Hurricanes

Hurricanes

Middle School

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Learning Objectives

• Define a hurricane and the conditions needed for it to form.

• Explain a hurricane's structure, including the eye, and how storms are classified.

• Identify the main ways hurricanes cause damage, including storm surge and high winds.

• Describe how a hurricane gains energy and what causes it to eventually dissipate.

Key Vocabulary

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Hurricane

A massive, rotating storm with high winds and heavy rain that forms over warm tropical waters.

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Cyclone

The general term for a large system of rotating air circulating around a low-pressure center.

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Storm Surge

An abnormal rise of sea level generated by a storm, which can cause severe coastal flooding.

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Hurricane Eye

The calm, clear, low-pressure center of a hurricane where air sinks instead of rises.

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Tropical Depression

A low-pressure cell with rotating winds that can intensify to become a hurricane over warm waters.

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What is a Hurricane?

• A hurricane is a large, powerful storm with strong winds and heavy rain.

• ​It is a type of rotating tropical storm, also called a cyclone.

• Wind speeds can exceed an incredible 251 kilometers per hour (156 mph).

• These massive storms can also sometimes produce smaller storms like tornadoes.

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Multiple Choice

Based on the definition provided, which statement accurately describes a hurricane?

• It is a specific type of tropical cyclone with high winds and heavy rain.

• It is another name for any storm that forms over land.

• It is a small storm that is unrelated to cyclones or tornadoes.

• It is a storm with wind speeds always under 100 kilometers per hour.

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How Hurricanes Form and Get Their Energy

• Hurricanes form over warm tropical oceans with water at least 28°C (82°F).

• ​Warm, moist air rises, creating a low-pressure area called a tropical depression.

• As air cools, condensing water vapor releases massive energy known as latent heat.

• This energy release allows the storm to grow stronger into a hurricane.

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Multiple Choice

What is the primary energy source that allows a tropical depression to build into a hurricane?

• The release of latent heat from condensing water vapor.

• The rotation of the Earth, known as the Coriolis effect.

• Pre-existing tornadoes that merge together.

• The friction between the wind and the ocean surface.

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Hurricane Structure and Movement

• At the center is the eye, an area of calm, clear weather.

• The eyewall surrounds the eye and has the most violent winds.

• Hurricanes move with prevailing winds, like the trade winds and westerlies.

• A hurricane weakens when it moves over cooler water or makes landfall.

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Multiple Choice

What happens to a hurricane when it moves over land or cooler ocean water?

• It immediately transforms into a tornado.

• It loses strength and slowly fades away.

• It intensifies due to the change in temperature.

• Its eye grows larger and more powerful.

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Hurricane Classification

• Hurricanes are classified into five categories based on their wind speed.

• Category 1 (119-153 km/h) causes minimal damage to buildings and vegetation.

• Category 2 (154-177 km/h) results in some damage to roofing.

• Category 3 (178-209 km/h) damages some buildings and destroys mobile homes.

• Category 4 (210-251 km/h) leads to complete roof failure on small homes.

• Category 5 (>251 km/h) results in catastrophic damage to most structures.

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Multiple Choice

A hurricane with wind speeds of 190 km/h that destroys mobile homes would be classified as what category?

• Category 1

• Category 2

• Category 3

• Category 4

Hurricane Damage

• Storm surge is a high water level that causes significant hurricane damage.

• Storm surge and high waves lead to catastrophic coastal flooding and major erosion.

• Heavy rainfall causes widespread inland flooding far away from the coast.

Multiple Choice

What is storm surge and why is it so destructive?

• A rise in sea level causing major flooding.

• The heavy rainfall in the eye of the storm.

• A series of tornadoes generated by the hurricane over land.

• The fastest winds in the hurricane, which tear roofs off buildings.

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Common Misconceptions About Storms

Misconception	Correction
Hurricanes, tornadoes, and typhoons are all the same thing.	They are all cyclones but differ in size and location.
The eye of the hurricane is the most dangerous part.	The eye is calm; the surrounding eyewall has the strongest winds.
Once a hurricane makes landfall, the danger is over.	Intense rainfall, flooding, and tornadoes can still cause immense damage.

Multiple Choice

Why do hurricanes typically form in the tropics over oceans, and not over land or in polar regions?

• There is less land to block the storm's path in the tropics.

• They require the energy from warm ocean water with surface temperatures above 28°C.

• Prevailing winds are strongest in the tropics, which initiates the storm's rotation.

• The air pressure is naturally lower in the tropics, making it easier for storms to form.

Multiple Choice

What is the key difference between the damage caused by a hurricane's high winds and the damage caused by its storm surge?

• Storm surge is only dangerous at low tide, while high winds are dangerous at all times.

• High winds cause flooding, while storm surge causes buildings to be blown over.

• High winds cause structural damage to buildings, while storm surge causes flooding and erosion.

• High winds only affect the upper floors of buildings, while storm surge only affects the lower floors.

Multiple Choice

A powerful Category 4 hurricane is moving west across the Atlantic Ocean. Predict the most likely sequence of events as it approaches and moves over Florida.

• It will turn into a series of small tornadoes immediately upon touching the coast.

• It will increase in strength as it moves over the land.

• It will cause major storm surge and wind damage upon landfall, then weaken as it is cut off from warm water.

• The eye of the storm will get stronger, but the winds will decrease.

Multiple Choice

What is the most likely difference in damage between a Category 5 and a Category 1 hurricane hitting the same coastal city?

• A Category 5 storm would primarily cause wind damage, while a Category 1 storm would primarily cause flooding.

• A Category 1 would cause more damage from storm surge, while a Category 5 would cause more damage from rain.

• Both categories would cause identical levels of damage, but the Category 5 storm would last longer.

• A Category 5 would likely cause complete building failures and catastrophic flooding, while a Category 1 might only cause minor structural and vegetation damage.

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Summary

• Hurricanes are large, rotating storms that form over warm ocean waters.

• They have a calm central eye surrounded by a powerful eyewall.

• High winds, heavy rainfall, and storm surges cause widespread damage.

• They are ranked by wind speed and weaken over land or cool water.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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