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Cold Spell Late Feb/ Early March Technical Discussion only MOD NOTE POST #1

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    #1232
    BLIZZARD7
    Registered Users Posts: 1,985 ✭✭✭BLIZZARD7


    No movement in temps here, 0.4c and DP at -4c in D14. Light snow blowing around for last few hours.

    Expecting all snow based on forcasts/charts to be honest.


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    #1233
    Artane2002
    Registered Users Posts: 1,987 ✭✭✭Artane2002


    cherryghost wrote: »
    I reckon only coast fringes may see wet snow/sleet. If you check some of the models you can see the rain on the precip type chart as this warming pushes up but keeps wet stuff out into the bay/coast

    It's worth noting DP in southern England/Wales before it hits us.
    How far inland do you think you would have to be to avoid the sleet?


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    #1234
    piuswal
    Registered Users Posts: 1,785 ✭✭✭piuswal


    Gaoth Laidir wrote: »
    The only thing I can see is the chance of elevated thunderstorms from CAPE originating from the approaching warm frontal inversion at around 850 hPa. Above that lapse rates will be fairly steep, but I wouldn't have though steep enough for severe storms.

    EDIT: Actually, lapse rates are nowhere near steep enough above the inversion imo. Not quite sure where the idea of thunderstorms is coming from. Will be watching this one with interest.

    Wexford, 6 am tomorrow,

    sondagewrf_294.57000732421875_523.6400146484375_24_1_1519907971.png

    The last few short range forecasts runs are showing a developing line of activity running down the east coast, something like what MT alluded to earlier (cannot find post at present)

    https://www.met.ie/forecasts/short-range.asp

    and becoming quite intense over the Wicklow Mountains. Not that unusual in a feature in an unstable flow being boosted by falling pressure caused by the approach of an entirely different system.

    No idea why on south coast yet.


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    #1235
    Reati
    Registered Users Posts: 1,922 ✭✭✭Reati


    wicklowdub wrote: »
    Temp and DP's rising in Wicklow for the last hour:mad:

    indeed! was down at -12 at one point.

    0.6 °C Feels Like -8.8 °C
    29.9 km/h Wind from ENE
    Gusts 39.9 km/h
    Dew Point: -5 °C
    Humidity: 73%
    Pressure: 992.44 hPa

    High Low Average
    Temperature -0.6 °C -3.9 °C -2.2 °C
    Dew Point -4.8 °C -12.2 °C -8.2 °C
    Humidity 78% 51% 64%


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    #1236
    MajesticDonkey
    Registered Users Posts: 2,213 ✭✭✭MajesticDonkey


    Would anybody be so kind to provide some technical info on possible reasons why inland areas such as where I am received little to no snow at all?

    4xs3BiY.jpg

    Is it simply because of the distance from the east coast, in a ENE direction?


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    #1237
    sdanseo
    Registered Users Posts: 9,233 ✭✭✭sdanseo


    HIRLAM temps for coastal fringes not expected to go above 1c overnight. Back down to around 0c or -1c before dawn. We should be fine.

    16Z Dublin TAF, no significant change:
    TAF: EIDW 011609Z 0116/0212 08025G35KT 4000 -SHSN SCT008 BKN020
    TEMPO 0116/0124 09030G45KT - wind gusting to 45kt until midnight
    TEMPO 0116/0118 0600 SHSN BKN008 - moderate snow showers until 1800
    BECMG 0118/0121 1500 SN BKN008 - moderate snow from 1800 to 2100
    TEMPO 0121/0209 0300 +SN OVC002 - heavy snow from 2100-0900
    BECMG 0200/0203 07030G45KT - wind gusting to 45kt from 0000-0300
    TEMPO 0203/0210 08035G52KT - wind gusting to 52kt from 0300-1000
    BECMG 0209/0212 8000 NSW BKN020 - no significant weather from 0900-1200

    Out the window 5km NE of the airfield by the coast, light snow.

    Cork TAF:
    TAF: EICK 011700Z 0118/0218 04017KT 9999 -SN SCT010 BKN015
    BECMG 0118/0120 1000 SN BKN008 - moderate snow until 2000 visibility 1000m
    TEMPO 0120/0210 06020G30KT 0300 +SN OVC002 - heavy snow from 2000 -1000, visibility 300m
    TEMPO 0210/0218 2000 SNRA BKN004 - sleet (more snow than rain) from 1000-1800, visibility 2000m


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    #1238
    ninebeanrows
    Registered Users Posts: 12,778 ✭✭✭✭ninebeanrows


    HIRLAM has Dps maxing around -1C near Howth with air temperature rising now higher than +1C, this would be good enough for snow right through


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    #1239
    nacho libre
    Registered Users Posts: 16,674 ✭✭✭✭nacho libre


    Just to remind people you can get cold rain with even -3c. It's all down to Gaoth Laidirs wet bulb temperature and dew points. That said it will surely only be the south coast that sees any rain in the next 24 hours.


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    #1240
    sternn
    Registered Users Posts: 929 ✭✭✭sternn


    This is an interesting visualization, not great for granularity but nice to track the progress of incoming Emma. Not sure on the accuracy of the readings either.

    https://earth.nullschool.net/#current/wind/surface/level/orthographic=-8.75,52.85,3000/loc=-6.105,53.224


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    #1241
    SleetAndSnow
    Registered Users Posts: 4,678 ✭✭✭SleetAndSnow


    Tips off emma starting to show on netweather off the south coast possibly?

    sftTgfK.png


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    #1242
    Oneiric 3
    Registered Users Posts: 6,235 ✭✭✭Oneiric 3


    Elmer Blooker wrote: »
    -0.5c and rising too. There's ALWAYS a warm sector lurking somewhere.
    These UK temperatures are quite odd? Compare Lancashire with Cornwall, and Belfast too. How the hell can the far south west of England be much colder than northern England? Answer: a small warm sector.
    edit: -0.4c now. same old .................

    SYNOPUK_16_5.png

    I reckon with the low moving closer, that it would be pulling up colder air from the near continent, where temps are much lower than they are over the North Sea, up over SW England.

    @17-PDR, a curious report alright. As Nacho said, it could be down to 'wet-blub' temps or something, which, as GL said before, (and if I remember correctly) need to be below 0.5c for snow. I have no idea what the wet blub temp would be in Valentia at the mo.

    New Moon



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    #1243
    RobertKK
    Registered Users Posts: 33,733 ✭✭✭✭RobertKK


    No warming here on the hills north east of Kilkenny, yesterday had a high of -1.5C, and today it got to -0.9C, currently -2.2C and DP of -4.2C.
    Should get a good fall of snow at 220m asl.
    Kilkenny city about 6 miles away is -0.8C at 60 metres asl.


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    #1244
    Gaoth Laidir
    Registered Users Posts: 8,219 ✭✭✭Gaoth Laidir


    Temperature is not the problem, it's that dewpoints rise several degrees to just below zero. With the whole lower 3 km hovering a few degrees below zero it's a heavy wet snow setup.

    e.g.
    443839.PNG


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    #1245
    ninebeanrows
    Registered Users Posts: 12,778 ✭✭✭✭ninebeanrows


    Gaoth Laidir wrote: »
    Temperature is not the problem, it's that dewpoints rise several degrees to just below zero. With the whole lower 2 km hovering below zero it's a heavy wet snow setup.

    e.g.
    443839.PNG
    So you mean you are expecting dinner plates?:pac::pac:


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    #1246
    BLIZZARD7
    Registered Users Posts: 1,985 ✭✭✭BLIZZARD7


    Gaoth Laidir wrote: »
    Temperature is not the problem, it's that dewpoints rise several degrees to just below zero. With the whole lower 2 km hovering below zero it's a heavy wet snow setup.

    e.g.
    443839.PNG

    1982 and indeed many of our heavy snowfalls were when temperatures were in and around 0 with quite wet (big flakes) snow at times too were they not?


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    #1247
    Reckless Abandonment
    Registered Users Posts: 1,495 ✭✭✭Reckless Abandonment


    pmpQMhYgg

    Euro4 looks a little snowy for south and east


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    #1248
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Frontal edge almost to the IoM now, but theres still streamer development in the north Irish sea.

    http://www.meteoradar.co.uk/


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    #1249
    piuswal
    Registered Users Posts: 1,785 ✭✭✭piuswal


    FastFullBack wrote: »
    Does every station report back on the hour? E.g. are all those temps as of 4PM. Or is this just the unspecified latest from each station?
    Pressures are exactly on the hour and I suspect that with AWS's other parameters such as temperature arealso from the hour.

    I think AWS's are polled regularly and frequently and its the hour value that is published. This maintains a global recording system and standard.

    When stations were manned, parameters like cloud etc were assessed in the ten minutes running up to the hour, temperatures were read in that period also. Then the wind values were read from the anemograph display within the station and finally the pressure was read exactly on the hour at all observing stations globally.

    The various values were then encoded into the standard WMO five figure group code (no language barriers) and then each station within a Met Services area of responsibility sent in their observations in a predetermined rotation. Following quality control, the Irish obs were sent onto Bracknell and thence to Paris, Offenbach and Washington so that eventually the Irish observations ended up in every operational Met Office in the world. Similarly, any observation, from the tip of South America to Vladivostok, the entire globe in fact could end up in ME if they wanted them.

    Modern comms and numerical models have changed that basic old system somewhat. Ireland would only need a limited amount of data for its limited area models.

    The ECMWF gathers all global met info now, satellite info being by far the greatest contributor (A few of the bigger services. DWD, UKMO NWS, etc would do likewise)and it produces a global analysis part of which is then used by the smaller services as the boundary for their limited area models.


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    #1250
    nacho libre
    Registered Users Posts: 16,674 ✭✭✭✭nacho libre


    Oneiric 3 wrote: »
    I reckon with the low moving closer, that it would be pulling up colder air from the near continent, where temps are much lower than they are over the North Sea, up over SW England.

    @17-PDR, a curious report alright. As Nacho said, it could be down to 'wet-blub' temps or something, which, as GL said before, (and if I remember correctly) need to be below 0.5c for snow. I have no idea what the wet blub temp would be in Valentia at the mo.

    I thought it was 0.5, but apparently it can snow at higher wet bulb temperature, but Goath dismisses it, as the snow is too wet for him if the wet bulb is above 0.5.


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    #1251
    Gaoth Laidir
    Registered Users Posts: 8,219 ✭✭✭Gaoth Laidir


    BLIZZARD7 wrote: »
    1982 and indeed many of our heavy snowfalls were when temperatures were in and around 0 with quite wet (big flakes) snow at times too were they not?

    The highest depths come from dry snow (like the past two days), and 82 was like this. More normal for us is the wetter variety.


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    #1252
    Donegal Storm
    Registered Users Posts: 2,023 ✭✭✭Donegal Storm


    Seems to have been a bit of a thaw here in Kildare in the past couple of hours as well, some icicles on the bottom of the car now for the first time and the sides of the car are all wet from water running down, that despite the fact it hasn't stopped snowing at all today.


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    #1253
    DOCARCH
    Moderators, Home & Garden Moderators, Science, Health & Environment Moderators Posts: 17,783 Mod ✭✭✭✭DOCARCH


    Mod Note: I have moved a number of 'chatty' posts over to the other thread. If your post is missing, it's here: https://www.boards.ie/vbulletin/showthread.php?p=106305961&posted=1#post106305961


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    #1254
    nacho libre
    Registered Users Posts: 16,674 ✭✭✭✭nacho libre


    BLIZZARD7 wrote: »
    1982 and indeed many of our heavy snowfalls were when temperatures were in and around 0 with quite wet (big flakes) snow at times too were they not?

    Yes. When it's marginal, as most frontal snow events are, we get wet snow- dinner plate snow. It would be great to get 24 hours of dry powdery snow, but for a front/ systems coming up from the south that is a big ask- dew points will always rise as the cold air is slightly mixed out.


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    #1255
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Reckless Abandonment wrote: »
    Euro4 looks a little snowy for south and east

    It actually appears more optimistic than the Hirlam for the first time with regards to the east anyway.

    18030203_2_0112.gif


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    #1256
    piuswal
    Registered Users Posts: 1,785 ✭✭✭piuswal


    MajesticDonkey wrote: »
    Would anybody be so kind to provide some technical info on possible reasons why inland areas such as where I am received little to no snow at all?

    4xs3BiY.jpg

    Is it simply because of the distance from the east coast, in a ENE direction?

    Probably topographic shielding with all those hills about


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    #1257
    DOCARCH
    Moderators, Home & Garden Moderators, Science, Health & Environment Moderators Posts: 17,783 Mod ✭✭✭✭DOCARCH


    Itssoeasy wrote: »
    Sorry I thought this was the thread for talking. Sorry about that.

    Talking technical....


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    #1258
    ninebeanrows
    Registered Users Posts: 12,778 ✭✭✭✭ninebeanrows


    If EURO4 can move the intense precip 20 miles north it would be great please :)


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    #1259
    Gaoth Laidir
    Registered Users Posts: 8,219 ✭✭✭Gaoth Laidir


    wet-bulb temperatures at 4 pm. No problem in the UK or Ireland right now, but the warmer air in northwest France (where it's now turned to rain) will be advecting northwards overnight and tomorrow. Above around 0.6 °C is the wrong side of marginal. Not saying we're going to get that tonight, it's just that they will be rising more towards zero after midnight.

    443843.png


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    #1260
    nacho libre
    Registered Users Posts: 16,674 ✭✭✭✭nacho libre


    Gaoth Laidir wrote: »
    The highest depths come from dry snow (like the past two days), and 82 was like this. More normal for us is the wetter variety.

    So is the sublimation process greater with wet snow than dry snow? Also what exactly happens when wet snow falls on dry snow?


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    #1261
    Oneiric 3
    Registered Users Posts: 6,235 ✭✭✭Oneiric 3


    Vertical profile for Howth Hd from the GFS12z for tonight and tomorrow in table form.

    h7jCptH.png

    Others might be able to make better sense of the data than I could.

    New Moon



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