1. Air Masses and Fronts

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

3. 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, Pacific Brings 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 Oceans Brings 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.

4. 6.Continental Polar Air Mass: Form over central and Northern Canada and Alaska Bring 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 causes Rain and thunderstorms.

5. 11.Warm Fronts: A rapidly moving warm air mass collides with a slow moving cold air mass and it goes over the cold air mass. Causes: showers, light rain, and fog in summer – Snow in winter Brings: Warm, humid weather 12.Stationary Front: Cold and warm air masses meet but neither Has 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 is Trapped 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.

6. 15.Cyclones and decreasing air pressure are associated with Storms and precipitation. 16. Anticyclones: High Pressure centers of dry air.