Chapter 25 Weather Chapter 25 The general name for a large body of air having uniform temperature and moisture content is called an air mass. During the summer continental tropical air masses flow over North America. Chapter 25 There are 4 types of air masses Continental Polar (cP) form over land that is covered by ice and snow. They bring cool or cold weather but it is usually dry. Continental Tropical (cT) form over deserts and usually bring clear, dry, and hot weather. Chapter 25 Maritime Polar (mP) form over the Northern and Southern Oceans with cool water. They usually bring snow in the winter. Maritime Tropical (mT) form over warm waters of the oceans. They usually bring heavy rain and thunderstorms. Chapter 25 Lightning causes a rapid expansion and collapse of the air that produces thunder. Chapter 25 Cold fronts are shown with only triangles Warm fronts are shown With only half circles Occluded fronts have alternating triangles and half circles on the same side Stationary fronts have alternating triangles and half circles on opposite sides Chapter 25 During the summers, air masses that form over the southwestern United States usually bring weather that is hot and clear. Warm fronts generally have a gradual slope and produce heavy precipitation over large areas. Warm fronts form when a warm air mass overtakes a cold air mass. Chapter 25 Tornados are short lived storms that have the highest wind speeds of any storm Hurricanes are the largest storms that have the most energy of any storm Chapter 25 Wind vanes measures wind direction. Satellite images made using infrared energy primarily reveal information about atmospheric temperatures Chapter 25 A liquid thermometer is shown in this diagram. Chapter 25 Satellites carry mounted cameras designed to photograph the tops of clouds in the uppermost layers of the atmosphere. A barometer is used to measure air pressure. Thermographs are used to measure temperature changes.