Greenland Express: Snow showers possible from Monday night

Shedbebreezy · 11-01-2018 5:50pm

Rebelbrowser wrote: »

Two very contrasting models this afternoon.

On closer inspection the 12z GFS is glorious for snow lovers. I have huge doubts about the GFS, especially when it comes to predicting snow, but it basically shows uppers between -6 to -8, thickness sub 524 (and well sub at some stages), and negative dew points, for all from Monday night to Friday night. If that happens there is going to be snow for many you have to think.

HOWEVER, the GFS is, sadly, out on its own here. The 12z GEM for example shows upper temps about 4 degrees warmer and shows snow for a time over mountainy man on Wednesday night. And that's it.

I am afraid I would expect the latter, not the former given the GFS' track record on these. If the ECM is similar to the GFS later though then I will get excited.

GEM ALWAYS shows uppers to be milder in these scenarios. Its a known bias.

squarecircles · 11-01-2018 5:50pm

18z should be fun so...

Captain Snow · 11-01-2018 5:55pm

squarecircles wrote: »

18z should be fun so...

It will be Legend

kod87 · 11-01-2018 5:56pm

Shedbebreezy wrote: »

GEM ALWAYS shows uppers to be milder in these scenarios. Its a known bias.

...and GFS tends to exaggerate how low the uppers are at this range.

So the truth will probably be a watered down version of GFS

Shedbebreezy · 11-01-2018 6:04pm

kod87 wrote: »

...and GFS tends to exaggerate how low the uppers are
So the truth will probably be a watered down version of GFS.

Not to the extent GEM underplays them. Anyway GFS is great for me in Donegal. I look forward to lots of snow next week.
To be fair I wouldn't be too enthusiastic if I was in Tipp either, certainly more watered down for there.

typhoony · 11-01-2018 6:09pm

GFS extends the cold spell all the way out to the 26th, although at that stage we're under light northerly winds

Malayalam · 11-01-2018 6:12pm

Ah for the love of God

I have a dental appointment for serious work that I have been waiting for for 6 months on Thursday. I live high enough in the north western hills for the snow to generally be our lot if there is any around, I have to walk 6 miles (in the very early morning) to get the bus to take me to town to go to said dentist, and now ye have me in a feckin' tizzy!

RobertKK · 11-01-2018 6:50pm

My weather on iPhone for the last few days has been showing snow for next week, initially on he Monday but then changed it to Tuesday, currently showing snow for Tuesday, Wednesday and Thursday with a high of 3C, after that it says it stays cold but drier.
But I am on high ground here in Kilkenny, for Kilkenny city it says rain for Tuesday and Wednesday and snow on Thursday, where it will be 1 to 2C warmer.

Here on the hills (part of the Castlecomer plateau) we get snow every winter, even if just a dusting in a very mild winter. Never had a winter where I didn't see snow fall.
Already had 10 hrs of non stop snow on December 8th.

pad199207 · 11-01-2018 6:59pm

Shedbebreezy wrote: »

Not to the extent GEM underplays them. Anyway GFS is great for me in Donegal. I look forward to lots of snow next week.
To be fair I wouldn't be too enthusiastic if I was in Tipp either, certainly more watered down for there.

Someone is going to be bitterly disappointed....

lapua20grain · 11-01-2018 7:04pm

At this stage i'll only believe it when I see it falling from the sky

pad199207 · 11-01-2018 7:06pm

lapua20grain wrote: »

At this stage i'll only believe it when I see it falling from the sky

Yep exactly, it’s what most of us say in a NWly

“Believe it when I see it”

Shedbebreezy · 11-01-2018 7:08pm

pad199207 wrote: »

Someone is going to be bitterly disappointed....

Not really. I'll be bitterly cold tho, already had a week of snow this Winter. Next week looks great for here, Not much to be excited about in Kildare tho

blast06 · 11-01-2018 7:09pm

Shedbebreezy wrote: »

GEM ALWAYS shows uppers to be milder in these scenarios. Its a known bias.

Why would a computer model have a deliberate ('known') bias ? I don't understand what the purpose of that would be, i.e.: if it is known to consistently misrepresent a specific scenario, then shouldn't that be programatically corrected ?

pad199207 · 11-01-2018 7:10pm

Shedbebreezy wrote: »

Not really. I'll be bitterly cold tho, already had a week of snow this Winter. Next week looks great for here, Not much to be excited about in Kildare tho

Nope exactly, not expecting anything here bar maybe some sleet showers

Shedbebreezy · 11-01-2018 7:12pm

blast06 wrote: »

Why would a computer model have a deliberate ('known') bias ? I don't understand what the purpose of that would be, i.e.: if it is known to consistently misrepresent a specific scenario, then shouldn't that be programatically corrected ?

You need to ask the Canadians that not me

blast06 · 11-01-2018 7:33pm

Shedbebreezy wrote: »

You need to ask the Canadians that not me

Who is it "known" by ... i.e.: is it your opinion based on your observations of it over a number of years ... or is there some empirical data maintained by someone ?

Gaoth Laidir · 11-01-2018 7:35pm

blast06 wrote: »

Why would a computer model have a deliberate ('known') bias ? I don't understand what the purpose of that would be, i.e.: if it is known to consistently misrepresent a specific scenario, then shouldn't that be programatically corrected ?

The bias is not deliberate. The GFS wasn't programmed to give snow charts every time there's a northwesterly, it's just a facet of the physics of the model. This error (bias) is known and allowed for by forecasting agencies, though not on public forums, it seems...:pac:

Gaoth Laidir · 11-01-2018 7:38pm

That's some snow alright on the GFS.

And now for a reality-check, brought to you by the ECMWF...

Larbre34 · 11-01-2018 7:40pm

There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know. - Donald Rumsfeld

Now can we for flip sake leave out these threads until we get to +36 and there is a genuine risk of disruptive snowfall. They are only contributing to the crying wolf issue.

Lenny5 · 11-01-2018 7:47pm

Wheres the fun in leaving it till 36 hrs. The fun of it is in the chase and the potential for snowy weather even this far out. Each and every upgrade and downgrade (Booo) adds to the suspence. Heres hoping that the optimists win this time :-)

Gonzo · 11-01-2018 8:38pm

right now it's looking like this cold spell could last an entire week. I've a feeling Northern Ireland in particular could do really well out of this one as will Donegal, Cavan, Sligo, Mayo and possibly Galway. The real cold won't be here till late Monday so still really 4 days away and alot can change between now and then. Even the east and south may see a few flurries out of this one. Two things will be certain, the nights will be very cold and the heating bills will be high.

Neddyusa · 11-01-2018 8:59pm

Gonzo wrote: »

I would say most of the greater Dublin region: Southern half of Meath, Dublin away from high ground, eastern half of Kildare, Wicklow away from high ground, Wexford, Waterford. These places really only get decent snow from a proper Siberian easterly and those are rare as hens teeth.

Perhaps some other areas like Tipperary, coastal areas of Cork, Clare and Kerry away from high ground and parts of the midlands see very little snow.

The counties that probably see snow each and every winter would be Donegal, Sligo, Mayo, Galway, Cavan, Monaghan, Leitrim, Roscommon, not all parts see lying snow on an annual basis but they certainly see more white gold action than the rest of Ireland.

Aye - but don't forget - us Westies also see a hell of a lot more rain too. :rolleyes:
I'd gladly give the East coast our biteen of extra snow if you take all our extra rain too

:D

lolie · 11-01-2018 8:59pm

Gonzo wrote: »

slightly OT but I just noticed RTE's lunchtime forecast has a new look with new graphics, map looks higher resolution and the 5 day outlook they were showing 0C for daytime on Monday and Tuesday with snow symbols over the west and north of the country.

On the 6:1 forecast it's now showing 7c for Monday and Tuesday.

maryk123 · 11-01-2018 9:00pm

Oh I would love some snow down south - just for a day mind so the kids could have a show day.

pauldry · 11-01-2018 9:14pm

lolie wrote: »

On the 6:1 forecast it's now showing 7c for Monday and Tuesday.

Just put 7c down for next 20 days and you wont be far wrong

TheRiverman · 11-01-2018 9:21pm

Outlook
Headline: Unsettled and changeableFriday night will be windy and very wet over the western half of the country, with heavy possibly thundery rain in many areas and some flooding. Winds will be strong to gale force and gusty southeasterly. Windy and mostly cloudy elsewhere too, with the rain spreading eastwards all the while and with some heavy rain in places by dawn. Lowest temperatures 4 to 8 C. Further rain in all areas during Saturday, with some heavy falls in more eastern areas. A misty, mostly cloudy day and a breezy start too, but the stiff southeast winds will moderate gradually. Top temperatures 7 to 10 C. The rain will peter out after dark and it will become misty. Some patches of fog will form and also some frost. Lows of zero to plus 3 C., are expected, in slack variable breezes, coldest in western areas. Sunday will be a mainly dry day, with just scattered patches of mist and drizzle. Overnight fog and any frost should clear. Top temperatures 7 to 10 C. At this stage, it looks as if Sunday night will turn wet and breezy.Early days of next week: Cool, windy and showery, with some wintry showers in places. Winds fresh to strong westerly much of the time. Cold at night, with some frost in places.

sdanseo · 11-01-2018 9:34pm

Met.ie do not use GFS as a primary forecasting tool so their outlook is not unexpected. Until more consensus appears (IF more consensus appears) this is a maybe.

When people can't reconcile that "maybe" and start throwing their toys out of prams I lose all hope for humanity. It may or may not snow. Let's enjoy the speculation and live in hope

Larbre34 · 11-01-2018 9:35pm

pauldry wrote: »

Just put 7c down for next 20 days and you wont be far wrong

Welcome to the modified muck express.

JanuarySnowstor · 11-01-2018 9:42pm

pauldry wrote: »

lolie wrote: »

On the 6:1 forecast it's now showing 7c for Monday and Tuesday.

Just put 7c down for next 20 days and you wont be far wrong

Not sure what you mean??
It will be very cold polar air.

munsterlegend · 11-01-2018 9:44pm

Gaoth Laidir wrote: »

The bias is not deliberate. The GFS wasn't programmed to give snow charts every time there's a northwesterly, it's just a facet of the physics of the model. This error (bias) is known and allowed for by forecasting agencies, though not on public forums, it seems...:pac:

Does the ECM have any bias in such situations? I read on another site that it can tend to underestimate uppers slightly.

KingdomRushed · 11-01-2018 10:06pm

The GFS bias is an absolute constant for wrongly predicting snow from marginal situations like this from a NW source at ground level for December and January. I would say at least 4/5 snow charts at 120 hours for Dublin for instance not materialising (when air mass from NW source) However, into February and March the model comes more in line with reality with more of its snow charts verifying. Probably cooling sea temps. Maybe it doesn’t quite handle the warmer sea temps in earlier winter?

booferking · 11-01-2018 10:09pm

A few need to chill Sunday night is when met Eireann will give warnings and through the coming days the wording in the forecast will change to snow showers there already mentioning wintry showers.

nacho libre · 11-01-2018 10:39pm

A promising forecast from M.T.Cranium for next week.

NEXT WEEK will become progressively colder in a northwest flow, showers becoming increasingly wintry each day to about Thursday which may be the coldest day, although Friday will see only limited recovery. Highs around 7 C on Monday, 6 C on Tuesday and only 3-5 C Wednesday to Friday, and slight frosts each night, in a persistently windy regime between westerly and northwesterly most of the time, in the range of 50 to 80 km/hr, making the temperatures feel more like +1 C in the daytime. Falls of snow are quite likely by mid-week in higher parts of Connacht, west Ulster and west Munster. These will be less likely near east and south coasts but mixed wintry showers will probably be rather widespread at times, with thunder and hail in the mix as well.

The further outlook calls for a somewhat less windy interval but staying rather cold, and any milder intervals will be very brief as this large scale pattern of cold, unsettled conditions shows little signs of moving away.

yorlum11 · 11-01-2018 10:41pm

Let's just hang in there until Monday. Synopsis look good for a few days next week. Potential is there. West and north obviously a good spot as per location but very often it's a now cast and areas not in the sweet spot now get on on the action last minute. Longer term it might be north east and east that is preferred. Hopefully exciting times ahead. #sneachta

Shedbebreezy · 11-01-2018 10:47pm

Gaoth Laidir wrote: »

That's some snow alright on the GFS.

And now for a reality-check, brought to you by the ECMWF...

Yes by 9pm Monday not much showing on the ECM as indicated by the ECM Snow accumulations(inches) for that time

The following day more across the NW

Copious amounts across the NW as week progresses. I'm expecting snow in donegal but not over 16 inches:p

I know they won't be accurate but it's forecasting snow to fall, not just rain as 9pm Monday indicates, and a snow fest at that for the Northern West. Not much of a reality-check to be fair lol.

typhoony · 11-01-2018 11:36pm

the one thing you don't get from the models in the predicted NW Polar Maritime setup is a flip flopping from run to run like the mythical scandi high.

could we get thundersnow next week, a definite possibility in the NW

M.T. Cranium · 11-01-2018 11:46pm

I haven't read this entire thread but hopefully it was mentioned that when we had the "Greenland express" in 2010 (my terminology IIRC) that air mass came south from northeast Greenland at a high rate of speed so it only spent 24 hours over waters over 7 C whereas this time it's coming the longer route from southeast Greenland and will take 48-72h to arrive, more time to modify -- although thicknesses on charts do support the idea of lying snow in higher parts of the north and west.

The situation could upgrade or perhaps not, will assess carefully overnight.

typhoony · 11-01-2018 11:51pm

M.T. Cranium wrote: »

I haven't read this entire thread but hopefully it was mentioned that when we had the "Greenland express" in 2010 (my terminology IIRC) that air mass came south from northeast Greenland at a high rate of speed so it only spent 24 hours over waters over 7 C whereas this time it's coming the longer route from southeast Greenland and will take 48-72h to arrive, more time to modify -- although thicknesses on charts do support the idea of lying snow in higher parts of the north and west.

The situation could upgrade or perhaps not, will assess carefully overnight.

was it not a shortlived NWesterly followed by a colder Northerly?

M.T. Cranium · 12-01-2018 12:16am

The Greenland Express reference was to a full-on northerly and it was moving south at over 50 knots (surface winds were not quite that strong). This present set-up is less extreme but maybe it will upgrade, we shall see.

pauldry · 12-01-2018 12:19am

Hasnt this Winter been the most exciting since 2010?

Even though its been borderline and 7c is quite possible for a few days or weeks and even as low as 5c at times theres been lots this Winter

Snow at start of December, Elanor!! with its tail of destruction and power cuts, lots of frost and then a day like today with 24 hour fog that reached a max of 1.6c and a min of -0.6c to name just a few

What Im saying is this Winter hadnt been meh at all in comparison to previous ones and certainly wont be described as a mild Winter

So far overall Id describe it as a cold and mixed Winter with a few storms plus of course 6 lightning strikes last Friday that have broke our sky box forever.

Add in a collapsed tree from Elanor and a snowman (mini) from the December Snow...i have weather memorobelia (htf do you spell that?) Everywhere

M.T. Cranium · 12-01-2018 12:27am

GFS bias may have something to do with trying to average out air mass conditions over hilly terrain, when everyone lives in the lowest 20% of the terrain, perhaps it leads to a disparity between validated weather over the grid square, and human experience of the weather predicted.

I think it's more than just that, but it would be a factor over higher parts of the north and west.

But yes it goes into the forecast calculation that GFS can have a cold bias in the medium term. ECM deep lows at 120h are not always to be trusted either.

What you like to see as a forecaster is ECM colder than GFS and GFS shifting towards that -- then you're talking.

nacho libre · 12-01-2018 1:12am

http://www.bbc.co.uk/weather/features/42657127

Interesting beeb(bbc) forecast

Look at all the snow waiting in the wings by Monday night. Mountainy man might be snowed in by Wednesday.

IMG_0193.JPG.260575fc5c3033a38849a03b7de4bb46.JPG

IMG_0193.JPG.260575fc5c3033a38849a03b7de4bb46.JPG

Donegal Storm · 12-01-2018 1:51am

typhoony wrote: »

was it not a shortlived NWesterly followed by a colder Northerly?

2010 was the real deal if we're talking about a Greenland Express, the airmass dropped from the deep Arctic in Northern Greenland to the north of Ireland in little more than 24 hours. The coming week could be interesting in the north and west but won't be remotely close to that event

Oneiric 3 · 12-01-2018 2:53am

Forecast chart (850 hPa temps + isobars) for the middle of next week:

Compare this with a chart from this day last year, very similar, but colder air over the nearby north Atlantic region in general:

Daily max temps on the 12th & 13th of January last year ranged between 3c and 7c over the country (highest along western coasts) while minima ranged between about -0.7c (Knock Apt) and 3.0c, with the weather being showery with a wintery mix of rain, hail sleet and some brief snowfalls for favoured areas.

Keep in mind that 850 temps got down to below -7.0c at times between the 12th & 13th last year, while current forecasts (from the ECMWF at least) do not have 850 temps falling below this threshold for the upcoming spell as of yet.

Images from the Icelandic Met Office.
Temp data from Met Éireann.

vickers209 · 12-01-2018 8:02am

Met eireanns forcast this morning

EARLY NEXT WEEK: Becoming increasingly blustery and showery; showers turning wintry later Monday into Tuesday with falls of sleet and snow increasingly more likely. The focus of the wintry showers will be across the north and west with some accumulations likely - but all areas will be at risk with some thunder occurring locally too. Much colder, with maxima of only 3 to 6 degrees Celsius (north to south). Feeling even colder with an added wind chill effect. Frost and ice also, mainly for sheltered areas owing to sustained brisk winds.

Villain · 12-01-2018 8:18am

Higher Resolution GFS shows closer to the likely reality.

M.T. Cranium · 12-01-2018 8:19am

Greenland all stops more like it perhaps?

Still it is coming from Greenland, this part is true.

Gaoth Laidir · 12-01-2018 8:29am

Oneiric 3 wrote: »

Forecast chart (850 hPa temps + isobars) for the middle of next week:

Compare this with a chart from this day last year, very similar, but colder air over the nearby north Atlantic region in general:

Daily max temps on the 12th & 13th of January last year ranged between 3c and 7c over the country (highest along western coasts) while minima ranged between about -0.7c (Knock Apt) and 3.0c, with the weather being showery with a wintery mix of rain, hail sleet and some brief snowfalls for favoured areas.

Keep in mind that 850 temps got down to below -7.0c at times between the 12th & 13th last year, while current forecasts (from the ECMWF at least) do not have 850 temps falling below this threshold for the upcoming spell as of yet.

Images from the Icelandic Met Office.
Temp data from Met Éireann.

Facebook tells me I posted this image 1 year ago today...

Kermit.de.frog · 12-01-2018 9:22am

Solid model forecasts this morning for the cold snap beginning on Monday.

I'll update OP after the 12 pm output.

Not counting chickens yet but looks good at the moment.

Rebelbrowser · 12-01-2018 9:42am

Gaoth Laidir wrote: »

Facebook tells me I posted this image 1 year ago today...

And sadly Id take that happily!

Greenland Express: Snow showers possible from Monday night

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