Thursday 1 February 2007 - Monthly Climate Summary for Sydney - Product code IDCKGC15L0

Sydney has a dry, sunny January

A dry January for Sydney with plentiful sunshine and mild coastal temperatures.

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Main points:

Rainfall

The total monthly rainfall of 45.4mm at Sydney Observatory Hill was well below the historic January average of 103.2mm and ranks in the lowest 30% of all totals.  There were 8 rain days, which was below the historic average of 12 rain days.   Metropolitan rainfall totals were highest in the north shore area and lowest in south-eastern and north-western suburbs.  January totals ranged from 111 mm at Castle Cove in Sydney's inner-north to only 15.5 mm at Seven Hills in the north-west.

Thunderstorms caused heavy but isolated rainfall in the lower Warragamba Dam catchment early in January, with Warragamba Dam recording 71mm on the 2nd.  However, the upper catchment (Goulburn area) received only light and patchy falls.  Monthly totals ranged from 80 - 120mm over the lower catchment to 10 - 20mm in the upper catchment.  Recent rainfall in Sydney's catchments can be found on the Sydney Catchment Authority web site at: http://www.sca.nsw.gov.au/dams/rainfall.html   

Temperatures

The average maximum (daytime) temperature at Observatory Hill was 26.4°C, or 0.4°C above the historic average¹of 26.0°C, making it the 7th consecutive January with above average maximum temperatures. Although this is still above the historic average, it is the lowest average maximum for January since 2000 (when 24.8°C). There were only 2 hot days (temperature exceeding 30°C) compared to the historic average of 3 hot days. Prevailing E-NE winds and lower than normal ocean temperatures contributed towards the mild temperatures along the coast.  However, warm to hot conditions prevailed in the western suburbs where average maximum temperatures were about 5°C warmer than coastal suburbs, due mainly to the absence of cooling sea-breezes. At Penrith there were 21 hot days (over 30°C), the highest for at least 12 years. The historic average is 15 hot days for January.

The average minimum temperature at Sydney (Observatory Hill) of 19.7°C was only 0.5°C above the historic average¹. This is also the coolest since 2000 (when 17.8°C). The far west and lower Blue Mountains recorded minimum temperatures 2 - 3°C cooler than coastal suburbs.  At Springwood (elevation 362 metres) the average minimum was 16.6°C, the lowest in the Sydney area.

The highest temperature at Sydney (Observatory Hill) during January was 38.7°C on the 21st while the lowest was 16.5°C on the 28th. Corresponding extremes across the Sydney metropolitan area ranged from 42.0°C at Badgerys Creek on the 21st to 11.7°C at Campbelltown on the 28th.

Other phenomena

Sydney recorded its sunniest January on record with an average of 9.4 hours of sunshine per day. The previous highest was 9.3 hours per day in 1985. The historic average is 7.5 hours per day.

Although no thunderstorms were recorded at the official Sydney site in the CBD, thunderstorms occurred over western and northern Sydney on the 2nd, 12th and 23rd and along the lower Blue Mountains on the 17th and 24th.  The highest rain recorded from these storms was 71mm at Warragamba Dam (2nd), 61mm at Willmot (2nd) and 32mm at Wisemans Ferry (24th).

Strong winds were recorded along the coast during January with 11 windy days at Sydney Airport, almost twice the historic average of 6 days.  This was due mainly to the persistence of fresh sea-breezes and numerous southerly changes.  However, wind strengths dropped off rapidly away from the coast with only 1 windy day recorded at Bankstown and nil recorded in the western suburbs.

Unusually cool water temperatures were experienced off Sydney's beaches during January.  Water temperatures recorded by Manly Hydraulics Laboratory's waverider buoy (MHL, data funded by Department of Natural Resources), located 12km NE of Sydney Heads, have been well below normal for this time of year, hovering around 17 - 21°C for most of the month, compared to the usual 22°C for January.  The water temperature fell to 17.3°C on 8 January, the lowest recorded in January since MHL records commenced in 1992. Anecdotal evidence from surf clubs suggest even lower temperatures at Sydney's surfing beaches.  This is colder than Sydney typically experiences in mid-winter. The cool water was caused by a period of prolonged NE winds circulating around a large, slow moving high-pressure system in the Tasman Sea early in the month.  This draws the surface water away from the coast, causing colder water in the deeper layers to upwell.  The cold waters also cause atmospheric heat loss and modifies the local climate, contributing towards coastal Sydney's mild January.

A large bushfire at Mt Kuring-gai in Sydney's north on the 23rd burnt out about 1000 hectares of bushland, threatened houses and closed the F3 freeway for about 6 hours.

Further information

Mike De Salis
NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1542
Email reqnsw@bom.gov.au

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Extremes

Hottest day Highest temperature	42.0 °C at Badgerys Creek on the 21st
Warmest days on average Highest mean daily maximum temperature	32.3 °C at Penrith
Coolest days on average Lowest mean daily maximum temperature	26.4 °C at Sydney (Observatory Hill)
Coldest day Lowest daily maximum temperature	20.8 °C at Springwood on the 1st
Coldest night Lowest temperature	11.7 °C at Campbelltown on the 28th
Coolest nights on average Lowest mean daily minimum temperature	16.6 °C at Springwood
Warmest nights on average Highest mean daily minimum temperature	19.8 °C at Sydney Airport
Warmest night Highest daily minimum temperature	23.0 °C at Sydney Olympic Park on the 22nd
Wettest overall Highest total rainfall	111 mm at Castle Cove
Driest overall Lowest total rainfall	15.5 mm at Seven Hills
Wettest day Highest daily rainfall	71 mm at Warragamba Dam and 61 mm at Willmot both on the 2nd, and 44 mm at Castle Cove on the 1st
Highest wind gust	72 km/h at Penrith on the 23rd

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Summaries 

Summary statistics for January 2007
	Maximum temperatures for January 2007 (°C)				Minimum temperatures for January 2007 (°C)				Rainfall for January 2007 (millimetres)
	Mean for January	Diff from normal	Highest for January		Mean for January	Diff from normal	Lowest for January		Total for January	Normal for January	Rank of January	Fraction of January normal
Sydney (Observatory Hill)	26.4	+0.4	38.7	21st	19.7	+0.5	16.5	28th	45.4	103.2	low	44%
Parramatta	29.7	+1.4	41.0	21st	17.5	+0.1	13.8	14th	21.7	107.9	very low	20%
Richmond	31.6	+2.4	40.9	12th	17.6	+0.1	13.4	5th	39.2	93.3	low	42%
Camden	31.3	+2.0	41.1	21st	16.8	+0.1	12.2	28th	18.0	83.6	very low	22%
Springwood*	29.2		38.1	12th	16.6		12.5	5th	77.4	124.7	normal	62%
Terrey Hills**	27.0		39.7	21st	17.7		14.4	28th	49.6

Summary phenomena for Sydney for January
	January 2007	Normal for January
Number of rain days	8	12
Average sunshine hours per day*	9.4	7.5
Average humidity at 3pm (%)	60	62
Number of thunderstorms	0	3
Number of windy days*	11	6

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Notes

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