Australian Monthly Climate Summary: September 2006
Tuesday 3 October, 2006
September was a generally warm month in most of Australia, particularly the southern half. It was also a rather dry month in most parts of the country, except for the east coast and parts of Western Australia. Overall it was Australia’s 7th warmest September on record with a mean temperature anomaly of +1.25°C, whilst mean national rainfall was 28% below normal.
Daytime maximum temperatures (national anomaly +1.48°C) were above normal through most of the country, the only large-scale exception being the northern half of Queensland, with other tropical areas north of about 20°S being near normal. Almost all the extra-tropics, except for coastal areas of north-eastern New South Wales and south-eastern Queensland, were at least 1°C above normal, and most of the extra-tropical mainland east had anomalies exceeding 2°C, except for the Victorian coast. Peak anomalies near 4°C occurred north of Canberra. Maximum temperatures were the warmest on record for September over most of northern Victoria, and large parts of southern inland New South Wales and eastern South Australia.
Overnight minimum temperatures showed weaker anomalies than maxima but were still well above normal (anomaly +1.02°C, 11th highest on record). The strongest warm anomalies in absolute terms were along a west-east belt stretching almost across the country and centred on 25°S, where anomalies were typically in the 2−3°C range. However, it was in the southern half of Western Australia where records were set, particularly on the southern coast around Albany, and in interior areas around and east of Kalgoorlie.
In contrast, minima were well below normal in most of the northern tropics, with anomalies reaching −3°C around Katherine in the Northern Territory, although few records were set. They were also slightly below normal in northern Tasmania, parts of southern inland New South Wales and western and central Victoria. Northern Victoria suffered damaging late-season frosts on 25−26 September, with minimum temperatures generally in the 0 to −2°C range around Shepparton causing heavy losses (estimated at US$50 million) to fruit crops (many of which were ahead of their usual development stage because of the warm conditions up to that point).
* Anomaly is the difference from the long-term average
There were two main areas of above-normal rainfall. One was along the eastern coast between Sydney and Cairns. The first half of the month was particularly wet on the New South Wales coast (107 mm at Sydney on the 7th). This area, however, was dry in the second half of the month (with significant bushfires on the 24th, driven by very strong winds and low humidities). Further north most of the rain fell during the first week of the month. The other major area of above-normal rainfall was in Western Australia north of Perth, particularly in the Pilbara region, where widespread 25−50 mm falls occurred during the first week in a region where significant September rain is very rare. This was sufficient for monthly record highs in the Port Hedland area.
Elsewhere conditions were rather dry, except in Tasmania where rainfall was generally close to normal; the above-normal rainfall along the east coast did not generally penetrate more than 100 kilometres inland. South Australia (86% below normal, second-driest September on record) was especially dry, with most of the Eyre Peninsula having its driest September on record, and no rain in the northern half of the state. (There was also no rain in western Queensland and most of the Northern Territory, but this is normal for September). Other areas with rainfall significantly below normal included parts of the far south of Western Australia, parts of Victoria east and north-east of Melbourne, and south-central New South Wales.
The rather dry September did little to alleviate longer-term drought conditions in much of southern Australia. It was the fourth-driest May-September period on record for southern Australia (south of 26°S), and inflows into the Murray-Darling basin are currently less than 10% of the long-term average for September.