Slide 1

Air Mass, Fronts and Local WEATHERAIR MASSES

Large body of air with similar temperature and moisture characteristics is an AIR MASS.

Air masses eventually move with prevailing winds and collide forming weather patterns.

Classification:Continental or maritime formed over land or waterPolar or tropical cold or warm

Weather forecasting is determining air mass characteristics and their movement.

FRONTS:Edge where two different air masses collide. Frontal boundary can be 1-100 km wide.

Front is both horizontal (across) and vertical (up).

1. Stationary Front

Two air masses next to each other but little/no movement.Weather is usually very stable - nothing severe.

2. Cold FrontsWarm, moist air mass, replaced by colder, drier air mass.Warm air is lifted up and over approaching cold air.

At the cold front:Occurs quicklysharp temperature change, moisture change, wind shift Produces high altitude, anvil shaped cumulonimbus clouds.can get intense showers/thunderstorms

3. Warm FrontsColder, drier air mass, replaced by warm, moist air mass.

At the warm front:Occur graduallyLots of various cloud types. A much longer slope than for cold fronts. Wide-spread precipitation for long periods.

Occluded Fronts4. Occluded Fronts (Occlusion)A new fast moving cold front catches up to a slow moving warm front.

Warm occlusion:Cold air in the fast front is WARMER than the cold air in the first front.

New cooler air runs up the colder air pushing the warm air in front and up.A variety of precipitation and cloud types formed.Long periods of heavy rains and strong wind changes.

Warm occlusion

Warm occlusion17