Monday, 3 March 2008 - Seasonal Climate Summary for Sydney extreme rainfall - Product code IDCKGC25x0

Sydney has coolest summer in 11 years

Details

  • coolest summer since 1996−97
  • zero days over 31°C, only occurred during 3 previous summers
  • wettest summer since 2001−02
  • cloudy summer, least amount of sunshine since 1991−92

Rainfall

The total summer rainfall of 438.6 mm at Sydney (Observatory Hill) was well above the historic summer average1 of 298 mm, making it the wettest summers for 6 years. There were 45 rain days, which is well above the historic average of 36 rain days and the highest for 9 years. The highest summer rainfall totals in Sydney were in the north shore area while the lowest were in southern suburbs. Totals ranged from a high of 607 mm at Turramurra to a low of 384.6 mm at Sydney Airport.

The cloudy, wet summer was caused by persistent and moist NE - SE winds over NSW including Sydney, and is consistent with the current ongoing La Nina event in eastern Australia. 

Sydney's Warragamba Dam catchment area recorded summer rainfall totals of 300−400 mm in the lower catchment which is a little above the normal summer rainfall in this area. The highest total was 572 mm at Katoomba on the catchment divide. In the upper catchment (Goulburn area) totals of around 250 mm were also above the normal summer rainfall. Recent rainfall in Sydney's drinking water catchments can be found on the Sydney Catchment Authority web site http://www.sca.nsw.gov.au/dams/rainfall.html.

Some sites had their highest total summer rainfall on record.

Temperatures

Sydney had its coolest summer in 11 years which stands in contrast to the frequent warm summers Sydney has experienced in recent years. The average maximum (daytime) temperature at Observatory Hill was 25.2°C, which is 0.7°C below the historic summer average1 of 25.9°C and the coolest since 1996−97. Well below average summer maximum temperatures were recorded over the entire metropolitan area, especially the far west. At Richmond, the average maximum temperature was more than 2.0°C below normal and the coolest since the summer of 1971−72.

The summer stands out as having virtually no hot days with zero days exceeding 31°C at Sydney Observatory Hill. This has occurred only 3 times before, in 1956, 1953 and 1873. The high frequency of cloudy days, subsequent lack of sunshine and persistent onshore winds from SE - NE contributed to the cool conditions during summer.

Sydney's summer nights, however, were quite mild. The average minimum temperature at Observatory Hill of 19.1°C was 0.3°C above the historic summer average1 of 18.8°C, though this is still the coolest for 8 years. Although average minimum temperatures in the western suburbs were a degree or two cooler than coastal suburbs, they were still slightly above the historic summer average at all recording sites.

Sydney has now experienced 8 consecutive years with above average minimum temperatures in summer.

The highest temperature at Sydney Observatory Hill during summer was a very mild 30.6°C on 13 January while the lowest temperature was 14.6°C on 10 February.  Corresponding extremes across the Sydney metropolitan area ranged from a high of 38.4°C at Penrith Lakes on 13 January to a low of 9.7°C at Campbelltown on 26 Dec 2007 and at Badgerys Creek on 24 Feb 2008.

Wind

There were 21 windy days* in coastal Sydney during summer, compared to the historic average of 19 windy days. The prevailing coastal wind direction was SE - NE for about 50% of the time during summer. The highest wind gust recorded in the Sydney metropolitan area was 102 km/h at Penrith Lakes on 13 January associated with thunderstorm activity.

Other phenomena

There were 15thunderstorms in Sydney during summer, the highest number since summer of 1962−63 (when 16 storms). Sydney averages around 10 storms in summer. It was a cloudy summer with well below average sunshine hours. Sunshine averaged of 6.7 hours per day, the lowest since 1991−92.

Further information

Mike De Salis
NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email mikede@bom.gov.au

Extremes for the Sydney area

Hottest day
Highest temperature
38.4°C at Penrith Lakes on 13 Jan 2008
Warmest days on average
Highest mean daily maximum temperature
27.3°C at Penrith Lakes
Coolest days on average
Lowest mean daily maximum temperature
24.2°C at Terrey Hills
Coldest day
Lowest daily maximum temperature
17.0°C at Springwood on 11 Dec 2007
Coldest night
Lowest temperature
9.7°C at Campbelltown on 26 Dec 2007 and at Badgerys Creek on 24 Feb 2008
Coolest nights on average
Lowest mean daily minimum temperature
15.8°C at Campbelltown (Mount Annan)
Warmest nights on average
Highest mean daily minimum temperature
19.1°C at Sydney (Observatory Hill) and at Sydney Airport
Warmest night
Highest daily minimum temperature
23.4°C at Sydney (Observatory Hill) on 30 Jan 2008
Wettest overall
Highest total rainfall
607.0 mm at Turramurra
Driest overall
Lowest total rainfall
384.6 mm at Sydney Airport
Wettest day
Highest daily rainfall
148.8 mm at Camden Airport on 5 Feb 2008
Highest wind gust
102 km/h at Penrith Lakes on 13 Jan 2008

Records for the Sydney area

Record highest total summer rainfall
Total rainfall
for summer 2007−08 (mm)
Previous highest
for summer
Years of
record
Normal for
summer
Campbelltown (Kentlyn)
498.0
408.6 in 1970
28
219.3


Summaries for the Sydney area

Summary statistics for summer 2007−08
Maximum temperatures
for summer
(°C)
Minimum temperatures
for summer
(°C)
Rainfall
for summer
(millimetres)
Mean for
summer
2007−08
Diff
from
normal
Highest for
summer
2007−08
Mean for
summer
2007−08
Diff
from
normal
Lowest for
summer
2007−08
Total for
summer
2007−08
Normal
for
summer
Rank of
summer
2007−08
Fraction of
summer
normal
Sydney (Observatory Hill) 25.2 −0.7 30.6 13 Jan 2008 19.1 +0.3 14.6 10 Feb 2008 438.6 298.2 high 147%
Camden Airport 26.7 −2.2 36.1 13 Jan 2008 16.4 +0.2 10.0 14 Dec 2007 448.8 234.5 very high 192%
Parramatta 26.0 −1.9 36.1 13 Jan 2008 17.1 +0.1 11.6 29 Feb 2008 514.0 301.1 very high 170%
Richmond RAAF 26.8 −2.1 37.7 13 Jan 2008 17.1 +0.1 11.4 24 Jan 2008 449.4 269.7 very high 166%
Springwood* 25.0   34.8 13 Jan 2008 15.9   10.0 29 Feb 2008 490.4 368.5 high 133%
Terrey Hills* 24.2   31.8 13 Jan 2008 17.1   11.6 29 Feb 2008 551.2

* new stations, no historic average temperatures available and no historic average rainfall available for Terrey Hills.

Additional climate data for Sydney (Observatory Hill) for Summer 2007−08
 

Summer 2007−08

Normal for Summer

Number of rain days

45
36

Average sunshine hours per day*

6.7
7.6

Average humidity at 3pm (%)

64
62

Number of thunderstorms

15
10

Number of windy days*

21
19

* recorded at Sydney Airport. Windy day defined as average wind speed of 40 km/hr or more over a 10 minute period.


Notes

This statement has been prepared based on information available at noon on Monday 3 March 2008. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

1Averages:  historic average temperatures for Observatory Hill and Richmond are based on the period 1961 to 1990 which is a convention of the World Meteorological Organisation.  Average temperatures for Parramatta are based on all available data, 1968 - 2006 and Camden 1972 - 2007.  Rainfall averages and extremes for Observatory Hill are based on all years of record 1859 - 2007.

Normals 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 "normal" 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, normal in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of normal shows how much rain has fallen this time as a percentage of the long-term mean.