Cold Spell - Feb 7th to 13th 2021 - Technical Discussion

Meteorite58

ECM 06Z

Looking decent enough along Southern counties into the SE, windy also along coasts and especially Kerry.

E Munster and W and S Leinster look to get a fair bit of snow.

GFS similar but a bit more gung ho perhaps, showing more in the W. A lot of areas getting a dusting at least it would seem.

Nqp15hhu

So why the big difference between the gfs and ECM? Does the GFS expect surface cold?

Meteorite58

UKMO and ICON


Fri evening into Saturday could be the big one, all the models showing it at this stage.

Rebelbrowser

kerrycork13 wrote: »

West cork but further east is showing snow. Prob marginal but If it comes in heavy and snows it will help keep temps down esp as it's slow enough moving. I'm hoping.

Not hugely confident for here tomorrow but i would, just as a general observation, say that those charts tend to exaggerate the coastal band when trying to show rain/sleet on coasts. I think its because they aren't that granular but if they want to show that, say, the 8km nearest the coast will be rain / sleet they often end up showing a 25km band because thats the size of the pixels they use.

compsys

Meteorite58 wrote: »

ECM 06Z

Looking decent enough along Southern counties into the SE, windy also along coasts and especially Kerry.

E Munster and W and S Leinster look to get a fair bit of snow.

GFS similar but a bit more gung ho perhaps, showing more in the W. A lot of areas getting a dusting at least it would seem.

Looking at that chart it looks as if most of the snow for Dublin is going to fall in the dead of night when no one is around to see it. Typical.

wicklowdub

Wonder will Wicklow Mts take all the steam out of it for SCD for those fronts Thu/Fri ?

lucernarian

Meteorite58 wrote: »

UKMO and ICON


Fri evening into Saturday could be the big one, all the models showing it at this stage.

]

UKMO showing mostly hill snow by the looks of it. Exact nature and amounts of snow seem quite uncertain for the populated coastal and low lying areas.

Zogabomb

wicklowdub wrote: »

Wonder will Wicklow Mts take all the steam out of it for SCD for those fronts Thu/Fri ?

I'm in Shankill too, I think because it's a SE Wind, the mountains won't be much of an issue, I'm more concerned about whether the front gets this far!

Nqp15hhu

lucernarian wrote: »

UKMO showing mostly hill snow by the looks of it. Exact nature and amounts of snow seem quite uncertain for the populated coastal and low lying areas.

These frontal events always seem to end up as hill snow here no matter how cold it is or has been prior to the front.

Warm air always races ahead.

DOCARCH

Nqp15hhu wrote: »

Warm air always races ahead.

I hear ya!

Not particularly looking forward to tomorrow. Not overly confident. Couple of sure thing events in the past ended up as icy rain events!

Tomorrow will be like driving down a big hill with dodgy brakes!

TTLF

wicklowdub wrote: »

Wonder will Wicklow Mts take all the steam out of it for SCD for those fronts Thu/Fri ?

Wicklow Mts shadows NCD more than SCD. Thursday could be fine, but it's probably based off where you live, although Thursdays low seems to spread up across the entire E coast towards Louth possibly as Kermit said. I think Friday's low should be fine for us because of the direction, I think.

It might be an issue if you're right beside or very east of the mountains, but places further toward Dublin suburbs and inland shouldn't have much issues with the shadow I don't believe

Supercell

wicklowdub wrote: »

Wonder will Wicklow Mts take all the steam out of it for SCD for those fronts Thu/Fri ?

I'd say the opposite, they'll enhance south county Dublin - especially the east and east Wicklow.
Artictree is going to be buried up in Roundwood I'd say, us down by the coast..well whether its sleet or snow is more the question, even if its snow it may be very wet and not settle much within a km or so of the coast, lets see..

bazlers

TTLF wrote: »

Wicklow Mts shadows NCD more than SCD. Thursday could be fine, but it's probably based off where you live, although Thursdays low seems to spread up across the entire E coast towards Louth possibly as Kermit said. I think Friday's low should be fine for us because of the direction, I think.

It might be an issue if you're right beside or very east of the mountains, but places further toward Dublin suburbs and inland shouldn't have much issues with the shadow I don't believe

Im open to correction here but i dont think the wicklow mountains will be a big factor as showing. It would be different if the front was coming from the south east but that is south west.
Just hope the temps hold up (or down) for ye in the south and intensity further north. Small margins but big gains. Best of luck.

Donegal Ken

Meteorite58 wrote: »

UKMO and ICON


Fri evening into Saturday could be the big one, all the models showing it at this stage.

The ARPEGE which is normally mild bias also showing a good risk into north Connacht, Ulster and north Leinster on Friday night and Saturday

Gonzo

davidsr20 wrote: »

Is easterly snow not the best snow?

Usually it is but unfortunately this one wasn't to be with too much going wrong such as air temperatures, poor ground temperatures, lack of freezing, lack of instability and a failure to get -10 to -12 uppers right through the entire country for a sustained period of time. To me this event is more like an easterly one would experience in the second half of March or early April as what we have experience was a glancing blow of an easterly, we were right on the edge of it. The full impact of this easterly did not make much of a journey past South-eastern England and Scotland with Netherlands and Germany getting the real deal.

If we get another bite of an easterly and it is more of a direct hit north-easterly it could deliver far better than this spell even well into March. I'm not a fan of cold spells in March but seeing how poor this one faired out, there is still a chance of something better in the next 6 weeks.

Donegal Ken

Status Yellow - Wind warning for Munster, Connacht and Leinster
Met Éireann Weather Warning

Strong to gale force southeast winds in conjunction with rain, sleet and snow will lead to poor visibility and hazardous conditions.

Valid: 08:00 Thursday 11/02/2021 to 08:00 Friday 12/02/2021

Issued: 15:00 Wednesday 10/02/2021

Supercell

Nqp15hhu wrote: »

The warm front is coming from the SW. the problem is that it usually clouds over before it arrives and some warm air filters through.

Yep, I think the models are overplaying this fronts snow potential this time, there is no embedded cold and snowfields to keep it..going to be mainly a hills and mountains event (imho)

wicklowdub

TTLF wrote: »

Wicklow Mts shadows NCD more than SCD. Thursday could be fine, but it's probably based off where you live, although Thursdays low seems to spread up across the entire E coast towards Louth possibly as Kermit said. I think Friday's low should be fine for us because of the direction, I think.

It might be an issue if you're right beside or very east of the mountains, but places further toward Dublin suburbs and inland shouldn't have much issues with the shadow I don't believe

Shankill so close to the coast but a good distance from the Dublin Mts.

Kermit.de.frog

Tomorrow, in a sense, is a free hit. Cold before and after. Friday night snow event...

Supercell

To show what I mean, when a warm sector or occlusion for that matter bumps into this, is it going to turn into settling snow readily at ground level? Would love to be proved wrong, just trying to take emotion out of what the numbers are actually saying.

Gonzo

Supercell wrote: »

Yep, I think the models are overplaying this fronts snow potential this time, there is no embedded cold and snowfields to keep it..going to be mainly a hills and mountains event (imho)

I think many of us will see falling wet snow between tomorrow evening and perhaps Friday night but the ground temperatures are not ideal and the air will become even more modified so I feel lying snow will be reduced and transitional. I could be wrong but 1 to 5cm is about the most I would expect away from high ground. Freezing rain is also a possibility in places and that could lead to tricky conditons in places. Wicklow Mountains will likely get hammered for a while at least.

TheMilkyPirate

12z has Friday night/sat mornings front staying as snow across the entire east coast

Kermit.de.frog

Gonzo wrote: »

I think many of us will see falling wet snow between tomorrow evening and perhaps Friday night but the ground temperatures are not ideal and the air will become even more modified so I feel lying snow will be reduced and transitional. I could be wrong but 1 to 5cm is about the most I would expect away from high ground. Freezing rain is also a possibility in places and that could lead to tricky conditons in places. Wicklow Mountains will likely get hammered for a while at least.

Have to disagree there. Frontal zone hitting this type of airmass. Not wet snow. It's intensity you need to watch.

850hpa temperatures tomorrow evening



Here is the aftermath on Friday...



Note the struggle to shift the deep cold air mass.

Ground temps are not freezing but it won't take much that is persistent to settle either.

Swings and roundabouts.

Inmate2020

Is it just snow or a storm due ? Bray TC preparing for flooding on the prom ????

Donegal Storm

Can anyone point to a frontal snow event that actually worked out for us over the past 20 years? Maybe I'm forgetting some but off the top of my head I can't think of anything memorable

Haven't looked at the models much this week but just off past experience I'd guess we'll end up with either a weak front with minimal accumulation apart from a few lucky spots or else a more active front that turns into a transitional mess for low ground. We get rarely hit the sweet spot in between

Hoping I'm wrong but the Irish climate rarely fails to disappoint

Oneiric 3

10 day forecast from the UK Met:

https://www.youtube.com/watch?v=i1ldY5qCgEY

https://www.youtube.com/watch?v=i1ldY5qCgEY

They talk of mild weather coming in for next week but they are not altogether certain either.

nacho libre

The problem with these situations is that even though the first front will fail to bring in milder weather, it may still modify the air to the extent that the later fronts may mix out the cold quicker than anticipated by forecasters. We've seen this happen before when milder air gains the upper hand quicker than expected. I would only take Thursday and early Friday as snow being certain for the east, south east, midlands and to the north. Those of us further west may only see snow until late Thursday.

By Saturday morning it could well be mild for most of the country, except Ulster. However, between then and now there is a good chance of snow and reasonable accumulations across the country, especially in those places that will have had clear skies for two nights running. Heavy snow will also help.
I just really hope there is some last minute backtrack by the models to a situation whereby we avoid flooding becoming a potential issue into next week. Although that is very unlikely, unfortunately.

Reckless Abandonment

Gonzo wrote: »

I think many of us will see falling wet snow between tomorrow evening and perhaps Friday night but the ground temperatures are not ideal and the air will become even more modified so I feel lying snow will be reduced and transitional. I could be wrong but 1 to 5cm is about the most I would expect away from high ground. Freezing rain is also a possibility in places and that could lead to tricky conditons in places. Wicklow Mountains will likely get hammered for a while at least.

Are ground temps ever ideal in ireland. We've had a colder winter than many I can remember even 2018. If it snows hard and long enough im sure it will build up. Just to add im not expecting much from all this. Im more concerned about flooding we so need a week or two of dry weather

bazlers

nacho libre wrote: »

The problem with these situations is that even though the first front will fail to bring in milder weather, it may still modify the air to the extent that the later fronts may mix out the cold quicker than anticipated by forecasters. We've seen this happen before when milder air gains the upper hand quicker than expected. I would only take Thursday and early Friday as snow being certain for the east, south east, midlands and to the north. Those of us further west may only see snow until late Thursday.

By Saturday morning it could well be mild for most of the country, except Ulster. However, between then and now there is a good chance of snow and reasonable accumulations across the country, especially in those places that will have had clear skies for two nights running. Heavy snow will also help.
I just really hope there is some last minute backtrack by the models to a situation whereby we avoid flooding becoming a potential issue into next week. Although that is very unlikely, unfortunately.

Agree about the cold nights. We should forget about getting the snow fields now. Hopfully there will be no more ridiculously tiny flakes and cloud cover before this event now.what we want is clear skies and slacker winds to get the temps down as low,as possible before the arrival of this front to give it every chance possible.

Gonzo

just taken a look at the latest models to see where we are at, I haven't looked at the models since yesterday evening.

Arpege shows tomorrow's front dying out over the south and it fails to make much progress into Leinster, however the west could see some snow from it.



Arpege looks more promising for Friday night into Saturday morning with Meath/Dublin/Louth/Wicklow/Cavan/Monaghan/Leitrim and Donegal more in the firing line for several hours of sustained snow.



5 to 10cm in many places, this is an upgrade on previous runs.



However dew points start going the wrong side of marginal early enough on Saturday.



GFS 12z shows several cm of lying snow up to Saturday afternoon for southeastern Leinster and far north of Leinster but very little for Dublin/Meath and Kildare.



WRF 2 to 5cm generally but up to 10cm north midlands and parts inland north-west