Tuesday, 4 January 2005

ANNUAL CLIMATE SUMMARY - ACT

Record hot, dry spell in a year to remember for the ACT

Weather in the ACT in 2004 was characterised by well below-average rainfall and the driest February-to-July period on record, though there were more thunderstorm days than normal. Daytime and night-time temperatures were above average for the year, the mean daily temperature was the equal highest on record, and there was a record low number of fogs. It was also windier than normal.

Rainfall: A total of 435.2 millimetres of rain was recorded at Canberra Airport in 2004, considerably below the average of 625.2 mm. Rainfall from January to July was considerably below average, and the period February to July was the driest on record. Falls in September and October were just below average, while rainfall in August, November and December was above average. The wettest month of the year was November when 85.8 mm was recorded. The driest month was April with only 2.4 mm. The highest 24-hour rainfall total to 9am was 34.0 mm on 12 November and was associated with a thunderstorm on the 11th. There was only one other occasion (31 August) when 30 mm or more was recorded. There were four occasions when 20-30 mm fell in a 24-hour period. The number of rain days for the year, 84, was much less than the average of 105 days, and there was no record of snow falling at Canberra airport during the year.

Thunderstorms: The number of thunderstorm days at the airport, 30, was more than the average of 23 thunderstorm days. Thunderstorm activity was particularly great in January, with seven days compared with the average of four. There were four thunderstorm days in September compared with the average of one, and nine thunderstorm days in December compared with the average of three. Four of the thunderstorms - on 2 November, 6 and 7 December, and 13 December - were classified as severe due to their heavy rain and/or large hail. Hail was recorded at the airport on four occasions, and in the northern suburbs on 7 December. On 2 November a rain rate of 44 mm an hour was recorded at the headquarters of the ACT Emergency Services Authority in Curtin. The intensity of rainfall during this thunderstorm occurs on average once every 50 years in the ACT. The storm also produced hail of 3-4 centimetres in diameter in southern suburbs.

Temperature: The mean daytime maximum temperature for 2004 was 21.0 degrees Celsius, well above the average of 19.6 degrees. The mean annual night-time temperature was 7.0 degrees, also above the average of 6.5. The mean daily temperature for 2004 was 14.0 degrees, well above the long-term average of 13.0, and the equal highest on record with 1980 and 1998. It was the eighth consecutive year that the mean daily maximum and minimum temperatures were either average or above average. The warmest month was February, with an average daily temperature of 22.2 degrees. The coldest was July with an average daily temperature of 5.9 degrees.

Max temps: Mean daily maximum temperatures were above average in all months. The highest average daily maximum was 30.6 degrees in February, while the lowest was 12.1 in July. The temperature reached 30.0 degrees or more on 45 days during the year compared with the average of 30 days. Of those, 15 occurred in February compared with the February average of eight days. The temperature reached 35.0 degrees or more on 14 days compared with the average of five. Of those, four occurred in January, eight in February and two in November. The highest maximum temperature of the year was 38.7 degrees on 14 February. The lowest was 6.5 degrees on 17 July.

Min temps: Mean daily minimum temperatures were below average in March and May, but above average in all other months. There were 89 frosts for the year compared with the average of 99. Of those, 51 occurred in winter (average 58), 15 in spring (average 21) and 22 in autumn (average 18). The first frost of the year was recorded on 8 April compared with the median date of 9 April. The last frost was on 29 December compared with the median date of 16 November. The lowest temperature of the year was minus 7.3 degrees on 21 July.

Fogs: There were only 20 fogs for the year, less than half the average of 44, a record low number. The previous record was 23 fogs in 1967. No fogs were recorded in January (average one), February (average one), April (average four), November (average one) or December (average one). All other months recorded either average or fewer then average fogs. The foggiest month was July with six fogs compared with the average of seven.

Wind: The mean daily wind run for the year was 205.8 kilometres a day, much more than the long-term average of 183.9 km/day. The record wind run of 209.6 km/day was set in 1986. The windiest month was June (270 km/day), a record for the month, while the calmest was April with 153 km/day. There were 39 strong wind days, well above the average of 25 days. The record number of strong wind days is 48, set in 1983. There were two gales recorded for the year compared with the average of one. The strongest wind gust was 87 km/h on 27 October.

Sunshine: Canberra had an average of 8.3 hours of sunshine a day for the year, much more than the mean of 7.6 hr/day. The year was the equal second sunniest year on record, along with 1997. The record is 8.4 hr/day set in 2002. September and October were the only months to have less than average sunshine, while March had a record high dose of sunshine. The evaporation of 1809.8 mm for the year was considerably more than the average of 1686.6 mm.

Pressure: The average daily pressure of 1016.6 hectopascals was close to the average of 1016.7 hPa. July had the highest mean daily pressure of 1022.6 hPa, while January had the lowest of 1009.1 hPa.

Summary for Canberra airport, 2004

Mean maximum temperature: 21.0°C (av 19.6°C)
Highest maximum temperature: 38.7°C (14 February)
Lowest maximum temperature: 6.5°C (17 July)
Mean minimum temperature: 7.0°C (av 6.5°C)
Highest minimum temperature: 21.8°C (1 December)
Lowest minimum temperature: minus 7.3°C (21 July)
Mean daily temperature: 14.0°C (av 12.9°C)
Lowest grass temperature: minus 12.0°C (21 July)
Annual rainfall: 435.2 mm (av 625.2 mm)
Annual evaporation: 1809.8 mm (av 1686.6 mm)
Mean daily sunshine: 8.3 hr/day (av 7.6 hr/day)
Mean daily pressure: 1016.6 hPa (1016.7 hPa)
Mean daily wind run (at 2 metres): 205.8 km/day (av 183.9 km/day)

Ends

Further information:
Clem Davis, Canberra Meteorological Office, tel: (02) 6249 6269, e-mail: c.davis@bom.gov.au