Air Masses & Fronts

What is an AIR MASS? WARM COLD WET DRY An air mass is a huge body of air that influences weather. Scientists classify air masses based on: TEMPERATURE and HUMIDITY WARM COLD WET DRY

Air Masses are named based on where they FORMED… = TROPICAL = POLAR = MARITIME (means sea… wet) = CONTINENTAL (means land… dry) WARM COLD WET DRY

How are Air Masses named? WET DRY MARITIME TROPICAL CONTINENTAL TROPICAL WARM MARITIME POLAR CONTINENTAL POLAR COLD

North American Air Masses MARITIME POLAR CONTINENTAL POLAR MARITIME POLAR MARITIME TROPICAL MARITIME TROPICAL CONTINENTAL TROPICAL

How do these air masses move? MARITIME POLAR CONTINENTAL POLAR MARITIME POLAR Jet Stream That’s why weather generally moves WEST to EAST in the U.S. Jet Stream Prevailing Westerlies Prevailing Westerlies MARITIME TROPICAL MARITIME TROPICAL CONTINENTAL TROPICAL

What happens when air masses meet? Air masses don’t mix easily. The line between air masses is called a front.

COLD FRONTS

WARM FRONTS

Watch the Met Office video on “Air Masses” and write down 2 things you learned. http://www.youtube.com/watch?v=G7Ewqm0YHUI

Use your textbook (pg.133-135) to fill out the chart.

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front Stationary Front Occluded Front

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front A warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary Front Occluded Front

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front A warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary Front Cold and warm air meet, but neither can move the other. Creates “standoff” Rain, snow, clouds, or fog that may last for days. Occluded Front

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front A warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary Front Cold and warm air meet, but neither can move the other. Creates “standoff” Rain, snow, clouds, or fog that may last for days. Occluded Front A warm air mass is caught between 2 cooler air masses. Warm air mass is pushed up. Temperature gets cooler. Clouds and rain may form.

Surface Map (Fronts & Precipitation) Warm Front H High Pressure Occluded Front L Low Pressure Cold Front Stationary Front

Temperature Map

H L What will happen to the weather in Little Rock? Which direction is the warm front moving? L H 12°C 19°C 14°C 20°C 25°C Tuesday Weather Little Rock, AR Clouds & Rain Warmer = 21°C Wednesday Weather Little Rock, AR Partly Sunny Warmer = 26°C Monday Weather Little Rock, AR Sun & clear skies Cool = 15°C 28°C 21°C 26°C 15°C 30°C Warm Front H High Pressure Occluded Front L Low Pressure Cold Front Stationary Front

Which direction is the cold front moving? What will happen to the weather in Nashville? 10°C 8°C 18°C 10°C 11°C Thursday Weather Nashville, TN Partly Sunny Warm = 20°C Saturday Weather Nashville, TN Sunny Cool = 10°C Friday Weather Nashville, TN Thunderstorms Cooler = 15°C 10°C 20°C 15°C Warm Front H High Pressure Occluded Front L Low Pressure Cold Front Stationary Front