1. Do Now 2/11/13 1. ________ is any form of condensed water vapor in the atmosphere falling back to Earth. 2. Name the global winds that blow from east to west and come from the poles. 3. _______ is the dropping off of sediments and the building up of land. 4. A ______ is a steep sided narrow cut in the sea floor. This is the deepest part of the ocean.

2. Key Questions Severe Weather 1. What is weather? 2.What is severe weather? 3. What is a thunderstorm? 4. What are the two atmospheric conditions that are needed to produce a thunderstorm? 5. What is lightning? 6. What is thunder? 7. What are the dangers of thunderstorms?

3. 1. What is weather?  The condition of the atmosphere at a particular place and time.

4. 2. What is severe weather?  Weather that can cause property damage, injury or death.

5. 3. What is a thunderstorm?  Small, intense weather systems that produce strong winds, heavy rain, lightning and thunder.  They can happen along cold fronts.

6. 4. What are the two atmospheric conditions that are needed to produce a thunderstorm?  Warm, moist air rising rapidly.  The atmosphere is unstable.  When the warm air reaches its dew point, the water vapor in the air condenses, forming cumulus clouds.  If the atmosphere is extremely unstable, the warm air will continue to rise, causing the cloud to grow into a dark, cumulonimbus cloud.

7. 5. What is lightning?  Lightning is a large electrical discharge that occurs between two oppositely charged surfaces.

8. 6. What is thunder?  When lightning strikes, energy is released.  This energy is transferred to the air, the air to expands rapidly and sends out sound waves.  Thunder is the sound from that rapid expansion of air along the lightning strike.

9. 7. What are the dangers of thunderstorms? 1. High winds 2. Hail 3. Flash floods 4. Tornadoes  Lightning from thunderstorms is responsible for thousands of forest fires each year.