Australian Monthly Climate Summary: January 2009
Monday 2 February, 2009
Over Australia as a whole, January 2009 was substantially wetter than normal, with slightly above normal temperatures. The national figures, however, disguised dramatic regional variations. Most of tropical Australia experienced a very wet and cool January, whereas in the south temperatures were generally well above normal – including one of the most intense heatwaves on record in the last week of the month – and much of the southeast was extremely dry.
Maximum temperatures were 0.14°C above the long-term average (28th lowest of 60 years), but every state and territory except Tasmania was in either the top or bottom 10. After a cool start to the month, the southeast became warm from mid-month onwards, and exceptionally so during an intense heatwave in the last week, which saw the highest temperature ever recorded in Tasmania (42.2°C at Scamander on 30 January), other record highs in southern Victoria and South Australia, and the highest temperatures since 1939 in many other parts of the southeast. Melbourne (45.1°C) and Adelaide (45.7°C) both narrowly missed 1939 records, and both cities set records for consecutive days above 43°C with three and four respectively.
The month’s cool start prevented many monthly mean records from being set (the only significant area was in NSW’s Hunter Valley), but maxima were still well above normal in most of the southeast, with anomalies reaching 3−4°C in most of southern New South Wales, northern Victoria and parts of eastern South Australia. State anomalies exceeded +2°C in South Australia, Victoria and NSW; for NSW, it was the ninth successive January with above-average maxima, with eight of the nine years at least 1°C above normal. The warm maxima extended into most of Western Australia apart from the far north, with anomalies above 2°C in much of the state’s southern half. In the southern interior the anomalies would have been even larger but for a cool final week after the passage of tropical cyclone Dominic; Emu Creek and Gascoyne Junction both averaged over 45°C for the first 25 days of the month, with Emu Creek reaching 43°C on 24 out of those 25 days.
In marked contrast, Queensland (anomaly −2.39°C) and the Northern Territory (−1.89°C) both had their coolest January since 1984. Maxima were below normal in most areas north of a Bundaberg-Charleville- Alice Springs line, except for the far northern Northern Territory. They were at least 2°C below normal over most of tropical Queensland away from the east coast and adjoining areas of the eastern Northern Territory, and as much as 6−7°C in northwestern Queensland. Few records were set, as January 1974 was even cooler in most of the region, but almost all the region was in the lowest decile. Mount Isa, which exceeded 35°C on 28 of the 31 days of December, failed to reach the mark once during January.
Minimum temperatures were more consistently above normal, but anomalies were much less dramatic, with the national figure of +0.58°C ranking as the 16th highest on record, although Western Australia (+0.90) had its second warmest January nights on record. There were only two major areas where minima were below normal. One covered northwestern Queensland and the central Northern Territory, although anomalies were much weaker than those for maxima, peaking at 2−3°C around Boulia. The other covered much of Victoria, except its northern fringe, and northern Tasmania, although the anomalies were mostly weak and reflected a cool first half of the month.
Minima were above normal in most of the rest of the country, and were at least 1°C above normal (locally reaching +2°C) in a region extending from western NSW and south-western Queensland across northern South Australia into much of the southern half of Western Australia, which largely ranked in the highest decile. No significant regional records, either positive or negative, were set.
* Anomaly is the difference from the long-term average
The nationally averaged rainfall was 35% above normal (12th wettest of 110 years, although the wettest only since 2007). The major contributors to this rainfall were Queensland (80% above normal, 6th wettest on record and wettest since 1991), and to a lesser extent the Northern Territory (44% above normal). In contrast, Victoria (82% below normal, 6th driest on record and driest since 1957), South Australia (80% below normal) and New South Wales (67% below) were all very dry.
The area with above-normal rainfall covered most of Queensland north of the Tropic of Capricorn, extending into the state’s southwest corner, along with most of the Northern Territory except for the far north and south, and most of the Kimberley region in Western Australia. Many parts of this region were in the highest decile, including most of Queensland north of a Bowen-Longreach-Birdsville line (except Cape York Peninsula) and the central Northern Territory. Some areas around and north of Mount Isa, which have already exceeded their annual average rainfall, had their wettest January on record, as did a small area inland from Townsville.
The other major area with above-normal rainfall was a belt in Western Australia along the path of tropical cyclone Dominic, which crossed the state in the last week of the month. This belt extended from near Onslow, where the cyclone made landfall, through Meekatharra and Kalgoorlie to Esperance on the south coast. Monthly rainfalls were locally in the highest decile in this region.
Almost all remaining areas were drier than normal, except for southwestern Tasmania. Most of South Australia, and Victoria north and west of Melbourne, had little or no rain, and were in the lowest decile, with records locally in the Melbourne-Ballarat area. Other areas in the lowest decile were the far southwest of NSW, patches scattered through the eastern half of that state, and much of eastern Tasmania.