1. FRONTS AND AIR MASSES (also the 6 important cloud types)

2. Cumulus Clouds Description – Thick and puffy and usually white Altitude – usually below 2000m Loc. in troposphere – low Composition – Water droplets Name meaning – heap Weather – fair weather

3. Stratus Clouds Description – Thin, flat, gray, and often look a single sheet of clouds Altitude – usually less than 2000m Loc. in troposphere – low Composition – water droplets Name meaning – layer Weather – light rain/drizzle

4. Cirrus Description – Thin, white and feathery Altitude – above 6000m Loc. in troposphere – high Composition – ice crystals Name meaning – curl Weather – none

5. Cumulonimbus Clouds Description – large and towering, white to dark gray, flat anvil-shaped top Altitude – from 1000m – 12000m Loc. in troposphere – low, extending high Composition – water droplets, ice crystals at high altitudes Name meaning – cumulus=heap, nimbus=rain Weather – rain, hail, thunderstorms, tornadoes

6. Nimbostratus Clouds Description – dark, thick, and gray Altitude – from 0m-3000m Loc. in troposphere – low to middle Composition – usually water droplets, but may have ice crystals Name meaning – nimbus=rain, stratus=layer Weather – rain/snow

7. Fog Description – thick, gray Altitude – ground level Loc. in troposphere – low Composition – water droplets

8. Air Masses An air mass is a large volume of air in which the temperature and moisture content are nearly the same throughout When air stays over a region for many days, the air gradually takes on the characteristics of the land or water beneath it When they move, they bring these characteristics with it Air masses can change temperature and humidity when they move to a new area

9. Fronts A front is a boundary between 2 air masses Fronts are formed when 1 air mass runs into another air mass Density differences between the 2 air masses keep them from mixing Cool air masses are denser than warm air masses The type of front that forms depends upon the temperature and moisture content of the air masses, and how they move in relation to each other They cause weather changes as they pass

10. Cold Front Marked on a map with a blue line and blue triangles pointing towards the warm air. Cold air mass pushes the warm air mass up If the warm air mass is moist, clouds will form Associated with cumulus and cumulonimbus clouds Produce short-lived showers, thunderstorms or heavy snow. Cooler, drier weather follows a cold front

11. Cold Front

12. Warm Front Marked on a map by a red line with red semi-circles pointed towards the cool air A warm air mass rises over a retreating cold air mass causing its moisture to condense into clouds Very commonly produce stratus type clouds Overcast skies, fog, and light rain or snow May also produce cirrus, cumulonimbus, and stratocumulus clouds Followed by warm clear weather

13. Warm Front

14. Short Video on Cold and Warm Fronts https://www.youtube.com/watch?v=huKYKykjcm0

15. Stationary Front Marked by alternating blue lines & blue triangles (pointed in the direction of the warmer air) and red lines & red semi- circles (pointed in the direction of the cooler air) A cold air mass and a warm air mass are touching, but not enough wind for either to move Not much movement along the front Can be clear, but can cause many days of bad weather

16. Stationary Front

17. Low Pressure System Air in a low pressure area rises As the air rises, it cools, reaches its dew point, and clouds form Low pressure systems often occur near the boundary between warm and cold air masses Causes rainy conditions Counter-clockwise motion Remember Low pressure means Lousy weather

18. High Pressure System Air is sinking and moving outward Sinking air is denser, so the pressure is higher As the air sinks, it warms and relative humidity drops Clouds often disappear High pressure systems usually bring clear skies and gentle breezes Clockwise motion Remember High pressure is Happy weather

19. Fronts on the Map

20. Air Masses (air masses activity)

21. Types of Air Masses Continental Polar, “cold and dry” Originates closer to the Poles over land- locked regions. Continental Tropical, “warm and dry” Originates closer to the Tropics over land- locked regions. Maritime Polar, “cold and damp” Originates closer to the Poles over water. Maritime Tropical, “warm and humid” Originates closer to the Tropics over water.