Air Masses and Fronts

1. Air Masses and Fronts I. Air masses A. Defined as a huge body of air that has similar temperature, humidity and air pressure throughout. B. Will it be HOT or COLD? 1. This depends on the temperature of the region over which it forms!

2. Air Masses and Fronts a. Tropical, or warm, air masses form in the tropics and have low pressure b. Polar, or cold, air masses for north of 50o north latitude or south of 50o south latitude and will have high pressure • Will it be HUMID or DRY? 1. This depends on whether it formed over water or land. a. Maritime air masses form over water and are humid. b. Continental air masses form over land and are dry.

3. Air Masses and Fronts D. Four types of air masses in the United States and are moved FROM the west to the East by the prevailing westerlies and jet streams. 1. Maritime Tropical (mT) - warm and humid 2. Maritime Polar (mP) – cool and humid 3. Continental Tropical (cT) – warm and dry 4. Continental Polar (cP) – cool and dry

4. Air Masses and Fronts II. Fronts 1. The area where air masses meet and do not mix are called fronts. 2. Types of fronts a. Cold Front: leading edge of a cold air mass. They move quickly, so they cause abrupt weather changes that eventually bring clear skies and cooler temperatures.

5. Air Masses and Fronts b. Warm Front: leading edge of a warm air mass. Clouds, storms and rain accompany a warm front. When it passes, the weather is usually warm and humid.

6. Air Masses and Fronts c. Stationary Front: nonmoving air mass. It may bring days of clouds and precipitation. d. Occluded Front: Cold air mass overtaking a warmer air mass. Warm air cools and water vapor condenses; may cause clouds, rain or snow.

7. Air Masses and Fronts 3. Front symbols for weather map: