Friday, March 13, 2009

Extreme weather sees records tumble

While northern Australia flooded, southern Australia was enduring a heatwave, near-record low rainfall and, in Victoria, unprecedented bushfires.

In the first six weeks of the year, 25 sites across northern Queensland received more than 2m of rain, with a top reading of 2873mm at Bulgun Creek, south of Cairns.

Over the same period, most of Victoria had less than 24mm, with Melbourne receiving less than 5mm.

Two tropical cyclones and a monsoon low brought heavy rains to northern Australia.

In some places records set in 1991 and the extraordinarily wet year of 1974 were broken. Northern coastal rivers flooded. Ingham experienced Queensland's worst flood for 30 years and was isolated for nearly two weeks.

In January, heavy rains caused flooding in Queensland's gulf rivers and its inland rivers, the Georgina and Diamantina.

More rain in February produced another flood peak.

The water from the two rivers is expected to reach Lake Eyre some time this month.

The Thomson River, which flows into Cooper Creek, also flooded.

By the end of the first week of January, one third of Queensland was flooded.

The state-wide average rainfall for Queensland that month was 229.3mm, almost twice its long-term average of 127.7mm.

The constant rainfall also resulted in the lowest state-wide maximum temperature since 1984.

Blair Trewin, from the National Climate Centre, says several stations around Mount Isa broke the 1974 rainfall records for January, "and those '74 records are fairly tough to break".

At the other end of the country, in South Australia, western and central Victoria and southwestern New South Wales, other records were under threat.

Trewin says a significant list of southeastern sites got no rain at all in January: "Port Pirie, Clare, Adelaide Airport although not Adelaide city, Renmark, Swan Hill, Nhill, Stawell, Bendigo, Yarrawonga, Maryborough in Victoria and Deniliquin, all of those got zero."

The first weeks of February brought no improvement.

Melbourne got just 0.8 mm, its second lowest on record, in January.

The city endured a 35-day spell with no rain.

But it was the heatwaves at the end of January and the beginning of February that really stressed southerners and set new records.

"The real standout heatwave of the last century in southeast Australia was 1939, and now 2009," Trewin says.

Mildura set a Victorian record with 12 consecutive days of more than 40C.

The heatwave climaxed on Black Saturday, February 7, when much of the state experienced its hottest day on record. In Melbourne the temperature reached a record 46.4C. The previous record was 45.6C on January 13, 1939, Black Friday.

Trewin points out the area that experienced severe bushfires on Black Saturday - Kinglake through to Marysville - is also the driest.

"Most of that area has been about 20per cent below the historic average (rainfall) over the last 12 years."

Victoria has essentially missed out on two years of rain in the past 12 years.

Trewin says the long-term drying "is consistent with climate change".

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