Dr. Kimberley Reid

A super El Niño doesn't mean a super drought or super bushfire.

The relationship between the impacts is not a direct relationship.

Whether or not there's an El Nino is a lot more important for us than the strength of an El Nino.

So El Niño and the counterpart La Niña, they're naturally occurring phenomena.

They've been going up thousands or millions of years even.

And they're variations in sea surface temperatures and winds across the Pacific Ocean.

So during El Niño, sea surface temperatures in the central and eastern Pacific are warmer than normal.

And the trade winds that typically blow from east to west across the equator weaken.

And as a result, a region of strong storm activity called the Walker Circulation shifts east out over the Pacific Ocean, drawing moisture and clouds away from Australia.

And La Nina is the reverse of all that.

So the ocean temperatures cool below normal, these trade winds strengthen, and that storm activity is pushed towards Australia.

So La Nina is typically associated with wetter than normal conditions, whereas El Nino is typically associated with

Hotter and drier conditions for eastern Australia.

Yeah, El Niño's been in the news for months now, but it was only just officially declared.

And that's because there's a specific set of criteria that has to be met before an El Niño is declared.

And so for the Bureau of Meteorology, three out of these four criteria have to be met.

And the first one is that these sea surface temperatures in the Central Pacific Ocean I mentioned must be greater than 0.8 degrees Celsius above normal.

The second criterion is that the trade winds that blow from east to west across the equator must have been weaker than average for about four months.

The third criterion is there's a measurement called the Southern Oscillation Index, which is a measure of the difference in atmospheric pressure between Tahiti and Darwin, and that must be lower than negative seven.

And then the final criterion is that the majority of these seasonal forecasting models from agencies around the world have to predict that these conditions are going to continue for at least three more months.