All Models Used By Bureau Now Point To El Nino By The End Of Spring

FairfaxPeter Hannam

All of the Bureau of Meteorology's eight international models it uses now predict an El Nino event by the end of spring, dimming hopes of quenching rains that would aid farmers and ease the bushfire risks.
The Bureau of Meteorology's latest El Nino-Southern Oscillation update shifts the odds slightly from a fortnight ago when only a majority of the models had forecast an El Nino by spring's end.
There's no early sign of a break in the drought - in fact it could get worse. Photo: AAP
Robyn Duell, a senior bureau climatologist, cautioned that model forecasts had picked an El Nino at this time in 2014, only for the drivers - namely a relative warming in the eastern tropical Pacific compared with the west - to back off.
"We need to see the [easterly] trade winds weakening - that's the key we're looking for," Ms Duell said. "Models are not enough."
Still, the Southern Oscillation index - which gauges pressure differences between Darwin and Tahiti - had recently become more "El Nino-like" the bureau said.
During El Ninos, spring rainfall in eastern and northern Australia is typically below average, while temperatures in the southern two-thirds of the country is above average.
Compounding the tendency towards drier-than-average rainfall across south-eastern Australia are cooler than usual waters off north-western Australia. These typically reduce the moisture streaming over the continent, and the models forecast this rainfall-suppressing trend to increase in the near term according to three of six models the bureau uses.
Much of Australia has had "exceptionally warm" daytime temperatures this winter, even if clear skies have made for frosty overnight conditions in many areas, Ms Duell said.

Recent rains had helped parts of northern NSW and southern Queensland but most other drought-affected areas received only a few showers.
Sydney, for instance, has collected less than 8 millimetres of rain in August while evaporation levels are running at about 132 millimetres, bureau data shows.
The outlook for the coming week offers some prospect of more falls early next week with as much as 15 millimetres tipped for Tuesday.


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