7 Maritime Polar Warm, humid air masses form over tropical oceans. In summer they bring hot humid air.Gulf of Mexico, and the Atlantic OceanWinter: can bring heavy rain or snow
8 Maritime Polar Cool, humid air masses form over icy cold North Pacific Summer: brings fog, rain and cool temperatures to the West Coast
9 Continental TropicalHot dry masses form in dry Southwest and northern MexicoHot dry weather to the southern Great PlainsCovers a smaller area than other air masses
10 Continental Polar Central and Northern Canada, and Alaska Air masses bring bitterly cold weather with very low humidityWinter: Air masses bring clear, cold, dry airSummer: milder
11 How Air Masses MoveIn the US, air masses are commonly moved by the prevailing westerlies and jet streams.Prevailing Westerlies: major wind belts and push aim asses from west to east.Jet Streams: bands of high speed winds above Earth’s surfaceFronts: huge air masses collide with each other but do not mix. They have different temperatures and humidity collide. Storms and changeable weather develops.
12 Reviewcold air is dense and sinks. Warm air is less dense and rises. When they run into each other the cold air slides under the lighter air. Warmer air is pushed up.
13 Types of Fonts Colliding air masses can form 4 types of fonts: Cold fronts- move quickly and cause abrupt weather changes. After it passes, drier air moves in and brings clear skies, a shift in wind and lower temperatureWarm fronts- move slowly weather may be rainy or cloudy. After is passes through the weather is warm and humid
16 Stationary fonts- where warm and cool air meet, the water vapor in the warm air condenses into rain, snow, fog or clouds. It will stall over an area, it may bring clouds and precipitationOccluded fronts- temperature near the ground become cooler. Warm air mass is cut off. As warm air cools, it condenses and weather becomes cloudy and rain or snow may fall.
19 Cyclones Wheel Swirling center of low air pressure Cyclones and decreasing air pressure are associated with clouds, wind and precipitationWarm air in the center rises and air pressure decreasesCooler air blows towards a high pressure area
21 Anticyclones High pressure centers of dry air “highs” on a weather map. HDescending air in an anticyclone generally causes dry, clear weather.Winds spiral outward from the center and moves to areas of lower pressure.