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Why there is no rain when clouds are scattered?

  1. Jul 24, 2015 #1
    Raining only occurs when there are dense clouds in the sky, when they are scattered the raining is stopped, why?
     
  2. jcsd
  3. Jul 24, 2015 #2

    Borg

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    In many clouds, it actually is raining. It's just that there isn't much rain falling and it evaporates before it gets to the ground. In a larger, denser cloud, the rain reaches the ground before it has a chance to evaporate.
     
  4. Jul 24, 2015 #3

    russ_watters

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    Rain comes from clouds. Clouds are opaque because they contain condensed water dropplets.
     
  5. Jul 24, 2015 #4

    rcgldr

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    This is not always true. When I lived in Houston Texas, there could be a medium sized single dark cloud pouring rain as it crossed over you, with otherwise clear skies. As the cloud was approaching or leaving, you could see a "wall" of water coming down from the leading or trailing edge of the cloud.
     
  6. Jul 24, 2015 #5

    russ_watters

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    Maybe I misunderstood the question. If he was asking why rain is more likely on very cloudy days than moderately cloudy days, it is because a very cloudy day has more moisture in the sky. On a moderately cloudy day, a cloud has an easier opportunity to dissipate instead of raining.

    But as per the above, certain weather patterns can cause rain from lone clouds, particularly pop-up thunderstorms.
     
  7. Jul 25, 2015 #6

    davenn

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    no, not necessarily .... you can have almost 100% humidity on a sunny summer day and not a cloud in sight. ie. the air/atmosphere is very moisture laden

    its the concentration of moisture per unit of volume combined with temperature that will cause condensation and then precipitation
     
  8. Jul 25, 2015 #7

    russ_watters

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    A cloud is at 100% RH (or greater), which is greater than "almost 100%.
    Agreed.
     
  9. Jul 25, 2015 #8

    davenn

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    just pointing out that you can have 100% humidity on a couldless day
     
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