2. Pressure Systems Low pressure: an area where the atmospheric pressure is lower than the surrounding area Air rises then it cools and condenses Weather: cloudy and rainy

3. Pressure Systems High pressure: an area where the atmospheric pressure is higher than the surrounding areas Air is sinking Weather: light winds, dry, clear skies

4. High vs. Low pressure air movement LOW PRESSURE HIGH PRESSURE

5. Warm Front Warm air mass moves into a cold air mass Weather: overcast or rain http://www.phschool.com/atschool/phsciexp/act ive_art/weather_fronts/index.html

6. Cold Front Cold air mass gets pushed into warm air mass Weather: Abrupt weather changes http://www.classzone.com/books/earth_science/terc/content/visualizatio ns/es2002/es2002page01.cfm?chapter_no=visualizatione

7. Occluded Fronts A warm air mass is caught between 2 colder air masses Weather: Severe storms

8. Stationary Front Warm and cold air mass meet but neither has greater force behind it to move the other mass Weather: Fog, clouds, rain, snow

9. Severe Weather Thunderstorm: rain, hail, wind and lightning Formation: rapidly rising air, warm or cold front Lightning: small ice crystals that are positively charged collide with large ice crystals that are negatively charged Tornado: a violently rotating column of air extending from a thunderstorm cloud

10. Severe Weather Cyclone: a tropical storm that is a low pressure region surrounded by spiral thunderstorms that produces heavy rain and strong winds Hurricane: a tropical cyclone that forms in the southern Atlantic, Caribbean Sea or the Gulf of Mexico

11. Severe Weather Blizzard: a severe snow storm characterized by strong winds and heavy snowfall Drought: an extended period of time when a region does not receive rainfall Flash Flooding: rapid flooding caused by heavy rainfall or rapid snow and ice melt

12. Severe Weather El Nino: The abnormal warming of the Pacific Ocean Causes: droughts in Asia, Flooding in Americas La Nina: The abnormal cooling of the Pacific Ocean Causes: flooding in Asia, Droughts in Americas

13. Severe Weather Monsoon Wind: a change in the direction of the wind due to abnormal heating of the surface of Earth Monsoon Rain: a rainy season that can last for months caused by the change in wind direction