Latitude from the equator. A low vertical wind shear

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Hundreds of kilometres in diameter, giant spinning whirls of wind that cause mass destruction. So powerful and their spinning is influenced by the Earth's rotation. A tropical cyclone is a strong but low pressure wind system that forms over warm waters and moves over land with force and can cause damage and destruction. What are cyclones, hurricane and typhoons? They're are all the same natural disaster. They can all go under the category of tropical cyclones. Why are they called different things then? The only difference is that they are called different things depending on where they occur. For example, in Australia they’re called cyclones, in the Atlantic they’re called hurricanes and in Japan they’re called typhoons. The reason they’re called different things is because different people call things different according to their culture. This text is about the cause + effect of tropical cyclones.

Cyclones are extremely dangerous but require a certain trigger and several specific necessary conditions to be able to form. The ocean waters have to be at least 26°C. A cyclone can only form if it’s at least 5° latitude from the equator. A low vertical wind shear is also required. There needs to be moisture in the middle of the troposphere. Unstable conditions is another necessary condition for the formation of a cyclone to commence. Lastly, a disturbance existing prior to the formation of the cyclone is vital. All six of these conditions are essential and a cyclone can’t form without them. However, it is not certain that a cyclone will occur even if all of these conditions are met. A cyclone is triggered by a combination of forceful winds driving water onshore and the lower atmospheric pressure. These necessary conditions and this trigger work together to form a cyclone. Things can also encourage the persistence of a tropical cyclone like the Earth’s rotation which influences the spinning and propelling of a tropical cyclone.

Tropical cyclones have some required necessary conditions and this paragraph will be explaining the climate needed. Tropical cyclones can only form near the equator over warm ocean waters. Generally, the sea-surface temperature needs to be at least 26oC. The air above the waters heats and rises while cool air moves in to replace the warm air. This process builds up large clouds. It often happens that pre-existing cyclones keep persisting even as they move over cooler waters. All these requirements are met when a tropical cyclone forms but people might not notice this fascinating process.

Tropical cyclones form over warm ocean waters and then move on to land to cause horrific damage and destruction. This paragraph will be talking about the seasons that they occur in and the different specific places they occur in. Approximately 75% of all cyclones form in the Northern Hemisphere. In Australia, the cyclone season goes for a period of 6 months from 1st November to 30th April. This is most of spring, all of summer and just the start of autumn. The Atlantic hurricane season starts June and ends November. The Eastern Pacific hurricane season runs from mid-May to November. The South Pacific cyclone season is from October to May. Natural disasters can be scary and unexpected but the tropical cyclone seasons comfort people more because they become less unexpected and therefore less scary.

Global warming is an issue and scientists are starting to think it could have an effect on tropical cyclones. It hasn’t yet been clearly proven that global warming is currently having a measurable effect on tropical cyclones. However, climate models have shown that tropical cyclones might intensify in the future if global warming continues. Climate models have also shown that the frequency of tropical cyclones will stay the same or even decrease as global warming continues. This means global warming could intensify tropical cyclones’ effect and do the opposite to the frequency.

Tropical cyclones can be brief issues or build up to being giant long-lasting catastrophes. The length of time a tropical cyclone lasts for depends on the favourability of the atmospheric environment, the movement of the tropical cyclone and sea surface temperatures. Most tropical cyclones persist for at least 3 days to even lasting for 7 days. Some weak tropical cyclones only just reach powerful wind force briefly. Some tropical cyclones can have a longer duration and persist for weeks if they stay in a favourable environment. Hurricane John is the longest tropical cyclone and lasted for 31 days. Hurricane Nancy stayed at category 5 status the longest, 5.5 days! This shows that there is a wide range of possible lengths for tropical cyclones to last for.

Tropical cyclones are strong but some things can stop them from persisting or even developing in the first place. A factor that can interfere with the formation and persistence of a tropical cyclone is if the vertical wind shear is high. Another way to stop a cyclone and its development is subsidence. This is when air sinks. Subsidence is also why any tropical storm that tries to form near a pre-existing tropical cyclone has a very hard time succeeding. These 2 possible occurrences can both very easily happen and prevent the formation and persistence of a tropical cyclone. This means affecting not just how they start but also their duration.

The idea that tropical cyclones and other weather can cause earthquakes is arguable. However, a new study shows the 2010 earthquakes in Haiti and Taiwan could’ve been triggered by tropical cyclones. The Haiti temblor happened 18 months after the same place was hit by 4 tropical storms. This can also happen in other mountainous areas that have been affected by tropical cyclones like Japan, the Philippines and possibly Central America. It would be very helpful to people in earthquake prone areas if this theory was clearly proven or not.

Other theories are presented about earthquakes’ timing and not everyone agrees. Geologists have ignored the idea that low atmospheric pressure linked with tropical cyclones can exert the timing of earthquakes. However, Dr Wdowinski says an investigation of the timing of earthquakes and tropical cyclones in Taiwan over the past 6 decades has shown a statistical correlation. A unique number of earthquakes with a higher magnitude than 6 occurred within 4 years of major tropical cyclones in the Far East. Even though some geologists ignore tropical cyclones could be connected with earthquakes other people like Dr Wdowinski has tried to prove there is some relation.

Another natural disaster that could possibly be caused by a tropical cyclone is a flood. Tropical cyclones are even dangerous because they can cause heavy rainfall and flooding. Tropical cyclones can cause different types of floods such as flash floods, urban/area floods, coastal flooding and river flooding. Floods can also be caused by a storm surge connected with a tropical cyclone.

Conclusion: Tropical cyclones are fascinating and can leave an awesome impact. This text is informative and will help people understand tropical cyclones better and therefore how to prepare for them. It’s very important to be informed of this to make sure people living in tropical cyclone-prone areas are aware. If this information is used in this manner people might design buildings better and sturdier to be ready for an incoming tropical cyclone. Never underestimate a cyclone because natural disasters might seem like a small occurrence but they can be unbelievably strong.


Latitude-the angular distance of a north or south place from the equator

Vertical wind shear-change of winds with height (strong jet of air)

Troposphere-the lowest layer of Earth’s atmosphere

Atmospheric pressure-pressure influenced by the weight of the atmosphere

Northern Hemisphere-part of Earth that is north of the equator

Atmospheric environment-envelope of air outside the earth

Subsidence-the sinking of air

Temblor-shaking of the earth's surface caused by underground movement from the tectonic plates (an earthquake)



Systems Analysis:

Necessary Conditions:

Ocean waters at least 26°C

Moisture in the mid-troposphere

Unstable conditions

latitude from equator

Low vertical wind shear

Pre-existing disturbance

System Steps:

  • A cluster of thunderstorms over warm ocean waters

  • Water evaporates and condenses to form clouds (this releases heat)

  • The heat energy combines with the rotation of the earth and exerts the cyclone's spinning and moves it forward

  • The cyclone moves over land or cooler waters and rapidly weakens

  • The cyclone will cause damage and destruction on land.

  • Most cyclones persist for 3-7 days. Weak ones can only briefly reach gale force but strong tropical cyclones can stay sustained for weeks.

If tropical cyclones didn’t weaken over land or cooler waters they would be more dangerous or move faster. This will mean that tropical cyclone-prone areas are in more danger. They could also become faster because they haven’t lost any strength. This means all tropical cyclones will change in terms of danger and strength.

Humans could invent more high-tech equipment to sense incoming tropical cyclones and be more prepared. We would have early alerts to signify people there is a dangerous tropical cyclone coming. They will be told to evacuate to avoid anyone getting hurt. We might also build more sturdy and safe buildings and structures.


Self assessment:

Click on this to access my self assessment:



I'm proud of the research I did and all the new information I learnt not only about cyclones but some other natural disasters as well. I think I worked very hard and packed a lot of info into a small amount of time. The main thing I'm proud of is my organisation and how I used my time well to achieve a finished product within the time limit. I could've improved on my diagrams to plan them better and have clearer features. Having more time to think about it so it turned out clear and had a reasonable scale was necessary. I wanted to fit in a bit more research to have a better system analysis because most of it was from what I already knew. However, it turned out better than expected and explained the key stages. Lastly, my actual text I could've edited more and checked in with the assessment matrix more often to make sure I had covered all of the required.

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