AIR MASSES & FRONTS

Air Masses

• A large body of air with similar temperature and moisture.

• Air masses form over large land or water masses and are named by where the form…over land-continental or over water-maritime and also named for where they originate from-near the tropic-tropical and from near the poles-polar

Description of air masses:

–Continental polar (cP)- cool and dry• Continental arctic-type of continental polar mass that is much

colder-forms in the arctic circle

–Continental tropical (cT)- warm (hot) and dry–Maritime polar (mP)- humid (wet) and cold;

unstable

–Maritime tropical (mT)- humid (wet) and warm; unstable

Interactive Air Mass Link

• http://www.usatoday.com/weather/tg/wamsorce/wamsorce.htm

FRONTS

• The boundaries between two air masses

• Different types of weather are brought about or left behind after the different fronts-warm, cold, stationary, or occluded

Cold Fronts

• A cold air mass is replacing a warm air mass.• Shown on a weather map by a blue line with

triangles pointing the direction in which the cool air (front) is moving.

• High air pressure is associated with cold fronts which means sunny and fair weather.

Weather Map

Warm Fronts

• A warm air mass replacing a cold (cooler) air mass.

• Shown on a weather map by a red line with half circles pointing the direction in which the warm air (front) is moving.

• Low pressure is associated with warm fronts which means cloudy, overcast, drizzly, and possibly rainy weather.

Weather Map

Comparing Warm and Cold Fronts• Cold fronts move faster than warm fronts. • The weather activity in a cold front is often

violent and happens directly at the front.• Cold fronts have sudden gusty winds high in the

air creating turbulence .• The weather activity in a warm front generally

happens before the front passes through an area. Steady rain or drizzle may fall for a long period of time.

• In a warm front the cloud formation is very low often creating situations of poor visibility.

Occluded Front

•When a warm front is trapped by (between) two cold fronts.

•Shown on a weather map by a purple line with alternating triangles and half circles pointing the direction the front is moving.

Stationary Front

• A front that is not moving or is moving very slowly.

• Shown on a weather map with alternating red semicircles pointing away from the warm air and blue triangles pointing away from the cold air.

• Stationary fronts can cause many days of dreary weather.

Weather Map

Practice & Assess

• Practice: Air Masses Over North America Worksheet

• Assessment: Air Masses Practice Quiz• http://www.quia.com/quiz/278988.html?AP_r

and=2099466504