean daily maximum temperature		 10.1°C at Mount Ginini AWS
19.6°C at Canberra Airport and Tuggeranong AWS
Coldest day
Lowest daily maximum temperature		 −1.7°C at Mount Ginini AWS on the 26th
10.2°C at Tuggeranong AWS on the 26th
Coldest night
Lowest temperature		 −5.0°C at Mount Ginini AWS on the 29th
1.8°C at Canberra Airport on the 29th
Coolest nights on average
Lowest mean daily minimum temperature		 2.8°C at Mount Ginini AWS
8.4°C at Canberra Airport
Warmest nights on average
Highest mean daily minimum temperature		 8.6°C at Tuggeranong AWS
Warmest night
Highest daily minimum temperature		 16.2°C at Tuggeranong AWS on the 2nd
Wettest overall
Highest total rainfall		 99.2 mm at Tuggeranong Creek
139.8 mm at Mount Ginini AWS
Driest overall
Lowest total rainfall		 67.2 mm at Kingston
Wettest day
Highest daily rainfall		 42.0 mm at Deakin West on the 14th
38.8 mm at Mount Ginini AWS on the 26th
Highest wind gust
 100 km/h at Mount Ginini AWS on the 25th
96 km/h at Canberra Airport on the 24th

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Records in the ACT

Record highest April daily minimum temperature
Highest daily minimum
temperature
in April 2009 (°C) 		Previous highest
for April		 Years of
record		 Average for
April
Tidbinbilla Nature Reserve 15.0 on the 3rd = 15.0 on the 4th in 2007 24 6.5

Summaries for the ACT

This table is very wide and may not fit if printed.

Summary statistics for April 2009
Maximum temperatures
for April
(°C)		 Minimum temperatures
for April
(°C)		 Rainfall
for April
(millimetres)
Mean for

2009		 Diff
from
average		 Highest for
April
2009		 Mean for
April
2009		 Diff
from
average		 Lowest for
April
2009		 Total for
April
2009		 Average
for
April		 Rank of
April
2009		 Fraction of
April
average
Canberra Airport 19.6 −0.4 28.6 3rd 8.4 +1.8 1.8 29th 71.0 46.4 high 153%
Mount Ginini AWS 10.1   17.0 3rd 2.8   −5.0 29th 139.8
Tuggeranong* 19.6 −1.7 28.1 3rd 8.6 +2.2 2.4 16th 98.6

* no rainfall averages due to short record 1996−2008.

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Notes

This statement has been prepared based on information available at noon on Friday 1 May 2009. 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 10 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

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