What’s in store for Australia this summer?

10 October 2011

Written by: JYADE OLD

Few have forgotten the horrific weather of last summer, with images of flooded towns and floating debris still in the minds of many Australians.

With summer only a couple of months away, it’s not unreasonable to wonder what nature has in store this time around.

Last summer saw flooding in almost every state due to the strongest La Nina in decades.

We have all heard enough about El Niño and La Nina to know one leads to drought and the other leads to floods.  But where on the climate chart do we sit now and how do climatologists make sense of something that seems so unpredictable?

Bureau of Meteorology climatologist, Dr Andrew Watkins, says many things are taken into consideration when looking at the weather. When it comes to El Niño and La Nina the two most important indicators are the Southern Osolation Index and the water temperature in the equatorial region of the Pacific Ocean.

To measure the index, the Bureau of Meteorology uses a standardised equation that looks at the average sea level pressure difference between Tahiti and Darwin. For the average farmer in rural Victoria, Tahiti may not seem like a very important place to be looking at, but it has a big impact on rainfall across the country.

The Southern Oscillation Index ranges from -35 to +35.  If the index is at 10 or higher it indicates that La Nina weather will occur.

‘This time last year we had a score of around +25 which is very strong,’ Dr Watkins says. Currently the Southern Oscillation Index score is at +2, which means the threat of torrential rains are significantly lower.

The temperature of the water in the Pacific Ocean around the equator is another main focus for climatologists. ‘This time last year the Pacific Ocean was about 1.5 degrees cooler than normal,’ says Dr Watkins. ‘At the moment that barrier is only about 0.5 degrees.’

These figures make it clear that we are a long way from where we were this time last year. ‘We are classified as being in a neutral state,’ says Dr Watkins. So unlike last year there may not be as much need to batten down the hatches from Cairns to Carnarvon.

However, this doesn’t mean that everyone will be out of harm’s way. ‘There is still a risk of flooding but not to the extent of last year,’ he says.

Dr Watkins says some weather models are indicating a slight chance that La Nina will return before the summer, but the unpredictable impact that climate change has on El Niño and La Nina is also a risk.

‘Last year the sea surface temperature to the north of Australia was the warmest on record. We do know that the high sea surface temperatures would also have been a contributor but we just don’t know how much. We are still trying to understand why the ocean and the atmosphere are behaving in different ways at the same time, ‘ he says.

Authorities are also turning their attention to the summer fire season. ‘We got so much water that we have seen grass and vegetation take off. Then we have seen a very dry three months…if we do see fires they will potentially be bigger and more widespread,’ said Queensland Premier Anna Bligh recently on the 7 pm project.

The Bureau of Meteorology will release its official summer forecasts this month but with many fires already recorded in central Queensland it could be a busy season for firefighters across the country.

Jyade Old is studying the Graduate Diploma of Journalism at La Trobe University and is part of upstart‘s editorial team. Follow her on Twitter: @jyadvantage.