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Tropical storms form over oceans warmer than 27°C, between 5° and 20° of the equator, with low wind shear and high humidity. Notes and 15 questions answered.
Understanding Weather Hazards is part of Section A: The challenge of natural hazards in GCSE AQA Higher Geography.
7 min
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25
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GCSE AQA Higher
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Tropical storms form over oceans warmer than 27°C, between 5° and 20° of the equator, with low wind shear and high humidity. Notes and 15 questions answered.
Use this lesson to stay inside Section A: The challenge of natural hazards while connecting the detail back to the wider Living with the physical environment topic.
Read the core explanations from Understanding Weather Hazards before testing yourself from memory.
Every year, tropical storms kill thousands of people and cause billions of pounds of damage. Understanding why they form, what they do, and how we manage them is not just exam content — it is one of the most pressing challenges facing the modern world.
Weather hazards are extreme weather events that pose a significant risk to people, property and the environment. Tropical storms are among the most powerful and destructive of these hazards, and they are the focus of this lesson.
Picture the surface of a warm tropical ocean in late summer. The water temperature is above 27°C, the air above it is humid and unstable, and the atmosphere is primed for something dramatic. These are the exact conditions that give birth to a tropical storm.
Warm ocean water heats the air directly above it. That warm, moist air rises rapidly, creating an area of low pressure at the surface. As it rises, the water vapour condenses and releases enormous amounts of heat energy — this is what powers the storm.
The Coriolis effect — caused by the Earth's rotation — deflects the rising air, causing the whole system to spin. In the Northern Hemisphere, storms rotate anticlockwise; in the Southern Hemisphere, they rotate clockwise. As the storm intensifies, a calm central eye forms, surrounded by the eyewall where conditions are most violent.
Tropical storms are self-sustaining as long as they remain over warm water. Once they move over land or cooler ocean, they lose their energy source and weaken rapidly — a process called dissipation.
Now that you know how tropical storms form, it helps to picture what one actually looks like. Imagine a giant spinning disc of cloud hundreds of kilometres wide, viewed from a satellite — that is a mature tropical storm.
| Feature | Description |
|---|---|
| Eye | Calm centre, 20-50 km wide, low pressure, clear skies, light winds |
| Eyewall | Ring of towering thunderstorms surrounding the eye; strongest winds and heaviest rain |
| Rainbands | Spiral bands of cloud and rain extending outwards from the eyewall |
| Wind speed | Must exceed 119 km/h to be classified as a hurricane/typhoon/cyclone |
| Diameter | Typically 300-500 km across, though some exceed 1,000 km |
The eye is deceptively calm — people caught in a storm sometimes think it has passed when the eye moves overhead, only to be struck by the violent eyewall on the other side. This is a dangerous and well-documented phenomenon.
Tropical storms do not just bring wind and rain — they trigger a cascade of hazards including storm surges, flooding, landslides and tornadoes. The impacts ripple outwards long after the storm has passed.
Geographers divide impacts into three categories: social (effects on people), economic (effects on money and infrastructure) and environmental (effects on natural systems). You need to be able to give specific examples of each for your exam.
| Impact Type | Examples |
|---|---|
| Social | Loss of life; injuries; displacement of communities; disruption to healthcare and education; psychological trauma; homelessness |
| Economic | Destruction of homes, businesses and infrastructure; loss of agricultural land and crops; cost of emergency response and rebuilding; reduced tourism revenue |
| Environmental | Coastal erosion; flooding of ecosystems; destruction of coral reefs and mangroves; contamination of freshwater supplies; deforestation from high winds |
A key exam skill is distinguishing between primary and secondary impacts. Primary impacts happen directly because of the storm — buildings destroyed by wind, people drowned by storm surge. Secondary impacts develop afterwards — disease outbreaks from contaminated water, economic recession from lost trade.
The scale of impacts varies enormously depending on a country's level of development. Wealthier countries tend to have stronger buildings, better early-warning systems and faster recovery capacity. Less economically developed countries often suffer far greater loss of life from storms of equivalent strength.
Exam questions often ask you to refer to a named example. The following step-by-step walkthrough shows you how to structure an impact answer using a tropical storm scenario — the kind of question that appears on Paper 1.
Worked example: Structuring an Impacts Answer for a Tropical Storm
Explain the social and economic impacts of a tropical storm you have studied. [4 marks]
Answer: A well-structured answer names the storm, gives specific social and economic impacts with supporting detail, and links each impact back to the storm's physical processes using connective language such as 'because' and 'as a result of'.
Knowing a storm is coming is one thing — being prepared for it is another. Management strategies fall into four broad approaches: monitoring, prediction, protection and planning. Each plays a different role in reducing risk.
Early warning systems are particularly effective at reducing loss of life. When communities receive accurate warnings with enough lead time, evacuation can be organised before the storm arrives. Bangladesh dramatically reduced its tropical cyclone death toll from hundreds of thousands in the 1970s to thousands by the 2000s–2010s, largely through improved warning systems and coastal shelters.
Building design also matters enormously. Reinforced concrete structures, storm shutters and elevated buildings on stilts all reduce the damage caused by wind and flooding. Wealthier countries can afford these measures more readily, which partly explains why death tolls differ so sharply between high-income and low-income countries hit by storms of similar strength.
Weather hazard questions on Paper 1 use a range of command words. Knowing what each one demands is the difference between a confident answer and a vague one that misses marks.
When a question says 'describe', give an account of what happens — no reasons needed. When it says 'explain', you must give reasons, using language like 'because', 'therefore' and 'as a result'. When it says 'evaluate', you need to weigh up evidence and reach a clear conclusion — sitting on the fence will cost you marks.
Every spec requirement in this lesson — storm formation conditions, social, economic and environmental impacts, and management strategies — can appear in any question type on Paper 1. The strongest answers combine precise terminology, specific examples and clear causal reasoning to show the examiner that you understand not just what happens, but why.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-23.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
The Coriolis effect is the deflection of moving air and water caused by the Earth's rotation. It makes tropical storms spin, anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. It is absent at the equator, which is why storms do not form there.
Tropical storms form over oceans warmer than 27°C, between 5° and 20° north or south of the equator, with low wind shear and high humidity. Warm, moist air rises rapidly, creating low pressure, and as the water vapour condenses it releases heat energy that powers the storm, while the Coriolis effect makes it spin.
Wind shear is the change in wind speed or direction with altitude. Low wind shear allows a tropical storm to build vertically without being torn apart, so it is one of the conditions needed for tropical storms to form.
A tropical storm has a calm central eye, 20-50 km wide, with low pressure and clear skies, surrounded by the eyewall, a ring of towering thunderstorms with the strongest winds and heaviest rain. Spiral rainbands extend outwards, and the whole storm is typically 300-500 km across.
Social impacts include loss of life, injuries, displacement and homelessness; economic impacts include destruction of homes, businesses, infrastructure and crops and reduced tourism revenue; environmental impacts include coastal erosion, destruction of coral reefs and mangroves and contamination of freshwater supplies.
Risk is reduced through monitoring with satellites, buoys and aircraft; prediction using computer models; protection such as sea walls, flood barriers and storm shelters; and planning such as evacuation routes and building regulations. Bangladesh cut its cyclone death toll from hundreds of thousands in the 1970s to thousands through warnings and coastal shelters.
Tropical storms rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The spin is caused by the Coriolis effect, the deflection of moving air by the Earth's rotation.
The eye of a tropical storm is its calm centre, 20-50 km wide, with low pressure, clear skies and light winds. It is deceptively calm: people sometimes think the storm has passed when the eye moves overhead, only to be struck by the violent eyewall on the other side.
The environmental impacts of tropical storms include coastal erosion, flooding of ecosystems, destruction of coral reefs and mangroves, contamination of freshwater supplies and deforestation from high winds. Storms also trigger storm surges, flooding, landslides and tornadoes.
Tropical storms need an ocean surface temperature of more than 27°C to provide sufficient heat energy. They also need low wind shear, high humidity in the lower atmosphere and a location between 5° and 20° north or south of the equator.
Tropical storms do not form on the equator because the Coriolis effect is zero there, so the rising air is not deflected and the system cannot spin. They form between 5° and 20° north or south of the equator, close enough for the Coriolis effect to act.
The eyewall is the ring of towering thunderstorms surrounding the eye of a tropical storm, where the strongest winds and heaviest rain occur. Spiral rainbands of cloud and rain extend outwards from it.
Tropical storms weaken over land, or over cooler ocean, because they lose their energy source, the warm water that heats the rising air. This rapid weakening is called dissipation; storms are self-sustaining only while they remain over warm water.
Wind speed must exceed 119 km/h for a storm to be classified as a hurricane, typhoon or cyclone. A mature tropical storm is typically 300-500 km across, though some exceed 1,000 km.
Bangladesh dramatically reduced its tropical cyclone death toll from hundreds of thousands in the 1970s to thousands by the 2000s–2010s, largely through improved warning systems and coastal shelters. Accurate warnings with enough lead time allow evacuation before the storm arrives.