1. WINDS & FRONTS 1/30 – 2/3 2012

2. Prevailing Winds Larger-scale winds that blow in the same direction

3. 60 o Warmer, moist air rises and condenses as it cools. The air could travel back to 30 o or up to 90 o 0 o Warm, moist air rises and heads to the cooler upper latitudes. This air cools and water vapor condenses as it rises. This process leads to much rain at this latitude and humid conditions (equator) 30 o Air from equator, now cooler and dryer, sinks to the surface. This dry air leads to arid conditions at this latitude. Air travels across the surface, picking up moisture, up to 60 o 90 o Cooler, dryer air falls at the poles and travels across the surface to 60 o (poles)

4. All these winds DON’T travel directly north or south due to the

5. smaller-scale, unlike prevailing winds Sea Breeze – occurs during the DAY along a shore. Land is heated quicker than water so warm air rises over the land. It sinks over the water and blows back into shore Land Breeze – occurs at NIGHT when the water is warmer than the land. Warm air rises over the water and sinks over the land Local Winds

6. Air Masses A large body of air with similar temperature and humidity throughout approximately the size of an ocean or continent determined by where they are formed Continental (c) – formed over land, dry air Maritime (m) – formed over water, humid air Arctic (A) – formed at a very high latitude, very cold air Polar (P) formed at a high latitude, cold air Tropical (T) – formed at a low latitude, warm air

7. m T c T m P c Pc P

9. The point where two air masses meet Precipitation happens at the front KEY QUESTION: What are conditions ahead of & behind the FRONT?

10. Cold front shoots air up over short area Occurs when a colder air mass displaces a warmer air mass. Colder air masses move FAST and stay CLOSE TO the ground. Warmer air is forced to rise and condense, causing brief but hard rain, winds, and thunderstorms. After the front passes, winds change direction, pressure rises, and temperatures drop

11. Warm front spreads air over longer area Occurs when warmer air displaces colder air. The warmer air is forced above the colder air. As a warm front passes, there is a gradual increase in the thickness of clouds, pressure decreases and a light but constant rain persists. Once the warm front passes the rain stops, wind direction changes, pressure stabilizes, and temperatures increase

12. Occluded front /midlatitude cyclone – lots of rain over long period Occurs when a warm and a cold air mass are circling around a low pressure area. The cold air mass completely overtakes the warm air mass, thus forcing the entire warm air mass above the cold. There is usually heavy precipitation with this front.

13. http://www.youtube.com/watch?v=DkgPZMBKEIs&feature=related specific animation found at [0:42 – 2:02]