Weather Fronts and Storms

Air Mass - large body of air in which temperature and humidity are the same. forms when air over a large region of Earth sits in one place for many days. 2. Air takes on characteristics of the land below it. example: cold land - cold air mass wet land - moist air mass hot desert - dry, hot air

1st word in an air mass's name tells about the moisture in the air mass. example: continental - over land, dry maritime - over water, moist 2nd word tells temperature example: tropical - formed near equator, warm; polar - far from equator, cold

Air masses travel away from where they form They move with the global wind patterns. Air masses can also change characteristics depending on the land they are moving over. Weather changes where air masses meet Front - boundary between air masses (different fronts produce different weather)

Cold Fronts 1. cold dense air pushes warmer air up 2. cold fronts move quickly 3. make brief heavy storms because water vapor in warm air condenses as it rises.

Warm Fronts 1. Warm air mass pushes colder air 2. Moves slowly 3. Warm air moves gradually up and over a mass of denser & colder air. 4. Moisture in warm air condenses all along the sloping front. 5. Brings hours of steady rain or snow.

Stationary Front 1. Occurs when a cold or warm front stops moving. 2. Two air masses push against each other without moving 3. When the front starts moving it becomes either a warm or cold front depending which air mass (warm or cold) moves first. cold mass - cold front warm mass - warm front

Occluded front An occluded front occurs when one front overtakes another. Occluded fronts are common in low-pressure systems.

Pressure Systems High Pressure Systems: Forms when air moves all the way around a high pressure center. High pressure systems bring clear skies and calm air or gentle breezes.   Low Pressure Systems: A large weather system that surrounds a center of low pressure (air moving up). Cools and condenses creating clouds (moves counter clockwise).