Sydney in 2011: Warm, wet year for Sydney

  • Wettest year since 2007
  • 19th consecutive year with above average temperatures
  • Most hot nights on record

Rainfall

Sydney Observatory Hill recorded 1369.2 mm of rain during 2011, above the historical average of 1137.0 mm and the wettest year since 2007. The year was wettest in northern parts of the city, reaching 1706 mm at Turramurra, its wettest year since 1998, while rainfall was closer to average in western Sydney. The rain fell over 175 days, the highest for Sydney since 1959 (179 days), although no days exceeded 100 mm compared to an average of 0.8 days. The wettest day at Observatory Hill was March 22nd, when 99.4 mm was recorded.

Following a dry start to the year, including the driest February in thirty years, rainfall was well above average during autumn, with both March and April the wettest in over a decade. This included a particularly severe event associated with a coastal low pressure system during March, with daily totals of up to 178 mm at St Ives on the 20th and flash flooding throughout the Sydney Metropolitan area.

Rainfall was closer to average during winter and spring, with most months between June and October recording close to median falls. The exception was during July, when an East Coast Low caused daily falls as high as 132.6 mm at Duffys Forest on the 22nd. This event caused four-day totals of 261.8 mm at Sydney Observatory Hill between the 20th and 23rd, the wettest four-day period in the city since an East Coast Low in August 1998, with the July rainfall total the highest in 50 years. This event was restricted to coastal areas, with much of western Sydney recording below average rainfall during the month, contributing to the lower annual totals in these regions.

Rainfall increased again towards the end of the year as a La Niña event developed in the Pacific. November was the wettest since 2007, with significant rain between the 23rd and 26th. The rain continued into December, which was close to average at Observatory Hill but well above average in western and northern Sydney.

Sydney's water storage is currently at 80.4% of capacity. This is similar to December levels, and 8% higher than at the beginning of 2011 (72.5%). Current water storage information can be found on the Bureau of Meteorology Water Storage web site.

Temperature

Sydney Observatory Hill recorded an average temperature of 18.7 °C during 2011, 1 °C above the historical average and the 19th consecutive year with above average temperatures in Sydney. Only two months were below average during the year, with temperatures 0.4 °C below average during May and 1.4 °C below average during December, the 9th coolest on record. In comparison, four months (January, February, August and November) fell in the warmest 5 years in more than 150 years of record at Sydney. Temperatures were warmest in eastern parts of Sydney, with closer to average conditions in the west.

The average maximum temperature in Sydney during 2011 was 22.6 °C, 0.9 °C above the historical average and the 19th consecutive warm year. Minimum temperatures were also 1 °C above average for the 41st consecutive year, although cooler than both 2010 and 2009. There were 24 days above 30 °C during the year, the highest since 2006, of which 5 reached 35 °C. There were also a record-breaking 7 nights above 24 °C, most of which fell during February; the previous record was 3 hot nights, set in 2010. In comparison, no nights during 2011 fell below 5 °C, compared to a historical average of 3 nights.

Temperatures were warmest at the start of the year, with January and February both the second warmest on record for minimum temperatures and among the top five for maximums. This was associated with generally sunny conditions and low rainfall, with a record-breaking heatwave during the first week of February. Record minimum temperatures were recorded at several stations, including 5 consecutive nights above 24 °C between the 2nd and the 6th (previous longest was 2 days). Sydney also experienced 7 consecutive days above 30 °C between January 31 and February 6th for the first time on record, reaching 41.5 °C on the 5th. For more information on this heatwave please see our Special Climate Statement 27, released February 8.

Both maximum and minimum temperatures were closer to average during autumn, with particularly cool temperatures during May. This was the coldest for Sydney since 1970, and well below average in western Sydney. Temperatures warmed again during winter & spring, with particularly warm conditions during August and November. There were ten consecutive days above 20 °C between July 28 and August 6th, only the fourth time on record for August and the closest to midwinter, while November was the 3rd warmest on record for minimum temperatures.

Temperatures cooled again during early summer, with the coldest December since 1960 for maximum temperatures at Sydney Observatory Hill, and the coolest on record at stations with shorter records in the west and south. The cool temperatures were a result of cloudy conditions and anomalously southerly winds, as well as a lack of any hot days during the month, with just 7 days above 25 °C and a maximum daily temperature of just 26.8 °C. In particular, a cold snap in early December caused 8 consecutive days below 23 °C between the 1st and 8th, the first time for summer since 1967, including two consecutive days below 20 °C on the 5th and 6th.

Some sites had their warmest night (highest daily minimum temperature) on record.

Wind

Prevailing wind directions at Sydney Airport during 2011 were N-W at 9am (52%) and NE-S in the afternoons (66%), similar to the average distributions. There were 46 strong wind days reported at the airport, below the historical average of 63 strong wind days, with a maximum wind gust of 85 km/hr associated with the East Coast Low on July 20. Strong winds also caused substantial damage in the Blue Mountains on July 7th and 8th, with numerous fallen trees causing damage to houses and trains and large areas without power. Minor wind damage was also reported on August 19, with gusts of 81 km/hr at Sydney Airport and up to 104 km/hr at Wattamolla, the strongest wind gust anywhere in Sydney during 2011.

Other phenomena

Sydney Airport recorded an average of 6.6 hours of bright sunshine during 2011, below the historical average of 7.2 hours and the lowest since 6.6 hours in 1998. Sunshine was average to below average for most of the year, including the cloudiest Autumn since 2001. There were only 69 clear days, well below the average of 104 days and the fewest since 65 clear days in 1950, but close to average cloudy days. There were only 8 thunderstorms reported at Sydney Airport during 2011, with 39 reported anywhere in the metropolitan region during the year. Four storms were associated with reports of hail during the year, although none were significant.

Further information

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Extremes in 2011
Hottest day 42.2 °C at Sydney Airport AMO on 5 Feb
Warmest days on average 24.0 °C at Penrith Lakes AWS
Coolest days on average 21.2 °C at Terrey Hills AWS
Coldest day 9.5 °C at Richmond RAAF on 13 Jul
Coldest night -3.1 °C at Richmond RAAF on 9 Jul
Coolest nights on average 10.5 °C at Camden Airport AWS
Warmest nights on average 14.8 °C at Sydney (Observatory Hill)
Warmest night 27.6 °C at Sydney (Observatory Hill) on 6 Feb
Warmest on average overall 18.7 °C at Sydney (Observatory Hill)
18.7 °C at Sydney Airport AMO
Coolest on average overall 16.8 °C at Springwood (Valley Heights)
Wettest overall 1706.0 mm at Turramurra (Kissing Point Road)
Wettest day 178.6 mm at St Ives (Richmond Avenue) on 20 Mar
Highest wind gust104 km/h at Wattamolla AWS on 19 Aug

Record highest annual daily minimum temperature
Highest daily minimum
temperature
in 2011 (°C)
Previous annual
warmest
Years of
record
Annual
average
Sydney (Observatory Hill) 27.6 on 6 Feb 26.6 on 6 Feb 1973 153 13.8
Sydney Airport AMO 26.4 on 6 Feb 25.8 on 23 Jan 2010 73 13.4
Bankstown Airport AWS 26.0 on 2 Feb 25.0 on 8 Dec 1990 44 12.0
Camden Airport AWS 24.0 on 3 Feb = 24.0 on 23 Dec 2000 38 10.2
Riverview Observatory 26.2 on 6 Feb 25.7 on 22 Dec 1997 30 12.3



Summary statistics for 2011
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean
for
2011
Diff
from
average
Highest
for
2011
Mean
for
2011
Diff
from
average
Lowest
for
2011
Total
for
2011
Average
annual
total
Rank
of
2011
Fraction
of annual
average
Badgerys Creek AWS 23.5   41.5 1 Feb 11.0   -1.7 12 Jul 734.0
Bankstown Airport AWS 23.1 -0.1 41.6 1 Feb 12.4 +0.4 0.6 8 Jul 884.6 874.3 average 101%
Camden Airport AWS 23.4 -0.2 41.3 1 Feb 10.5 +0.3 -2.1 8 Jul 757.4 787.9 average 96%
Campbelltown (Mount Annan) 23.4   40.6 5 Feb 10.6   -2.0 8 Jul 702.8
Canterbury Racecourse AWS 22.7   41.0 1 Feb 12.4   0.9 8 Jul
Holsworthy Control Range 23.0   41.7 1 Feb 11.4   -1.8 8 Jul
Horsley Park Equestrian Centre AWS 23.1   41.9 1 Feb 12.0   0.1 8 Jul 755.6
Parramatta North (Masons Drive) 23.0 -0.3 41.0 1 Feb 12.4 +0.2 1.0 9 Jul 1141.7 967.3 high 118%
Penrith Lakes AWS 24.0   41.8 1 Feb 12.4   -0.3 9 Jul 704.6
Prospect Reservoir 23.0 -0.2 41.3 1 Feb 12.4 +0.2 0.8 8 Jul 829.2 870.6 average 95%
Richmond RAAF 23.4   40.0 5 Feb 11.3   -3.1 9 Jul 729.8
Riverview Observatory 22.5 +0.3 41.3 5 Feb 13.2 +0.9 2.9 8 Jul 1316.1 1133.1 high 116%
Springwood (Valley Heights) 21.6   38.8 1 Feb 11.9   0.9 9 Jul 1006.4 1090.6 average 92%
Sydney (Observatory Hill) 22.6 +0.9 41.5 5 Feb 14.8 +1.0 5.5 8 Jul 1369.2 1215.0 high 113%
Sydney Airport AMO 22.6 +0.4 42.2 5 Feb 14.7 +1.3 5.4 15 Jul 1248.6 1084.2 high 115%
Terrey Hills AWS 21.2   40.3 1 Feb 13.0   1.9 9 Jul 1404.2

Notes

A Annual Climate Summary is prepared to list the main features of the weather in Sydney - Greater Sydney 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

Media
(03) 9669 4057
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