WAFarmers CEO Trevor Whittington explains how to become an amateur meteorologist and look for crucial weather signs that will impact farmers
Every time a farmer glances at the Bureau of Meteorology forecast, the same terms pop up: Indian Ocean Dipole, El Niño–Southern Oscillation, Southern Annular Mode, cold fronts from the Great Southern, tropical moisture feeds, and the Leeuwin Current.
We nod as if we understand, but do we really grasp how these moving parts interact to bring the break, or deny it?
In this guide, we’re unpacking the jargon and grounding it in real-world terms.
Next time you stare at a satellite map or seasonal outlook, you’ll see more than squiggly arrows and acronyms – you’ll see the story behind the symbols.
Start with a simple image: the Earth as a ball floating in a fish tank, heated at the equator by a giant lamp. That heat warms the water, which rises and begins to circulate.
Add the Earth’s spin and you get wind patterns and ocean currents – most importantly for us in Western Australia, you get the Leeuwin Current.
This warm ocean flow travels down WA’s coastline like a marine conveyor belt of heat and moisture.
It’s the reason we’re not living in a cold, foggy wasteland like coastal Chile or Namibia.
The Leeuwin Current lifts our coastal sea surface temperatures by several degrees, fuelling cloud formation and moderating our weather in autumn and early winter.
In strong years, it powers all the way past Albany; in weak ones, it barely nudges Geraldton.
Here’s your first forecasting tip: warm water means more atmospheric moisture.
If you’re watching ocean temperatures off the northwest coast in April and they’re dropping fast, that’s your early clue to how much rain might come in May.
The rock lobster fishers already know this – warm water equals strong Leeuwin flow.
Then comes the Indian Ocean Dipole (IOD), often described as the Indian Ocean’s version of El Niño.
When the IOD is negative, warm water pools near Indonesia, pushing moisture toward Australia and boosting winter rain.
When it’s positive, that warmth shifts west toward Africa, shutting off the moisture tap.
A neutral IOD is anyone’s guess.
Next up, the Southern Annular Mode (SAM), which measures how far north or south the westerly wind belt around Antarctica is sitting.
A negative SAM shifts the belt northward, pushing cold fronts into southern WA – which is often a good thing.
A positive SAM pushes the westerlies away, leaving high-pressure systems parked stubbornly over the Great Australian Bight, whichis when we get blue skies and dry paddocks.
Toss in ENSO – El Niño and La Niña – and you’ve got the big three drivers of global climate. But here’s the catch: they rarely work alone.
A negative IOD plus a negative SAM can bring the goods. Add a La Niña and you’re likely looking at an early break.
But reverse those signs – positive IOD, positive SAM, and El Niño – and you’re probably looking at a Decile 1 rainfall.
To play along at home, bookmark the NOAA and BOM sea surface temperature (SST) anomaly maps.
Learn to read the rainbow bands and spot the hot blobs off Indonesia, west of Broome, and south of Madagascar because they are all moisture signals.
Dive deeper and you’ll find sub-surface temperature maps showing warm patches 100 metres below the surface. These “heat blobs” can rise to the top and feed rainfall events weeks later.
Now add in the Agulhas Current – the Leeuwin’s cousin – running down the east coast of Africa. When it “retroflects” (loops back into the Indian Ocean), it can send warm eddies drifting toward our quadrant of the ocean.
Those eddies add a few tenths of a degree to the northern Indian Ocean basin and as we’ve said, a few tenths matter.
Another important factor is ocean temperature gradients.
For instance, a warm patch off Exmouth and a cold patch off Albany can create instability in the atmosphere.
The sharper the contrast, the higher the likelihood of triggering a rainband as a front approaches.
Uniform temperatures? Not so helpful. It’s the contrasts that spark convection.
On the local scale, WA farmers also need to look at what’s happening in their own backyard. The micro-influences of topography, soil type, ground cover, and even stubble management can make or break whether a paddock gets 5mm or 15mm from the same cloud.
A cold hollow might trap dew and fog but block warm air from lifting, whereas a sandy ridge may heat up faster, drawing moisture up and kick off a passing shower.
These local effects are rarely captured by the big forecasting models, but they matter – sometimes more than the IOD or SAM.
Here’s the final tip: pay attention to the timing of moisture feeds.
A cold front hitting dry air or dry soil often fizzles, but if the soil has been primed by earlier showers – or if there’s lingering moisture from the tropics – you’ve got the setup for proper rainfall.
These dynamics explain why two years with similar forecasts on paper can deliver vastly different on-ground results.
All up, weather forecasting – especially in WA – is part science, part art, and part gut feel.
The science gives us the tools: satellite feeds, SST maps, supercomputer models, and climate indices. The art comes from interpreting it. And the gut feel? That comes from decades spent staring at the sky and the paddock.
So next time someone throws around acronyms like ENSO, SAM, or IOD at the pub, you can nod with more confidence.
You may not have a PhD in atmospheric physics – but if you understand the heat lamp, the spinning ball, the Leeuwin Current, and the warm blob off Broome, you’re already halfway to being an amateur meteorologist.
If you get it wrong? Just blame SAM.