1. Severe Weather

2. Key Terms
Thunderstorms
Tornado
Hurricane

3. Severe Weather
Severe weather is weather that can cause property damage and even death.
Examples are:
Thunderstorms
Tornadoes
Hurricanes

4. Thunderstorms
A thunderstorm is a small, intense weather system that produces strong winds, heavy rain, lightning, and thunder.
Thunderstorms can occur along cold fronts.
In order to produce thunderstorms:
The air near the surface must be warm and moist.
The atmosphere must be unstable

5. Thunderstorms In order to produce thunderstorms there must be:
Moisture
Unstable air
Lift
There needs to be moisture to form clouds and rain. The unstable air is relatively warm and can rise rapidly. Finally, lift can form from fronts, sea breezes or mountains.

6. Lightning
Lightning is a large electrical discharge that occurs between two oppositely charged surfaces.
When lightning strikes, energy is released.
This causes the air to expand rapidly and send out sound waves.

7. Describe what a thunderstorm is like.

8. Tornadoes
A tornado is a small, rotating column of air that has high wind speeds and low central pressure and that touches the ground.
They frequently occur with severe thunderstorms.

9. Tornadoes
Formation:
Wind traveling in two different directions causes a layer of air in the middle to begin to rotate.
The rotating column of air is turned to a vertical position by strong updrafts, which then also begin to rotate.

10. Tornadoes
The rotating column of air works its way down to the bottom of the cloud and forms a funnel cloud.
The funnel cloud is called a tornado when it touches the ground.

11. What is the air pressure like in a tornado?

12. Hurricanes
A hurricane is a large, rotating tropical weather system with wind speeds of at least 119km/h.
They are the most powerful storms on Earth.
It begins as a group of thunderstorms moving over warm ocean waters.

13. Hurricanes
Winds traveling in different directions collide, causing the storm to rotate over an area of low pressure.
It turns counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
They are fueled by the contact with warm ocean water.

14. Hurricanes
The hurricane continues to grow as long as it is over its source of warm, moist air.
It begins to die as it moves over land.
The eye is the calm, clear center of the storm.

15. Why do hurricanes form only over certain areas?