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FI Charts ( T120+ onwards) Autumn 2020 **READ MOD NOTE IN FIRST POST**



  • Banned (with Prison Access) Posts: 2,254 ✭✭✭Nqp15hhu

    You can still get cold weather with snow from the NW. It just requires colder atmospheric parameters than typical, due to a moistening of the air column.

  • Moderators, Science, Health & Environment Moderators Posts: 11,511 Mod ✭✭✭✭Meteorite58

    Current charts to me looking like a good taste of winter from the middle of the week, certainly cold with a mix of rain, hail and sleet to lower levels, possibly snow on mountain tops, more so the NW, W, SW. Could be fair bit of convection coming in of the Atlantic so wondering if we might get a few rumbles also around the coasts. ECM showing very windy on the coasts next Saturday , could be pronounced wind chill. Some very cold nights now showing up in parts, icy roads might be a feature. Looks like we will have LP close by Thurs to Sat with the center sinking down over the UK and keeping the pressure low over us also. I have observed getting snow / wet snow when the pressure is low even with it not being very cold in the mid levels, certainly not the powdery type and might not last long but can settle on hilly terrain for a time so it is of interest to me to see if anything comes of it or not. A good few days to sharpen up on brining all he parameters together, fine tuning the forecasting skills !!

    UKMO chart for Thurs showing the 528dam line well below Ireland.



    Friday is the pick of the ECM cold charts atm.


  • Banned (with Prison Access) Posts: 2,254 ✭✭✭Nqp15hhu

    Lower atmospheric pressure at the surface (under 1000 hPa) results in a “lower” 500hPa and 850hPa level (as the surface pressure is lower). So the 850hPa temperature is not measured at 5,000 feet in a scenario with a sea level pressure of under 1000hPa.

    Hence the snow at low levels with warmer 850 hPa.

    For example, with 983hPa:
    1000-850 = 150x10 =1500m

    983-850 = 133 x10 = 1330m

    This is because 850hPa measures the temperature at the altitude at which the air pressure is 850hPa which does vary and is not always 5000 feet.

    On Friday, the 850hPa temperature is -4c at 1350 metres/4,400 feet.

    So the freezing level will be around 700 metres.

    On Thursday, it is -5c at 1420 metres in Ulster.. meanings a freezing level of 500-600 metres.

  • Banned (with Prison Access) Posts: 2,254 ✭✭✭Nqp15hhu

    Anyway having looked at the Icon, it would appear that it could snow in any showers early Thursday from Dublin northwards. The freezing level is below 500 metres from 7am and dew points are approaching freezing.

  • Registered Users Posts: 6,647 ✭✭✭pauldry

    The reason I say Christmas will be mild is I've looked at charts every day for weeks. Even days ago the cold at start of December has trended but so too has fantasy mild after. Also in previous cold spells bar 2010 it gets mild after predominantly. So that's my hunch. A cold possibly snowy at least for one morning in the Northwest and some other areas start to December then mild moist Southwesterlies or Westerlies till Christmas

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  • Registered Users Posts: 929 ✭✭✭snowstorm445

    I'm going to be arriving back from Belgium next weekend to self-isolate before Christmas. I know it's 2020, but after all the pandemic-related drama about travelling this year, it would be very poor form if it was snow of all things that gets this flight cancelled lol :pac:

  • Registered Users Posts: 15,677 ✭✭✭✭nacho libre

    It's interesting that the UKMO long range had this cold spell flagged a couple of weeks ago. Hopefully we'll get some snow out of it at lower levels, with possible night time accumulations, but mountainyman is the most likely person to see it.
    As regards Christmas, while the UKMO don't suggest a beast from the east, it may not be mild south westerlies all the time either. There maybe periods of cold northwesterlies- it may not be great for those wanting a siberian onslaught, but some parts of the country could see wet snow at times in such a set up.

  • Registered Users Posts: 591 ✭✭✭Captain Snow

    Looks like we have a SHP setting up over scandinavia.

    And Deep cold ready to tap into.


    xA6PM8B.png Gavs last 13th winter Update.

  • Moderators, Science, Health & Environment Moderators Posts: 11,511 Mod ✭✭✭✭Meteorite58

    Still out past +120hs but the ECM has been showing very strong winds running along the Atlantic Seaboard as isobars tighten from later Fri afternoon into Saturday giving a considerable Windchill , Met Eireann mentioning 'Remaining cold through the end of the week and into the weekend in a biting fresh and blustery northerly wind that will feed in further showers, some turning wintery over higher ground'



  • Registered Users Posts: 17,796 ✭✭✭✭hatrickpatrick

    If only, if only, the woodpecker sighs...


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  • Registered Users Posts: 6,647 ✭✭✭pauldry

    They indeed are nice charts.

    I wonder how it will get fcuked up

    Probably mild sectors in the lows abound.

    e.g "How come the temperature has gone up to 6c suddenly"

  • Moderators, Science, Health & Environment Moderators Posts: 16,299 Mod ✭✭✭✭Gonzo

    Autumn has ended and I've opened the Winter long range FI thread.

This discussion has been closed.