How can weather be predicted


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How can weather be predicted

  1. 1. How can weatherbe predicted?Grade 4
  2. 2. Have you everwondered why theweather changes?
  3. 3. When a large body of air movesit causes weather changes.Air massLarge body of air.
  4. 4. Air massescan be:Hot air mass Cold air massAll of an air mass has the sametemperature and same amount ofmoisture level (amount of water inthe air).
  5. 5. Blue arrows are cold air massesRed arrows are hot air masses
  6. 6. Temperature and moisture level depend onwhere the air masses where formed.Dry airmassFormedover landWet air massFormed overoceans orseasHot airmassCome fromthe southCold airmassCome fromthe north
  7. 7. Type of weather caused by different airmasses:Cold, dryair massesCoolweather, withlittle or noprecipitationWarm, moistair massesLot ofprecipitationWarm, dryair massesWarmweather +little or noprecipitationCold, Wetair massesSnow
  8. 8. Air massesStay separateWhy?Because warm air is lighter than coldair.So, warm air masses are pushedupward and cold air masses sink.
  9. 9. Air massesmoveThe border between one air mass andthe other is called a front.
  10. 10. Air frontscan be:HotfrontColdFrontStationaryfront
  11. 11. 1) Cold FrontCold air moves under warm air.Warm air mass moves up and cools down.Water vapor condenses and moves up.It might rain or thunderstorms develop alongthe frontAs the cold air mass moves forward theweather becomes cooler.
  12. 12. 2) Warm FrontWarm air moves slides over cold air.Warm fronts moves slowly.Steady rain instead of thunderstorms.Warm fronts are followed by clear, warmweather.
  13. 13. 3) Stationary frontA front that stays in one place for many daysHappens when two air masses do not haveenough energy to move.Steady rain instead of thunderstorms.Weather along the stationary front is oftencloudy and wetThis kind of front can leave inches of snow orcause flooding.
  14. 14. Types ofclouds
  15. 15. Stratus cloudsOccuralongwarmfronts
  16. 16. Nimbostratus cloudsBringslight rainor snow
  17. 17. Cumulus cloudsCommononclear, warm days.
  18. 18. Cumulonimbus clouds(Thunderstorm clouds)Developsfromcumulusclouds.
  19. 19. Cirrus cloudsIndicatecool, fairweather.
  20. 20. Weathermaps
  21. 21. Weather maps helpyou know what theweather is like in anarea.Weather maps use symbols toshow the weather.
  22. 22. Weathermapsymbols
  23. 23. Many weather maps show temperatures.The temperature can be:Written on a map. Shown using colors.Red (Very hot)Orange (Warm)Green (Cool)Yellow (mild)Blue (Very cold)
  24. 24. L(Low air pressure)H(High air pressure)
  25. 25. In the USA the temperature unit is Fahrenheit (°F)
  26. 26. Read thefollowingweather maps.
  27. 27. Where does all the informationon a weather map come form?Weather stations
  28. 28. Some Weather instruments1) BarometerMeasures air pressure
  29. 29. 2) ThermometerMeasures air temperature
  30. 30. 3) Wind vaneShows which direction wind is moving
  31. 31. 4) AnemometerMeasures wind speed
  32. 32. 5) Rain gaugeMeasures amount of precipitation