Weather Lesson Seven Air Masses and Fronts AIR
- Slides: 30
Weather Lesson Seven Air Masses and Fronts
AIR MASSES • Large bodies of air in the troposphere with similar temperature, moisture and pressure characteristics. • Forms over large areas called source regions. • Air mass stays over an area for a while to pick up characteristics of that region.
AIR MASS SOURCE REGIONS 1. POLAR (P) - cool air from the north (Canada or Arctic). 2. TROPICAL (T) - warm air from the south. 3. CONTINENTAL (c) - air mass formed over land - DRY. 4. MARITIME (m) - air mass formed over water - MOIST.
m c P c. T - dry and warm c. P - dry and cold m. T - moist and warm m. P - moist and cold T
m. P c. A m. P c. T m. T
FRONTS • The boundary between two air mass. • Little mixing of air occurs at fronts. • Unstableness of fronts is the cause of precipitation. • 4 types of fronts and they are. . .
COLD FRONT • The boundary between an advancing air mass pushing a warmer air mass. • Underlying cold air pushes warm up and over like a plow. • A fast moving front. • Symbol used on maps is
WARM FRONT • The boundary between an advancing warm air mass on a retreating wedge of a cold air mass. • Warm air rises up and over as its advances because it is less dense. • A slow moving front. • Symbol used on maps is
OCCLUDED FRONT • Occurs when a cold front overtakes a warm front and pushes the warm air between them up off the ground. • Symbol used on maps is
STATIONARY FRONT • Boundary between two adjacent air masses of different characteristics remaining in approximately the same position. • Symbol used on maps is
Symbols point in the direction the air mass is moving.
WAVE CYCLONE • The typical pattern of storms (or low pressure systems) as they travel across the United States. • Storms have a low pressure center with a wedge of a cold front and a warm front extending from the center.
STORM TRACKS • Low pressure storms generally track (move) to the east (or northeast) across the United States. • Due to the wind belt in which the United States is located.
WEATHER PREDICTION • Weather prediction is based on probability. • A few days predictions are more accurate and reliable than long term predictions. • Computer analysis and satellite images have improved forecasting in recent years.