The Bureau of Meteorology says the hot weather many parts of Australia has experienced over the last month is likely to continue until at least the end of the year.
In this interview, Aaron Coutts Smith, Manager of NSW Climate Services at the Bureau of Meteorology, explains how Australia's weather is expected to shape up this summer.
What sort of weather conditions are we seeing across Australia at the moment?
We are generally seeing some very warm conditions across northern Australia, and these conditions are really intensifying today, particularly in the south-east Queensland region, and the north-east of New South Wales. It's possible that we could break temperature records for September in some of those areas. In south-east Queensland and central Queensland, we are seeing temperatures even 10 or 15 degrees higher than what we would normally expect.
Does the Bureau of Meteoreology expect a really hot summer?
Our outlook currently covers the next three months, and that takes us into December and over that three-month period we are expecting warmer than average conditions across the majority of Australia, so we are expecting the warmth that we are seeing so far to continue.
Will we see more hot weather ahead for Sydney?
Sydney is currently on track to set a record for its warmest year on record and is also on track to have its warmest September on record.
What about the rest of Australia?
At the moment, the majority of the states across Australia would be in the top 10 of warmest years and, based on forecast, indications are that Australia is on track to set a record.
Why are we experiencing this heat?
What we are seeing is a real dominance of high-pressure systems. They have been helping to drive north-westerly and westerly winds, in particular into south-eastern Australia and also to keep the cold fronts at bay. And then what we have seen is a cold front coming through now, and just ahead of that change we see these really strong north-westerly winds and dry air, and that leads to an intensification of that heat.
Also, one of the contributing factors are warm sea surface temperatures that we have around Australia.
Why are surface sea temperatures warmer?
In part, we have seen a gradual increase in temperatures associated with climate change, and just generally the patterns of sea surface temperatures have placed well above average in this part of the year.
So could you say that this heat is connected to climate change?
In terms of the longer term perspective, what we have seen is an increase in temperatures, and that plays a part in adding a little bit of extra heat to the overall situation.
Can we call this heat a heatwave?
I guess by the definitions that we have, we haven't really experienced any heatwaves, as yet. There have certainly been some warmer conditions for this part of the year, but nothing that poses any threat to people.
So are we going to have fewer heatwaves than last year?
It's a little bit too far into the future for us to forecast. The warmest part of the year comes in that January to February period and that is just outside of our forecast range at the moment.
Would the current warm conditions possibly lead to a drought?
There's certainly areas in central Queensland that have been very dry; they missed out on a lot of rainfall during their wet season, which was over that summer period of late last year and the beginning of this year, and throughout the dry season this year, they haven't had much rainfall, if any at all, so there's areas in central Queensland and also extending into northern NSW that have seen very low rainfall for this time of the year.
Can we expect more rainfall in these areas?
In terms of our rainfall outlook over the next three months, odds are actually favouring dry conditions through central Queensland and far north NSW, so it doesn't appear that we are going to see any relief over the next couple of months.
Compared to past years, when we had really bad droughts, could you say that conditions are similar?
No. We have seen some really warm, dry conditions, but what we haven't seen is the dominating driver being El Nino. We are currently in a neutral phase of El Nino-La Nina oscillations, but if we were in El Nino, that would certainly increase the risk. So it's too early to say whether we'll see a continuation of the warm, dry conditions beyond the next couple of months.
INFLUENCES OF EL NINO AND LA NINA
So you said we are neither in El Nino or La Nina. Could you please explain that further?
We look at sea surface temperatures in the Pacific Ocean to tell us at what state we are currently in and we are in what we consider neutral, so it's neither La Nina nor El Nino, so we are not under the direct influence of either at present.
How do El Nino and La Nina work?
There's a general circulation in the Pacific Ocean, which sees warm sea surface temperatures to the north of Australia, and that generates moisture being put into the atmosphere, which can then fall as rain. That's the neutral pattern and, when we are in La Nina, we see that pattern enhanced, so we see stronger trade-winds, we see more moisture in the atmosphere, which can then enforce rain. During the El Nino phase, we actually see cooler sea surface temperatures to the north of Australia and warmth in the central Pacific Ocean that weakens the trade winds and moves that zone of active convection into the central Pacific, which means that there's not as much moisture to the north of Australia to then fall as rain.
Do you foresee in coming months conditions which can favour bushfires?
At the beginning of September, the Bushfire Cooperative Research Centre released a bushfire outlook, and that paints a bit of a picture of where they expect above-normal fire activity, or potential throughout the coming season, and for NSW that was pretty much across the ranges and in the slopes regions of NSW, as well as the coast, south of Seal Rocks.
So will the bushfire risk be really high in these areas?
In terms of the background risk, south-eastern Australia is probably one of the more fire-prone regions in the world, so even if we say normal fire activity is expected, then that can be quite high in relative terms. There is potential there for above-normal activity, but it really does come down to those extreme fire-danger days that we can see throughout this period.
Is this outlook worse than what was forecast a year ago?
No. The difference from this year to last year, is that in the far west of NSW we are expecting normal fire activity, as opposed to last year, when we were expecting above-normal fire activity and the in coastal regions south of Seal Rocks there's currently potential for above-average fire activity, which we didn't see last year.