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What are the optimum conditions for snow?

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  • 16-12-2009 8:46am
    #1
    cinnamon
    Closed Accounts Posts: 226 ✭✭


    I have been glued to the other cold snap thread and Ive seen it mentioned that there a number of conditions required for snow. All I know about is dew points (that I learned from this board last year!) and precipitation.
    Can anyone provide me with a list of these conditions and explanations.
    Thanks :)


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    #2
    paulhac
    Registered Users Posts: 112 ✭✭paulhac


    Check this out . You will get a very detailed and knowledgeable explanation here courtesy of Karl on IWN.http://www.irelandsweather.com/forum/index.php/topic,572.0.html


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    #3
    cinnamon
    Closed Accounts Posts: 226 ✭✭cinnamon


    paulhac wrote: »
    Check this out . You will get a very detailed and knowledgeable explanation here courtesy of Karl on IWN.http://www.irelandsweather.com/forum/index.php/topic,572.0.html

    Thanks for that link. Very interesting read. It's amazing we have snow at all in Ireland with all those conditions :)

    I am a little confused on the Dam Thickness 528:
    This is 5280m high. With lower heights comes a colder atmosphere towards the ground. It can snow above the 528 line in some parts of the world but in Ireland this is the maximum we wish to have it at. In a severe easterly or northerly outbreak, Dam thickness can fall to 520. This is almost better for conditions favouring snowfall. But again other parameters are needed. There could be well a Dam of 528 but we could have a higher than normal surface temperature by an undercutting low pressure making for things marginal.

    I thought the air is colder the higher the altitude? Maybe he hasn't explained it that well here.


    Also, what are SST's?


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    #4
    Rougies
    Registered Users Posts: 2,677 ✭✭✭Rougies


    SST = Surface Sea Temperature


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    #5
    owenc
    Banned (with Prison Access) Posts: 5,524 ✭✭✭owenc


    cinnamon wrote: »
    Thanks for that link. Very interesting read. It's amazing we have snow at all in Ireland with all those conditions :)

    I am a little confused on the Dam Thickness 528:


    I thought the air is colder the higher the altitude? Maybe he hasn't explained it that well here.


    Also, what are SST's?


    looks good for us from tomorrow -8c 850s dp of -2c and 520 level thickness you can chek on nw it tells you everything you need to get snow you dont even need to look.


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    #6
    Su Campu
    Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    cinnamon wrote: »
    Thanks for that link. Very interesting read. It's amazing we have snow at all in Ireland with all those conditions :)

    I am a little confused on the Dam Thickness 528:


    I thought the air is colder the higher the altitude? Maybe he hasn't explained it that well here.


    Yes it's not correct. The dam thickness is not the height of the 500mbar pressure level, it's the thickness of the layer between the 500 and 1000mbar levels. This is proportional to the average virtual temperature of that layer - ie. the colder the layer, the denser the air, so the thinner the layer, and vice versa. Also, the drier the layer, the denser it is too. Adding moisture to air reduces its density.

    That's why in arctic regions the troposphere is on average only about 8kms while in the equator it's around 15kms


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