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Guide to...........DAM lines


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  • Location: Aviemore
  • Location: Aviemore

    A dam line is basically the height that you would have to go up to before the pressure falls to 500hPa.

    From a typical 500hPa chart, the best way to work out the 1000-500 thickness is:

    (1000-SLP) + 500hPa height


    SLP - Sea Level Pressure

    And the 500hPa height can be found by using the scale on the right hand side of the chart.


    Basically, all we need to worry about are the actual figures: the main figures to look for in the UK are:

    528DAM and below for an increasing chance of seeing snowfall, preferable values of 522 and below.

    546DAM tends to be associated with the mild and wet conditions in winter - so isn't very popular! In the summer this line is usually close to the northwest of the country.

    564DAM and above is usually found with a very warm airmass in summer, and most often in a Spanish plume affair. Very warm or hot conditions are likely.

    Usually we don't see much above 570DAM or much below 515DAM in the UK.

    Originally posted on UKww forum by Paul B (copied here with their permission)


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