6.ESS2.6: Explain how relationships between the movement and interactions of air masses, high and low-pressure systems, and frontal boundaries result in weather conditions and severe storms.

AIR MASS &

AIR FRONTS

An air mass is an extremely large body of air that is fairly similar in any horizontal direction and shares properties of temperatureand moisture content at any given altitude.

AIR MASS

Air masses can cover hundreds of thousands of square miles.

The longer the air mass stays over its source region, the more likely it will acquire the properties of the surface below.

AIR MASS

1. Polar latitudes (P) - located 60° north and south toward the poles

2. Tropical latitudes (T) - located within about 25 degrees of the equator

3. Continental (c) - located over large land masses--dry

4. Marine (m) - located over the oceans--moist

4 GENERAL AIR MASS CLASSIFICATIONS

4 GENERAL AIR MASS CLASSIFICATIONS

A front is defined as the transition zone between two air masses of different density.

The differences in density are most often caused by temperature differences or air masses with a different humidity as well.

AIR FRONTS

1. Cold Front

2. Warm Front

3. Stationary Front

4. Occluded Front

FOUR TYPES OF AIR FRONTS

A cold front is defined as the transition zone where a cold air mass is replacing a warmer air mass.

Cold fronts generally move from northwest to southeast.

The air behind a cold front is noticeably colderand drier than the air ahead of it.

COLD FRONTS

COLD FRONTS

A cold front is represented by a solid line with triangles along the front pointing towards the direction of movement.

COLD FRONTS

COLD FRONTS

A warm front is defined as the transition zone where a warm air mass is replacing a cold air mass.

Warm fronts generally move from southwest to northeast.

The air behind a warm front is warmer and more moist than the air ahead of it.

WARM FRONTS

WARM FRONTS

A warm front is represented by a solid line with semicircles pointing in the direction of movement.

WARM FRONTS

WARM FRONTS

When two air masses come together but neither can move the other, the boundary between them is referred to as a stationaryfront.

It is difficult for meteorologists to predict the weather along a stationary front, though it often resembles that of a warm front.

STATIONARY FRONTS

STATIONARY FRONTS

A stationary front is represented by a solid line with semicircles pointing in one direction and triangles pointing in the other direction.

STATIONARY FRONTS

STATIONARY FRONTS

When a cold front overtakes and pushes a warm front up into the air, trapping it away from the ground.

OCCLUDED FRONTS

OCCLUDED FRONTS

An occluded front is represented by a solid line with alternating triangles and semicircles pointing the direction the front is moving.

OCCLUDED FRONTS

OCCLUDED FRONTS

FRONTS IN ACTION