1. Severe Weather Thunderstorms

2. Cold Fronts Begins with humid air rising, cooling, and condensing into a single cumulus cloud. Cloud builds as they are “fueled” by warm, moist air from below.

3. Thunderstorms The droplets of water grow larger until they are so big that they fall as rain.

4. Thunderstorms (con’t) Lightning may be associated with Thunderstorms Lightning hits somewhere on Earth 100 times per second Over 200 people in the US die each year from lightning.

5. Lightning Lightning is the cause of thunder – Lightning causes vibrations in the air as it travels to the ground – Lightning travels at the speed of light and thunder travels at the speed of sound Returns usable nitrogen to the soil Frequently causes forest fires

6. Lightning Formation During thunderstorms, strong updrafts cause molecules to bump together and the charged particles to separate Negative charges concentrate at the bottom of the clouds

7. Lightning Formation The ground has lost electrons, giving it a positive (+) charge Opposites attract: The (-) from the cloud base is “pulled” to the (+) The first downward movement of a negative particle (-) is called a leader

8. Lightning Formation When the (-) and (+) touch, they create a conductive path to the ground. The other negative particles(-) rush down this path = lightning

9. Lightning on L.Superior

10. Lightning on L.Michigan

11. Lightning strike