THE most populous regions of Australia can expect another year of above-average fire risk as the long-term decline in cool season rainfall combines with the strengthening El Nino in the Pacific.
A swath of land stretching from south-eastern South Australia to the north of Rockhampton in Queensland, and the south-western corner of Western Australia, are among the regions likely to have a busier than usual fire season, according to the Southern Australia seasonal bushfire outlook for 2015-16 report released today.
While late winter rains have reduced the risk of an early fire season in much of NSW and eastern Victoria, a series of dry years have left soil moisture levels relatively low over large parts of the country, said Richard Thornton, chief executive of the Bushfire and Natural Hazard Co-operative Research Centre, which helped to compile the report.
"Forested areas are still suffering a long-term deficit in rainfall," Mr Thornton said.
These areas include the Otway ranges to the south-west of Melbourne and much of coastal NSW.
David Jones, head of climate prediction services at the weather bureau, said most parts of southern Australia have had consistently below-average rainfall during the cooler half of the year, from April to October, since the last big El Nino event in 1997.
This year is shaping up to extend the pattern.
"We've basically got this very long, slow drying of the landscape in the background," Dr Jones said. "Whenever warm conditions hit, things dry out very quickly."
Late winter rains in NSW have lifted moisture levels but will also mean vegetation growth, especially for grass, will accelerate, Rob Rogers, deputy commissioner for the NSW Rural Fire Service, said.
The rain has also hindered hazard-reduction efforts by reducing controlled burning.
"It's fair to say we didn't get the targets we'd like to have got because of the rain," he said.
Competing weather patterns, though, are complicating predictions.
On the one hand, the strengthening El Nino in the Pacific is already among the five strongest over the past century, leading to a drier influence for eastern Australia, Dr Jones said.
However, record warmth in the Indian Ocean off Australia's west coast has also meant more clouds and rainfall streaming over the continent, benefiting NSW in particular.
"Thus far Australia has been quite insulated from the El Nino by the Indian Ocean," Dr Jones said.
Still, warmer-than-average temperatures are also expected in the spring, particularly at night, the bureau said.
Dr Thornton said the 2009 Black Saturday bushfires showed that "really, really bad fire weather days can happen in any year whether there's an El Nino or not".
In Victoria, the major concern extends across the west of the state after another dry season, said Craig Lapsley, the state's first Emergency Management Commissioner.
Mr Lapsley said residents should prepare for a long fire season, noting that many Victorians typically put off fire preparations from about a week before Christmas through January as holidays take priority. "We traditionally lose most in February and January" from fires, he said.
In NSW, the large bushfire near Wentworth Falls in the Blue Mountains in August showed how dry conditions were.
"If replicated in summer with low humidity, high temperatures and strong winds...it would have posed a lot more problems for us," Mr Rogers said.
RFS volunteer numbers are holding up after a surge of several thousand following widespread fires in the spring of 2013, which destroyed more than 200 homes, and now stand at about 74,000, he said.