8 CLOUDSAs the Sun warms the land, clouds form when moisture laden warm air rises and expands.Above the surface this air reaches an altitude where the temperature is below the dew point.It then cools and condenses and cloud droplets form on condensation nuclei.
9 PRECIPITATIONThe falling of any form of water from the air to Earth’s surface.Occurs when cloud droplets grow into drops heavy enough to fall to Earth.Type of precipitation depends on temperature.
10 AIR MASSESMuch of the weather in the U.S. is a result of the invasion of air masses.An air mass is a large body of air with similar characteristics of air pressure, temperature and moisture.
12 Characteristics of Air Masses Air masses that form over land (continental) are dry.If they form in Canada they are also cold. (cP)If they form in the Southwest or Mexico they are warm. (cT)Air masses that form over water are moist.If they form off the coast of Canada they are also cold. (mP)If they form in the Gulf of Mexico they are also warm. (mT)
14 Cold Front Cold air is advancing and replacing warm air Cold fronts are steeper and move faster than warm frontsThe air rises upward rapidly forming cumulonimbus cloudsHeavy precipitation and thunderstorms which start and end quickly are associated with cold frontsWhen the front passes the air is cooler and dryer.
17 Warm Front Warm air is advancing and replacing cold air. Warm fronts move slower; Warm fronts have a gentle slope.Warm air may travel 1,000 km before rising 2 or 3 km.Warmer temperature follow the passing of a warm front.
20 Highs and LowsHigh pressure systems are associated with fair weather Winds blow clockwise and out.Low pressure systems are associated with stormy weather. Winds blow counterclockwise and in.
21 Occluded FrontA cold front is advancing and combining with a warm front.Warm air is lifted above the surface between cold and cool air.Occluded fronts move the slowest of all (20 mph).
22 Occluded FrontPrecipitation occurs for about 400 miles, most of which is in front of the frontal boundaryCool air is in front, as warm air is forced up by cold air which follows the passing occluded front
24 Stationary FrontA stationary front is a boundary between two different air masses, neither of which is strong enough to replace the other. When a warm or cold front stops moving, it becomes a stationary front.
26 Why does it rain on one side of a mountain range? Orographic precipitation - precipitation generated by a forced upward movement of air upon encountering mountains.Upon ascent, the moisture laden air that is being lifted will expand and cool and clouds form.More cooling causes precipitation.A wetter climateprevails on the windward side of a mountain.Drier air is left on the descending, generally warming, leeward sidewhere a rain shadow is formed.LeewardWindward
27 Cortlandt Manor – Average Annual Precipitation is 52 in.