1. Air Pressure & Fronts

2. Air Pressure The force pushing down on an area
Decreases as you go up (mountain)
Changes in pressure result in wind
Measured with a barometer
970 millibars – 1040 millibars

3. High Pressure Systems Air tends to sink Air moves outward (clockwise)
Usually clear skies
Gentle breezes
Air moves outward (clockwise)

4. Low Pressure Systems Air tends to rise
Clouds
Storms
Wind
Air moves inward (counter-clockwise)
Low pressure systems tend to have fronts associated with them

5. Air Mass
Large volume of air with consistent temperature and moisture content
Depends on where it originates
Air masses are separated by fronts

6. Fronts Cold Front  Warm Air Warm Front  Cold Air Stationary Front
Can produce short-lived thunderstorms
Warm Front  Cold Air
Long, steady rains
Stationary Front
Not much movement
Occluded Front
Thunderstorms, Rain