La Nina May Yet Make It Pour
The Sunday Age
Sunday February 17, 2008
VICTORIA may yet be drenched by drought-breaking rains if the La Nina climatic event continues well into the year, according to the Bureau of Meteorology.
Reservoirs in NSW and Queensland have filled rapidly over recent months, and water restrictions have been eased, thanks to the rains brought by La Nina. The La Nina-El Nino cycle is driven by the temperature of the equatorial Pacific Ocean. Water temperatures that are cooler than average tend to bring more rain over Australia, and temperatures warmer than average tend to result in less rainfall.There are also neutral years, when there is no effect either way.Blair Trewin, a climatologist at the bureau's National Climate Centre, said Victoria had yet to feel any effect from La Nina."In summer, the impact of La Nina tends to be weaker in Victoria than it is in Queensland and NSW," he said. "That's reflected in what we've seen so far in Victoria. "We've seen fairly close to normal rainfall in the last few months, leaning to above normal in the north. But we certainly haven't seen the very heavy falls that we've seen further north."The La Nina event was confirmed only in November. According to the bureau's six computer models, it will continue until at least the end of the southern autumn. Of the five that predict beyond four months, four predict La Nina conditions to decay to neutral by the middle of 2008."Present indications are that it will last into mid-year," said Mr Trewin. "Beyond that it's a bit uncertain. Autumn is the time of year when the climate system becomes a bit unpredictable."Mr Trewin said that if La Nina lasted beyond autumn, Victoria would get good rain in the second half of 2008."If it were to persist into winter and spring, that would be quite encouraging for rainfall," he said. "The relationship in Victoria between La Nina and rainfall tends to be stronger in winter and spring than it is in summer."Mr Trewin said La Nina was well established. "It looks like the strongest La Nina event we've seen since the event of 1988-89," he said.
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