Rain On Horizon As Dry Old Nino Makes Way For Cool Sister

Sydney Morning Herald

Friday February 23, 2007

Deborah Smith Science Editor

PROSPECTS for relief from the drought have improved with the El Nino weather event declared ended and early signs that a La Nina could develop in its place.

La Nina events are usually associated with wetter than normal conditions across much of the eastern half of the country from about autumn onwards.

A senior climatologist at the Bureau of Meteorology, Grant Beard, said the developments were encouraging.

"We can be cautiously optimistic that we could get a turnaround in rainfall patterns in the next one or two seasons."

The El Nino event, a warming of the central and eastern Pacific which had been making the current drought worse for the past year, underwent a rapid decay during the past two months.

The chances of a La Nina event developing were considered higher than the usual one in five, he said. "It could be one in four or one in three."

These events occur when the eastern Pacific is much cooler than normal. They have a tendency to follow an El Nino, and the early demise of the latest El Nino meant there was time for a La Nina to begin developing during the critical March to June period.

A large pool of cold water has already developed in the central to eastern tropical Pacific Ocean.

Dr Beard said the end of an El Nino was usually associated with a return to normal rainfall patterns, and this could benefit farmers planting crops. But it did not mean the drought was about to break.

Water supplies in many areas of the country had been severely depleted, he said. "For the reservoirs, only several years of abundant rainfall will do any lasting good. One or two years of even heavy rainfall won't make a dint."

The 1950s and 1970s in Australia were dominated by La Nina events, but El Nino, which brings drier conditions, has been more prominent in recent decades.

The most recent La Nina lasted from 1998 to 2000 and, although it was moderate, 2000 ended up being Australia's second wettest on record.

The La Nina in 1988 and 1989 during the Bicentennial celebrations was a strong one. Vast areas of inland Australia had record rainfall in March 1989.

"The effects of La Nina are more widespread and more consistent and more long lasting than El Nino," Dr Beard said.

© 2007 Sydney Morning Herald

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