Severe Weather

Severe Weather

Middle School

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Learning Objectives

• Define and compare severe weather like thunderstorms, tornadoes, and hurricanes.

• Describe the three conditions that are necessary for severe weather to form.

• Explain the formation, characteristics, and measurement of tornadoes and hurricanes.

• Distinguish between a weather 'watch' and 'warning' and know the safety actions.

Key Vocabulary

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Storm

A violent weather disturbance with strong winds, often bringing rain, snow, or hail from pressure changes.

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Tornado

A violently rotating, funnel-shaped column of air extending from a thunderstorm to the ground over land.

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Hurricane

A large, swirling, low-pressure system forming over tropical oceans with winds of at least 74 mph.

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Storm Surge

A dangerous rise in sea level where ocean water is pushed ashore by a storm's strong winds.

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Mitigation

The action of reducing the severity and impact of a natural hazard on people and their property.

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Drought

A long period with very little or no rainfall in an area, leading to a water shortage.

Conditions for Severe Weather

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Energy Source

• Storms are fueled by a source of heat energy.

• This can come from the sun warming the Earth's surface.

• It can also come from differences between two air masses.

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Moisture

• Energy from the sun causes water to evaporate into vapor.

• This water vapor holds onto energy as it rises upward.

• The vapor condenses into a cloud, releasing heat that fuels storms.

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Unstable Air

• Unstable air happens when cold air is above much warmer air.

• This large temperature difference causes the storm to grow much faster.

• The storm can grow higher and with much greater intensity.

Multiple Choice

Which of the following are the three essential conditions for the formation and growth of severe storms?

• High air pressure, cold temperatures, and dry air.

• A lack of wind, low humidity, and a consistent temperature.

• An energy source, moisture, and unstable air.

• Stable air, a moisture source, and low-altitude clouds.

Thunderstorms: Formation and Features

• Warm, humid air rises and builds a tall storm cloud.

• In the Mature Stage, downdrafts pull heavy water down, producing rain or hail.

• Lightning and thunder release the storm’s intense energy.

Multiple Choice

During which stage of a thunderstorm's formation do downdrafts start to pull heavy water downward, leading to precipitation?

• Lightning Stage

• Dissipating Stage

• Mature Stage

• Cumulus Stage

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What Is a Tornado?

• A tornado is a rotating, funnel-shaped column of air touching the ground.

• They form in thunderstorms as warm air rises and starts to spin.

• Most last only a few minutes and are common in the spring.

• A tornado that forms over water is known as a waterspout.

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Multiple Choice

What is the key process that causes a tornado to begin rotating within a thunderstorm?

• The rapid heating of the ground by the sun, which creates a low-pressure zone.

• A change in wind direction or speed at different altitudes, causing an updraft to spin.

• The formation of a waterspout over a large body of water that then moves over land.

• The collision of two separate thunderstorm clouds, forcing air to rotate.

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Tornado Damage and the Enhanced Fujita Scale

• Tornado winds can exceed 250 mph, causing immense destruction to communities.

• The Enhanced Fujita (EF) Scale measures a tornado's strength and intensity.

• The EF Scale rates tornadoes based on their wind speed and related damage.

• EF0-EF1 tornadoes cause light damage like broken branches and damaged roofs.

• EF2-EF3 tornadoes can uproot trees and tear roofs off well-built houses.

• EF4-EF5 tornadoes are devastating, leveling houses and throwing cars far distances.

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Multiple Choice

What does the Enhanced Fujita (EF) Scale use to measure the intensity of a tornado?

• The duration of the tornado on the ground.

• The geographic region where the tornado occurs.

• The diameter of the funnel cloud.

• Wind speed and the level of damage caused.

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Hurricanes, Cyclones, and Typhoons: One Storm, Many Names

• These are all names for the same powerful, swirling tropical storm.

• A hurricane is in the Atlantic and North Pacific Oceans.

• A typhoon is in the Southwest Pacific, a cyclone elsewhere.

• It becomes a hurricane when winds reach 74 miles per hour.

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Multiple Choice

A large, rotating storm forms in the Indian Ocean. What is this type of storm officially called?

• Cyclone

• Typhoon

• Hurricane

• Tornado

Hurricane Structure and Impact

• A hurricane has a calm eye, a powerful eyewall, and a storm surge that floods coastlines.

• It weakens on land because it loses its warm-ocean energy source.

• Hurricanes are rated 1 to 5 based on their wind speed.

Multiple Choice

What is considered the most destructive and dangerous aspect of a hurricane when it makes landfall?

• The winds in the eye

• The storm surge

• The formation of tornadoes

• The heavy rainfall

Other Weather Extremes

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Blizzards

• A blizzard is a severe snowstorm with very low temperatures.

• It features strong winds of over 35 miles per hour.

• Heavy snow reduces visibility for three hours or more.

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Mid-latitude Cyclones

• These are large, rotating systems of low-pressure air.

• They form where cold polar air meets warmer, moister air.

• They rotate counterclockwise in the Northern Hemisphere.

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Droughts & Heat Waves

• A heat wave is a prolonged period of unusually hot weather.

• A drought is a long period with little to no rainfall.

• Droughts can lead to water shortages affecting farms and cities.

Multiple Choice

What is the main characteristic of a drought?

• Extremely hot temperatures lasting several days

• Heavy storms followed by flooding

• A long period with little or no rainfall, causing water shortages

• Strong winds that damage crops

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Forecasting and Safety

• Forecasting predicts weather by analyzing data like temperature, clouds, and air patterns.

• Mitigation lessens a storm's impact with technologies like satellites and storm shelters.

• A storm watch means severe weather might develop, so it's time to prepare.

• A storm warning means dangerous weather is coming, so you must take shelter.

Multiple Choice

What is the key difference in the action you should take for a 'storm watch' versus a 'storm warning'?

• A watch means the storm is already happening, while a warning means it is still forming.

• A warning means you should take shelter immediately, while a watch means you should prepare and stay aware.

• A watch requires evacuation, while a warning means to stay indoors.

• A warning is for a large area, while a watch is for a specific neighborhood.

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Common Storm Misconceptions

Misconception	Correction
A tornado’s path skips because it lifts off the ground.	Damage occurs where smaller, rotating funnels touch down.
The wind is the most dangerous part of a hurricane.	The storm surge and flooding cause the most destruction.
All thunderstorms produce tornadoes.	Only strong thunderstorms called supercells can create tornadoes.
Thunder is dangerous.	Thunder is only a sound; the lightning is the danger.
A storm is a hurricane when it starts rotating.	It is a hurricane at wind speeds of 74 mph.

Multiple Choice

Why do hurricanes typically weaken when they make landfall?

• The friction from land surfaces slows the wind.

• They lose their energy source of warm ocean water.

• They encounter colder air masses immediately.

• The air pressure on land is always higher.

Multiple Choice

What is a primary difference in the formation conditions for a hurricane versus a mid-latitude cyclone?

• Hurricanes form over warm tropical waters, while mid-latitude cyclones form at polar fronts where air masses with different temperatures meet.

• Hurricanes rotate clockwise in the Northern Hemisphere, while mid-latitude cyclones rotate counterclockwise.

• Mid-latitude cyclones form from a single thunderstorm, while hurricanes require a line of storms.

• Hurricanes require strong wind shear, while mid-latitude cyclones need calm, stable air.

Multiple Choice

At what wind speed does a developing tropical storm officially become a hurricane?

• 50 mph

• 74 mph

• 60 mph

• 90 mph

Multiple Choice

Which condition is required for a snowstorm to be classified as a blizzard?

• Light snowfall with calm winds for less than an hour

• Temperatures below freezing with no wind

• Strong winds over 35 mph and heavy snow reducing visibility for at least three hours

• Heavy snow falling during warm weather

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Summary

• Severe weather needs an energy source, moisture, and unstable air to form.

• Thunderstorms have three stages and can produce powerful tornadoes.

• Hurricanes are large ocean storms that can cause dangerous storm surges.

• A weather watch means be prepared; a warning means take shelter.

Poll

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

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• 3

• 4