Summer forecast: scorching heat and heightened bushfire risk


Catherine Ganter, Australian Bureau of Meteorology

Large parts of Australia are facing a hotter and drier summer than average, according to the Bureau of Meteorology’s summer outlook.

Drier than average conditions are likely for much of northern Australia. Most of the country has at least an 80% chance of experiencing warmer than average day and night-time temperatures.

The threat of bushfire will remain high, with few signs of the sustained rain needed to reduce fire risk or make a significant dent in the ongoing drought.

Expect extreme heat

Large parts of Western Australia, most of Queensland and the Top End of the Northern Territory are expected to be drier than usual. Further south, the rest of the country shows no strong push towards a wetter or drier than average summer, which is a change for parts of the southeast compared to recent months.


Bureau of Meteorology

Queensland has already seen some extraordinary record-breaking heat in recent days, with summer yet to truly begin. With the summer outlook predicting warmer days and nights, combined with recent dry conditions and our long-term trend of increasing temperatures, some extreme highs are likely this summer.


Bureau of Meteorology

All of this means above-normal bushfire potential in eastern Australia, across New South Wales, Victoria and Queensland. The bushfire outlook, also released today, notes that rain in areas of eastern Australia during spring, while welcome, was not enough to recover from the long-term dry conditions. The current wet conditions across parts of coastal New South Wales will help, but it will not take long once hot and dry conditions return for vegetation to dry out.




Read more:
Sydney storms could be making the Queensland fires worse


What about El Niño?

The Bureau is currently at El Niño ALERT, which means a roughly 70% chance of El Niño developing this season.




Read more:
Australia moves to El Niño alert and the drought is likely to continue


However, not all the ducks are lined up. While ocean temperatures have already warmed to El Niño levels, to declare a proper “event” there must also be a corresponding response in the atmosphere to reinforce the ocean – this hasn’t happened yet.

That said, climate models expect this event to arrive in the coming months. The outlook has factored in that chance, and the conditions predicted are largely consistent with what we would expect during El Niño. In summer, this includes drier weather in parts of northern Australia, and warmer summer days.

Once an El Niño is in place, weather systems across southern Australia tend to be more mobile. This can mean shorter but more intense heatwaves in Victoria and southern South Australia. However, in New South Wales and Queensland, El Niño is associated with both longer and more intense heat waves.

The exact reason why the states are affected differently is complicated, but relates to the fast-moving cold fronts and troughs that sweep through Victoria and South Australia in the summertime, creating cool changes. These weather systems don’t influence areas further north so when hot air arrives, it takes longer to clear.




Read more:
Drought, wind and heat: when fire seasons start earlier and last longer


The heavy rains seen in parts of eastern Australia in October and November have provided some welcome short-term relief to drought-stricken farmers, but longer-term rainfall relief has not arrived yet. If El Niño arrives, this widespread relief may only be on the cards in autumn.The Conversation

Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Winter warmth is in the forecast (but don’t celebrate yet)



File 20170606 16856 8un8ng
It might feel nippy, but look out for winter heatwaves.
REUTERS/David Gray

Andrew King, University of Melbourne

The Bureau of Meteorology has issued its seasonal forecast for the winter, and it should be a warm one throughout southern Australia and the very tips of the Top End.

After a warm autumn, particularly in the east, this winter is forecast to be warmer and drier than usual – especially over the southern half of the continent.

Warmer-than-average conditions are likely for most of Australia.
Bureau of Meteorology

Not your everyday weather forecast

Seasonal forecasts are very different from your standard weather forecast for the day or week ahead.

Instead of giving exact temperatures or rainfall totals, the bureau provides probabilities of above or below average conditions. So if the bureau says there’s a 70% chance of above-average temperatures, that’s the same as saying there’s a 30% chance it will be below average.

These probabilities are estimated by looking at what’s going on in the Pacific and Indian Oceans, as they strongly influence Australia’s weather, and by running a set, or “ensemble”, of forecasts through the bureau’s seasonal forecast model.

A very different winter from last year

Looking back to last year, while most of Australia experienced quite a warm winter, it was also very wet. Nationally, it was the second-wettest winter on record, with the centre and the east of the continent copping the brunt of the rain. Last winter’s weather was driven by very warm seas in the east Indian Ocean, which meant a lot more moisture was available to deliver rainfall across the country.

Last winter was very wet for the east, although dry around Perth.
Bureau of Meteorology

This year we are seeing roughly average temperatures in the Indian Ocean, and a slight El Niño in the Pacific. This increases the likelihood of warmer, drier weather for the winter as a whole.

Winter heatwaves on the way

So can we expect to keep the thick coats in the wardrobe and enjoy some winter warmth? Perhaps.

Of course, winter heatwaves aren’t going to bring 40℃ days to Melbourne and Sydney, but we could get warm spells and temperatures into the low twenties in Sydney or the high teens in Melbourne.

It’s also worth noting that the seasonal forecast only looks at whether we’re going to have temperatures above or below average. It’s harder to predict whether we will see bursts of heat, or if the weather will consistently be a little bit warmer than normal through much of the season.

We’ve seen an increase in heatwaves in late autumn and winter in Australia over the past few decades. Notably, in May 2014 Sydney and large areas of southeast Australia had much-warmer-than-average conditions. A study found that this heat event was made at least 20 times more likely by the human influence on the climate.

We’re also seeing trends towards less frequent cold conditions in winter, with frosts becoming much rarer over a substantial part of Australia. Most of Australia is also experiencing fewer cold days. These trends are in line with what we expect from climate change, and are projected to continue.

Australia’s experiencing fewer frosty nights than it used to.
Bureau of Meteorology

While winter warmth can be pleasant for most of us, it can also cause plenty of problems. Warmer and drier winters can worsen drought – an effect we saw during the Millennium Drought in southeast Australia – by increasing evaporation and reducing soil moisture.

The ConversationSo while many of us in the south will gladly welcome a warm winter, it’s not good news for everyone. If warm and dry conditions were to persist into spring and summer – which is a distinct possibility with an El Niño watch in place – that would pose even more problems in terms of bushfire prevention, among other hazards.

Andrew King, Climate Extremes Research Fellow, University of Melbourne

This article was originally published on The Conversation. Read the original article.