1. Severe Weather. Tornadoes… Cyclones… Typhoons… Hurricanes… And more!
Chapter 21.3

2. Severe Weather
A thunderstorm is usually a brief, heavy storm that consists of rain, strong winds, lightning, and thunder.

3. Severe Weather Thunderstorms develop in three distinct stages.
In the cumulus stage, warm, moist air rises, and the water vapor within the air condenses to form a cumulus cloud.

4. Severe Weather
In the mature stage, the cloud rises and becomes a dark, cumulonimbus cloud from which heavy, torrential rain and hailstones may fall.

5. Severe Weather
During the dissipating stage, the strong downdrafts stop air currents from rising. The thunderstorm dissipates as the supply of water vapor decreases.

6. Severe Weather
During a thunderstorm, clouds discharge electricity in the form of lightning.

7. Severe Weather
The released electricity heats the air, which rapidly expands and produces a loud noise known as thunder.

8. Severe Weather
A hurricane is a severe storm that develops over tropical oceans. Its strong winds spiral in toward the intensely low-pressure storm center.
To be a hurricane, a storm’s winds must be 75 miles per hour or greater.

9. Severe Weather
A fully developed hurricane has of a series of thick cumulonimbus cloud bands that spiral upward around the center of the storm.

10. Severe Weather
The most dangerous aspect of a hurricane is a rising sea level and large waves, called a storm surge.

11. Severe Weather
Tornadoes are the smallest, most violent, and shortest-lived severe storm.

12. Severe Weather
A tornado forms when a thunderstorm meets high-altitude horizontal winds. These winds cause the rising air in the thunderstorm to rotate.

13. Severe Weather
If the funnel does touch the ground, it generally moves in a wandering, haphazard path.
Last week of April, 2011

14. Severe Weather
The destructive power of a tornado is mainly due to the speed of the winds, which may reach speeds of more than 250 mph.