2. Sun = Energy driving weatherSun = Energy driving weather Equator = warm; Poles = cold  why?Equator = warm; Poles = cold  why? Daytime: air over land warmer than over water; reverse at night  why?Daytime: air over land warmer than over water; reverse at night  why? Convection currents  explain!Convection currents  explain!

3. large bodies of air classified by * temperature (warm/cold) * amount of water vapor (wet/dry) Characteristics of air masses are the same as those of the area over which it forms. large bodies of air classified by * temperature (warm/cold) * amount of water vapor (wet/dry) Characteristics of air masses are the same as those of the area over which it forms.

4. Can you describe the air masses on the map that affect weather in the United States? 5 4 1 3 2 Wet & Warm Dry & Warm Dry & Cold Wet & Cold 6 Dry & Warm

5. Leading edge of an air mass 4 kinds of fronts: –Cold front –Warm front –Stationary front –Occluded front Leading edge of an air mass 4 kinds of fronts: –Cold front –Warm front –Stationary front –Occluded front front boundary

6.  Cold Front: mass of cold air moving into area of warmer air  Warm Front: mass of warm air moving into area of cooler air  Stationary Front: masses of cold & warm air meet from opposite directions and stop moving  Occluded Front: mass of cold air overtakes mass of warm air moving in same direction

7.  mass of cold air moving into area of warmer air  cold air forces warm air up & over the cold air; often creating storms  mass of cold air moving into area of warmer air  cold air forces warm air up & over the cold air; often creating storms Image courtesy of PhysicalGeogrpahy.net PhysicalGeogrpahy.net

8.  mass of warm air moving into area of cooler air  As front enters, rain showers, then light rain, then clearing and warmer  mass of warm air moving into area of cooler air  As front enters, rain showers, then light rain, then clearing and warmer Image courtesy of PhysicalGeogrpahy.net PhysicalGeogrpahy.net

9.  air masses are not moving against each other  forms when a cold front or warm front stops moving  may stay put for days  often cloudy with rain or snow  air masses are not moving against each other  forms when a cold front or warm front stops moving  may stay put for days  often cloudy with rain or snow

10.  forms when a cold air mass overtakes a warm front  Light to moderate rain before and during  Clearing and cooler after  forms when a cold air mass overtakes a warm front  Light to moderate rain before and during  Clearing and cooler after Image courtesy of the University of Illinois WW2210. University of Illinois WW2210

17. Jet Stream – is a band of fast moving air in the stratosphere. Formed where Westerly winds meet the Easterly winds Jet Stream Video 1

18. Weather Fronts18 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. 19 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.

21. Temperature Wind Direction Wind Speed Precipitation Humidity & Dew Point Thermometers Wind vanes Air Pressure Rain Gauges Anemometer Psychrometer Barometers