explainer

'Will it ever stop?' All the questions you have about the never-ending rain, answered by a meteorologist.

For the last month, Aussies have been watching on in despair over the sheer amount of rainfall across eastern Australia. 

We've seen firsthand this year just how devastating flooding can be, with residents in parts of Lismore and northern NSW now experiencing "flood fatigue" after once again being evacuated due to heavy rainfall.

And with more rain expected in the coming days across the eastern region, many of us have been left feeling confused and overwhelmed about rain bombs and La Niña.

So what does this all mean?

Mamamia asked Bureau of Meteorology (BOM) Senior Meteorologist Sarah Scully to answer all of our questions. Here's what she had to say.

Watch: Lismore's future questioned after two catastrophic floods in five years. Post continues below.

Video via ABC News.

Why have we been experiencing so much rain over the past few months?

According to Scully, it's due to a combination of climate drivers and the ordinary weather pattern.

So for climate drivers, this is catalysed by the current La Niña event. La Niña is part of a cycle known as the El Niño-southern oscillation, involving a natural shift in ocean temperatures and weather patterns in the Pacific Ocean, essentially bringing high levels of rain, floods and cyclones. 

"The above average sea surface temperatures increase the amount of moisture in our atmosphere over northeastern Australia and that actually increases the chance of above average rainfall across this area," Scully said to Mamamia.

The other factor in the high levels of rainfall is due to weather patterns. 

For example, during that catastrophic 'rain bomb' a month ago, there was "a coastal trough that was held in place by a block in the high pressure system in the Tasman Sea," Scully explains.

And so that combined with that extra moisture due to above average sea surface temperatures left a whole lot of rain to be dumped over southeast Queensland and NSW.

How unusual is this constant rain?

Above average rainfall is typical with La Niña. But the sheer amount of rain Australia's east has experienced is unprecedented to say the least. 

And this is shown by the fact rainfall records have been broken throughout these recent times.

We've been hearing the term 'rain bomb' a lot in the news: is this an accurate way to describe what has been happening in some parts of Australia?

In late February, Brisbane locals woke up to major flooding across their city, severely impacting homes and businesses. At the time, Brisbane mayor Adrian Schrinner referred to the weather phenomenon as "a rain bomb", and ever since the definition has stuck with many. 

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What Schrinner was referring to was the sheer amount of rain that fell in such a short period of time, making it a pretty apt description in layman's terms. 

Explaining how exactly this 'rain bomb' occurred, Scully said: "Usually weather systems move from the west to the east across Australia. But in this instance, there was quite a 'blocking high pressure system' that prevented that usual west to east movement." 

What this did was force that amount of rain to sit dormant for days, and as a result, we witnessed a whole lot of water dumped.

Has climate change played a role?

Yes. At least 15 people died in the Lismore floods. Half a million Australians were either evacuated or told to prepare. Towns were underwater, reeling from the shock of experiencing a "one-in-1000-year event". 

And of all developed nations, Australia has been identified as one of the most vulnerable to climate change.  

Last month, a report by the Intergovernmental Panel on Climate Change found that "unprecedented weather events" will become a greater normality if we don't do more to address climate change in Australia.

When is the end in sight?

The system is expected to slowly weaken over autumn, which the Bureau anticipates will return to neutral conditions over the next few months. 

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BOM head of operational climate services Andrew Watkins says the La Niña weather pattern is expected to persist in eastern, northern and central parts of Australia for a bit longer. 

But is heavy rainfall and flooding something we should expect to see more of in the future? Potentially.

Should northern NSW and southeast Queensland expect more rain? More flooding? 

Ultimately, many locals in northern NSW and southeast Queensland are concerned by what's to come. Should they expect more rain? Will these flood-affected areas experience even more flooding again?

They are valid concerns when considering the clean-up in Lismore is still in full swing, and the damns throughout the region are all full. As Queensland Fire and Emergency Services said: "We're monitoring the weather situation and are ready to respond. The recent flood event means some previously saturated areas may react quickly to heavy rain. Floodwater can rise in minutes and conditions may become life-threatening," they said. "If it's flooded, forget it."

Listen to The Quicky: Grantham, the whole town that moved out of the flood zone. Post continues after audio.


NSW State Emergency Service assistant commissioner, Nicole Hogan noted: "Our catchments are very wet, and our dams are full, so it will not take a lot for floods to occur. We need people to be mindful of their flood risks and be prepared. In some areas floods may be different than previous or expected flooding due to the impact of recent events."

When southeast Queensland and NSW were bombarded with rain last month, BOM has warned that similar weather patterns are about to occur again.

Scully said to Mamamia: "There's a lot of weather warnings at the moment for heavy rainfall and and flash flooding, flash or riverine flooding, again due to a coastal tropical depression. We have to wait and see what will happen in the coming days."

Are there any other areas in Australia that should expect heavy rainfall?

Along with the rest of Australia's east coast there is another part of the country that is also expected to experience high rainfall levels. The Top End.

"Soil moisture is really high over eastern Australia and it's catchments are saturated. But it is also still the wet season across northern Australia at the moment, so there is the potential for heavy rainfall right across that area for the remainder of the wet season," Scully said.

To keep up to date with weather patterns in your region, you can visit the Bureau of Meteorology.

Feature Image: Getty/Twitter.

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