1. Guided Notes on Thunderstorms
Chapter 13, Section 1

2. Describe the 3 conditions that must exist for a thunderstorm to form:
Abundant moisture in the lower levels of the atmosphere
A mechanism must lift the air so that moisture will condense and release latent heat
The portion of the atmosphere through which the cloud grows must be unstable

3. 2. Typical thunderstorms last only about 30 minutes, and individual storms are only about 24 kilometers in diameter.

4. 3. Thunderstorms are classified according to the mechanism that caused the air to rise. An air mass thunderstorm forms if the air rose because of unequal heating of Earth’s surface within one air mass. This reaches its maximum during mid-afternoon, so air-mass thunderstorms are most common then.

5. 4. Mountain thunderstorms occur when an air mass rises because of orographic lifting.

6. 5. Sea-breeze thunderstorms are local air-mass thunderstorms caused by temperature differences between the air over land and the air over water. They are most common in coastal areas during the summer, especially in the tropics and subtropics.

7. 6. Frontal thunderstorms are produced by advancing cold fronts and rarely, warm fronts. Because they are not dependent on daytime heating, these thunderstorms can persist long into the night.

8. Describe the 3 stages of thunderstorm development:
Cumulus Stage: air rises vertically, creating updrafts which transport moisture to the upper reaches of the cloud
Mature Stage: as precipitation falls, it cools the air around it, creating downdrafts that produce gusty surface winds
Dissipation Stage: the supply of warm, moist air runs out because downdrafts spread in all directions as they reach the surface