1. Chapter Resources Menu
Study Guide
Section 13.1
Section 13.2
Section 13.3
Section 13.4
Chapter Assessment
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Chapter Resources Menu

2. Section 13.1 Study Guide
Section 13.1 Main Ideas
For a thunderstorm to occur, there must be abundant moisture in the lower levels of the atmosphere and a mechanism to lift the moisture so it can condense. In addition, the air must be unstable so that the growing cloud will continue to rise.
Thunderstorms are classified according to the mechanism that caused the air to rise. In an air-mass thunderstorm, the cloud rose because of unequal heating of Earth’s surface within one air mass. In a frontal thunderstorm, the air rose because it was pushed up by an advancing air mass.

3. Section 13.2 Study Guide
Section 13.2 Main Ideas
Lightning is produced when an advancing stepped leader unites with an upward-moving return stroke. Thunder is the sound made by the rapid expansion of air around the lightning bolt as a result of extreme heating of the lightning channel.
Thunderstorms can damage property and cause loss of life. The hazards of thunderstorms include lightning, violent winds, hail, floods, and tornadoes.
The Fujita tornado intensity scale classifies tornadoes according to wind speed, path of destruction, and duration.

4. Section 13.3 Study Guide
Section 13.3 Main Ideas
Tropical cyclones derive their energy from the evaporation of warm ocean water and the release of heat.
The Saffir-Simpson hurricane scale classifies hurricanes according to intensity.
Hurricane hazards include violent winds, floods, and storm surges. The National Hurricane Center tracks hurricanes and issues advance warnings to help reduce loss of life.

5. Section 13.4 Study Guide
Section 13.4 Main Ideas
Examples of persistent weather events include floods, droughts, cold waves, and heat waves.
The heat index assesses the impact of humidity combined with excessive heat on the human body. The wind-chill index estimates the heat loss from human skin caused by a combination of cold air and wind.

6. Chapter Assessment
Multiple Choice
1. Which of the following states experiences the highest number of thunderstorm days annually?
a. Oklahoma c. Florida
b. Tennessee d. Iowa
Almost the entire state of Florida experiences more than 70 thunderstorm days annually.

7. Chapter Assessment
Multiple Choice
2. The ____ causes the illumination that you see as lightning.
a. stepped leader c. channel
b. return stroke d. thunder
The stepped leader is the invisible channel of negatively charged air that moves from the cloud toward the ground. The return stroke rushes upward from the ground to meet it, illuminating the channel with about 100 million V of electricity.

8. Chapter Assessment
Multiple Choice
3. Which classification on the Fujita tornado intensity scale represents a strong tornado?
a. F0 c. F3
b. F1 d. F5
F0 and F1 are classified as weak tornadoes. F2 and F3 are classified as strong tornadoes. F4 and F5 are classified as violent tornadoes.

9. Chapter Assessment
Multiple Choice
4. Which of the following areas is least likely to be hit by a hurricane or typhoon?
a. western Africa
b. eastern United States
c. southern Japan
d. eastern India
As a general rule, the most likely areas to be hit by a hurricane are on the eastern side of continents. Australia is the exception; both its east and west coasts are vulnerable.

10. Multiple Choice 5. Cold waves are caused by ____.
Chapter Assessment
Multiple Choice
5. Cold waves are caused by ____.
a. high-pressure systems
b. low-pressure systems
c. mT air masses
d. cT air masses
Cold waves are brought on by large high-pressure systems that originate in the polar regions.

11. Chapter Assessment
Short Answer
6. Explain why cold-front thunderstorms can last through the night?
Cold-front thunderstorms get their initial lift from the push of cold air. They are not dependent on daytime heating. The thunderstorm can persist as long as the flow of moist, warm air into it is not disrupted.

12. Chapter Assessment
Short Answer
7. What is wind shear and why is it important in the formation of tornadoes?
Wind shear is when wind speed and direction change suddenly with height. This can produce a horizontal rotation near Earth’s surface. If this occurs close to the thunderstorm’s updrafts the twisting column of wind can be tilted from a horizontal to vertical position.

13. Chapter Assessment
True or False
8. Identify whether the following statements are true or false.
______ Tornadoes can occur virtually anywhere on Earth.
______ Typical thunderstorms last about two hours.
______ High instability in the atmosphere limits thunderstorms.
______ Air-mass thunderstorms generally occur during mid-afternoon.
______ Tropical disturbances have a cyclonic circulation.
true
false

14. Image Bank
Chapter 13 Images

15. Image Bank
Chapter 13 Images

16. Image Bank
Chapter 13 Images

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