A project by Jo Dalstead based on Tropical Cyclone Yasi
What causes tropical cyclones to form and what characteristics of them do we need to be concerned by?
Tropical cyclones form above water that is deep and warm, they often occur in the narrow band of the world known as the tropics- as this part of the world gets the most sunlight. This water has to have a temperature above 26.5°C, and its depth must be at least 50 metres from the surface to the ocean floor.
As these waters are of a high temperature, this allows the speed of evaporation to accelerate. Once the warm gas evaporates and condenses into cloud droplets above the ocean, it encourages the activity of tropical thunderstorms. However, not all tropical thunderstorms create tropical cyclones. When the thunderstorm is occurring, energy is released and begins to circulate. Water moves naturally (this is called outflow), and the rotation of the Earth works alongside the outflow and helps to maintain a low-pressure system. This outflow, paired with winds that do not vary much over a vertical height, begins another certain movement of the ocean. These precise conditions are required for a tropical cyclone to form, it is scientifically proven that tropical cyclones are not extemporaneous; instead tropical cyclones are a result of evident natural conditions.
Many characteristics of cyclones are very concerning to us as human beings. These include:
· Immensely heavy rain. These rains are so powerful and bring an unbelievably huge volume of water onto the land. Many tropical cyclones have up to and beyond 400 mm of rainfall in one day. This rainfall causes flooding of roads, destruction of crops, flooding of rivers and a lot more damage that is harmful to people and land.
· Wind in cyclones is extremely strong. The wind at the outside of a cyclone can travel up to 200 km/h. The wind is so powerful that it can destroy structures; this is dangerous to us as humans because large and heavy objects can come hurtling down on us and often kill us.
· The bulk of a cyclone is a very concerning characteristic. Cyclones have been recorded up to 2,170 kilometres wide. As they are so wide and so strong, storm surges often occur. Storm surges cause damage over a wide area. The rain and flooding caused by one cyclone can affect people and land hundreds of kilometres away, and it can take a long time to recover from one cyclone.
· The eye of a cyclone is a very confusing weather condition for humans. When you are in the eye of the cyclone, which can be very large (around 40km wide), you can easily assume that the danger has passed. This is because there are very calm skies and light wind in the eye of the storm. However, if you are in the eye of the cyclone, there is more strong wind coming for you.
Region is a KGI that applies to this question because tropical cyclones occur in a tropical region. This region is generally 8-20 degrees south of the equator.
Movement is an obvious KGI that applies to this question. The movement of the water, the movement of the wind and the movement of the earth are all necessary factors for a tropical cyclone to start. Without movement, tropical cyclones wouldn’t exist- they would just be wild storms.
Location is a relevant KGI for this question because tropical cyclones definitely need to occur in a certain location. They have to begin over an ocean, and then relocate themselves towards land. You also have to be concerned by the location of these cyclones if you live in an area prone to tropical cyclones, such as the northern regions of Queensland.
What was the pathway of Yasi and how did this affect the cyclone?
Cyclone Yasi first formed just off the northwest coast of Fiji, 330km out to sea. On the Janurary 26, 2011, it was classified as a “tropical disturbance”. It took time for it to be eventually classified as a tropical cyclone- it had moved a fair way and was now 370km northeast of Vanuatu. Cyclone Yasi then travelled across the Coral Sea. Yasi hit the mainland of Australia at midnight, on February 3, 2011. It first hit the mainland at a location near Mission Beach.
This diagram shows the path of the devastating Cyclone Yasi. Each different colour represents the overall strength of the cyclone at that point in time. Blue is quite weak, whereas red is strong and more destructive. Cyclone Yasi began near Fiji as a tropical depression. As it moved closer to Australia, it became stronger and more powerful- becoming a category 4 cyclone. As it hit the Australian continent, a large cluster of land, it weakened. You can see how the pathway becomes more random, scattering and weakening until it faded away to nothing.
This diagram shows the strength of winds throughout the different stages of the cyclone. Wind with this much power has the ability to knock over parts of houses and has the strength to haul large, heavy objects into the air. Cyclone Yasi had its strongest wind whilst over the ocean, and it slowly died of when the cyclone hit land.
There is minimal landmass between Vanuatu and Australia, the only land being New Caledonia. This means Cyclone Yasi travelled approximately 2396 km over warm water, all the time building in energy and mass. So, by the time it hit Australia’s mainland, it had gained an incredible amount of power. Yasi was a massive wall of wind, supercharged from a long journey across tropical water.
Distance is probably the most obvious KGI that relates to this question. The distance Yasi travelled, and how it travelled there are some main things to consider when looking at the pathway of Cyclone Yasi. Knowing how far Yasi could travel and why it could span that distance is important when determining how dangerous cyclones in the future will be and if they will be able to travel a far distance to reach Australia’s mainland.
Spatial interaction is a KGI that relates to this question because the pathway of Yasi and the reason it was so strong all comes down to the spatial interaction between the warm water and the cyclone. Without the large body of warm water and the strong winds between Vanuatu and Australia, Cyclone Yasi wouldn’t have been nearly as powerful and might have stopped before reaching Australia’s mainland.
A cyclone has a lot of movement, in particular the movement of wind and water. These extreme movements help the cyclone travel, and without movement the cyclone would stay in the same place. The pathway of a cyclone is very dependent upon movement.
What were the characteristics of Yasi?
Cyclone Yasi was one of the worst cyclones to ever hit Queensland. The immensely heavy rainfall caused floods across many areas of the state. 470mL of rainfall was recorded in just 24 hours, at South Mission Beach (143 km south of Cairns). Mount Eliza’s average rainfall in 2011 in the month of February was 52.8mL. This comparison shows just how much rain Queensland received in that 24-hour period.
Such a colossal amount of rain from Cyclone Yasi just added to damage previously done by La Niña in January 2011. Residents have reported that their houses were at least 1 metre underwater. Photos from Rockhampton (located 600 km north of Brisbane) showed men walking through murky water up to their necks.
A typical characteristic of a tropical cyclone is strong winds. Cyclone Yasi was no different; it brought huge winds with it. These wind gusts were extremely destructive and dangerous. The highest official wind gust was recorded at midnight near Lucinda Point at 185km/h. However, there were other estimated wind gusts that couldn’t be confirmed. Tully and Innisfail suffered winds estimated at 220km/h while the Bureau of Meteorology guessed that the highest unconfirmed wind gust reached 290km/h.
Tropical cyclones are well known to cause storm surges. A storm surge is when the incredible power of the cyclone forces tides to go against their normal astrological pattern and create a “wall of water”. Cyclone Yasi brought a storm surge 5 metres high to Cardwell, 2.3 metres higher than the normal tide lines. This surge was so strong that it washed boats from the marina up onto the shore and on top of one another. This destructive storm surge had the power to travel a total of 300 metres inland. This was the largest surge, however, two smaller surges hit between Cairns and Townsville. These smaller surges flooded the esplanades with murky brown water and a thick sludge of sediment.
Cyclone Yasi had to move a lot as it travelled across the Coral Sea. The characteristics of Yasi are mostly moving natural things such as wind, and it is the movement of a tropical cyclone that causes such immense and thorough destruction of an area.
The characteristics of Yasi are very reliant on region. Without the storm occurring in a tropical region, Cyclone Yasi would not even have begun. Yasi also hit Australia in a specific region, and although the cyclone occurred just in northern Queensland, it in turn affected the whole of Australia.
-Spatial change over time
Yasi changed its characteristics over a period of time, therefore the KGI spatial change over time is applicable. Over time, the cyclone changes from a tropical storm to a cyclone, and it changes in intensity, especially when it hits land. As it travels, the tropical cyclone also changes the space around it. When hitting Australia, it completely morphs the landscape and floods land.
How were the natural and cultural landscape affected by Yasi?
-Spatial change over time
This KGI is applicable to this question because the natural and cultural landscapes had to learn to adapt after Cyclone Yasi hit. If they didn’t adapt, then north Queensland would be a wasteland. The natural landscape was destroyed, leaving animals without a home. The cultural landscape was also destructed, leaving humans without homes, electricity and basic modern necessities. The natural landscape then changed by plants springing up and growing to take the place of older plants, whereas the cultural landscape changed with donations of money, hard work and support from other communities.
I think spatial association is relevant because there is quite a strong spatial association between tropical forestland and the region of northern Queensland. These rainforests are in an area where the climate is warmer and wetter; therefore the plants can flourish at a more incredible rate. When Yasi hit theses forests, a main reason these plants could recover was because of their spatial association with their location, the climate in which they were growing etc. Without the strong spatial association, the affects of Yasi could have been even more devastating- and recovery would have been a longer process.
I think mostly situation and site can be applied to this question. The areas that felt the most of the affect of Cyclone Yasi were towns situated near Mission Beach. Houses, fences, and cars are just some of the manmade structures that were destroyed because of the severity of Yasi. The site near Mission Beach, the natural features, also suffered- large ecosystems now suddenly weak and animals now homeless. The location of where Yasi hit is important because where it hit determined who and what it would affect, and whether or not the natural and cultural landscape could make a recovery.
Focus on two effects of Yasi e.g. economic impact upon banana plantations.
The Great Barrier Reef
Cyclone Yasi principally affected the Great Barrier Reef. Coral suffered the affects of Yasi, and this is very unfortunate as so many marine life forms depend of coral to sustain a healthy lifestyle. The damage was wide spread, randomly distributed and scattered, some reefs were completely reduced to rubble whereas some were barely touched. However, expert marine biologists predicted that the coral could take up to 20 years to make a full recovery. The storm surge set off by Cyclone Yasi also caused severe flooding, allowing toxic chemicals and debris to enter the reef and damage fragile coral. This is devastating to Australians, as the Great Barrier Reef is a natural wonder that we are proud of. It is not just damaging to our national pride, destruction of the Great Barrier Reef is damaging to our economy. Tourism to the reef contributes $5.4 million to the Australian economy every year. Without such a large amount of money, Australia could have to look elsewhere for money- which would have a negative effect on many Australian citizens.
This KGI applies to this question because of the way destruction of coral was distributed amongst the reef. The way it was distributed was scattering, it was random scattered destruction where some parts of the reef suffered more than others.
Region is a relevant KGI because the places that suffered the effects of Yasi are all in the same region, a tropical northern region of Australia. If this region wasn’t surrounded by tropical water, Yasi wouldn’t have gotten near Queensland.
-Spatial change over time
The banana plantations and the Great Barrier Reef both changed after Yasi hit. It was predicted that it would take two whole decades for the reefs to recover. The effects of the cyclone are extreme, and it takes time for the natural environment to change back to the balanced ecosystem it was before the cyclone.
What changes for the region and for wider Australia will occur due to Cyclone Yasi?
The location of where Yasi hit Australia was unfortunate for the people living there and the crops in that area. Although this location is on a relatively small scale compared to the rest of the world, it hit an area that is a large source of money for Australia. Bananas and sugar cane are things that not only Australia but also other countries need. If Yasi had hit another location, the aftermath might not have been as drastic.
There is a spatial interaction between Queensland and the rest of the world because of shipping of sugar. As Queesland really felt the affects of Cyclone Yasi, its crops declined because of the intense wind and water. This also affected the rest of Australia and the world, with the prices of sugar everywhere rising. This proves the strength of the spatial interaction.
Although the whole of Australia and the world were affected in some way by the devastating Cyclone Yasi, it was the region in northern Queensland that was most affected. Region is a very relevant KGI for this reason, as the region in which Yasi did the most damage was the region that suffered the most. The people, animals and environment in this region of Australia had to take time to recover.