1. Severe Weather

2. Thunderstorms Three Causes: Air Mass Thunderstorms
Abundant moisture in lower layers of atmosphere
Mechanism to lift air, allowing condensation
Unstable air mass
Air Mass Thunderstorms
Unequal heating within 1 air mass
Occur midday, last ~ ½ hour
Frontal Thunderstorms
Caused by cold front

3. Lightning
Lightning occurs when there is a charge separation in the cloud.
As a thunderstorm grows, electrical charges build up within the cloud, with positive charges at the top, and negative charges at the bottom.
Oppositely charged particles gather at the ground below the cloud.

4. Tornadoes
A tornado is a violent, whirling column of air in contact with the ground.
Come from supercells – most intense thunderstorms
Most tornadoes form in the central and southern United States
Continental polar air collides with maritime tropical air from Gulf of Mexico

5. How are Tornadoes Measured?

6. Hurricanes Hurricanes are large, rotating, low-pressure, storms
Form from energy in warm, tropical oceans
Air rises due to existing disturbance and low-pressure system is formed
What causes rotation?
Coriolis effect
Hurricane Season is from June to November