2. Large body of air with properties the same as the part of Earth’s surface it formed over. Can cover thousands of kilometers. A change in weather = movement of air masses.

3. Wind blows from the center of an area of higher pressure to an area of lower pressure.

4. Anemometer: measures wind speed Wind Vane: determines the direction from which the wind is blowing. Wind Sock: measures direction & speed

5. Large swirling areas of low pressure.

6. High pressure area means fair weather.

7. A front is a boundary between two areas of different density, moisture, temperature. 4 types of fronts: cold, warm, occluded, and stationary.

8. Cold air wedges under warm air like a plow. Creates rain storms. Big temperature differences = storms/tornados.

10. Advances over a cold front. Warm air moves towards cold air.

12. Cold/cool/warm air. Formed as a cold front takes over a warm front.

14. The boundary between air masses quits advancing. When cold and warm air cannot overtake each other (tie). There is light wind precipitation.

17. Occur in warm, moist air masses and along fronts. Sinking rain, cooled air, and strong updrafts of warm air cause strong winds. If winds reach 89 km/h or faster, it is a severe thunderstorm. Flash floods, strong winds, hail.

19. A violently rotating column of air in contact with the ground. In severe thunderstorms, wind at different levels blow at different direction and speed. This is called wind shear. Rips apart building, uproot trees, blow through glass. Can lift animals, cars and houses in the air.

21. Winds at 56 km/h Blowing snow Visibility less than 400m These conditions must persist for 3 hours or more.

23. In a storm cloud, warm air is lifted rapidly as cooler air sinks. This movement causes different parts of the cloud to become oppositely charged. When the current flows between opposite charges, lightning flashes. Occurs in 3 places: within a cloud, between clouds, cloud and the ground.

25. Results from rapid heating of air around lightning. (Lightning is 30,000 degrees celsius.. 5x the surface of the sun!!) The extreme heat causes air around the lightning to expand rapidly. Then it cools and contracts. The rapid movement of molecules forms sound waves heard as thunder.

27. Large, swirling, low pressure system that forms over the Atlantic Ocean. Must have winds of at least 119 km/h. Category 1-5 (250 km/h) Typhoon- forms over the Pacific Ocean. Cyclones- Form over the Indian Ocean.

30. Begin as low pressure systems west of Africa. Steered by surface winds. travel west. Gains strength from heat + moisture of warm ocean water. When it hits land, it loses power and dumps water. Strongest winds are within 80 km of the eye. (50 miles)

31. watch- conditions are favorable warning- weather exist, take cover!