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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Why predicting the weather and climate is even harder for Australia’s rainy northern neighbours



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Clouds roll across Samosir in northern Sumatra.
Shutterstock.com

Andrew King, University of Melbourne and Claire Vincent, University of Melbourne

Australians love to complain about weather forecasts, but compared with some other parts of the world ours are impressively accurate. Our large, mostly flat continent surrounded by oceans makes modelling Australia’s weather and climate relatively straightforward.

The same cannot be said about our neighbours to the north.

For Southeast Asian countries such as Indonesia and Papua New Guinea – which we collectively refer to as the “Maritime Continent” – things are a lot more complicated. With their mountainous terrain and islands of different shapes and sizes, it’s much harder to model the weather and climate of this region.




Read more:
The tropics are getting wetter: the reason could be clumpy storms


The models we use to make the most of our climate projections have to simulate the climate for many decades to provide us with useful information. To run such long simulations we have to compromise on resolution; even state-of-the-art global climate models divide the world into grid boxes more than 100km across. The Maritime Continent doesn’t come out too well at these resolutions.

If you squint you can see it! The world’s surface looks a bit like a 1980s video game to a global climate model. The Maritime Continent region (in the black box) is especially messy.
Author provided

It’s unfortunate the Maritime Continent’s weather and climate are so tricky to simulate on long time scales. Due to its location right on the Equator and between the Indian and Pacific Oceans, this region has a defining influence on the global climate, being a major source of heat and water vapour to the atmosphere. If we don’t simulate the climate over the Maritime Continent well, we can get errors appearing on the global scale.

Besides that, the Maritime Continent is also home to hundreds of millions of people, and includes major cities such as Jakarta and Singapore. We need our weather and climate models to simulate the processes behind the severe storms, heatwaves, and droughts that these cities and the broader region experience. Accurate weather forecasts, seasonal outlooks and climate projections require models to simulate the atmosphere over the Maritime Continent well.

In our new study, published in Geophysical Research Letters, we show that many state-of-the-art global climate models struggle to simulate the climate of the Maritime Continent. But fortunately, a higher-resolution model captures more of the major processes in this area.

The benefits of high resolution

Like in Australia, much of the Maritime Continent region is wetter during La Niña seasons and drier in El Niño, although for some western coasts and Sumatra it’s the other way round. Many global climate models fail to reflect accurately this rainfall response to El Niño and La Niña.

We found that for climate models to do a good job in capturing the year-to-year variability in rainfall over the Maritime Continent, they need to do a few things well. Specifically, they need to represent accurately the amount of moisture held in the atmosphere, as well as the pattern of winds in the region. This gives the right pattern of rainfall response to El Niño and La Niña.

Our higher-resolution regional climate model does a much better job at simulating the Maritime Continent’s rainfall patterns than many of the global models we looked at. As the region has such a complex landscape, global models simply cannot capture enough detail on all the different processes between the land and the ocean, and the coasts and the mountains. But higher-resolution regional models can.

We can capture the processes behind rainfall in the Maritime Continent more realistically when we use a high-resolution model. In particular we can better represent the thunderstorms and heavy rain that tends to occur in the afternoons and evenings in the tropics.



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


As the Maritime Continent is so important for the global climate but so difficult to model, there is a concerted effort to improve our models and to get more atmospheric observations across the region.

International projects such as the Years of the Maritime Continent are taking place, with millions of dollars and dozens of researchers working on improving our understanding of the region’s weather and climate.

Ultimately, we hope that through better, higher-resolution model simulations, we can capture the processes behind the Maritime Continent’s weather and climate much more accurately. This should lead to better climate projections and seasonal forecasts not only for the region, but for the world as a whole.The Conversation

Andrew King, ARC DECRA fellow, University of Melbourne and Claire Vincent, Lecturer in Atmospheric Science, University of Melbourne

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

Trust Me, I’m An Expert: Australia’s extreme weather



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Australia’s cyclone season lies ahead.
NASA / ESRSU / Seán Doran, CC BY-NC-SA

Madeleine De Gabriele, The Conversation and Wes Mountain, The Conversation

It’s easy to write off Australia’s extreme weather as business as usual. We deal with floods, droughts, cyclones and other wild events every year. But as climate change raises global temperatures, are the droughts happening more often? Are the floods getting worse?

The October episode of Trust Me, I’m An Expert looks back through colonial evidence and prehistoric records, and forward to the Bureau of Meteorology’s Cyclone Weather Outlook for the year ahead.

The full episode will be released on October 8, but today you can catch a little of our interview with the Bureau of Meteorology’s Andrew Watkins. Keep an eye out for the full episode, where we ask: are we in uncharted territory, or is this life as usual on a changeable continent?




Read more:
Trust Me, I’m an Expert: Risk


Trust Me I’m An Expert is a monthly podcast from The Conversation, where we bring you stories, ideas and insights from the world of academic research.

You can download previous episodes of Trust Me here. And please do check out other podcasts from The Conversation – including The Conversation US’ Heat and Light, about 1968 in the US, and The Anthill from The Conversation UK, as well as Media Files, a brand new podcast all about the media.

You can find all our podcasts over here.

Music:




Read more:
Trust Me, I’m An Expert: How augmented reality may one day make music a visual, interactive experience


The Conversation


Madeleine De Gabriele, Deputy Editor: Energy + Environment, The Conversation and Wes Mountain, Deputy Multimedia Editor, The Conversation

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

Curious Kids: where do clouds come from and why do they have different shapes?



File 20180912 181254 s09p4f.jpg?ixlib=rb 1.1
Sometimes air goes up past the condensation level then falls back below the condensation level, then up, then below, again and again. This creates clouds that are stripy, often with lines between the clouds.
Robert Lawry/Author provided, Author provided

Robert Lawry, Australian Bureau of Meteorology

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.


Where do clouds come from and why do they all have different shapes? – Ryan Potts, age 7, Canberra.


Hi Ryan, great question!

When it comes to understanding clouds, it helps first to understand water.

You know the water you drink out of a glass? That’s liquid water. There is also solid water, such as ice from the freezer or a slushy.

But water also exists as a gas. It’s called water vapour. You can’t can’t see, taste or feel this water but it’s everywhere. It’s all around you right now. Water vapour is in the air we breathe. When it’s warm and there is a lot of water vapour in the air, it can feel very sticky and sweaty.




Read more:
Curious Kids: Why do you blink when there is a sudden loud noise close by?


Now let’s go back to clouds.

For clouds to form, air needs to be cooled to a temperature at which the water vapour turns into liquid water. The best way to do this is to make the air rise, because the higher we go in the atmosphere the colder the temperature. There are many reasons air might lift, but one reason is because during the day the sun heats up the surfaces around us.

Imagine the oval near your school on a warm day. Starting in the morning the sun warms the surface of the oval and before too long the entire oval is warming up.

Warm air weighs less than cooler air. So a big bubble of warm air, filled with water vapour, slowly lifts off your school oval.

As the bubble of air (filled with water vapour) rises upwards, it starts to cool down. The higher it goes the cooler it gets.

Bubbles of warm air that have reached and passed beyond the condensation level.
Robert Lawry, Author provided

Eventually, well off the ground above your school, the bubble of air has cooled so much that the water vapour turns into liquid water. We call this point the condensation level. When the water vapour turns into tiny specks of liquid water, a cloud forms.

Clouds are simply liquid water: very, very small drops of liquid water. So small in fact, that they can be held up in the air by rising air currents.

Back on the school oval: the day keeps getting warmer, more and more bubbles of rising air race upwards, cooling as they rise. When these bubbles of air reach the condensation level, more cloud forms.

A fluffy, bumpy cloud, formed by rising warm air currents.
Robert Lawry, Author provided

Clouds formed by rising warm air currents are called “convection clouds”. Because of all the rising air coming up, these clouds can be bumpy on the top, sometimes producing very high thick clouds looking like cotton wool or cauliflower heads.



The Conversation, CC BY-ND

When air rises very slowly and gently over an area and reaches the condensation level you get a cloud that is very smooth looking, like this:

A smooth cloud.
Robert Lawry, Author provided

Sometimes air goes up past the condensation level then falls back below the condensation level, then up, then below, again and again. This creates clouds that are stripy, often with lines between the clouds.

The way the air moves creates all the different clouds we see.



The Conversation, CC BY-ND

All the grey clouds that you see contain liquid water. However, as we discussed earlier, water can also exist as a solid (ice). Clouds that are very high are extremely cold and may appear pure white. These clouds contain ice.

I used to wonder what it would feel like to touch a cloud. Would it be fluffy? Hard, soft, warm or cold?

Well, we don’t need to wonder. Because every time we see fog, we are looking at cloud.

Fog is simply air that has cooled to the point where the water vapour has turned into liquid water. That forms fog – which is really just a cloud on the ground.

So next time you see fog, go outside and touch a cloud!

Fog is really just cloud at ground level.
Robert Lawry, Author provided



Read more:
Curious Kids: Why don’t dogs live as long as humans?



Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:

* Email your question to curiouskids@theconversation.edu.au

* Tell us on Twitter by tagging @ConversationEDU with the hashtag #curiouskids, or

* Tell us on Facebook


CC BY-ND

Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.The Conversation

Robert Lawry, Hydrologist, Australian Bureau of Meteorology

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

Melbourne and Adelaide have been Australia’s most vulnerable major cities to killer heatwaves


Thomas Longden, University of Technology Sydney

Melbourne and Adelaide have been most prone to deadly heatwave conditions among Australia’s five largest cities, according to my new research published in Climatic Change.

My study shows that between 2001 and 2015, Melbourne and Adelaide suffered the most exposure to temperatures beyond a crucial threshold of 7.26℃ above the average. Above this threshold, deaths are more likely because people are not acclimatised to the extreme weather.

I estimated that there were 151 deaths in Melbourne and 144 in Adelaide due to extreme heatwaves – those above this 7.26℃ threshold – between 2001 and 2015.

Heatwaves can cause significant numbers of deaths, especially among vulnerable groups of people who are not prepared for or acclimatised to extreme hot temperatures.

Even though Melbourne and Adelaide are located in more temperate areas (in comparison with more northerly cities such as Brisbane), they have been periodically hit by severe heatwaves.




Read more:
We’ve learned a lot about heatwaves, but we’re still just warming up


In my research, I looked at the “Excess Heat Factor”, a measure used by the Bureau of Meteorology as part of its heatwave forecasts. It is the difference between the 3-day average temperature and the 30-day average, and is therefore a measure of how “unusually hot” it is during a heatwave. It captures how much residents are likely to struggle to cope with the heat.

The graphs below show the frequency of excessively hot or cold weather for each of Australia’s major cities from 2001 to 2015. These charts show that most days had temperatures where the 3-day average was 2℃ higher or lower than the 30-day average.

A grey dashed line shows the extreme heat threshold that my study found was associated with higher deaths, relative to moderately warm and cool days.
I then estimated the threshold at which there is a significantly increased risk of deaths.

The death rate (per 100,000 people) that coincides with the extreme heat acclimatisation measure is shown as a black line on each of the graphs. This is an average impact of temperature on death rates, adjusted for different cities’ population sizes and baseline death rates.

Between 2001 and 2015, most of the events above the 7.26℃ extreme heat threshold occurred in Adelaide, Melbourne and Perth. Brisbane and Sydney had fewer days above this threshold.

Figure 1 – Histograms of the Excess Heat Index for major Australian cities between 2001 and 2015.

The importance of acclimatisation

Several previous studies have linked excessive heat to adverse events such as deaths (see here, here and here), and emergency department visits and ambulance call-outs (see here, here and here). But my study is the first to solely focus on the extreme heat index acclimatisation measure, and to identify a temperature threshold in this way. This measure is important, as it identifies the times when residents of cities with different background climates begin to struggle with the heat.

The Bureau of Meteorology does not currently use the 7.26℃ threshold identified in my paper. Doing so may improve predictions of which heatwaves are most likely to turn deadly for significant numbers of people living in our major cities.

Implications for policy

Since the severe heatwaves of 2009, many states and territories have implemented or revised their heatwave response plans, or conducted awareness campaigns to educate people about the health risks. But more can be done to make vulnerable people aware of upcoming heatwave events.

A 2016 review proposed that heatwave response plans and early warning systems should be evaluated and updated at least every five years, to ensure that they remain effective, and to incorporate up-to-date knowledge about population-level vulnerability to heat stress.

While my research has focused on Australia’s five largest cities, this does not mean that extreme heat is any less dangerous in other areas. Nor is the danger limited to prolonged heatwaves – individual hot days can catch people out too. A NSW study found that emergency hospital admissions due to dehydration and other heat-related injuries rose significantly on individual hot days, as well as during hot spells lasting at least three days.

This suggests that we need to develop more complex heat risk management plans, with targeted responses for different health issues based on the longevity of extreme heat events.

Implications for the future

We also need to consider the patterns of extremely hot temperatures that we are likely to encounter in the future. Recent research found that changes in the frequency and duration of heatwaves will be larger in the north of Australia than the south. But the same study also found that “heatwave amplitude” – the intensity of the hottest day of the hottest heatwave – will increase more in southern parts of Australia.

The ConversationThis research suggests that cities south of Brisbane will experience the most severe temperature spikes beyond what their residents are used to dealing with.

Thomas Longden, Senior Research Fellow, University of Technology Sydney

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