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Thread: Weather forecasts

  1. #1 Weather forecasts 
    Forum Professor WVBIG's Avatar
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    Why are weather forecasts so innacurate? With all the instruments involved, they should never be wrong. But they are almost always wrong


    Steven
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  3. #2  
    WYSIWYG Moderator marnixR's Avatar
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    depends on how accurate you want your forecasts

    if the weather forecast says that there's a 50% chance you'll have rain today in the Cardiff area, then i'd make sure to take an umbrella with me

    however if you want to know whether Cardiff Bay will have a rain shower at 4.15pm then that's beyond the accuracy that can be guaranteed - even small variations in the speed of weather systems, or a slight deviation to the path it takes will throw your forecast off if you look in too much detail

    in general however, i find that a 24-hour forecast gives a fair reflection of the day to come


    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  4. #3  
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    By most objective measurements weather forecast are accurate to about 72 hours....sometimes longer sometimes shorter depending on the circumstances. We just tend to notice and remember the ruined softball games and picnics than the more numerous times we stayed inside writing forum post because of a forecast calling for rain.
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  5. #4  
    Forum Professor WVBIG's Avatar
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    Well for example. Last Monday & today were both suppose to be beautiful days & there was enough rain last Monday to cause flooding & we had rain & thundershowers today. Last Friday, Friday night, & Saturday in the AM we were suppose to get heavy downpours of rain & thunderstorms. We didn't get a drop of rain during the period
    Steven
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  6. #5  
    WYSIWYG Moderator marnixR's Avatar
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    sometimes a high pressure system may remain strong for longer than envisaged, which might then mean that a weather system gets pushed from its predicted path, or delayed, so that instead of getting the rain today, you're getting it tomorrow, or someone north of you gets the rain that they thought you would get

    small variations in initial conditions can have a large enough effect to make a difference on a very local scale, even though the overall picture remains true
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  7. #6  
    Forum Professor WVBIG's Avatar
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    Quote Originally Posted by marnixR
    sometimes a high pressure system may remain strong for longer than envisaged, which might then mean that a weather system gets pushed from its predicted path, or delayed, so that instead of getting the rain today, you're getting it tomorrow, or someone north of you gets the rain that they thought you would get

    small variations in initial conditions can have a large enough effect to make a difference on a very local scale, even though the overall picture remains true
    There are no instruments to determine how long a high pressure swystem will remain strong?
    Steven
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  8. #7  
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by WVBIG
    There are no instruments to determine how long a high pressure swystem will remain strong?
    In general there are no instruments that can measure the future.
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    Forum Professor WVBIG's Avatar
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    Quote Originally Posted by John Galt
    Quote Originally Posted by WVBIG
    There are no instruments to determine how long a high pressure swystem will remain strong?
    In general there are no instruments that can measure the future.
    Ok. I thought a system remained strong until it encountered another system. I think I understand why forecasts aren't more accurate now. Thanks
    Steven
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  10. #9  
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    Quote Originally Posted by WVBIG
    There are no instruments to determine how long a high pressure swystem will remain strong?
    Models. Most are tuned to trend towards climatology after about 5 days, which is about the limit of their accuracy.
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