Australian Seasonal Climate Summary: Autumn 2009 (March-May)
Tuesday, 2 June 2009
Autumn 2009 saw below-normal rainfall over most of Australia, although it was not quite as dry as autumn 2008 had been. Rainfall was below the long-term mean in all states and territories. Temperatures during the season were mostly unexceptional, with daytime maximum temperatures mostly slightly above normal and overnight minima very close to normal.
Daytime maximum temperatures over Australia were 0.51°C above normal (19th warmest of 60 years). All states and territories were above normal but none ranked in the top ten. The strongest warm anomalies were along the west coast of Western Australia, where anomalies in the +1−2°C range between Shark Bay and Perth ranked in the highest decile. Anomalies also exceeded +1°C in much of the Kimberley and the western and northern Northern Territory (reaching the highest decile in the Top End), as well as much of southern inland Queensland.
Below-normal maximum temperatures covered most of western South Australia, the southeast of South Australia and southwest coast of Victoria, western Tasmania and patches in northern Queensland. Anomalies were below 1°C almost everywhere and no areas were in the lowest decile.
Minimum temperatures for the season were within 1°C of normal almost everywhere, and the national average was very close to normal (0.02°C below, 27th highest of 60 years). The only area in the lowest decile was the Gascoyne coast in Western Australia, where anomalies were around −1°C.
The most significant warmth was in Tasmania (where a state anomaly of +0.45°C was 8th highest on record). Other areas with above-average minima included eastern New South Wales, far eastern Victoria, much of Queensland (except for a band along the Tropic of Capricorn), most of South Australia (except the eastern fringe and Eyre Peninsula), the northern half of Western Australia, and the south of the Northern Territory, along with the northern coastal fringe. None of these areas reached the highest decile.
* Anomaly is the difference from the long-term average (1961−90)
Only small parts of the continent were wetter than normal during autumn. The most significant of these was the east coast in southern Queensland and northern New South Wales, extending from the Hunter Valley to Fraser Island. Much of this area had autumn rainfall in the highest decile, with seasonal totals approaching double the long-term average. Rainfall was also above average in much of the Nullarbor, and in a band extending south-east through the interior of Western Australia from Port Hedland to Newman (in the latter case, most of the rain fell as a result of a single tropical low in the first two days of March), although only a few patches reached the highest decile. Smaller areas of above-normal rainfall were found in western Tasmania, and in eastern Arnhem Land in the Northern Territory.
Rainfall was below normal over the remainder of the continent, and all states and territories were below normal for the season (ranging from 9% in Tasmania to 66% in the Northern Territory), although none ranked in the lowest 10 years. (It was the fourth-driest autumn on record for the southwest of Western Australia). The national average was 42% below normal (15th lowest of 110 years). For the Murray-Darling Basin (33% below) and Victoria (34%) it was the ninth consecutive year with below-normal autumn rainfall; these regions have also had below-normal autumn rainfall in 17 and 16 of the last 19 years respectively.
Seasonal rainfall was in the lowest decile in most of western Western Australia, west of a line Esperance-Meekatharra-Karratha, with records set locally around Carnarvon and south of Perth. It was also in the lowest decile in much of the northern tropics, extending from the north Kimberley through most of the northern half of the Northern Territory (except Arnhem Land) into the Gulf region of northwest Queensland. There were also patches in the lowest decile in Victoria, west of Melbourne and in east Gippsland. Melbourne and Perth both narrowly missed records for the driest January-May period.