1. AIR MASSES AND FRONTS

2. AIR MASSES A section of air that has similar characteristics (temperature, weather, humidity, etc.) throughout it from the area which it formed over. Types of Air Masses  Continental Arctic – very cold, dry cA  Continental Polar – cold, dry cP  Maritime Polar – cold, moist mP  Continental Tropical – hot, dry cT  Maritime Tropical – warm, moist mT

3. FRONTS A change in weather from one day to the next is due to the movement of air masses. Air masses with different temperatures and humidity do not mix well together! Where two air masses meet a squall line often forms (line of heavy thunderstorms). Front – boundary between any two air masses of different densities

4. WARM FRONTS Forms when a warm air mass meets and replaces a cold air mass Cirrus clouds often signal the advance of a warm front Nimbostratus clouds often produce steady day-long rain

5. WARM FRONT

6. COLD FRONTS Forms when a cold air mass meets and replaces a warm air mass Cumulus and cumulonimbus clouds form & produce heavy rain and thunderstorms The leading edge of a cold front is much steeper than a warm front

7. COLD FRONTS

8. STATIONARY FRONTS Fronts that do not move forward are called stationary fronts Sometimes pressure differences can cause a warm or cold front to stop moving forward Light wind and precipitation all along this type of front These can remain in place for several days

9. OCCLUDED FRONTS If a cold front catches up to a warm front the result is an occluded front Two cold air masses meet and force a warmer air mass between them to rise Strong winds and heavy precipitation may develop

10. OCCLUDED FRONT

11. AT EACH FRONTAL BOUNDARY YOU WILL FIND: Low Pressure – because along all fronts warm air is being forced upward, cooled to its dew point, and condensing to form clouds Precipitation is found at most frontal boundaries!