Nicole Hasham July 04, 2012
Surface tension ... waves wash onto Clovelly Beach last night under a full moon. Temperatures have been rising in the Pacific Ocean for the past few months, suggesting a return to El Nino and less rainfall. Photo: Wolter Peeters
OUR dams are full, the lambs are fat and the sprinklers are running again. But weather experts are warning Australia's east coast to brace for a return to dry conditions, perhaps even drought, as another El Nino event looms.
After two consecutive years of record rainfall and devastating floods brought on by La Nina, the Bureau of Meteorology warned yesterday that climate indicators show a shift towards drier weather patterns, and a potential swing to the opposite phenomenon, El Nino.
Warmer waters in the Pacific Ocean can trigger an El Nino, which brings less rainfall and drought such as the one that drained Warragamba dam to one-third of its capacity five years ago. Cooler waters bring on La Nina and associated wetter conditions, including those that spurred this year's floods across NSW, and the devastating Brisbane floods the previous summer.
A bureau climatologist, Acacia Pepler, said conditions along the equator were yet to reach El Nino thresholds, but most climate models were predicting the event would develop in late winter and early spring.
''The chances of us reaching El Nino are growing,'' Ms Pepler said. ''It's not certain yet, but probability is increasing as the weeks pass.''
But the Weather Channel, which measures the event using different indices, called the result early, declaring yesterday that El Nino had returned. ''Sea surface temperatures through the central tropical Pacific Ocean have gradually warmed during the past few months and are now more than 0.5 degrees above average, passing the threshold for El Nino conditions,'' said senior meteorologist, Tom Saunders, adding that the rise must persist for five months before the event is ''fully fledged''.
Following Australia's wettest two years on record, which fuelled massive vegetation growth, a spell of dry, hot weather could lead to drought and ''a devastating bushfire season'', he said.
El Ninos typically occur every two to seven years. The most recent occurred in 2009, bringing with it extremely dry weather in winter and spring.
But with Warragamba Dam now sitting at a healthy 99.2 per cent capacity and crops sown in soil rich with moisture, a spell of low rainfall is unlikely to immediately devastate the eastern states, said a water resources expert at the University of Southern Queensland, Roger Stone.
''This El Nino has been … fairly slow in developing, and that's allowed a bit more rain to come in across many parts of Australia,'' he said.
''But we don't quite know how long this one will last, and it's probably worth revisiting the situation in a few months to see how intense it's becoming.''
Wayne Dunford, a farmer who runs sheep and grows crops on his property west of Parkes, described the dry predictions as ''a blip in the weather pattern''.
''You don't metaphorically go and slash your wrists because the [climate indicators] have fallen … because that happens quite often, and it doesn't mean we are going into another drought,'' he said.