Australian Monthly Climate Summary: August 2009
Wednesday 2 August, 2009
Australia had its warmest August on record in 2009. Mean maximum temperatures, and monthly mean temperatures, both broke previous records by substantial margins, and the maximum temperature anomaly of +3.20°C was the highest on record for any month, beating the +3.11°C observed in April 2005. Overnight minimum temperatures were not as extreme but still fell only just short of a record. It was also a rather dry month over mainland Australia, particularly in Queensland and New South Wales, but was very wet in Tasmania.
Daytime maximum temperatures were above average almost everywhere in Australia, the only exceptions being small areas around Broome and in the northeast Victorian highlands. In addition to the national record, Queensland (4.24°C above average) and the Northern Territory (3.97°C) both had their highest August maximum temperatures, and their largest monthly anomaly for any month, while Western Australia (2nd), South Australia (3rd), New South Wales (3rd) and Victoria (5th) all ranked in the top five.
Maximum temperatures were at least 3°C above average over a vast area of Australia, comprising most areas between about latitudes 20°S and 33°S (equating approximately to Townsville and Sydney respectively) except for the western half of Western Australia. They were more than 5°C above average over much of the southern Northern Territory and the southern half of Queensland away from the coast, with anomalies reaching as high as +6.5°C at Mitchell. The monthly averages set records over 49% of Australia, comprising almost all of Queensland and the Northern Territory except for Cape York Peninsula and the northern Top End respectively, eastern border areas of Western Australia, and northeastern New South Wales north of a Newcastle-Bourke line. There was also a small area of record highs on the coast of far southern New South Wales and far eastern Victoria.
The national minimum temperature anomaly was +1.75°C, ranking second behind the record of +1.78 set in 1998. State records were set in South Australia (+2.57) and Tasmania (+2.21), and the Northern Territory, Queensland and Victoria all ranked second.
Above-average minimum temperatures were not quite as widespread as above-average maxima, with below-average areas scattered across the northern tropics, as well as in northeastern New South Wales, especially away from the coast. Elsewhere they were above normal, and were at least 2°C above normal in a large area covering the northern half of South Australia and the southern halves of Queensland and the Northern Territory (except for Queensland's southeast corner), as well as in most of Tasmania. They reached 4−6°C above average in parts of far southwest Queensland and the southern Northern Territory. Records were set over much of the central continent between Port Augusta and Tennant Creek, extending into southwestern Queensland, as well as over almost all of Tasmania and central Victoria around Melbourne.
The abnormal warmth became particularly notable during the last ten days of the month, with many stations setting record high maximum or minimum temperatures (or both) for August, in some cases by large margins. This included new state records for both maximum and minimum temperature for NSW and Queensland. In NSW these were 37.8°C at Mungindi on the 24th and 23.3°C at Lismore on the 25th respectively, while the Queensland equivalents were 38.5°C at Bedourie on the 29th and 26.5°C at Urandangi on the 25th. The month's highest temperature, 39.7°C at Wyndham Airport on the 31st, fell only 0.3°C short of the Australian record for August.
*Fractional ranks denote tied values. **Anomaly is the departure from the long-term average.
It was also a generally dry month over mainland Australia. The national mean was 44% below normal, the 12th lowest on record for August, with Queensland (4th, 93% below normal) and New South Wales (8th, 74% below normal) both in the driest ten Augusts on record. The only substantial parts of the mainland to experience above-average rainfall in August were southwestern Victoria also with parts of south Gippsland, and parts of southwestern Western Australia, especially around Perth. Much of Queensland had no rain (although a rainless August is not unusual in the state's west), and most of the eastern half of the state ranked in the lowest decile, along with large parts of northern and central New South Wales.
Conversely, it was a very wet month in Tasmania, which had its third wettest August on record (99% above normal). Rainfall was in the highest decile almost throughout the state except on the southeast coast, and reached record levels over parts of the island's west and central east.
*Fractional ranks denote tied values.
**A new area-averaging method has been adopted for rainfall from May 2009. Current and historical totals for Tasmania are substantially higher than under the old scheme, but differences for other states, and nationally, are negligible.