3. Air and the Sun * Weather reporter  meteorologist  wind, air pressure, and temperature. * Weather starts with the sun; source of heat. * Sun’s rays  direct rays at equator  more heat; slanting rays at Poles  less heat. * Uneven heating causes air to move and make weather.

4.  A large body of air with similar temperature and moisture.  Air masses form over large land or water masses. MAP TAP 2002-2003Weather Fronts3

5. When 2 air masses meet, they do not mix. They form a border called a front. Most of the weather happens along fronts.

6. Cold Fronts  Heavy, cold air forces the warm air up.  Warm air goes up, cools and forms clouds. This leads to rain and thunderstorms at a cold front.  Temperature drops after a cold front has passed.

7.  blue line with triangles; show where cold front is moving

8. Warm air slides over the cold, dense air. Stratus clouds form. Steady rain or snow. After front passes, clear skies, warm temperatures.

9.  Red line with half circles pointing where warm front is moving.

10. COLD FRONTS Move faster. Often violent weather. Gusty winds; turbulence Weather change happens when front is passing through. WARM FRONTS Slow, gradual change. Weather change happens BEFORE front arrives. Low clouds (stratus) cause poor visibility. Tall, cumulonimbus clouds.

11.  When a warm front is trapped by 2 cold fronts.  Purple line with alternating triangles and semicircles pointing the direction the front is moving. MAP TAP 2002-2003Weather Fronts

12.  A front that stops moving or is moving very slowly.  Alternating red semicircles pointing away from the warm air and blue triangles pointing away from the cold air. MAP TAP 2002-2003

18. Weather Fronts17 You are planning to travel to Alabama in 2 days. The high temperature there for today is 68 º F. Use the map to help you predict whether the temperature in Alabama will increase, decrease, or stay the same. Explain why you think so.

19. 18 There is a cold front approaching. The temperatures will probably be cooler behind the front.

20.  Of course, meteorologists (weather forecasters) use much more data than fronts and air masses to help them forecast the weather more accurately. But any forecast is just a prediction of what might happen. Even with the best data, weather forecasts can be wrong. MAP TAP 2002-2003Weather Fronts19