Australia: Now It’s Wild Weather


How drought is affecting water supply in Australia’s capital cities


Ian Wright, Western Sydney University and Jason Reynolds, Western Sydney University

The level of water stored by Australia’s capital cities has steadily fallen over the last six years. They are now collectively at 54.6% of capacity – a decline of 30% from 2013.

We’re going into a hot summer and Sydney has just announced level 2 restrictions, the toughest for any capital. Data from the Bureau of Meteorology shows other capital cities facing mixed results.

The results show that Darwin’s water supply has lost about 25% over the last year. On the plus side, Melbourne’s supply actually increased over 2019, having fallen below 50% earlier this year, and now sits on 63.9%.

While the national average is trending downwards, the patterns for each city are very different. Sydney and Perth water supplies have had contrasting journeys over the last six years. In October 2013 Perth’s supply was a very low 33.8% and Sydney was a comfortable 91%.

Now, for the first time in many years Perth does not have Australia’s lowest level of all capital city water storages. As of last week, Sydney has taken this unwanted distinction from Perth.

For Perth residents, the news is good as their surface water storages are at a six-year high of 46.4%. In Sydney they are worried, as they have a six-year low of 46.2%.

Sydney has experienced a steep decline over the last 30 months, from nearly full storages (96%) in April 2017. The speed and severity of the Sydney drought is starting to resemble previous dry spells. One was in the 1940s and the other was the Millennium drought.

Perth has lived with the most water stress of any capital city. They have had to contend with a steady 45-year decline in rain. The inflow of water into Perth’s dams has also fallen dramatically.

Perth has adapted to its drying climate by sourcing water from many different supplies. It now uses its surface water storages for about 10% of its water supply. Much larger proportions of Perth’s supply comes from its two desalination plants, which unlike the other capitals are constantly in operation. It makes greater use of groundwater and highly treated recycled water. Perth also has permanent water restrictions.

Sydney’s desalination plant, after hibernating for 7 years, is now supplying water. It was switched on in late January 2019 when Sydney supply hit 60%, and can supply 15% of water demand. Unusually perhaps, the desalinated water does not reach all parts of Sydney.

Sydney Water has announced plans to double the capacity of the desalination plant. Construction is expected to begin soon.

Melbourne and Brisbane water supplies are currently at similar levels. However, since 2013 Melbourne’s storages have generally been lower than Brisbane’s. Melbourne’s supply has risen in 2019 after good winter rainfall in its catchments. The storages have increased from under 50% (49.6%) in late May 2019. Today, Brisbane storage levels are now at 59.2%.

Melbourne residents use less water than the other capital cities. In 2018 the average Melbourne resident used 161 litres per day, approximately 30% less than Sydney residents.

Melbourne’s supplies have also been supplemented with the reactivation of its Wonthaggi desalination plant in 2019. It is Australia’s largest desalination plant, capable of producing 410 million litres a day.




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Brisbane also built a desalination plant after the Millennium Drought. In addition, they also made very large investments in Australia’s largest waste water recycling scheme. The Western Corridor recycled water scheme opened in 2008, cost $2.5 billion and features three advanced waste water treatment plants, with more than 200 km of pipelines and three advanced waste water treatment plants.

Hobart, Darwin and Canberra are the three Australian capital cities without desalination plants. Canberra has had a steady decline in its supply over three years. It was full in October 2016, gradually dropping to 51.6% in November 2019. Hobart’s storages were above 80% for most of the last six years. They were just above 90% 12 months ago and have since fallen to their current level of 72%.




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Darwin’s water supply was full as recently as April 2018. Now, 18 months later, it is just touching 54%. This is its lowest level in six years. Darwin, our tropical capital, has the most seasonal rainfall of Australia’s capitals. Typically, they have almost no rain June to September during their dry season, and a wet season of heavy rains from October to April.
However, the last wet season was one of the driest on record.

Adelaide’s water storage has fluctuated over the last 6 years. Adelaide gets more rain in winter and has dry summers, an opposite pattern to that of Darwin. Over the last 3 years the level has dropped from over 97% in October 2017 to just below 58%.




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The desalination plant in Adelaide can supply up to 50% of its water supply. It has been operating in 2019, although not in the wetter months of July and August. The Murray also continues to supply a large proportion of Adelaide’s water supply. The Commonwealth has agreed to use drought funding for the Adelaide desalination plant, so more river water can be used by farmers upstream to grow fodder for livestock.

Australia is set for a dryer and hotter summer than average, particularly in the east. Coupled with continued high levels of household demand, we can expect further declines in water storage levels through the first half of 2020.The Conversation

Ian Wright, Senior Lecturer in Environmental Science, Western Sydney University and Jason Reynolds, Research Lecturer in Geochemistry, Western Sydney University

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

A hot and dry Australian summer means heatwaves and fire risk ahead


Catherine Ganter, Australian Bureau of Meteorology and Andrew B. Watkins, Australian Bureau of Meteorology

Summer is likely to start off hot and dry, according to the Bureau of Meteorology’s summer outlook, released today.

Much of eastern Australia is likely to be hotter and drier than average, driven by the same climate influences that gave us a warmer and drier than average spring.




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But these patterns will break down over summer, meaning these conditions may ease for some areas in the second half of the season. Despite this, we’re still likely to see more fires, heatwaves, and dust across eastern Australia in the coming months.

Rainfall outlook for December 2019.
BOM

What drove the climate in 2019

Our current weather comes in the context of a changing climate, which is driving a drying trend across southern Australia and general warming across the country.

In southern Australia, rain during the April to October “cool season” is crucial to fill dams and grow crops and pasture. However, like 17 of the previous 20 cool seasons, 2019 was well below average, meaning a dry landscape leading into the summer months.

The frequency of high temperatures has also increased at all times of year, with the greatest increase in spring.

But summer, like spring, will also be influenced by two other significant climate drivers: a change in ocean temperatures in the Indian Ocean, and warm winds above Antarctica pushing our weather systems north.

Indian Ocean

The first driver is a near-record strong positive Indian Ocean Dipole (IOD). A positive IOD occurs when warmer than average water develops near the Horn of Africa, and cooler waters emerge off Indonesia.

This pattern draws moisture towards Africa – where in recent weeks they have seen flooding and landslides – and produces higher pressures over central and southern Australia. This means less rain for Australia in winter and spring.

Usually the IOD events break down by early summer, when the monsoon arrives in the southern hemisphere. However, this year the monsoon has been very sluggish moving south – in fact it was the latest retreat on record from India – and international climate models suggests the positive IOD may not end until January.

Rainfall outlook for summer 2019-20.
BOM

Southern Ocean

The other unusually persistent climate driver is a negative Southern Annular Mode (SAM), which means weather systems over the Southern Ocean – the fronts and lows and wild winds – are further north than usual. This means more days of westerly winds for Australia.

In western Tasmania, where those winds are coming off the ocean, it means cooler and wetter weather. In contrast, in southeast Queensland and New South Wales, where westerlies blow across long fetches of land, this air is dry and hot.

This persistent period of negative SAM in 2019 was triggered by a sudden warming of the stratosphere above Antarctica – a rare event identified in early September.




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Models suggest the negative SAM will decay in December. This means the second half of summer is less likely to be influenced by as many periods of these strong westerlies.

But while both these dry climate drivers are expected to be gone by midsummer, their legacy will take some time to fade.

The positive IOD and the dry conditions we have seen in winter and spring are associated with severe fire seasons for southeast Australia in the following summer.

And while the drying influences are likely to ease, the temperature outlook indicates that days are very likely to remain warmer than average.

We also know that any delay in the monsoon will keep air drier for longer across Australia, and potentially aid in heating up the continent.

Maximum temperature outlook for summer 2019-20.
BOM

What about the wet season?

For areas of southern Queensland and northeastern NSW, the wet season will eventually bring seasonal rains, although heatwaves are likely to continue through summer.

So, while the outlook for below average rainfall may ease over summer months for some areas, the lead-up to summer means Australia’s landscape is already very dry. Even a normal summer in the south will mean little easing of the dry until at least autumn.

With dry and hot conditions looking likely this summer, it’s important to stay safe, have an emergency plan in place, look after your friends and neighbours in the hot times, and always listen to advice from your local emergency services.




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You can visit the Bureau of Meteorology website to view the latest outlook, or subscribe to receive climate outlooks via email.The Conversation

Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology and Andrew B. Watkins, Head of Long-range Forecasts, Australian Bureau of Meteorology

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

This is why nuking a hurricane will not work, Mr Trump


Liz Ritchie-Tyo, UNSW

President Donald Trump has reportedly suggested on more than one occasion that the US military explode nuclear bombs inside hurricanes to disrupt them before they reach land.

As reported in National Geographic, this is not the first time a suggestion like this has been made – although Trump now denies having said it.

On the surface, it would seem like a simple solution to the devastation that occurs in the US each year during the hurricane season. However, there are several problems with this idea.




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What is a hurricane?

Hurricanes are low-pressure weather systems covering an area of more than 500,000km². They form over warm tropical oceans, which are their primary energy source. The low pressure at the centre of the hurricane – the eye – draws in the surrounding warm, moist air. This air then rises and condenses into deep thunderstorm clouds surrounding the centre – the eyewall – and also in cloud bands spiralling out from the eye called rainbands.

As the air is pulled into the eye, Earth’s rotation causes it to spin cyclonically – anticlockwise in the northern hemisphere and clockwise in the southern hemisphere. The continuous supply of air into the deep thunderstorms surrounding the eye allows the hurricane to intensify until it reaches a steady state of equilibrium with the oceans and the environment.

Would a nuclear bomb put a dent in a hurricane?

The average hurricane can be likened to a very inefficient heat engine. As the warm moist air rises, it releases heat energy through the formation of clouds and rain at a rate of about 5.2 x 10¹⁹ joules per day. Less than 10% of this heat is then converted into the mechanical energy of the wind.

To give some perspective of this energy, the heat released in a hurricane is equivalent to a 10-megatonne nuclear bomb exploding every hour. This energy is also on the order of the global energy consumption in 2016, according to the United States Energy Information Agency.

It seems unlikely that exploding a bomb in the hurricane would make much impact on such a powerful weather system, and it is impossible to run controlled experiments to determine whether it would.

Not to mention that there could be shocking effects from the fallout of radioactive material from such an explosion. These materials would be transported widely via the trade winds through the lower levels of the atmosphere, and potentially around the entire planet in the stratosphere – similar to the effects from the volcanic fallout from Mount Pinatubo in the Philippines in 1991.

Have people tried to stop hurricanes before?

There have been previous attempts to modify the impacts of hurricanes. Between 1962 and 1983 the US government funded experimental research on hurricane modification known as Project STORMFURY. The fundamental premise was, because the potential of damage from hurricanes increases rapidly with the hurricane’s wind speed, a reduction in wind speed of as little as 10% could make a large difference in the impacts when hurricanes reach land. By seeding the air outside the eyewall with silver iodide, a chemical used to seed clouds, it was thought a new ring of thunderstorms may develop outside the eyewall – robbing it of energy and weakening the hurricane.




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Modification was attempted in four hurricanes on eight different days. On four of those days, a 10-30% reduction in wind speed was measured. The lack of response on the other fours days was initially interpreted to be the result of faulty execution of the experiment, but was later attributed to an imperfect understanding of the microphysics of clouds in hurricanes.

Successful cloud seeding using silver iodide requires that supercooled water droplets freeze onto the silver iodide seeds.

Recent observations show hurricanes have too many naturally occurring ice crystals and too few supercooled water droplets for cloud seeding to be effective. So any change in hurricane wind speed observed during the STORMFURY experiments was almost certainly due to the natural behaviour of hurricanes rather than human intervention.

Although Project STORMFURY was abandoned, the hurricane observation program is still run under the Hurricane Research Division of the National Oceanic and Atmospheric Administration (NOAA). The original aircraft used in Project STORMFURY were replaced in the 1970s by WP-3D aircraft, which still reside under NOAA and are operated by its officers.




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The observations collected by these aircraft continuously over a period of more than 60 years has helped improve hurricane forecasting. Furthermore, these observations have allowed researchers to develop vital insights into the structure, intensity, and physical processes of this most destructive of natural phenomena.The Conversation

Liz Ritchie-Tyo, Associate Professor, School of Physical, Environmental, and Mathematical Sciences, UNSW

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

The stubborn high-pressure system behind Australia’s record heatwaves



File 20190124 135136 p47dl4.jpg?ixlib=rb 1.1
Parts of Australia have broken multiple heat records over the past week.
Vicki/Flickr, CC BY-NC-SA

Steve Turton, CQUniversity Australia

If you think the weather this month has been like Groundhog Day (albeit much hotter), you’d probably be right! Much like a stuck record, weather systems seem to have stalled over most of the country.

Brisbane residents are questioning the lack of rain, storms and heat. Darwin has just endured its second-latest monsoon onset on record after weeks of heat and humidity. Interior towns and cities have experienced significantly hot weather with a number of new maximum and minimum temperature records broken, along with records for consecutive days over 35℃.




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Perth has largely escaped the heat so far this summer, while Sydney and Hobart have had a mixed bag. Coastal sea breezes have tempered conditions in the south and southeast of the continent. However, heatwaves are forecast for Melbourne and much of the southeast, with the arrival of strong, hot northerly winds. This will also bring extreme or severe fire weather conditions in many areas, including Tasmania. Adelaide, meanwhile, has sweltered through the hottest day on record for any Australian capital.


Bureau of Meteorology

These weather patterns across the country are largely due to a stubborn blocking high-pressure system that has remained over the Tasman Sea since early January, affecting weather on both sides of the ditch. This type of strong high-pressure system typically forms further south than usual, and remains almost stationary for an extended period, thus blocking the west-to-east progression of weather systems across southern Australia.




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Sometimes, these blocking highs position themselves over the Great Australian Bight. They can occur at any time of year, and can stay in the Australian region from several days to several weeks.

This schematic shows a ‘blocking high’ preventing weather systems moving across Australia.
Understanding Climate Change in Australia report

Winds rotate anticlockwise around high-pressure systems in the Southern Hemisphere. On the northern flank of the blocking high, southeast trade winds have been affecting northern New South Wales and eastern Queensland due to a persistent ridge of high pressure. These winds have been largely cool and dry, with only the far north of Queensland experiencing significant showers. The ridge has kept the inland trough further west over inland NSW and Queensland, preventing normal afternoon thunderstorm activity in the inland, and adding to the woes of the extended drought.

Cool, moist weather from the Southern Ocean is being displaced southeast by the blocking high, resulting in prolonged continental heatwaves and lack of rain. On the western flank of the blocking high, hot dry northerly winds from the arid centre are pushing through South Australia and Victoria, generating heatwave conditions.




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Across the ditch, cooler and drier southerly winds are affecting much of New Zealand. Only the southwest of the South Island is getting any significant rain due to persistent moist westerlies on the southern flank of the blocking high.

An unusually strong ridge of high pressure across Queensland, extending up to Cape York, has kept the monsoon trough north of the continent. This pattern is forecast to change as a deep tropical depression forms in the Gulf of Carpentaria over the coming days and moves south into northern Queensland. Unfortunately, the stubborn ridge of high pressure over central Queensland is likely to block the rain-bearing low from moving much further south over drought-stricken parts of inland Queensland and NSW.




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While parts of the country have sweltered, the far southwest of Australia has experienced cooler and wetter than average conditions this month. Cape Leeuwin, Australia’s most southwesterly point, set a 123-year daily rainfall record for January, recording a massive 57mm of rainfall.


Bureau of Meteorology

In the short term, there is no indication that the blocking high will break down or move eastward. Forecasters on both sides of the Tasman expect the pattern to continue until February at least.




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The Conversation


Steve Turton, Adjunct Professor of Environmental Geography, CQUniversity Australia

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

Sydney storms could be making the Queensland fires worse


Claire Yeo, Australian Bureau of Meteorology

A strong low-pressure system has meant severe thunderstorm and hail warnings are in effect for much of the New South Wales South Coast. At the same time, very dry conditions, strong winds and high temperatures are fuelling dozens of bushfires across Queensland.

The two events are actually influencing each other. As the low-pressure system moves over the Greater Sydney area, a connected wind change is pushing warm air (and stronger winds) to Queensland, worsening the fire conditions.




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These lows over NSW are the kind we might see a couple of times a year – they’re not just regular weather systems, but neither are they massively out of the ordinary.

However, when combined with the current record-breaking heat in Queensland, the extra wind is creating exceptionally dangerous fire conditions. Queensland’s emergency services minister, Craig Crawford, has warned Queenslanders:

We are expecting a firestorm. We are expecting it to be so severe that it won’t even be safe on the beach […] The only thing to do is to go now.

Conditions in Queensland

At least 80 bushfires were burning in Queensland on Wednesday, with more than a dozen fire warnings issued to communities near the Deepwater blaze. Queensland Police Deputy Commissioner Bob Gee said that “people will burn to death” unless they evacuate the area.

These fires have come during a record-breaking heatwave. On Tuesday Cooktown recorded 43.9℃, beating the previous November high set 70 years ago by more than two degrees. Cairns has broken its November heatwave record by five whole degrees.

Grasslands and forests are very dry after very little rain over the past two years. Adding to these conditions are strong winds, which make the fires hotter, faster and harder to predict. This is where the storm conditions in NSW come in: they are affecting air movements across both states.

NSW low is driving winds over Queensland

A large low-pressure system, currently over the Hunter Valley area, is causing the NSW storms. As it moves, it’s pushing a mass of warm air ahead of it, bringing both higher temperatures and stronger winds across the Queensland border.

Once the low-pressure system moves across the Hunter area to the Tasman Sea east of Sydney, it will drag what we call a “wind change” across Queensland. This will increase wind speeds through Queensland and temperatures, making the fire situation even worse.

This is why emergency services are keeping watch for “fire tornado” conditions. When very hot air from large fires rises rapidly into a turbulent atmosphere, it can create fire storms – thunderstorms containing lightning or burning embers. Strong wind changes can also mean fire tornadoes form, sucking up burning material. Both of these events spread fires quickly and unpredictably.




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What does this mean for the drought

Unfortunately, it’s not likely the heavy rains over NSW will have a long-term effect on the drought gripping much of the state. While very heavy rains have fallen over 24 hours, the drought conditions have persisted for years.




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The wet weather may bring some temporary relief, but NSW will need much more rain over a longer period to truly alleviate the drought.

In the meantime, the Bureau of Meteorology will be monitoring the Queensland situation closely. You can check weather warnings for your area on the bureau’s website.The Conversation

Claire Yeo, Supervising Meteorologist, Australian Bureau of Meteorology

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

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


Skie Tobin, Australian Bureau of Meteorology; Catherine Ganter, Australian Bureau of Meteorology, and Robyn Duell, Australian Bureau of Meteorology

The chances of an El Niño developing late in 2018 have increased and this week the Bureau moved to El Niño ALERT. This means that model outlooks and observations indicate there is approximately a 70% chance that El Niño will develop in the coming months. Current patterns in the Pacific are similar to the early stages of past El Niño, with warm water shifting east towards South America.

We’re also seeing indications a positive Indian Ocean Dipole (IOD) has likely started, in which warmer waters near Africa drag moisture away from Australia. El Niño and positive IOD events typically mean below-average spring rainfall in central and southern Australia, and a drier start to the wet season in Queensland and the Northern Territory.




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The development of either would favour continued dry weather, and increase the likelihood that widespread drought relief will be delayed until 2019. Higher than average temperatures, heatwaves, and more severe bushfire weather are also more likely during El Niño and positive IOD events.

A dry year so far

September 2018 was a very dry month, adding to low rainfall seen across many parts of Australia so far this year. September 2018 was not only the driest September in 119 years of record for Australia, but it was also the second-driest for any month of the year (behind only April 1902).

Rainfall for the year to date has been exceptionally low over the mainland southeast, with much of the region experiencing totals in the lowest 10% of records for January–September. Many locations in eastern New South Wales, eastern Victoria, and southeast Queensland have received about 400 mm less rainfall than they usually would have by this time of the year.

Rainfall deciles for January to September 2018.
Bureau of Meterology

Much of southern Australia has experienced a persistent rainfall decline spanning several decades, which is adding to drought stress by drying the landscape.

Southwest Western Australia has experienced significantly lower cool season (April to October) rainfall since the mid-1970s, compared to observations since 1900, while for the southeast the drop has been more recent, emerging in the mid-1990s. These rainfall declines have been linked to circulation changes in the southern hemisphere influenced by the increase in greenhouse gases.

These rainfall changes have also been accompanied by much larger reductions in streamflow, particularly in the southwest of Australia where high flows have become much less frequent.

April to October rainfall anomalies (mm) for southwestern (left) and southeastern (right) Australia, showing the decline in totals with respect to the 1961 to 1990 average. The main feature of the decline is significantly fewer wet years, meaning recovery from the dry years is patchy.
Bureau of Meteorology

And it’s also been unusually warm

Low rainfall has also been accompanied by very high daytime temperatures so far this year. Of course, Australian temperatures are warming in line with global trends, but in individual years variations which are likely to be largely natural (such as droughts) may add to or subtract from the broader trends.




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Historically, droughts have often brought hot conditions, and this has been borne out in 2018. Maximum temperatures for January to September were the warmest on record for the Murray–Darling Basin and New South Wales, with neighbouring regions also much warmer than average.

These extremely warm days, combined with extremely low rainfall, have caused an intense drying of the Australian landscape in 2018, resulting in an early start to the bushfire season in New South Wales and Victoria, where damaging fire were observed as early as late winter.

So how might the year end?

Like all Australians, the Bureau hopes farmers and those suffering through drought get the rainfall they need, but unfortunately, the outlook indicates dry conditions are likely to continue for some time.

Large parts of southern and eastern Australia are likely to see a drier than average end to the year, though odds favouring drier than average conditions tend to moderate as we head towards summer. Most of the country is likely to see a dry October, though local heavy falls can occur against a backdrop of broadly suppressed rainfall.

Chance of exceeding median rainfall between October to December 2018.
Bureau of Meteorology

While some parts of New South Wales and southeastern Queensland have received very welcome rainfall in the first days of October, rainfall has been below average over much of over eastern Australia for so long (since early 2017) that this rainfall event hasn’t been enough to break the drought.




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Looking at temperature, outlooks show a very high chance of warmer than average days and nights through to the end of 2018. Considering the year so far has already been very warm, this means 2018 has the potential to rank as another significant warm year. Seven of Australia’s ten warmest years have occurred since 2005, with just one cooler than average year in the last decade (2011), highlighting how warmer than average temperatures now dominate Australia’s climate.The Conversation

Change of exceeding median maximum temperature between October to December 2018.
Bureau of Meteorology

Skie Tobin, Climatologist, Australian Bureau of Meteorology; Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology, and Robyn Duell, Senior Climatologist, Australian Bureau of Meteorology

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

Spring is coming, and there’s little drought relief in sight


Jonathan Pollock, Australian Bureau of Meteorology; Catherine Ganter, Australian Bureau of Meteorology, and David Jones, Australian Bureau of Meteorology

So far, 2018 has been very warm and exceptionally dry over large parts of mainland Australia. The Bureau of Meteorology’s climate outlook for spring, released today, shows that significant widespread relief is unlikely.

The chance of a spring El Niño, along with other climate drivers, is likely to mean below-average rainfall for large parts of the country in the coming months.

A dry winter for most of Australia

Winter rainfall has been below average over most of Australia’s eastern mainland. Large parts of New South Wales are on track to have winter rainfall in the lowest 10% of records. This has compounded drought conditions in the east after mixed rainfall last year and a dry start to 2018 for much of the country.

But it’s not just the lack of rainfall that has made the impact of drought severe. Another factor was the warmer than average daytime temperatures.




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Warmest January-August on record for some

The 2017-18 summer average temperature was Australia’s second-warmest in 108 years of records, while autumn was Australia’s fourth-warmest on record. Winter 2018 is likely to be among the five warmest winters on record in terms of maximum temperatures.

Many of the above-average daytime temperatures have been focused over the country’s southeast. In fact, South Australia, New South Wales and Victoria are all on track for their warmest maximum temperatures for the January to August period.

The below-average rainfall combined with above-average maximum temperatures resulted in a rapid and intense drying of the landscape. This has led to unusually severe fire weather conditions in July and August – conditions more typically seen at the end of spring than the end of winter.




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In contrast, low rainfall, cloud-free skies and dry soils mean it has been colder than usual overnight across most of the country during winter.

Climate conditions favour low rainfall

Will spring see a break in the warmer days and below average rainfall? Probably not. Both the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), can be major influences on Australia’s seasonal rainfall and temperature patterns.

During winter, both ENSO and the IOD were neutral, meaning that neither of them provided a large influence on winter’s weather (so we can’t blame them this time).




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However, most international climate models have been forecasting a spring El Niño since June. Sea surface temperatures in the central Pacific have been gradually warming since autumn and are rising towards El Niño thresholds. At the beginning of June the Bureau went on El Niño watch, which indicates a roughly 50% chance of El Niño forming in 2018 – double the usual likelihood. El Niño during spring typically means below-average rainfall across eastern and northern Australia.

Three out of five international models are forecasting that a positive Indian Ocean Dipole event is also possible this spring. A positive IOD during spring typically means below-average rainfall in central and southern Australia. When El Niño and a positive IOD coincide, their drying influences can be exacerbated.

So, what’s the outlook for spring?

With a reasonable chance of both El Niño developing and a positive Indian Ocean Dipole, the outlook for spring shows below-average rainfall is likely over much of the southeast and parts of the northeast and southwest. The rest of the country has a neutral outlook, showing no strong push towards a wetter or drier than average three months.

Inland areas are typically dry at this time of year, so the neutral outlook in the arid interior typically implies that low rainfall is likely. No part of the country favours above-average rainfall in the spring outlook.

Spring days are likely to be warmer than average across Australia, with the highest chances (greater than 80%) over northern and western Australia. Most of the country is likely to have warmer than average nights this spring, except for areas around the Great Australian Bight which have roughly equal chances of warmer or cooler than average minimum temperatures.

What does this mean for the drought and bushfires?

Like the rest of the country, the Bureau is hoping that farmers in drought-affected areas get the rainfall they need soon. But this outlook isn’t the news many want to hear.

Last weekend’s rainfall over northeastern New South Wales and southeastern Queensland was welcomed by most, but unfortunately it was well short of what was required for a recovery from the longer-term rainfall deficits. Many locations on the east coast are well below their average year-to-date rainfall totals.

Rainfall deficiencies for the first seven months of 2018 in areas of western NSW, northwest Victoria and eastern South Australia widely show rainfall totals in the lowest 5% of the 118 years of record. It would take many months of above-average rainfall to return to average levels.




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The above average temperatures in 2018 so far, combined with below average rainfall and dry vegetation, mean a higher likelihood of fire activity in parts of southern Australia. The warm and dry outlook for spring means the drought in parts of the country’s east is likely to continue.


Learn how climate outlooks are made.The Conversation

Jonathan Pollock, Climatologist, Australian Bureau of Meteorology; Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology, and David Jones, Climate Scientist, Australian Bureau of Meteorology

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

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


Owen Price, University of Wollongong

The New South Wales Rural Fire Service declared the earliest total fire bans in its history this week. The entire state was declared to be in drought on the same day.

The combination of winter drought and hot, dry weather has made dangerous fires increasingly likely.




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After the firestorm: the health implications of returning to a bushfire zone


Already this week two fires on the south coast have escaped containment lines and destroyed houses. The weather during these fires was 6℃ warmer than the August average, dry and extremely windy. The wind speed peaked at 104 kilometres an hour in Bega and 85km/h in Nowra, two towns close to where fires broke out.

Under these conditions, bushfires will spread quickly, produce large numbers of embers and are hard to stop.

Our fire seasons now start earlier and last longer. This means we’re increasingly likely to see repeats of historically large fires threatening residential areas.

Fire seasons are longer

Current dry conditions are reflected in the maps of live fuel moisture produced by Dr Rachael Nolan of Western Sydney University.


Nolan R.H., Boer M.M., de Dios V.R., Caccamo G., Bradstock R.A. (2016), Large-scale, dynamic transformations in fuel moisture drive wildfire activity across southeastern Australia. Geophysical Research Letters 43, 4229-4238.

This method tracks the weekly moisture content of the forests in southern Australia, as observed by NASA’s MODIS satellite. The latest map shows a patchy distribution of dry areas and a drying trend over recent weeks.

It looks like NSW’s fire season has already started, and it’s likely to be bad. Last year’s fire season also extended well into autumn, with serious bushfires burning in mid-April.

Fire agencies usually enjoy a six-month break from bushfires between April and September, but this year they had only three months’ respite.

This reflects evidence of a trend toward more extreme fire weather over the past 30 years, and lengthening fire seasons.

This problem is being keenly felt in western United States, where fire agencies have warned that the fire season now lasts all year round. Not only that, there is clear evidence climate change is increasing fire activity in the United States; the record for the largest fire in California history has been broken two years in a row.

Alarming precedents

The most damaging fire season for NSW in the past 30 years was in October 2013 when the Linksview fire destroyed 200 houses in the Blue Mountains.

The build-up to that season was eerily similar to this year, with a winter drought and bushfires in September, but the moisture maps show that the forests are drier now than at the same time in 2013, and we have already seen serious bushfires in August.




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As we move into September and October, the weather will warm, which means any remaining moisture in the ground and plants will evaporate even faster than at present, and fires will be more intense and spread faster. The only thing that will reduce the risk is soaking rain of at least 100mm.

Whether or not that will occur in the next two months is almost impossible to predict. At the moment it seems unlikely. The Bureau of Meteorology’s latest seasonal forecast, issued on August 16, considers it likely that dry conditions will persist for the next three months.

The heightened risk of bushfire this season should be a wake-up call for residents in bushfire-prone areas. Most people in really risky areas such as the Blue Mountains are well prepared, but many people who are a little more removed from the forests are not aware of the risk.




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For example, many residents of Wollongong probably don’t know this October is the 50th anniversary of the great 1968 fires that swept down the Illawarra Escarpment into the suburbs of Figtree, Bulli, Austinmer and others.

The footprint of the 1968 Illawarra fires, which burned through residential areas.

If the same footprint of fire were to occur again, some 5,000 houses would be affected. The present indicators suggest a repeat of this event is more likely than at any time for decades.

Residents need to prepare a bushfire survival plan, which includes a decision on whether to stay and defend or to leave as soon as they learn about a nearby bushfire.




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Current research at University of Wollongong suggests that the biggest influence on the risk of house loss during a bushfire is the actions that the residents themselves take. This includes ensuring that natural and man-made fuels are kept to a minimum in the garden, especially close to the house, and also defending the house from spot-fires caused by embers.

The Rural Fire Service has a wealth of advice for preparing for bushfires on its website.

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We’re look at a torrid upcoming fire season, dependent on the vagaries of the Australian climate. Either way, now is the time for people to brace themselves and get prepared.

Owen Price, Senior Research Fellow, Centre for Environmental Risk Management of Bushfires, University of Wollongong

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