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Weather Patterns

Weather Patterns. Air Masses. Large body of air that has properties similar to the part of Earth’s surface over which it developed. Air Pressure. Winds blow from areas of high pressure to areas of low pressure. Low Air Pressure. When air rises in low pressure areas it cools,

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Weather Patterns

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  1. Weather Patterns

  2. Air Masses • Large body of air that has properties similar to the part of Earth’s surface over which it developed

  3. Air Pressure Winds blow from areas of high pressure to areas of low pressure

  4. Low Air Pressure When air rises in low pressure areas it cools, condenses and makes clouds Air rises in areas of low pressure

  5. High Air Pressure Air sinks in high pressure areas and makes it difficult to form clouds Winds blow away from the center of high pressure

  6. FRONTS A boundary between two air masses of different density, moisture, or temperature.

  7. Cold Front • Colder air advances toward warm air • Cold air wedges under warm air • As warm air is lifted up, it cools and condenses, forming clouds • If temperature difference between air masses is large, severe weather may occur • Cold fronts are drawn on weather maps as blue lines with triangles going in the directions the front is moving

  8. Warm Front • Lighter, warmer air advances over heavier, colder air • Can lead to hours or days of wet weather • Drawn on weather maps as red lines with semicircles

  9. OCCLUDED FRONT • Three air masses of different temperatures • Warm air mass is trapped between and above two cold air masses • Drawn on weather maps as purple lines with triangles and semicircles Warm

  10. STATIONARY FRONT • Neither air mass moves • Can stay in same place for several days • Light wind, and precipitation • Drawn on weather map as alternating red and blue line with red semicircles pointing in the direction the warm air is moving and blue triangles in the direction the cold air is moving

  11. Thunderstorms • Occur in warm moist air masses along fronts • Warm air is forced upward by cool air • Air cools and condenses to form cumulonimbus clouds • Sinking cool air and strong updrafts of warm air cause strong winds • The movement of warm air and cold air can cause parts of clouds to become oppositely charged • When current flows between these regions, lightning flashes • As the extreme heat cools sound waves are given off and causes thunder

  12. Tornadoes • Wind at different heights blows in different directions and speeds called wind shears • Wind shears create a rotating column parallel to the ground • Updrafts can tilt the rotating column upward creating an area of low pressure in the form of a funnel cloud • If the funnel cloud comes in contact with the Earth’s surface it is a tornado.

  13. Hurricane • Large, swirling low-pressure system that forms over the Atlantic ocean • Winds of at least 119 km/h • Similar storms are called typhoons in the Pacific Ocean and cyclones in the Indian Ocean • The strongest hurricanes affecting North America usually form east of Africa and travel west • When hurricanes strike land, high winds, tornadoes, heavy rains and waves can cause damage

  14. Blizzards • Winter storm • Winds are 56 km/h • Temperature is -7 0 C or below • Visibility is < 400 m • Conditions consist for three hours or more

  15. Weather • 4 major air masses affect weather in the United States • An air mass has the same characteristics as the area over which it formed • Air masses, pressure systems, and fronts cause weather to change • Fair weather is associated with high pressure areas • Cloudy weather and severe weather are associated with low pressure areas

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