Air Masses & Fronts

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

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

How are Air Masses named? MARITIME TROPICAL MARITIME POLAR CONTINENTAL TROPICAL CONTINENTAL POLAR

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

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

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 BrainPop video on “Weather” and write down 2 things you learned.

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

Compare/Contrast Chart - Types of Fronts FrontHow it FormsType of Weather Cold Front 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 FrontHow it FormsType of Weather Cold Front 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 FrontA 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 FrontHow it FormsType of Weather Cold Front 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 FrontA warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary FrontCold 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 FrontHow it FormsType of Weather Cold Front 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 FrontA warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary FrontCold and warm air meet, but neither can move the other. Creates “standoff” Rain, snow, clouds, or fog that may last for days. Occluded FrontA 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) Stationary Front Occluded Front Warm Front Cold FrontH High Pressure L Low Pressure Precipitation

Temperature Map

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

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