Friday 1 February 2008 - Monthly Climate Summary for Sydney extremes - Product code IDCKGC1xx0

Sydney has cool to mild and humid January

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Details

• Cool to mild, partly cloudy days with close to average maximum temperatures
• Warm, humid nights with above average minimum temperatures
• Persistent warm nights, 19 nights with minimum temperature above 20°C (normally 11 nights above 20°C)
• Below average rainfall, except far western suburbs
• Slightly below average sunshine

Rainfall

The total January rainfall of 57 mm at Sydney Observatory Hill was below the historic January average¹ of 102.8 mm. There were 11 rain days during the month, slightly below the January average of 12 rain days. Rainfall distribution indicates the highest totals in northern and western suburbs while the lowest totals were in the south-east. Below average rainfall occurred throughout the metropolitan area except for the Penrith - Springwood area which recorded slightly above average January rainfall. Monthly totals ranged from 142 mm at Springwood and 118 mm at Glenmore Park on Sydney's extreme western edge. In the east, the highest total was 110 mm at Terrey Hills AWS. The lowest total was 38 mm at Sydney Olympic Park.

Persistent high-pressure systems near Tasmania for most of the month caused moist, prevailing NE to SE airstreams on the NSW coast including Sydney. A low pressure system which drifted south from Queensland through central NSW mid-month brought tropical moisture and the majority of Sydney's rain for the month.

The Warragamba Dam catchment generally received moderate rainfall during January contributing to a slight rise in storage levels. Monthly totals over the catchment were in the 60 - 90 mm range with heavier falls of 200 mm at Katoomba on the north-east catchment divide. 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.

Temperature

Below average maximum temperatures were recorded over most of the Sydney metropolitan area during January. The average maximum temperature at Observatory Hill was 26.0°C, which equals the historic¹ average maximum. However, over the remainder of the metropolitan area, maximum temperatures were generally below the historic average by up to 1°C. The main moderating effect on temperatures were the frequent cloudy and partly cloudy days, persistent onshore winds and the absence of any hot NW winds. Afternoon winds were between SE to NE for 80−90% of the time along the coast.

Night-time temperatures were above the historic average over the whole Sydney metropolitan area during January. The average minimum temperature of 20.3°C at Observatory Hill was 1.2°C above the historic¹ January average. Nights were persistently warm - there were 19 nights when the temperature did not fall below 20°C at Observatory Hill. Normally Sydney would expect 11 nights above 20°C. Although average minimum temperatures were 2−3°C cooler in far western suburbs they were still above the historic January average at all inland sites.

The highest temperature at Sydney (Observatory Hill) during January was a mild 30.6°C on the 13th while the lowest overnight temperature was also a mild 15.9°C on the 24th. Corresponding extremes in the Sydney metropolitan area ranged from a daytime high of 38.4°C at Penrith Lakes on the 13th to an overnight low of 10.9 °C at Camden on the 24th.

Wind

The prevailing direction over coastal Sydney during the afternoon was between SE to NE for 80−90% of the time, which is well above the normal frequency from this direction at this time. The highest wind gust recorded was 102 km/hr from the ESE at Penrith Lakes on the 13th due to thunderstorm activity.

Other phenomena

Only 2 thunderstorms were reported from the official Sydney Observatory Hill site during January, against an historic average of 3 storms. However, a severe thunderstorm in the NW suburbs on the 16th brought strong winds, heavy rain and 2cm size hail. Another severe thunderstorm on the 20th affected southern suburbs with very heavy rain and flash flooding. Two people were drowned when caught by floodwaters in a stormwater drain at Maroubra in Sydney's south-east.

Associated with the moist SE-NE winds was the high humidity. The average relative humidity at Sydney Observatory Hill at 3pm was 66%, one of the highest levels in recent years. The normal at this time is 62%.

It was a partly cloudy month, the average daily sunshine was 7.4 hours per day, slightly below the historic average of 7.5 hours per day. During a dull, rainy spell from 17th to 21st, only 7 hours of sunshine were recorded out of a possible maximum of 64 hours.

Further information

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

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Extremes for the Sydney area

Hottest day Highest temperature	38.4°C at Penrith Lakes on the 13th
Warmest days on average Highest mean daily maximum temperature	29.1°C at Penrith Lakes
Coolest days on average Lowest mean daily maximum temperature	25.5°C at Terrey Hills AWS
Coldest day Lowest daily maximum temperature	18.1°C at Springwood on the 14th
Coldest night Lowest temperature	10.9°C at Camden Airport on the 24th
Coolest nights on average Lowest mean daily minimum temperature	16.9°C at Campbelltown and at Springwood
Warmest nights on average Highest mean daily minimum temperature	20.3°C at Sydney (Observatory Hill) and at Sydney Airport
Warmest night Highest daily minimum temperature	23.4°C at Sydney (Observatory Hill) on the 30th
Wettest overall Highest total rainfall	142.0 mm at Springwood. In the east 110.2 mm at Terrey Hills AWS
Driest overall Lowest total rainfall	39.4 mm at Sydney Olympic Park AWS.
Wettest day Highest daily rainfall	44.2 mm at Springwood on the 20th. In the east 39.6 mm at Terrey Hills AWS on the 19th
Highest wind gust	102 km/hr from the ESE at Penrith Lakes on the 13th

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Summaries for the Sydney area

Summary statistics for January 2008
	Maximum temperatures for January (°C)				Minimum temperatures for January (°C)				Rainfall for January (millimetres)
	Mean for January 2008	Diff from normal	Highest for January 2008		Mean for January 2008	Diff from normal	Lowest for January 2008		Total for January 2008	Normal for January	Rank of January 2008	Fraction of January normal
Sydney (Observatory Hill)	26.0	normal	30.6	13th	20.3	+1.2	15.9	24th	57.0	102.8	normal	55%
Camden Airport	28.5	−0.8	36.1	13th	17.4	+0.7	10.9	24th	68.0	81.6	normal	83%
Parramatta	27.5	−0.8	36.1	13th	18.3	+0.9	12.2	24th	78.6	105.8	normal	74%
Richmond RAAF	28.4	−0.8	37.7	13th	18.1	+0.6	11.4	24th	76.6	93.3	normal	83%
Springwood*	26.5		34.8	13th	16.9		12.3	24th	142.0	124.4	normal	114%
Terrey Hills*	25.5		31.8	13th	18.3		14.2	24th	110.2

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

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Additional climate data for Sydney (Observatory Hill) for January 2008
	January 2008	Normal for January
Number of rain days	11	12
Average sunshine (hours per day)*	7.4	8.0
Average humidity at 3pm (%)	66	62
Number of thunderstorms	3	3
Number of windy days*	10	7

* recorded at Sydney Airport

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Notes

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