Australian Monthly Climate Summary: December 2008
Friday 2 January, 2009
December was a relatively wet month over much of Australia, with above-normal rainfall in most areas outside Queensland. Over the country as a whole temperatures were close to normal, with the northern half of the continent (especially Queensland) generally warmer than normal, and the southern half cooler.
National maximum temperatures were 0.37°C below the long-term average (25th lowest of 59 years). It was a warm month in Queensland, which had its ninth-warmest December maxima on record. Days were 1°C or more warmer than normal over most of the state except Cape York Peninsula and the far north-west, with anomalies reaching 3°C west of Mackay and around Gayndah. These warm conditions extended into the northern fringe of New South Wales and its coast as far south as Sydney, but elsewhere the only areas with above-normal maxima were a band through the central Northern Territory, and patches in western WA, especially the northern wheatbelt.
In contrast, days were at least 1°C cooler than normal in December across almost all of Victoria, South Australia and south-western New South Wales, along with the NT Top End, a strip running along the eastern WA border, and north-western Tasmania. Anomalies peaked at −2 to −3°C in the east Kimberley, eastern Victoria and near the Victoria-SA border.
Above-average minimum temperatures were also most prominent in Queensland, where they were the fifth-highest on record for December, but were more extensive than above-average maxima were, producing a national anomaly of +0.36°C (13th warmest of 59 years). Most of Queensland, extending into the eastern Northern Territory, was 1−2°C above normal, with records set in some areas around Richmond, Hughenden and the Atherton Tableland. Weaker positive anomalies covered the remainder of the Northern Territory, the northern half of South Australia, the Gascoyne and east Pilbara regions of WA, and south-eastern New South Wales. While large parts of southern Australia had below-normal minima, anomalies were mostly weak, reaching −1°C only in north-western Tasmania and on the WA west coast south of Geraldton.
* Anomaly is the difference from the long-term average
National rainfall was 38% above the long-term (1961−90) average (25th wettest of 109 years), with all states and territories above normal except Queensland, and South Australia (184% above normal) experiencing its fifth-wettest December on record.
The majority of the country was wetter than average. The largest relatively dry area covered most of Queensland (except for Cape York Peninsula and an area north-east of Charleville), extending south along most of the New South Wales coast, as well as into parts of that state’s northwest inland. It was also drier than normal in central and southern Tasmania, a band through the central Northern Territory centred on Tennant Creek, and parts of western WA between Perth and Carnarvon. Even these areas were not exceptionally dry, with only a few small scattered patches in the lowest decile, mostly in western Queensland.
Two major regions of Australia had rainfall in the highest decile (wettest 10% of all years). The first was a band extending across most of the NT Top End and the northern Kimberley (WA), essentially coinciding with the track of Tropical Cyclone Billy and its precursor low-pressure system. Areas around Wyndham and south-west of Darwin had their wettest December on record. The second area extended from south-eastern WA across most of South Australia (except the far northeast and around Adelaide) into south-western Victoria, with records set in places around Coober Pedy and on the Nullarbor coast.