1. Tracking the

2. Air Masses
-Air mass-a large region of air that has nearly the same properties throughout -They form all the time, usually near the poles or the equator. -As an air mass moves, it brings weather with it.

3. Types of Air Masses in North America
-Polar dry air mass -Polar moist air mass -Tropical moist air mass -Tropical dry air mass

5. Fronts
-Front- the boundary between two air masses that have different temperatures -Fronts usually cause a change in the weather. -There can be a warm front, a cold front, or a stationary front.

6. Warm Front
-Warm front- a warm air mass pushes into a cold air mass -layers of clouds form and the cold air retreats -often brings light, steady rain

7. Cold Front
-Cold front- a cold air mass pushes under a warm air mass and forces the warm air mass upward quickly -thick clouds form -often bring stormy weather

8. Cold Front
Warm Front
-pushes into warm air
-warm air rises quickly
-rising air cools rapidly
-produce cumulonimbus clouds
-heavy rain/thunderstorms/ tornadoes
-moves toward cold air mass
-slides slowly over cold air
-gently rises
-produces wispy clouds, followed by thicker clouds
-rain or snow for several days
-brings warmer, milder weather

9. Stationary Front
-Stationary front- a boundary between air masses that are not moving -can cause rainy weather to last for days

10. Weather Map
-Shows weather conditions at a certain time and place -tell about air temperature, air pressure, precipitation, and winds -also show the location of fronts

11. Weather Map

12. Weather Map Key

13. Forecasting
-Forecast- to predict weather conditions -scientists use weather maps to make forecasts -a scientist who studies weather and what affects it is called a meteorologist

14. Forecasting
-scientists also use different technologies in forecasting -satellites take pictures of the atmosphere -computers help scientists analyze weather data and produce better maps -radar- device that uses radio waves to detect far away objects

15. Severe Weather
-Thunderstorm- a rain shower that has thunder and lightning -thunder- the booming sound made when lightning quickly heats the air around it -Tornado- a rotating column of air that touches the ground during a thunderstorm -Hurricane- a very wide storm that forms over warm water in the ocean

16. Storm Safety
-Thunderstorm -stay away from water and trees -Tornadoes -head for a sturdy shelter -Hurricanes -move inland -Always listen to instructions and follow warnings