Cold Spell - Feb 7th to 13th 2021 - Chat

Steopo

Good explanation here on the sea effect snow (streamers) that hopefully we’ll be experiencing on east coast from roughly Mon-Wed. Written from UK perspective but same principles apply for Ireland expect sea fetch is shorter for Irish Sea so depending on wind direction the Isle of Man or Anglesey headland will mean a shorter sea fetch so few/no showers for some. Wind (speed, direction, shear..) will also affect the type of showers and how far inland they encroach so still a lot of unknowns. Looks to me like precipitation charts from models aren’t very good at showing streamers overland certainly in the medium range and small changes in wind can result in significant snow for some as streamers keep coming over the same area but very little for others just down the road

https://www.netweather.tv/weather-forecasts/news/8748-sea-effect-snow---the-uk-version-of-lake-effect-snow-very-cold-air-across-the-north-sea

wirelessdude01

highdef wrote: »

A couple of photos I took in my (northern) part of Kildare from 2018, just to get everyone even more excited!

The first is when I was out for a walk the day before Emma hit. Visibility was near zero at times.


The second was taken the day after the storm cleared. A stop sign can also be seen plus a man VERY slowly trying to make his way back to his house which was about 200m behind me. I'm standing in the middle of the road and you can see the line of the road between the hedges. What's of note is that those hedges are close to 2m high in places. As the road is orientated in a roughly north/south axis and the wind was mainly easterly, the snow collected between the hedgerows on either side of the road, right up to the tops of them so you could walk straight into the fields so I was in fact standing well above the road. This road was not cleared for several days as a driver had to abandon the car a few nights before and it became completely covered - for all I know I could have been standing directly above the car taking the photo.

Also of interest is the areas of green to be seen in the fields. Again, this was due the strength of the wind combined with the snow being extremely fine and dry so local topography played a massive role with regards to how deep the snow was at any particular point, unlike when you get the more usual wetter snow, often combined with light winds resulting in fairly even coverage.

Newtown?

Kermit.de.frog

Kermit.de.frog wrote: »

EC 96 hrs...this will help enhance shower activity for Monday anyway



Difference with GFS...

-10 uppers right on the east coast noon Monday and the whole Irish sea
Air pressure low
Showertastic

red_bairn

Forgot my ski pants in my parents place and we are 45 mins drive so I've asked the rents to send over by An Post.

Mum: I sent my wedding dress to Cork and it took 6 days...

Doesn't leave me with much confidence in getting the pants before the big snow.

Ursulal

Loughrea Co.Galway 2nd March 2018

Calibos

arctictree wrote: »

I remember Feb 2009, we were buried in the Wicklow hills with streamer snow. In fact there's probably a thread here on it if you go back far enough!! Only other event to top it since was 2018 aka the beast...

Took these on the flight back from a Skiing Trip to Livignio in February '09. Roundwood may have got snowed in but Bray didn't see much from it as usual.

Calibos

AuntySnow wrote: »

-10 uppers right on the east coast noon Monday and the whole Irish sea
Air pressure low
Showertastic

BANK!!

Course, you'll tell me those pressure lines don't indicate wind direction??

Calibos

red_bairn wrote: »

Forgot my ski pants in my parents place and we are 45 mins drive so I've asked the rents to send over by An Post.

Mum: I sent my wedding dress to Cork and it took 6 days...

Doesn't leave me with much confidence in getting the pants before the big snow.

Have mine in the Wardrobe.

...but I've put on about 40lb since I last wore them :mad:

Gonzo

Little snowy old me wrote: »

The duration of this spell is getting shorter as per each run. The latest talk on the technical thread has a swift return to mild muck by Wednesday. So if you are lucky enough to get some snow on Monday or Tuesday, you'll have 1 or 2 days maximum to enjoy it.

This is very disappointing. What was promising to be a fairly potent cold period looks like a brief spell of cold weather with some snow for some in the east. I'm annoyed that I allowed myself to get excited.

This cold spell has always looked like a 2 to 4 day event depending on what model you look at. Sunday to Tuesday is still looking good. There is alot of uncertainty from Tuesday night onwards. Nobody was guaranteeing this cold spell to last into Friday. The models are upgrading and downgrading on a daily basis and more changes still to come over the next few days in relation to what happens throughout next week.

Calibos

Wednesday onwards is still too far out and the models are as likely to flip back as Wednesday onwards comes into the more reliable time frames. Whatever the models say about Wednesday onwards on Saturday or Sunday is likely what will happen be that good or bad.

Seymour20

Little snowy old me wrote: »

The duration of this spell is getting shorter as per each run. The latest talk on the technical thread has a swift return to mild muck by Wednesday. So if you are lucky enough to get some snow on Monday or Tuesday, you'll have 1 or 2 days maximum to enjoy it.

This is very disappointing. What was promising to be a fairly potent cold period looks like a brief spell of cold weather with some snow for some in the east. I'm annoyed that I allowed myself to get excited.

Pretty sure it always up in the air as to how long it would be and according to other posts on here the conditions were never favourable for a prolonged spell anyhow. Also worth noting that the charts are +144 now for the breakdown and this is out of the reliable timeframe. You said yourself you probably wouldn’t get any snow out of it in Donegal and would be happy with a few frosts which you’ll probably still get so don’t see the issue.

Hooter23

Yes many times when we had air as cold as this coming from the east it tended to get more prolonged in each forecast after it had arrived...the cold could definately get upgraded and prolonged...if the weather we got in the past is anything to go by

Little snowy old me

Little snowy old me wrote: »

The duration of this spell is getting shorter as per each run. The latest talk on the technical thread has a swift return to mild muck by Wednesday. So if you are lucky enough to get some snow on Monday or Tuesday, you'll have 1 or 2 days maximum to enjoy it.

This is very disappointing. What was promising to be a fairly potent cold period looks like a brief spell of cold weather with some snow for some in the east. I'm annoyed that I allowed myself to get excited.

You're swift to write it off, when we're still several days away from the cold spell proper. I wouldn't be advertising your disappointment just yet, long way to go and there is plenty of scope for change. I live in west Munster which isn't exactly ground zero, however I haven't been this optimistic about a serious snowfall in years.

Oneiric 3

Snowfall forecast from the latest ECMWF for between Sun eve and Wed after. This could be Gonzo's moment:

Speak Now

Little snowy old me wrote: »

The duration of this spell is getting shorter as per each run. The latest talk on the technical thread has a swift return to mild muck by Wednesday. So if you are lucky enough to get some snow on Monday or Tuesday, you'll have 1 or 2 days maximum to enjoy it.

This is very disappointing. What was promising to be a fairly potent cold period looks like a brief spell of cold weather with some snow for some in the east. I'm annoyed that I allowed myself to get excited.

Read Liz Walshs excellent update, no way is that decided yet.

Even daily snow falls will be now casting.
Those charts predicting where heaviest snow falls are notoriously inaccurate.

Nqp15hhu

Are those showers on the north coast in reality out in the North Channel? I can't see how showers would come down from the north in an easterly wind?

Oneiric 3

Nqp15hhu wrote: »

Are those showers on the north coast in reality out in the North Channel? I can't see how showers would come down from the north in an easterly wind?

Keep in mind that these are running 24hr forecast totals. The odd flurry can't be ruled out from popping anywhere really I reckon.

Tyrone212

Ecm snowfall accumulations are a downgrade on the previous run. Out to day 6 tiny to negligible amounts for most of the country.

https://weather.us/model-charts/euro/ireland/snow-depth-in/20210210-1200z.html

Tyrone212

Tyrone212 wrote: »

Ecm snowfall accumulations are a downgrade on the previous run. Out to day 6 tiny to negligible amounts for most of the country.

https://weather.us/model-charts/euro/ireland/snow-depth-in/20210210-1200z.html

Tonights ECM version of Thursday is plausible plausible but as liikely only as last Thursday's for today

Tyrone212

AuntySnow wrote: »

Tonights ECM version of Thursday is plausible plausible but as liikely only as last Thursday's for today

Yes but over Sunday,Monday ,Tuesday and Wednesday its expecting next to nothing to have accumulated. That's what the chart I supplied shows.

Oneiric 3

Only took one photo during the 2018 even and that was when the pre-Emma showers started rolling in from the midlands. Took this as one of those dust showers was passing over. Before I took this pic the vis was even lower and it nearly impossible to see the end of the (very small) back garden:

Tyrone212

Tyrone212 wrote: »

Yes but over Sunday,Monday ,Tuesday and Wednesday its expecting next to nothing to have accumulated. That's what the chart I supplied shows.

Yes but tonights run,missing I suppose a Thursday snow event
According to the ecmw 12 z last Thursday we are under an easterly now
We are not
Just saying

Cork2021

If I remember rightly. The storm Emma build up was something similar to this.
It ramped up from the Sunday and red warning issued on the Wednesday... still loads of time for upgrades!!

sparrowcar

I edited this pic for ourselves.
Simple explanation for lake/sea effect snow.

Doctor Jimbob

Gonzo wrote: »

This cold spell has always looked like a 2 to 4 day event depending on what model you look at. Sunday to Tuesday is still looking good. There is alot of uncertainty from Tuesday night onwards. Nobody was guaranteeing this cold spell to last into Friday. The models are upgrading and downgrading on a daily basis and more changes still to come over the next few days in relation to what happens throughout next week.

Deleted User wrote: »

You're swift to write it off, when we're still several days away from the cold spell proper. I wouldn't be advertising your disappointment just yet, long way to go and there is plenty of scope for change. I live in west Munster which isn't exactly ground zero, however I haven't been this optimistic about a serious snowfall in years.

I wouldn't even bother responding. Poster does this every time there's a cold spell forecast.

lolie

And of course the nonsense has started already on the radio already.
Mention in the news report of Met Éireann saying a possibility of snow next week followed by Cathal nolan talking about an event on par with Emma in 2018.

Little snowy old me wrote: »

The duration of this spell is getting shorter as per each run. The latest talk on the technical thread has a swift return to mild muck by Wednesday. So if you are lucky enough to get some snow on Monday or Tuesday, you'll have 1 or 2 days maximum to enjoy it.

This is very disappointing. What was promising to be a fairly potent cold period looks like a brief spell of cold weather with some snow for some in the east. I'm annoyed that I allowed myself to get excited.

You just can't help yourself can you.
What happened to your "cool heads needed" earlier?
As Gonzo, Kermit and co said from the start take what the charts are showing in the middle of next week with a pinch of salt for now.

JanuarySnowstor

For Cork,

Snow showers should start piling in from Sunday night with lying snow likely from Monday to Thursday morning.
Tuesday looks the sweet spot for showers to be at their most potent!!
A lot will be coastal so Cork city should do well but further inland probably won't (similar to 2018)

It isn't as potent as '18 but does come close.
Uppers are -6 to -8 then they were -8 to -12 going by memory. Also Storm Emma attacked from a much better angle which isn't showing on any charts for Thursday.

Folks the fact that this is the fourth major event since 2009 is extraordinary! Can anyone remember the 90s we hardly saw a flake for 12 to 15 years!

Will the end of next week upgrade? I really hope so because most proper wintry spells last for about 7 to 10 days and a 3 day event would be a bit disappointing.

And no Munsterlegend you won't see snow lol (joking)

Croohur1

I know it's been mentioned before, but what sort of fetch is needed at a minimum for streamers to occur in the Irish Sea?

Monkeynut

sparrowcar wrote: »

I edited this pic for ourselves.
Simple explanation for lake/sea effect snow.

Somebody explained it well before, i can't. but it is like going to the toilet outside when its cold and the steam comes from it. think of the irish sea without the yellow being into it as a big outdoor toilet. its huge and creates water vapor rising as the sea is warmer than the air above. winds coming towards the east coast can leave a good snowfall. we probably get a sprinkling a poolbeg waste water. :pac::pac::pac:

munsterlegend

JanuarySnowstor wrote: »

For Cork,

Snow showers should start piling in from Sunday night with lying snow likely from Monday to Thursday morning.
Tuesday looks the sweet spot for showers to be at their most potent!!
A lot will be coastal so Cork city should do well but further inland probably won't (similar to 2018)

It isn't as potent as '18 but does come close.
Uppers are -6 to -8 then they were -8 to -12 going by memory. Also Storm Emma attacked from a much better angle which isn't showing on any charts for Thursday.

Folks the fact that this is the fourth major event since 2009 is extraordinary! Can anyone remember the 90s we hardly saw a flake for 12 to 15 years!

Will the end of next week upgrade? I really hope so because most proper wintry spells last for about 7 to 10 days and a 3 day event would be a bit disappointing.

And no Munsterlegend you won't see snow lol (joking)

Wednesday/Thursday was my big hope but gone a bit pear shaped this evening.

Rougies

Croohur1 wrote: »

I know it's been mentioned before, but what sort of fetch is needed at a minimum for streamers to occur in the Irish Sea?

Around 100 km is considered the minimum, but you'd only get light showers/flurries even in ideal conditions. Around 150 km is needed for anything decent.

Croohur1

Rougies wrote: »

Around 100 km is considered the minimum, but you'd only get light showers/flurries even in ideal conditions. Around 150 km is needed for anything decent.

Wouldn't that mean that much of Dublin City and Wicklow would get very little snow streamers because of Anglesey and North West Wales/Snowdonia if this is a direct Easterly?

JanuarySnowstor

munsterlegend wrote: »

Wednesday/Thursday was my big hope but gone a bit pear shaped this evening.

Ya you will surely see some showers making it though from the coast.Should be similar to '18 if you did okay then (barring Emma itself which won't happen)
The Southeasterly element to the wind makes me think Cork could do very well maybe even better than Dublin
18z rolling soon

Reckless Abandonment

Croohur1 wrote: »

Wouldn't that mean that much of Dublin City and Wicklow would get very little snow streamers because of Anglesey and North West Wales/Snowdonia if this is a direct Easterly?

Yep. Thats why we need north east winds.

Rougies

Croohur1 wrote: »

Wouldn't that mean that much of Dublin City and Wicklow would get very little snow streamers because of Anglesey and North West Wales if this is a direct Easterly?

Yep! The wind direction will usually change around a bit though, it doesn't take much of a shift towards ENE to bring the whole of Dublin into play. Wicklow does tend to struggle with the Anglesey shadow quite often.

Easterly is fine for Dublin,fetch is over 100kms
Wickliw head to cahore,they're dry because there's not enough fetch to wales

Rougies

Rougies wrote: »

Around 100 km is considered the minimum, but you'd only get light showers/flurries even in ideal conditions. Around 150 km is needed for anything decent.

60 actually
100 for decent
150 fetch would be epic

munsterlegend

JanuarySnowstor wrote: »

Ya you will surely see some showers making it though from the coast.Should be similar to '18 if you did okay then (barring Emma itself which won't happen)
The Southeasterly element to the wind makes me think Cork could do very well maybe even better than Dublin
18z rolling soon

Had no snow where I was until Emma arrived in 2018. From city down the coast should do well from streamers alright. Anyway a lot can happen/change in the next 7/8 days.

Rougies

AuntySnow wrote: »

Easterly is fine for Dublin,fetch is over 100kms
Wickliw head to cahore,they're dry because there's not enough fetch to wales

Direct easterly is fine for north county Dublin only, from Malahide/Swords north. The rest of Dublin would be under the Anglesey shadow. It's almost bang on 100k from Dublin port to Holyhead.

Scrabbel

AuntySnow wrote: »

60 actually
100 for decent
150 fetch would be epic

Interesting! Dublin is 120 from IoM and 100 from Anglesey.

Calibos

Rougies wrote: »

Around 100 km is considered the minimum, but you'd only get light showers/flurries even in ideal conditions. Around 150 km is needed for anything decent.

The Isle of Man would beg to differ. Its 150km away from Bray and my Nemesis

Only a NNE with 190km between me and Scotland or an ENE with 220km between me and Morecambe Bay/Blackpool delivers for Bray.

150km IOM doesn't, 100km Angelsey doesn't and I'm not sure I've ever had a -8+ Upper from the SE originating in 160km distant Cardigan Bay in SW Wales.

Rougies

AuntySnow wrote: »

60 actually
100 for decent
150 fetch would be epic

I disagree both from experience and from anything I've read on the subject.

Rougies

Rougies wrote: »

Direct easterly is fine for north county Dublin only, from Malahide/Swords north. The rest of Dublin would be under the Anglesey shadow. It's almost bang on 100k from Dublin port to Holyhead.

But Docarch is in South Dublin and had plenty snow in South Dublin in February 2018 in that direct easterly
I've lived there too and experienced the same

Rougies

AuntySnow wrote: »

But Docarch is in South Dublin and had plenty snow in South Dublin in February 2018 in that direct easterly
I've lived there too and experienced the same

I'm in the same postcode as Docarch. I can't remember the specifics of the streamers, but anything that fell here was probably from more of a ENE direction than direct E.



Storm Emma doesn't count because it was a frontal event.

Calibos

AuntySnow wrote: »

But Docarch is in South Dublin and had plenty snow in South Dublin in February 2018 in that direct easterly
I've lived there too and experienced the same

I'd wager it was slightly north of Easterly originating in Liverpool with the Northern Tip of Anglesey not ruining the show too much....or a due Easterly Streamer that fanned out by the time it hit the East Coast and caught SOCODU at the southern edge of the Fan.

Oneiric 3

UK Met map for Monday:



And shows a good example of why you don't 'follow the isobars back' to see where the source of the airmass is coming from, as social media amateur forecasters often like to tell us. If that was the case, then the air mass over us on Monday will have come via eastern Europe from the Med, which in turn originated in the Atlantic.

Rougies

AuntySnow wrote: »

Well I'll disagree with your disagreement, I'm not going to have a row about it

Fair enough. I've probably scrutinized every single frame of the radar in Irish Sea snow events for about 12 years now and never saw more than a flurry of lake effect snow forming below 100k of fetch. Everything I can find online says 80k or 100k as minimum in ideal conditions.



We'll leave it at that, lets see what happens next week.

Calibos

If AuntySnow in Arklow was correct that 100km was needed for decent snow and 150km was needed for epic snow, then he would have nothing to fear from an IOM Shadow or Angelsey Shadow, them being 160km and 100km distant respectively from him in Arklow...

...Yet he fears those Shadows as much as me in Bray 40km to his North

Scubadevils

Rougies wrote: »

Direct easterly is fine for north county Dublin only, from Malahide/Swords north. The rest of Dublin would be under the Anglesey shadow. It's almost bang on 100k from Dublin port to Holyhead.

I remember in 2009 the snow missed me here in Lusk - I literally drove up the road towards Swords and there was snow, even more then further into Dublin. Thankfully we made up for it in 2010 and 2018. Must have been in the Isle of Man shadow in 2009.

Squidvicious

Rougies wrote: »

Around 100 km is considered the minimum, but you'd only get light showers/flurries even in ideal conditions. Around 150 km is needed for anything decent.

Of course, an important factor is tge contrast between the sea temperature and the air temperature. An ideal scenario is very cold airstream travelling over the sea in early winter. Sea temps are higher so the high contrast between the sea and air will generate more powerful convection, though it's not regularly that you'll sea an airflow cold enough to bring snow. Late November 2010 was one example with the relatively warm seas at that time of year producing heavy snowfall.

At this time of year, it's a little trickier to generate convection in the Irish Sea as the sea is now close to its coldest. Obviously, still a real possibility but I'm not sure if this airflow will be quite cold enough. We'll have to wait and see. Of course, little fronts can easily spring up at short notice. If so, you're not entirely dependent on convection and then it's a different ball game. In a very good way if you like snow.