Australian Monthly Climate Summary: May 2008
Tuesday 3 June, 2008
May 2008 was Australia’s driest on record. Below-normal rainfall covered almost the entire continent, and most areas more than a few hundred kilometres from the eastern or southern coasts received no rain for the month. As would be expected in such a dry month, the diurnal temperature range was well above normal, with daytime maximum temperatures mostly above normal and overnight minimum temperatures above normal. Overall mean temperatures were slightly above normal.
Maximum temperatures were above normal over most of the country, with the national average anomaly above the long-term (1961−90) mean of +1.48°C being the seventh-highest on record for May. Western Australia (+2.45, 4th highest) was particularly warm, and New South Wales (6th) and South Australia (8th) also ranked in the top ten. Only relatively small areas experienced below-normal maxima, the largest being northern Queensland, the northern Kimberley (WA) and the north-western Northern Territory, and the eastern half of Victoria. Conversely, much of the remainder of the continent was 1°C or more above normal, increasing to 2°C or more in much of the southern two-thirds of Western Australia away from the coast, and 3−5°C in parts of the state’s interior. Maxima were in the highest decile in most of the state away from the Kimberley and the southwest, with records set in the interior in the area from Kalgoorlie to Meekatharra. They were also in the highest decile in an area covering much of northern and central inland New South Wales and extending south-east to Canberra.
In contrast, minimum temperatures were generally below-normal, with the anomaly of −0.81°C ranking 14th lowest of 59 years. (The diurnal temperature range for the month was the second-highest on record, just behind May 1994). Queensland experienced particularly cool nights with an anomaly of −1.86°C (7th lowest). Minima were above normal in Tasmania, and in most of the southern half of Western Australia (where anomalies locally reached +1°C), but were below normal in most other areas.
It was particularly cool in most of the northern tropics and near the east coast. Minima were at least 2°C below normal in a broad belt extending from north-eastern New South Wales northwards through much of eastern Queensland, as far north as Cape York Peninsula. Anomalies of this size also covered the Kimberley and most of the northern half of the Northern Territory except for the north coastal fringe. A belt extending from the Gulf coast near Borroloola westwards through Kununurra to Derby was 4−6°C below normal with numerous monthly records being set (as they were on Cape York Peninsula, south-eastern Queensland and parts of northern New South Wales). The cool conditions were marked by their consistency; few site records were set, but at many tropical locations almost every night during the month was cooler than normal. Kowanyama (Queensland) and Kalumburu (Western Australia) have not recorded an above-normal minimum temperature since 4 April and 5 April respectively.
Whilst the month as a whole was unexceptional in the region, extreme low minimum temperatures occurred in the Snowy Mountains and in parts of Tasmania late in the month as the area was influenced by an extremely dry air mass, particularly at high elevations. Charlotte Pass set a new Australian record low temperature for May of −13.4°C on the 24th, breaking the previous record of −13.0°C set on three separate occasions, and site records were set at a number of other locations, including Thredbo (NSW) and Grove and Fingal (Tasmania).
* Anomaly is the difference from the long-term average
Rainfall averaged over the continent was 73% below normal, and the national area-average of 7.86 mm broke the previous May record of 8.27 mm, set in 1961. All states and territories (as well as the Murray-Darling Basin) were at least 40% below normal, with deficits ranging from 42% in Tasmania to 80% in Western Australia and 99% in the Northern Territory. The month ranked in the driest ten Mays for New South Wales (76% below normal, 7th), Western Australia (4th) and the Northern Territory (3rd).
Only a handful of areas of any size reached their average May rainfall, the largest being the southwestern tip of Western Australia and the Wide Bay region of Queensland (which experienced a major rain event on the last two days of the month). Locally above-normal rainfall also occurred in the Mid-North of South Australia and around Ingham on the North Queensland coast.
On the other hand, no rainfall was observed over most of Western Australia away from the southwest and the Nullarbor, almost all of the Northern Territory except for northeast Arnhem Land, Queensland west of Richmond, South Australia north of Woomera and the northwestern corner of New South Wales. A few locations near the New South Wales coast were also rainless, including Camden, Eden and Merimbula. Apart from the rainless areas, rain was in the lowest decile on the New South Wales coast from the Hunter southwards, east Gippsland, south-eastern Tasmania and parts of central New South Wales, with May records set locally in all of these regions (including Sydney).