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Study Guide
Continental Arctic (CA) | Extremely cold temperatures and very little moisture. These usually originate north of the Arctic Circle, where days of 24 hour darkness allow the air to cool to sometimes record-breaking low temperatures. |
Continental polar (CP) | Cold and dry, but not as cold as Arctic air masses.These usually form farther to the south and often dominate the weather picture across the USA during winter.Continental polar masses do form during the summer, but usually influence only the northern USA. |
Maritime polar (MP) | Cool and moist. They usually bring cloudy, damp weather to the USA. Maritime polar air masses form over the northern Atlantic and the northern Pacific oceans. They most often influence the Pacific Northwest and the Northeast. |
Maritime tropical (MT) | Maritime tropical air masses are most common across the eastern USA and originate over the warm waters of the southern Atlantic Ocean and the Gulf of Mexico.These air masses can form year round, but they are most prevalent across the USA during summer. |
Maritime tropical (MT): | Hot and very dry.They usually form over the Desert Southwest and northern Mexico during summer.They can bring record heat to the Plains and the Mississippi Valley during summer, but they usually do not make it to the East and the Southeast. |
Cold front | Forms when a cold air mass pushes under a warm air mass, forcing the warm air to rise. |
Warm Front | Forms when a moist, warm air mass slides up and over a cold air mass. |
Stationary Front | Forms when warm and cold air meet and neither air mass has the force to move the other. They remain stationary, or “standing still.” |
Occluded Front | Forms when a warm air mass gets caught between two cold air masses. The warm air mass rises as the cool air masses push and meet in the middle. |
High Pressure System | A high pressure system is a whirling mass of cool, dry air that generally brings fair weather and light winds. When viewed from above, winds spiral out of a high-pressure center in a clockwise rotation in the Northern Hemisphere. These bring sunny skies. |
Low Pressure System | A low pressure system is a whirling mass of warm, moist air that generally brings stormy weather with strong winds. When viewed from above, winds spiral into a low-pressure center in a counterclockwise rotation in the Northern Hemisphere. |