Air Masses and Fronts

OBJECTIVE: IDENTIFY THE MAJOR TYPES OF AIR MASSES THAT EFFECT WEATHER IN NORTH AMERICA.

1. Air Mass: A huge body of air that has similar temperature, humidity, and air pressure throughout.

2. Air masses are classified by temperature and humidity:TROPICAL, POLAR, MARITIME, AND CONTINENTAL

3. Maritime Tropical Air Mass:Forms over oceans near the tropics – Gulf of Mexico, PacificBrings Hot humid weather in summer, Heavy rain and snow in winter

4. Maritime Polar Air Mass:Forms over icy cold North Pacific and N. Atlantic OceansBrings Fog, rain and cool temperatures to the west coast.

5. Continental Tropical Air Mass:Forms only in summer over dry areas of the Southwest and Northern Mexico-Brings Hot, Dry weather to S. Great Plains.

6. Continental Polar Air Mass:Form over central and Northern Canada and AlaskaBring clear, cold, dry air to most of North America in winter and Storms in summer.

7. How air masses move: From West to East.

8. Front: The area where the air masses meet and do not mix.

9. There are 4 types of fronts – warm, cold, stationary, & Occluded.

10.Cold Front: Rapidly moving cold air mass runs into a slow Moving warm air mass pushing the warm air mass up and causesRain and thunderstorms.

11.Warm Fronts: A rapidly moving warm air mass collides witha slow moving cold air mass and it goes over the cold air mass.Causes: showers , light rain, and fog in summer – Snow in winterBrings: Warm, humid weather

12.Stationary Front: Cold and warm air masses meet but neitherHas enough force to move the other.Causes: Rain, snow, cloudy weather & fog.Brings: many days of the same.

13.Occluded Front: Most complex situation – A warm air mass isTrapped between two cold air masses. They push the warm air Above them and the two cool masses mix.

14.Cyclone: A swirling center of low air pressure – from the Greek meaning Wheel.

15.Cyclones and decreasing air pressure are associated withStorms and precipitation.

16. Anticyclones: High Pressure centers of dry air.