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Snow - Saturday December 12th

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    #62
    konman
    Registered Users Posts: 234 ✭✭konman


    Carnacalla wrote: »
    What temps does it usually begin to Snow?

    Have a read of this link. Its a very good explanation of conditions needed for snow from Su Campu. Hope this helps.

    http://www.boards.ie/vbulletin/showthread.php?t=2056447334


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    #63
    Swiftly
    Closed Accounts Posts: 59 ✭✭Swiftly


    Carnacalla wrote: »
    What temps does it usually begin to Snow?

    I can't post link but this from the UK Met office

    How is snow formed?

    
    Snow is formed when temperatures are low and there is moisture - in the form of tiny ice crystals - in the atmosphere.

    When these tiny ice crystals collide they stick together in clouds to become snowflakes. If enough ice crystals stick together, they'll become heavy enough to fall to the ground.

    How cold does it have to be to snow?
    Precipitation falls as snow when the air temperature is below 2 °C. It is a myth that it needs to be below zero to snow. In fact, in this country, the heaviest snow falls tend to occur when the air temperature is between zero and 2 °C. The falling snow does begin to melt as soon as the temperature rises above freezing, but as the melting process begins, the air around the snowflake is cooled.

    If the temperature is warmer than 2 °C then the snowflake will melt and fall as sleet rather than snow, and if it's warmer still, it will be rain.

    'Wet' snow vs. 'dry' snow
    The size and make up of a snowflake depends on how many ice crystals group together and this will be determined by air temperatures. Snowflakes that fall through dry, cool air will be small, powdery snowflakes that don't stick together. This 'dry' snow is ideal for snow sports but is more likely to drift in windy weather.

    When the temperature is slightly warmer than 0 °C, the snowflakes will melt around the edges and stick together to become big, heavy flakes. This creates 'wet' snow which sticks together easily and is good for making snow men.

    
    Snowflakes
    Snowflakes are collections of ice crystals that can occur in an infinite variety of shapes and forms - including prisms, hexagonal plates or stars. Every snowflake is unique, but because they join together in a hexagonal structure they always have six sides.

    At very low temperatures snowflakes are small and their structure is simple. At higher temperatures the individual flakes may be composed of a very large number of ice crystals - making a complex star shape - and can have a diameter of several inches.

    Find out more on our page all about snowflakes.


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    #64
    weatherfiend
    Registered Users Posts: 541 ✭✭✭weatherfiend


    Swiftly wrote: »
    I can't post link but this from the UK Met office

    How is snow formed?

    
    Snow is formed when temperatures are low and there is moisture - in the form of tiny ice crystals - in the atmosphere.

    When these tiny ice crystals collide they stick together in clouds to become snowflakes. If enough ice crystals stick together, they'll become heavy enough to fall to the ground.

    How cold does it have to be to snow?
    Precipitation falls as snow when the air temperature is below 2 °C. It is a myth that it needs to be below zero to snow. In fact, in this country, the heaviest snow falls tend to occur when the air temperature is between zero and 2 °C. The falling snow does begin to melt as soon as the temperature rises above freezing, but as the melting process begins, the air around the snowflake is cooled.

    If the temperature is warmer than 2 °C then the snowflake will melt and fall as sleet rather than snow, and if it's warmer still, it will be rain.

    'Wet' snow vs. 'dry' snow
    The size and make up of a snowflake depends on how many ice crystals group together and this will be determined by air temperatures. Snowflakes that fall through dry, cool air will be small, powdery snowflakes that don't stick together. This 'dry' snow is ideal for snow sports but is more likely to drift in windy weather.

    When the temperature is slightly warmer than 0 °C, the snowflakes will melt around the edges and stick together to become big, heavy flakes. This creates 'wet' snow which sticks together easily and is good for making snow men.

    
    Snowflakes
    Snowflakes are collections of ice crystals that can occur in an infinite variety of shapes and forms - including prisms, hexagonal plates or stars. Every snowflake is unique, but because they join together in a hexagonal structure they always have six sides.

    At very low temperatures snowflakes are small and their structure is simple. At higher temperatures the individual flakes may be composed of a very large number of ice crystals - making a complex star shape - and can have a diameter of several inches.

    Find out more on our page all about snowflakes.

    That's really interesting.

    We were just discussing the snowfall on New Year's Eve 2009. We were in wexford and it was fantastic snow but we were remembering that it was powdery snow (dry snow you mention above I assume) and the kids were giving out that the snowballs wouldn't stick together long enough to lob them at each other. The difference then in November 2010 - the snowballs were brilliant...........and hard!!


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    #65
    konman
    Registered Users Posts: 234 ✭✭konman


    Swiftly wrote: »
    I can't post link but this from the UK Met office

    How is snow formed?

    
    Snow is formed when temperatures are low and there is moisture - in the form of tiny ice crystals - in the atmosphere.

    When these tiny ice crystals collide they stick together in clouds to become snowflakes. If enough ice crystals stick together, they'll become heavy enough to fall to the ground.

    How cold does it have to be to snow?
    Precipitation falls as snow when the air temperature is below 2 °C. It is a myth that it needs to be below zero to snow. In fact, in this country, the heaviest snow falls tend to occur when the air temperature is between zero and 2 °C. The falling snow does begin to melt as soon as the temperature rises above freezing, but as the melting process begins, the air around the snowflake is cooled.

    If the temperature is warmer than 2 °C then the snowflake will melt and fall as sleet rather than snow, and if it's warmer still, it will be rain.

    'Wet' snow vs. 'dry' snow
    The size and make up of a snowflake depends on how many ice crystals group together and this will be determined by air temperatures. Snowflakes that fall through dry, cool air will be small, powdery snowflakes that don't stick together. This 'dry' snow is ideal for snow sports but is more likely to drift in windy weather.

    When the temperature is slightly warmer than 0 °C, the snowflakes will melt around the edges and stick together to become big, heavy flakes. This creates 'wet' snow which sticks together easily and is good for making snow men.

    
    Snowflakes
    Snowflakes are collections of ice crystals that can occur in an infinite variety of shapes and forms - including prisms, hexagonal plates or stars. Every snowflake is unique, but because they join together in a hexagonal structure they always have six sides.

    At very low temperatures snowflakes are small and their structure is simple. At higher temperatures the individual flakes may be composed of a very large number of ice crystals - making a complex star shape - and can have a diameter of several inches.

    Find out more on our page all about snowflakes.

    There are a few more parameters than just a temp of 0-2 degrees. It was 1 degree and raining this morning in tuam as an example. Dew point and DAM are other parameters that need to be right.


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    #66
    snaps
    Registered Users Posts: 7,138 ✭✭✭snaps


    konman wrote: »
    There are a few more parameters than just a temp of 0-2 degrees. It was 1 degree and raining this morning in tuam as an example. Dew point and DAM are other parameters that need to be right.

    And usually 850hpa temps of around -8 for the Island of Ireland.


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    #67
    Oneiric 3
    Registered Users Posts: 6,235 ✭✭✭Oneiric 3


    konman wrote: »
    There are a few more parameters than just a temp of 0-2 degrees. It was 1 degree and raining this morning in tuam as an example. Dew point and DAM are other parameters that need to be right.

    Dewpoint was lowest here between 5 and 6am this morning when it hovered around 0c, rose a little thereafter. The brief wet snow blip also occurred while prep was at its heaviest so no doubt was the result of 'evaporative cooling', at least in part. Chart shows temp (red) and DP temp (dark green) for Tomb between midnight and 9am this morning.

    371546.PNG

    New Moon



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    #68
    Gaoth Laidir
    Registered Users Posts: 8,219 ✭✭✭Gaoth Laidir


    Wet-bulb temperature is key. This lies between the temperature and dewpoint, nearer to the temperature, and in general needs to be at most 0.5 °C but preferably zero or below. WBT determines the amount of evaporative cooling that can take place.

    The most important factors for snow in Ireland are these:

    ●850-1000 thickness of <1290 m
    ●500-1000 thickness of <522 dam (but less important than the 850-1000 thickness.
    ●For heavy snow, a deep saturated profile up to at least 700 hPa/-20 °C.

    Generally if these conditions are met then the others (850 hPa temp, etc.) are too.


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    #69
    cian1500ww
    Registered Users Posts: 2,904 ✭✭✭cian1500ww


    We got a surprising amount of snow this morning in South Leitrim
    2cahYPL.jpg


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    #70
    joujoujou
    Registered Users Posts: 13,499 ✭✭✭✭joujoujou
    Unregistered Users


    Sorry, I'm late. :o

    371557.jpg

    371558.jpg

    371559.jpg

    371560.jpg


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    #71
    Pretzill
    Registered Users Posts: 4,683 ✭✭✭Pretzill


    Snow still lying on hills around here (South Sligo) but just checked the temperature in the yard tonight minus 4!

    Surprised at that - there's a hoar frost and a hanging fog in the air - too cold to snow but lovely and wintery - which makes a nice change from all the wet and mud!


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    #72
    Drum Maigh Eo
    Registered Users Posts: 90 ✭✭Drum Maigh Eo


    Carnacalla wrote: »
    Any Pictures?

    Sorry for the late reply. Too few posts to upload directly or provide a link so I've put a couple on photobucket......

    s410.photobucket.com/user/mayofan77/library/


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