Weather patterns


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Weather patterns

  1. 1. Weather Patterns
  2. 2. Weather Patterns <ul><li>Constant movement of air and moisture change the atmosphere </li></ul><ul><li>This is related to the development and movement of air masses </li></ul><ul><ul><li>Air Mass: large body of air with the same properties as the surface it develops over </li></ul></ul>
  3. 3. Air Masses <ul><li>Where the air mass develops will give it it’s characteristics. </li></ul><ul><li>Over water, the air will be moist and over land it will be dry </li></ul>
  4. 4. Pressure Systems <ul><li>Molecules push down from above, creating atmospheric pressure </li></ul>
  5. 5. Pressure Systems <ul><ul><li>Variation in atmospheric pressure determines the weather </li></ul></ul><ul><ul><ul><li>Areas of high pressure = descending colder air </li></ul></ul></ul><ul><ul><ul><ul><li>Sinking high pressure air makes it more difficult for air to rise and clouds to form </li></ul></ul></ul></ul><ul><ul><ul><ul><li>High pressure = good weather </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Low pressure = clouds </li></ul></ul></ul></ul>
  6. 6. Pressure Systems
  7. 7. Fronts <ul><li>Front: a boundary between two different air masses </li></ul><ul><ul><li>Storms and precipitation occur here </li></ul></ul><ul><ul><li>Air in a front will move from high pressure to low pressure </li></ul></ul><ul><ul><ul><li>When two air masses with different characterizations meet, they do not blend </li></ul></ul></ul>
  8. 8. When Air Masses Have Different Characteristics <ul><li>The cold air mass will move under the warm air mass and the warm air will rise and winds begin </li></ul><ul><li>Winds blow from high pressured air to low pressured air </li></ul>
  9. 9. Four Types Of Fronts <ul><li>Warm </li></ul><ul><ul><li>Develop when a less dense warm air mass slides over departing cold air mass </li></ul></ul><ul><li>Cold </li></ul><ul><ul><li>Cold air mass moves under a warm air mass and pushes it along a steep front </li></ul></ul><ul><ul><li>Move at twice the speed of a warm front </li></ul></ul><ul><ul><li>Creates a narrow band of violent storms </li></ul></ul><ul><li>Occluded </li></ul><ul><ul><li>Result of two cool air masses merging, and forcing warm air between them to rise </li></ul></ul><ul><ul><li>May cause strong winds and heavy precipitation </li></ul></ul><ul><li>Stationary </li></ul><ul><ul><li>Pressure differences cause a warm or cold front to stop moving </li></ul></ul><ul><ul><ul><li>May stay in the same place for several days </li></ul></ul></ul><ul><ul><ul><li>Causes light wind and precipitation </li></ul></ul></ul>
  10. 10. Severe Weather <ul><li>These types of weather pose a danger to people and animals </li></ul><ul><ul><li>They include: </li></ul></ul><ul><ul><ul><li>Blizzards </li></ul></ul></ul><ul><ul><ul><li>Thunderstorms </li></ul></ul></ul><ul><ul><ul><li>Tornadoes </li></ul></ul></ul><ul><ul><ul><li>Hurricanes </li></ul></ul></ul>
  11. 11. A Thunderstorm <ul><li>Air speed can reach 89km per hour </li></ul><ul><li>Occurs inside warm moist air masses and at fronts </li></ul><ul><li>Downdrafts- </li></ul><ul><ul><li>Raindrops collide with other droplets and grow larger </li></ul></ul><ul><ul><li>Heavy raindrops fall, dragging down air </li></ul></ul><ul><ul><li>This causes downdrafts, which make strong winds </li></ul></ul>
  12. 12. <ul><ul><li>Lightning </li></ul></ul><ul><ul><ul><li>Rapid uplift of air builds electric charge in clouds </li></ul></ul></ul><ul><ul><ul><li>Currents of opposite electric charge flowing in between regions makes lightning flash </li></ul></ul></ul><ul><ul><ul><li>Can leap cloud to cloud or cloud to earth </li></ul></ul></ul><ul><ul><li>Thunder </li></ul></ul><ul><ul><ul><li>Lightning rapidly heats air around it, the air expands and molecules crash into eachother </li></ul></ul></ul><ul><ul><ul><ul><li>Can reach 5x the temperature of the surface of the sun </li></ul></ul></ul></ul>
  13. 13. Tornadoes <ul><li>Tornado – violent, whirling wind, which moves in a narrow path over land. </li></ul><ul><li>Wind shear- difference in wind direction and speed </li></ul><ul><ul><li>Strong updraft will tilt wind shear and produce rotation inside </li></ul></ul><ul><ul><ul><li>Funnel cloud will appear </li></ul></ul></ul><ul><ul><ul><li>Can go up to 500km per hour </li></ul></ul></ul><ul><ul><ul><li>Most occur in United States </li></ul></ul></ul>
  14. 14. Hurricane <ul><li>Most powerful storm </li></ul><ul><li>Hurricane – large, swirling, low pressure system that forms over tropical oceans </li></ul><ul><ul><li>Turns heat energy in ocean into wind </li></ul></ul><ul><ul><ul><li>Must be 120km per hour to be classified as hurricane </li></ul></ul></ul><ul><ul><ul><li>Similar to low pressure systems on land but stronger </li></ul></ul></ul>
  15. 15. Section Wrap Up <ul><li>Why do high pressure areas usually have clear skies? </li></ul><ul><li>Explain how a tornado develops from a thunder storm. </li></ul><ul><li>How do two fronts form at a low pressure area? Which would bring the most severe weather? </li></ul>