Australia's Winter Forecast: Unusually Warm and Dry Conditions Expected

The Bureau of Meteorology is forecasting winter to be unusually warm across the entire country, as an El Niño climate pattern is increasingly likely to take hold.

Large parts of the south-east and south-west are also being tipped to be drier than normal.

Let's take a look at what's in store around the country.

Rainfall below average in the south-west and south-east

Rain is often the big ticket item for winter, especially in southern Australia, which gets most of its annual rain during the cool part of the year.

This winter, the outlook is forecasting pockets of Australia to have below-average rainfall across the season as a whole.

This includes south-west Western Australia and large parts south-eastern Australia, particularly Victoria.

This dry signal appears to strengthen later in the season, although June rainfall is also slightly leaning toward below average for south-eastern Australia.

"For July, that's where we start to see that [dry] signal emerge across parts of the south and the east … with early indications of a strengthening of that signal into August," BOM senior climatologist Caitlin Minney said.

While rain is forecast to be be below-average, for most areas it's unlikely to be severely dry.

There are some pockets of the country with roughly double their normal chance of having an "usually dry" winter, however.

This includes parts of southern WA, south-eastern parts of SA, western Victoria and parts of central and southern NSW.

That risk is slightly lower for New South Wales and eastern Tasmania, which have already faced a very dry year to date.

Both regions are in "severe" to record low rainfall deficiencies, meaning they are in dire need of rain.

"We are keeping in mind the potential for further increases in those rainfall deficiencies for the region, and carefully monitoring those regions," Ms Minney said.

Loading...

Warmer-than-normal temperatures 'very likely'

One part of the forecast that is looking clear is the temperature.

The BOM is predicting both day and night-time temperatures are "very likely" to be warmer than average across Australia for the winter season.

There is also a strong chance these temperatures will be "usually" warm, meaning they fall into the top 20 per cent of all records.

Hope for snow season despite warm outlook

The combination of drier-than-average conditions and warmer-than-average temperatures is not promising for Australia's snow season.

But Ms Minney said it was far from a write-off with "just one system" able to change the outcome of a season.

"Snow levels can change rapidly based on just one system, like a frontal system coming through, as long as there's enough rainfall and the temperatures are cool enough for it to be snowing," she said.

El Niño not the only ingredient

There are still many factors that can play a part in the final outcome of Australia's weather, not just El Niño.

Every El Niño event is different. A look back at past events shows, in some cases, the driver has had no impact at all.

However, they are overwhelmingly associated with lower than normal rainfall during winter and spring months across eastern Australia, and warmer temperatures through to summer.

This is why the driver is often affiliated with drought and bushfire.

While it has not yet developed, Ms Minney said it was likely to playing a role in the on the rainfall forecasts this winter, alongside warmer-than-normal ocean temperatures and long term-drying trends.

But the region with the strongest chance of a dry winter, WA's south-west, is unlikely to be affected by the looming El Niño, with the driver historically not having an impact on that region.

There, the stronger influence is likely to be climate change, which has caused a long-term decline in cool-season rainfall.

When will an El Niño be declared?

Before the BOM declares an El Niño underway, the agency needs to see both the ocean and the atmosphere reach certain thresholds.

These have not been met yet, but oceanic indicators appear well on the way, with expectations that an event will be declared during winter.

In Australia, El Niño events tend to have a bigger influence when combined with a "positive" Indian Ocean Dipole (IOD) event, which we currently do not have.

The IOD is a similar climate driver to El Niño, which forms in the ocean to the west of the country rather than the east.

Ms Minney said the BOM's climate model was currently forecasting neutral IOD conditions through to early spring.

Other international models, however, were forecasting a positive IOD to develop.

"It is still too soon to tell what's going to happen," she said.