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Cyclones - A Path of Destruction
The Structure of a Cyclone
What Is A Cyclone?
A cyclone begins as a low pressure system that develops over warm tropical water. The system must have a gale force winds of at least 63 km/hr to be classified as a tropical cyclone. The winds can extend hundreds of kilometers from the center of the cyclone and once they reach a speed of 118km/hr and higher the system is then called a severe tropical cyclone.
The center of the cyclone is called the eye, typically the diameter of a tropical cyclone is 40km, but can vary in size from under 10km to over 100km. The eye of a cyclone is quiet calm, only producing light wind and clear skies.
Cyclones can last for several days, bringing heavy rain, storm surges and strong winds to a large area. Once a cyclone makes landfall and begins to move inland it starts to dissipate.
Eastern and Northern Australia (Queensland and Northern Territory) generally experience cyclones between November and April, with an average of 6 cyclones affecting the region during the season. The Western Region of Australia (Western Australia) have cyclones year round, most forming and dissipating over the Indian Ocean. It is important to know, not all tropical lows develop into cyclones and not all tropical cyclones make landfall.
A cyclones category is determined by the maximum mean wind speed which is the average wind speed over a 10 minute period and wind gust which are measured over a 3 second period.
Cyclones are very unpredictable and can change categories several times.
The table below shows the category, maximum wind speed (km/hr) and types of damage expected.
Cyclone Category Table
The Naming Process
Australia currently has a list of 104 names being used to name cyclones. The list runs in alphabetical order from A to Z and alternated between male and female names. But if a cyclone forms in another region, then it will be given a name from that regions list.
There are a number of things taken into consideration when naming a cyclone. The following information comes from The Australian Bureau of Meteorology (www.bom.gov.au)
- If two or more cyclones are occurring simultaneously, similar sounding names (eg June & Jane) are avoided to minimise confusion
- Names should not be capable of being construed to subject the Bureau to criticism or ridicule (eg naming a sequence of cyclones after politicians)
- Lists of names are coordinated with neighbouring meteorological services to avoid duplication
- When a significant cyclone affects Australia (like TC Tracy in 1974 or TC Larry in 2006), the name is "retired" and replaced in the list with a name of similar initial and gender.
- A name may be skipped if it is not deemed appropriate when it is due to be used (eg it is the same as the name of a public figure who is in the news for a sensitive or controversial reason)
- A name may be skipped if a similarly named cyclone is active in the area.
- Cyclones may not seem to follow alphabetical sequence as cyclones named in an adjoining area move into the Australian region.
- Cyclones moving westwards across the Indian Ocean are usually renamed by the TCWC at La Reunion, when they move out of Australia's zone of responsibility. Otherwise cyclones retain their name throughout their existence.
- Sometimes a decayed cyclone will re-generate (eg after crossing land) and will usually retain the name it had before it weakened.
Cyclone Narelle off Western Australia in 2009
A Quick Look at the Cyclones of Australia
The following are some of the cyclones that have hit Australia in the last 40 years
Cyclone Tracy Crossing into Darwin
Cyclone Tracy Leaves Darwin in Ruins
Reminders of Tracy
Cyclone Tracy 25/12/74
Until 2006, Cyclone Tracy was the most devastating cyclone ever to hit the Australian Coast.
Cyclone Tracy formed in the Arafura Sea approximately 370km northeast of Darwin, the capital of the Northern Territory on December 21st, 1974. Over the next couple of day the cyclone moved to the southwest, passing just north of Darwin and residents were told via radio broadcasts that the cyclone posed no immediate threat to Darwin. However, early on December 24th, the cyclone turned southeast and was headed right for Darwin and by 10pm that night the damage became serious, it was only then that the residence of Darwin, who were completely unprepared realised the cyclone would not be passing them by, but passing directly over the top of them as a category 4 cyclone.
By 3:30am December 25th, the cyclone eye passed over Fannie Bay and by 6;30am the winds began to die down and by 8:30am the rain had stopped. The city of Darwin was left in ruins, 70% of buildings and 80% of houses were destroyed, out of the cities population of 47 000, 41 000 were left homeless and 71 people had been killed. Cyclone Tracy caused $837 million in damages.
Help began to arrive late in the afternoon of December 25, and immediately set about restoring power, water and sanitation as there was a fear of disease outbreaks, the residents were immediately vaccinated for typhoid and cholera. The army was given the grim task of searching houses for the dead bodies of animals and people, once a house had been searched and cleared, they would make the house with S & C on an external wall. The city was also sprayed with Malathion to control any mosquito outbreaks. Attempts also began to reconnect Drawin to the rest of Australia, as the only link to the outside was local radio station 5DR, it would remain that way for the next two days.
Large scale evacuations also began, with over 30 000 people being evacuated over the coming days. Many of those who were evacuated never returned. For those that did, they would spend the next several months living in temporary housing, caravans, hotels and even a cruise liner.
Rebuilding was a very slow process and received a great deal of criticism, but it wasn't until April 1976 that the first lot of new houses, 3000 in total were completed and homes that had received damage but remained standing were repaired. By 1978 most of the city and houses had been rebuilt. All of the building were built using more modern materials in the hopes of preventing a disaster of this magnitude happening in the future.
Cyclone Tracy was only a small cyclone, measuring only 50km wide with winds reaching 175km/hr.
The name Tracy was retired and will not be reused.
Cyclone Kathy 22/3/84
Kathy formed as a tropical low off the southern coast of Papua New Guinea on the 16th of March, 1984. During the following day, the system quickly intensified as it headed for Cape York Peninsula. Although considered a cyclone, it was only a weak system when it made landfall just north of Weipa, QLD on March 19th. Kathy began to weaken as it headed towards the Gulf of Carpentaria.
Once Kathy reached the warm waters of the Gulf the weakened system began to quickly reintensify and continued towards the Northern Territory Coast. Kathy struck the Pellew Islands as a powerful cyclone on March 22nd and continued on to mainland Australia making landfall near the remote town of Borroloola, NT. The system dissipated over the Northern Territory on March 24th.
Kathy caused around $12 million worth of damage as well as environmental damage to the mangroves along the McArthur River.
The name Kathy was retired and replaced and will not be used again.
The Aftermath of Cyclone Vance
Cyclone Vance 22/3/99
Vance formed in the Timor Sea on March 19th, 1999 and traveled west-southwest becoming a category 5 cyclone and weakening to a category 4 cyclone as it crossed the West Australian Coast near Exmouth on March 22nd. After making landfall, Vance turned south-southeast heading inland and weakening to a tropical storm the following day.
Hundreds of people were evacuated and several roads were closed in preparation and due to this advanced preparation there was no loss of life, however there was server damage, leaving 70% of buildings in Exmouth with server damaged. Cyclone Vance caused $100 million worth of damage.
Devastation Caused by Cyclone Larry
Banana Crops Decimated
Cyclone Larry 20/3/06
Cyclone Larry developed from a tropical low, which formed over the Coral Sea on March 16th, 2006. The system developed quickly and by March 18th was a category 5 cyclone.
Larry made landfall just north of the town of Innisfail on March 20th as a category 4 cyclone, with wind speeds reaching 240km/hr and dissipated over land quite quickly.
Cyclone Larry caused a vast amount of damage and was the most costly cyclone to hit the Australian coast, causing and estimated $1.5 billion is damages. That is until Cyclone Yasi hit in 2011.
Within hours of making landfall, the Australian Defence Forces deployed troops to help with the clean-up as well has help from the Australian Air Force and Navy and the Thuringowa group of the Queensland Rural Fire Service. Over the coming weeks they would help with bring supplies to the area, health care and provide makeshift accommodation to those who needed it. As well as help from the Defence Forces, about 150 tradesmen from across Australia came to Innisfail and worked to reopen schools, other public buildings and to make homes habitable.
The cyclone destroyed up to 90% of the areas' banana crops, causing the price of bananas to rise 400-500% for the remainder of 2006.
Larry was retired from the cyclone name list and will not be used again.
The Sheer Size of Cyclone Yasi Would Have Covered Most of the United States
The Main Street of Tully After Yasi
Cyclone Yasi (left) Hurricane Katrina (right)
Cyclone Yasi 3/1/11
Yasi began to form on January 26th, 2011 about 330km south-southwest of Tuvalu. By January 31st the system developed into a category 3 cyclone as it continued to head towards the east coast of Australia. By late afternoon on February 1st Yasi had intensified to a category 4 and early February 2nd had become a category 5 server tropical cyclone. Yasi had already caused damage to the Solomon Islands, Vanuatu and Papua New Guinea.
Yasi was an enormous system, over 500km wide with winds measuring just under 300km/hr. The only system to come close to matching its size and power was Hurricane Katrina and cyclone Tracy for the amount of damage it caused.
Yasi crossed the East Coast of Australia at Mission Beach, a couple of minutes after midnight on February 3rd, 2011 leaving a path of destruction not only at Mission Beach but several other towns including Tully, Tully Heads, Silkwood, Innisfail, Cardwell and Townsville. Yasi not only affected Queensland but New South Wales, Victoria, Northern Territory and South Australia.
Hundreds of thousands of homes and businesses were destroyed and tens of thousands of people evacuated as well as thousands of homes and businesses damaged and without power and wide spread flooding.
The total damage caused by Yasi was estimated at $3.5 billion, the tourism industry lost $1 billion and agriculture, mining and local government lost and estimated $2 billion, $505 million of that was just sugar cane. Making Yasi the most costly cyclone to ever hit Australia. The Australian Defense Force was deployed to the area under Operation Assist Yasi, but they would be unable to enter the disaster zone for 24 hours after.
The name Yasi was retired and replaced. The name will not be used again.
The Yasi Experience
Cyclone Lam (top of picture) and Cyclone Marcia (bottom of picture)
Damage Left by Cyclone Lam
Cyclone Marcia Says Hello
Cyclone Marcia's Effects Felt in Brisbane
Cyclone Lam and Cyclone Marcia 20/2/15
Cyclone Lam developed into a category 4 cyclone late in the afternoon of February 19th, 2015. It made landfall between Milingimbi Island and Elcho Island, Northern Territory at approximately 2am on February 20th, 2015.
Residence in the cyclones path, mainly small Aboriginal communities were evacuated to Darwin. Significant damage to houses were reported as well as water and power outages, which were expected to be restored within a week.
Cyclone Lam is estimated to have caused $82.4 million in damages.
Cyclone Marcia was being tracked off the Queensland coast as a category 3 cyclone on February 19th, 2015, but within hours had developed into a category 5 cyclone.
Cyclone Marcia crossed the Queensland coast between St Lawrence and Yeppoon shortly after 7:30am on February 20th, 2015 as a category 5 cyclone, being downgraded to a category 4 cyclone shortly after making landfall. Marcia continued down the coast and passed by Rockhampton as a category 3 cyclone about 2:30pm that afternoon. The system was downgraded to a category 1 cyclone late on the afternoon of the 20th.
The effects of Cyclone Marcia were felt all the way down the Queensland coast and into northern New South Wales. With several areas losing power and receiving flooding.
Work started immediately to restore power and water to the effected towns and damage assessments. Some areas were without power for up to 10 days after the cyclone hit. It is estimated that Marcia caused $67 million in damages.
This is the first time two cyclones have ever crossed the Australian Coast within hours of each other.
A Message to Cyclone Marcia
Part of Australian Life
Extreme weather events, like cyclones are part of life for Australians living on the coasts of Queensland, Northern Territory and Western Australia. When we are struck we don't let the wind and the rain knock us down, we unite, pick ourselves up and rebuild. That is one thing that makes us who we are.