How Do Meteorologists Predict Weather?

Air Masses and FrontsWhat causes the weather to change?

•Air mass: a large body of air that has about the same temperature and humidity throughout it

•Can be warm or cold

•Can have a little or a lot of humidity

Air Masses and Fronts• So large only 2

or 3 can cover the U.S. at a time

• Move west to east

• Cold and warm air masses stay separate when they meet

• The line where air masses meet is called a front

What Happens When a Cold Air Mass Pushes into a Warm Air Mass?

A Cold Front

Cold air, pushes warm air upward quickly. Tall storm clouds form and may bring heavy rain , thunderstorms or in winter, a snow storm.

What Happens When a Warm Air Mass Catches up to a Cold Air Mass?

•A Warm Front

•The warm air slowly rises over the cold air forming cirrus clouds.

•These are followed by lower thicker clouds.

•A warm front may cause rain or snow for several days.

Tracking and Predicting Weather

• Keep track of humidity, air pressure, precipitation, air masses and fronts

• Speed and direction of wind help predict where air masses will move

Study Jams Air Masses and Fronts