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

Sydney has cool to mild and humid January

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

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

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

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


Notes

This statement has been prepared based on information available at 10am on Friday 1 February 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 - 2007 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.