Australia is a country of extremes. When Dorothea Mackellar wrote the iconic Australian poem “My Country” with the line referring to droughts and flooding rains in 1904, she recognised Australia as a place of extremes. Extreme heat, extreme rains, and extreme landscapes. We are going to look at 7 Australian weather extremes.
1. Extreme rainfall and floods
As world temperatures rise due to greenhouse gas emissions-induced climate change, the air is retaining more moisture globally, which means that heavy rainfalls will become more prevalent in Australia and worldwide.
Scientists are united in this view and believe extreme flooding is becoming more common in Australia. Scientists attribute this to warmer oceans that increase the amount of moisture moving from the sea to the atmosphere and will most likely increase the intensity of extreme rainfall.
We have witnessed the recent floods in Queensland and New South Wales that took their toll on the people and property of the areas affected. In addition, Sydney and parts of New South Wales endured over 1000mm of rain over a week, affecting around 10 million Australians.
Extreme flooding is not a new occurrence on the east coast of Australia. The Yugara and Yugarabul people have traditional stories about great floods in the Brisbane River region long before European colonisation. For example, 1841 and 1893 are two years recorded as having the highest waters in Brisbane.
Scientists believe that climate change, along with La Niña, certainly contributed to the recent floods and think we may see an increase in extreme one-day rainfall events, which could lead to flash flooding in New South Wales.
Large commercial aircraft can fly safely in most weather conditions, even in heavy rain; however, flooding of the tarmac can prevent safe take-off and landing. For example, during the recent floods, flights out of RAAFs Williamtown’s runway at Newcastle Airport were stopped due to excess water on the tarmac.
2. Extreme temperatures & fires
On the other hand, South Australia has experienced a decrease in rainfall and a tendency toward drought with rising temperatures and no chance of rain.
In 2009 Southeast Australia experienced extremes in heat never recorded in history. Hopetoun, Victoria, recorded a historic 48.8 degrees Celsius, the highest ever temperature in the state, while Melbourne recorded its highest temperature, 46.4 degrees Celsius.
This heatwave caused extreme bushfire conditions leading to the “Black Saturday” bushfires in 2009 that claimed 173 lives in Victoria. Sadly, more than twice this number of people died due to the heatwave leading up to the fires (374 deaths).
Tasmania is no stranger to fires, with the unprecedented and catastrophic burning of world heritage areas in the Central Highlands of Tasmania in 2016. These remote areas made it impossible for firefighters to access the site, and scientists claim that some of the damage is irreversible.
More recently, New South Wales experienced the 2019-20 bushfires, unprecedented in their extent and intensity. The fires in NSW burnt 5.5 million hectares (6.7% of the state), including 2.7 million hectares in national parks (37% of the state’s national park estate). Sadly, 26 lives were lost, and 2,448 homes were destroyed.
Extreme heat across central Australia is also responsible for moderate to severe thermal turbulence. 30 – 40 degrees Celsius heat can produce uncomfortable flying conditions below 15000 feet.
According to the Australian Academy of Science, “Since records began, the frequency, duration and intensity of heatwaves have increased over large parts of Australia, with trends accelerating since 1970.” Scientists have also calculated projections to say that cold days will be less cold over time.
The following article in Simple Flying states, “Considering the range of temperatures aircraft can fly in, you might think extreme heat would not put much stress on a modern plane. But extreme heat can have a big impact on a plane’s ability to operate efficiently and safely. As a result, extreme heat is a risk many airlines have to manage and mitigate.”
3. Extreme winds & tropical cyclones
Tropical cyclones are considered the most destructive larger-scale storms in the world. “Tropical cyclone” is a generic term to describe these storms originating over tropical oceans. In Australia, a tropical cyclone is mainly experienced in northwest Australia between Exmouth and Broome in Western Australia and northeast Queensland between Port Douglas and Maryborough.
Tropical cyclones are classified according to the wind speed, as follows:
- A tropical disturbance is a region of enhanced convection with light surface wind speed and a diameter of 200-600 km.
- Tropical depression – A weak tropical cyclone with the highest sustained wind speeds (averaged over one minute or extended period) of less than 34 knots.
- Tropical storm – A tropical cyclone with closed isobars and highest sustained wind speeds of 34 to 63 knots
- Tropical cyclone/typhoon/hurricane – A tropical cyclone with the highest sustained wind speeds of more than 64 knots
Meteorologists grade tropical cyclones on a scale of one to five (the latter being the most severe). Darwin’s Cyclone Tracy was a category four cyclone.
Tropical cyclones are a part of life if you reside in Northern Australia. Cyclone Tracy, the cyclone that decimated the city of Darwin in 1974, was not the first cyclone to destroy Darwin. In 1897 a cyclone that came to be known as “The Great Hurricane” knocked Darwin down. There were 28 fatalities, and the cyclone destroyed entire fleets of pearl luggers in the harbour.
According to the Australian Government’s National Environmental Science Program, scientists say that there has been a significant decrease in the number of tropical cyclones recorded in the Australian region in recent decades. While scientists are not sure of the physical mechanisms behind this decrease, they think it is likely due to a combination of both natural variability and the changing climate.
Tropical cyclones occur in the wet season in the northern Australian region and generally track more erratically than in other parts of the globe. It is for this reason that they hold challenges to weather forecasters.
According to the Bureau of Meteorology, the wet season is the most hazardous time to fly in the tropics. The wet season generally extends from October to April, a time of unstable atmospheric conditions due to high humidity and temperatures. In addition, tropical cyclones and active monsoon troughs may produce heavy rainfall, squally winds and thunderstorms for prolonged periods.
Mechanical turbulence can also result from strong winds atop mountain ranges. For example, the McDonnel Ranges in Central Australia frequently create turbulent conditions for aircraft.
4. Dust storms
The tropical cyclone may be the most destructive large-scale storm, but the dust storm is also a force to be reckoned with. The BOM identify a dust storm as ” an area of raised dust that moves with the prevailing wind system. The size of the dust particles can range from 0-1000 micrometres.”
Major dust storms have occurred on the east coast of Australia in Melbourne and Sydney. The storms can carry dust particles up to 4.5 km into the atmosphere. The average height of a dust storm can reach 1-2 km. Dust storms have been known to move particles halfway across the Earth and as fast as the prevailing weather system. Long periods of drought contribute to the severity of a dust storm.
Dust storms on record:
- 3 February 2005. At Bourke, visibility was reduced to 500m, and at Moree, visibility was reduced to 600m.
- 23 October 2002. This storm was one of the most severe dust storms recorded. Visibility in Sydney was reduced to a few kilometres, and pilots reported that the dust extended upwards of 3km into the atmosphere. The west experienced the most severe conditions, with many areas having visibility of just 300m. For example, in the suburb of Roma, southwestern Queensland, visibility was reduced to just 100m.
- In January 1942, the most severe dust storm to hit Sydney reduced visibility at Sydney airport to 500 metres.
While fog is not as extreme as a tropical cyclone it can be a disruption to aviation in Australia. Fog is most common in tropical Australia, near the coast during the dry season. According to the BOM, fogs:
- are reported from Broome and Port Hedland in Western Australia around fifteen times a year.
- also occur in north Queensland, more commonly on the coast and during the cooler months. Fogs are usually expected at Rockhampton airport more than thirty times yearly.
- and low stratus also occur about coastal valleys in the Northern Territory’s top end during the dry season, occasionally extending as far inland as Tindal.
- Sea fogs form along the coast a few times yearly and can last all day. Sea fogs are a regular occurrence during the dry season around the Gulf of Carpentaria coast and can affect aerodromes such as Ngukurr, Borroloola and McArthur River Mine.
6. Rising seas and the threat to airports
Rising seas are a result of climate change and while this may not be having an immediate or direct effect on airports at the present time, there are fears that some aerodromes will be adversely affected in the future.
Landing strips are usually built on low-lying flat areas (wetlands, marsh, or floodplains) to capitalise on the extended space for take-off and landing. In an article in The Conversation, 2019 the following significant Australian airports were identified as being at risk from rising sea levels due to climate change: Cairns (less than 3m above sea level), Sydney and Brisbane (under 4m), and Townsville and Hobart (both around under 5m) were identified as airports among the most vulnerable.
7. Storm Surges
We can’t mention rising seas without also talking about storm surges. According to the BOM, “Storm surges are powerful ocean movements caused by wind action and low pressure on the ocean’s surface. This raises the sea level and strong winds at the coast that can create large waves, enhancing the impact. These types of events can swamp low-lying areas, sometimes for kilometres inland.”
The most substantial storm surge to hit Australia was during the Mahina cyclone in Bathurst Bay, Australia, in March 1899. Over 400 lives were lost. The final high-water line was estimated at 14.6 metres (48 feet) and is claimed by some as a world record.
Storm surges are very difficult to predict, but the damage they can cause to coastlines and potentially human lives is substantial.
Ask the Experts
Australia certainly is a sunburnt country with droughts and flooding rains. If you are already in the business of flying or operating aircraft you will know up-to-date information about any aviation weather information or extreme weather events, is available from the Bureau of Meteorology. For consultants with industry know-how and many years of aviation experience please get in touch with the Civil Aviation Academy today.