You’re either a weather person or you’re not. If you live in the country, chances are that you’re as obsessed with it as I am.

The rainfall of this year’s long-awaited Autumn break was disappointing in both its duration and its quantity. It seems that there’s a reason for this beyond El Niño and La Niña, those twins of hope or despair.

El Niño was believed to bring sustained warming of the central and eastern tropical Pacific Ocean, a diminished strength of the Pacific Trade Winds and a reduction of rainfall over eastern and northern Australia.

La Niña applies to that part of the cycle when the central and eastern Pacific Ocean cool. During that phase, it was believed that eastern Australia could expect good rain. 

I say ‘was’ because now there’s a new kid on the block who intends to give us much more to think about in terms of weather. It’s called the Indian Ocean Dipole.

If a story that aired on Catalyst on Thursday evening is to be believed, the Indian Ocean Dipole is ‘a rain making cycle in the Indian Ocean that drives drought conditions in Southern Australia’.

Never heard of the Indian Ocean Dipole? Neither had we, until then.

Please forgive me if the following is less than comprehensive but with the Dreaded Lurgy befuddling my grey matter, anything more complicated than opening and closing the fridge door arises as a bit of a challenge. 

According to research, when the IOD is in its negative phase, the Indian Ocean to the west of Australia cools and combines with the warm Timor Sea, generating winds. These winds then pick up moisture from the ocean and deliver it as rainfall to southern Australia.

In its positive phase, the IOD’s influence is reversed. It weakens the winds, reducing the amount of moisture that’s picked up and transported across Australia. During a positive phase of the IOD, rainfall in the south-east of the country is well below average.

According to the Catalyst story, the three great droughts in Australia have all occurred during positive phases of the IOD. And in the last 15 years, there have been no negative phases of the IOD. That might explain the prolonged drought here in Victoria.

While IOD events occur only in about one in four years, there are still three years left of the four in which it doesn’t occur. How, then, are changes in rainfall explained?

While the answer to that is still a work-in-progress, it’s now clear to meteorologists that traditional long-range weather forecasting methods are obsolete.

In the fast-changing environment of climates generated by global warming, new methods have to be found.

In an effort to more accurately forecast our weather, dynamic computer models – rather than the old statistics-based models – are being fast-tracked to analyse the physics of the climate system.

There’s still some way to go before weather boffins completely understand how the interaction of the Pacific, Indian and Southern Oceans affects our climate. But there is one thing they can definitely forecast: we have some highly challenging times ahead of us.

B&W shots by John Mayger.