Australian Monthly Climate Summary: September 2007
Wednesday 3rd October, 2007
September 2007 was exceptionally dry over large parts of the continent. It was also a very warm month in much of southern Australia, especially in the central to western southern regions. Overall, mean temperatures were 1.33°C above the 1961−90 normal (6th warmest of 58 years) and rainfall was 54% below normal (12th driest of 108 years).
Daytime temperatures were above normal throughout much of the country. Anomalies exceeding +2°C (locally +4°C) covered most of SA, the southern half of the NT, much of WA (excluding the northern and southwestern parts), southwestern Queensland, the western two-thirds of NSW and just the northwest corner of Victoria. Monthly records were set in a few places, notably in a large area extending out from Broome, WA, and in SA on the Eyre and York Peninsulas and on Kangaroo Island. state-wide maxima were the third-warmest on record for September in SA, and the fourth-warmest in WA. Tasmania was the only state not in the top ten warmest Septembers on record for maximum temperatures. There were only small areas along the east coast, especially in Queensland, that recorded below average temperatures. However, these were only generally up to 1°C below average and so did not register in the lowest three deciles.
The pattern of minimum temperatures anomalies was fairly scattered across the continent. In the centre of the country, in northern SA, anomalies greater than +4°C were recorded in a small area, typically though, positive anomalies were between +1 and +2°C. Warm anomalies exceeded +1°C through much of the southern parts of the NT and Queensland and also in small patches throughout WA. Areas in southern WA and northern SA had minima in the highest decile and records were set in the Lake Eyre region. Similarly warm conditions also extended to eastern Victoria and Tasmania, and state-wide means ranked in the top six in NSW, Queensland and Tasmania.
Below-normal minima, with anomalies between −1 and −2°C, covered northern parts of the NT and north-central Victoria extending into NSW. Areas of minima in the lowest decile covered northern NT, northern Queensland and northeastern Victoria, where a large area recorded lowest on record minimum temperatures.
* Anomaly is the difference from the long-term average
The most significant area of below-normal rainfall was in NSW, with a large area of lowest on record rainfall in the central northern half of the state. Much of the rest of the state was in decile 1(very much below average), making it the fourth driest September on record over NSW. South Australia, and to a lesser extent Victoria, were also covered by areas of below average and very much below average rainfall, with SA also recording some areas of lowest on record. The Murray Darling Basin (MDB), Australia's main agricultural region which spans these four states, experienced its driest September on record (74% below normal). Western Australia and the NT also recorded large areas of below average rainfall (although it's a seasonally dry time of year over much of these regions), with WA recording some areas of decile 1 in the southern half of the state. Elsewhere, Queensland and Tasmania had state-wide means close to average, though in Queensland this was due to wetter than average conditions in the eastern half of the state and drier than average conditions in the southwest.
Whilst much of Australia experienced below average rainfall for the month of September, there were some parts of the country that recorded wetter than normal conditions. These were mainly in Queensland, with unseasonable falls of greater than 100 mm to the north of Brisbane and also in the area around Rockhampton. Above normal falls were also recorded in the southwest corner of the country, in an area stretching from Perth to Albany.