1. Thunderstorms Section 13-1 p 329-333 Thunderstorms Section 13-1 p 329-333

2. HOW DO THUNDERSTORMS FORM ? Three Conditions that are Responsible –lots of moisture in lower levels of the atmosphere –air has to rise so water vapor can condense to release latent heat –Portion of atmosphere where clouds mature must be unstable

3. Two types of Thunderstorms 1. AIR-MASS THUNDERSTORMS When air rises because unequal heating within one air mass of the Earth’s surface 2.FRONTAL THUNDERSTORMS Formed by advancing cold fronts or in some cases advancing warm fronts(rare)

4. Two Common Types of Air-Mass Thunderstorms 1. Mountain Thunderstorms - result of orographic lifting - air travels up the side of a Mt.

5. 2. Sea-Breeze Thunderstorms - result of extreme temperature changes in the air over land and air over water Two Common Types of Air-Mass Thunderstorms

7. 1.Cold Front: cold air pushing warm air quickly up cold-front boundary –this motion produces a line of storms along leading edge of cold front, can be 100’s of km long –Initial lift from push of cold air –Can continue long into night Two Common Types of Frontal Thunderstorms

8. Frontal Thunderstorm – COLD FRONT

9. Warm Front: warm air slides up and cold air mass, very mild t-storms can occur. Last for short period of time (less than an hour) Two Common Types of Frontal Thunderstorms

10. Frontal Thunderstorm – WARM FRONT

12. CUMULUS STAGE Air rises vertically upward creating updrafts Moisture transported to upper portions of clouds Moisture condensed into droplets, releasing latent heat

13. MATURE STAGE Precipitation Falls cooling surrounding air Creation of cool more dense air sinks to ground with precipitation Up & down drafts exist side by side in cumulonimbus clouds Convection cells form developing gusty winds

14. DISSIPATION STAGE Characterized by the lingering of downdrafts Lack of warm air stops updrafts and the development of precipitation Cloud runs out of previously formed raindrops