Australian Monthly Climate Summary: October 2009
Monday 2 November, 2009
October was a rather dry month through most parts of Australia, with widespread above-average falls largely confined to the east coast. Temperatures were closer to normal than they have been in recent months, but monthly mean temperatures for the continent were still slightly above average, due principally to generally above-average daytime maximum temperatures.
Daytime maximum temperatures for the month were 0.71°C above average, the 16th highest of 60 years but still the coolest for October since 2003. The most pronounced warmth was in Western Australia and the northern Northern Territory. Maxima were at least 2°C above average over most of the southern interior and Pilbara region of Western Australia, reaching 3−4°C above average in interior areas south of the Tropic of Capricorn. They were also near 2°C above average in the northern Top End of the Northern Territory, and Darwin’s mean monthly maximum of 34.8°C was the highest on record for any month.
Elsewhere, maxima were closer to normal, although they were still 1−2°C above average in eastern Queensland south of Townsville, and north-eastern New South Wales, as well as in parts of southern inland NSW centred on the Riverina. The most pronounced cool conditions were in eastern Victoria and south-eastern NSW, with anomalies generally below ?1°C and approaching ?3°C around Omeo. Most of the remaining coastal strip from the Eyre Peninsula (SA) to the Hunter region (NSW) was slightly cooler than normal, as was a broad area centred on the NT-Queensland border, extending into northern and eastern South Australia.
Cool overnight conditions predominated with minimum temperatures 0.17°C below average (24th lowest of 60 years). They were most pronounced in the tropics, covering most of the Northern Territory (8th lowest on record) except the far north, the Kimberley region of Western Australia, and most of Queensland except the coastal fringe. Anomalies below −1°C extended from the Kimberley through the NT into northwestern Queensland, reaching −2°C along parts of the Queensland-NT border and around Wyndham. Records were set in parts of the central Kimberley and along the Queensland-NT border. Minimum temperatures were also slightly below normal in most of New South Wales except the south coast and far southwest, and in most of Victoria and southern South Australia.
In contrast, minima were warm in much of Western Australia away from the north, and were at least 1°C above average over most areas south of a Port Hedland-Giles line, except near the west coast. They reached 2−3°C above average in places and were locally highest on record around Kalgoorlie, while most of the state south of Meekatharra and Shark Bay was in the highest decile, except for some parts of the west coast north of Perth and south coast east of Esperance.
*Fractional ranks denote tied values. **Anomaly is the departure from the long-term average.
Australian rainfall for the month was 45% below average (21st lowest of 110 years). The low rainfall was consistent across most areas with all states and territories at least 27% below average. After a wet winter and early spring along much of the southern coastal fringe of Australia, dry conditions returned to this region in October. Southwestern WA had its fifth-driest October on record (67% below normal) and Tasmania its eighth-driest (49% below), with most of southwestern WA and western Tasmania in the driest 10% of all years.
The most substantial region with above-average rainfall was the southeast coast, encompassing most of coastal New South Wales except the far north and south, along with eastern Victoria from Bairnsdale eastwards. Totals reached the highest decile around Coffs Harbour and Bellingen, mostly as a result of a single event late in the month in which daily totals locally exceeded 300 mm. There were also scattered areas of above-average rainfall along a band stretching south through Queensland and northern New South Wales, from Townsville through Charleville to around Coonamble, and in some patches favoured by early-season storms in interior and northern Western Australia, the Tiwi Islands and western Cape York Peninsula.
Large areas of the interior, including north-eastern South Australia, far western Queensland and much of the southern Northern Territory, received little or no rain, conditions which also extended to parts of eastern Cape York Peninsula. The other significant area in the lowest decile was coastal Queensland between about Rockhampton and Hervey Bay.
*Fractional ranks denote tied values.
**A new area-averaging method has been adopted for rainfall from May 2009. Current and historical totals for Tasmania are substantially higher than under the old scheme, but differences for other states, and nationally, are negligible.