1. Fronts and Pressure Systems

2. Review What is an air mass? What is an air mass? a large volume of air in which temperature and humidity are nearly the same in different locations over a large area. a large volume of air in which temperature and humidity are nearly the same in different locations over a large area.

3. What happens when air masses meet? Weather can change. Weather can change. New air moving into an area brings different weather. New air moving into an area brings different weather.

4. Fronts A front is a boundary between two air masses. A front is a boundary between two air masses. As one air mass pushes another, warm air at the boundary will be pushed upwards. As one air mass pushes another, warm air at the boundary will be pushed upwards. This forms clouds. This forms clouds.

5. So it forms clouds… Often weather will become cloudy or stormy when a front passes. Often weather will become cloudy or stormy when a front passes. Once the front has passed you will experience the temperature and humidity of the new air mass. Once the front has passed you will experience the temperature and humidity of the new air mass.

6. How do I know which one it is? The names tell you which way the temperature will change and which type of front it is. The names tell you which way the temperature will change and which type of front it is. Colder air comes with a cold front. Colder air comes with a cold front. Warmer air comes with a warm front. Warmer air comes with a warm front.

7. Cold Fronts When cold air moves into an area of warmer air you have a cold front. When cold air moves into an area of warmer air you have a cold front. Move quickly. Move quickly. Has a steep front edge. Has a steep front edge. Warm air rises steeply and quickly. Forms Cumulonimbus Clouds Warm air rises steeply and quickly. Forms Cumulonimbus Clouds

8. Cold Front

9. Rising Air Quickly rising warm air cools and water vapor condenses on condensation nuclei producing tall cumulonimbus clouds and usually precipitation. Quickly rising warm air cools and water vapor condenses on condensation nuclei producing tall cumulonimbus clouds and usually precipitation. After the storm the air is usually cooler and very clear. After the storm the air is usually cooler and very clear.

11. Example What would the weather be like if a cold front moved into Muncy today? What would the weather be like if a cold front moved into Muncy today?

12. And on a weather map… The blue triangles represent a cold front.

13. Review Explain a cold front. Explain a cold front. How air rises? How air rises? What cloud type forms? What cloud type forms? What type of weather follows? What type of weather follows? What do we use to show a cold front on a map? What do we use to show a cold front on a map?

14. Warm Fronts When warm air moves into an area of cooler air you have a warm front. When warm air moves into an area of cooler air you have a warm front. Moves slowly. Moves slowly. Air rises slowly. Air rises slowly. Warm air moves up and over the mass of colder air. Warm air moves up and over the mass of colder air.

16. Clouds Warm air rises slowly and water vapor condenses forming clouds. Warm air rises slowly and water vapor condenses forming clouds. There are a series of cloud types as warm fronts approach. There are a series of cloud types as warm fronts approach. 1 st – cirrus 1 st – cirrus 2 nd – altocumulus or altostratus 2 nd – altocumulus or altostratus 3 rd – stratus / nimbostratus 3 rd – stratus / nimbostratus Brings hours of steady rain or snow. Brings hours of steady rain or snow.

17. Warm Front

18. On a weather map… Red semicircles represent a warm front.

19. Review

20. High and Low Pressure Cyclone – location with the lowest pressure Anticyclone – location with highest pressure

21. Pressure High pressure rotates clockwise and outward as air moves to areas of low pressure. Low preesure rotates counterclockwise and inward then lifts upward.

23. Low Pressure System High Pressure System

24. On a weather map…

26. Activity When you are done with the power point notes open the following link and complete “Precipitation Along Fronts” scaffolding activity. When you are done with the power point notes open the following link and complete “Precipitation Along Fronts” scaffolding activity. http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/fpr.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/fpr.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/fpr.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/fpr.rxml

27. Activity 2 When you are done with the power point notes open the following link and complete “Pressure” scaffolding activity and complete all work 1-5. When you are done with the power point notes open the following link and complete “Pressure” scaffolding activity and complete all work 1-5. http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/prs.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/prs.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/prs.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/prs.rxml

28. Activity 3 When you are done with the power point notes open the following link and complete “Midlatitude Cyclone” scaffolding activity and complete questions 1-5. When you are done with the power point notes open the following link and complete “Midlatitude Cyclone” scaffolding activity and complete questions 1-5. http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/cyc.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/cyc.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/cyc.rxml http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr clm/act/cyc.rxml