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

Humberto Salazar

nacho libre wrote: »

Yes, it looks like we'll pay for this cold spell with several mild and wet days, but there are tentative signs the cold could return sometime after mid month. It will be interesting to see if we see a change in the UKMO long range for the worst, as per recent ECM runs, or if they will stick to ebbing and flowing theme.

I don't think I could handle a weeks buildup to the next event. I haven't got the stamina anymore. God be with the days you knew about snow coming the day before. If that. And hanging on to the 12.55 or 5.55 radio weather forecasts because there was nothing else.

Squidvicious

MJohnston wrote: »

Apps take a model run and programatically turn that into an auto-generated forecast for a given location. It's essentially the same as looking at a model and taking it as absolute gospel.

The app coder could have added some algorithmic adjustments on top of a model, but these will be very generalised (and in the case of the Weather Channel, US-specific). The whole point of these apps is to require zero human intervention in the forecast generation.

In short, I think they're usually rubbish. Met Eireann's app I want to give the benefit of the doubt and say that (a) they're using their own model which is better tuned for Irish meteorological conditions and (b) they might possibly be hand-tuning the model generated forecasts for parts of the country anyway, and they can feed that into their app.

Am I correct in thinking that they are not necessarily 100% accurate geographically either? I recall reading somewhere that an auto generated forecast for, say, Dublin, could actually be a forecast for a point which could be a few miles away and perhaps at a point located at sea!

nacho libre

Humberto Salazar wrote: »

I don't think I could handle a weeks buildup to the next event. I haven't got the stamina anymore. God be with the days you knew about snow coming the day before. If that. And hanging on to the 12.55 or 5.55 radio weather forecasts because there was nothing else.

:pac: You just can't help but take a peek at the models and get your hopes up. I remember those days with my late father of turning on the radio at 5 to midnight to see what was in store for us. Also the days of just opening the curtains to see the ground covered in white from a seemingly ninja snow event. They were great times as you say.

froog

Anyone know what model the yr weather app uses? Its linked to norweigan met.

Larbre34

I used to run up the bill on the house phone ringing 1550 123 854 something wicked!!

Donegal Ken

The Met Éireann app I think uses its own model the Harmonie which auto generates a forecast for 54hours ahead. After that it's the Ecmwf model it uses.

Gaoth Laidir

09Z ICON Flash (hi-res ICON run at out to 30 hours at 03, 09, 15 & 21Z) shows some good snow for much of Munster tomorrow morning, even the south Cork coast, especially around midday. This is its last frame. The 15Z should be out at around 17Z.

munsterlegend

Gaoth Laidir wrote: »

09Z ICON Flash (hi-res ICON run at out to 24 hours at 03, 09, 15 & 21Z) shows some good snow for much of Munster tomorrow morning, even the south Cork coast, especially around 6-8 am. This is its last frame. The 15Z should be out at around 17Z.

You have made my afternoon GL. It usually starts to go downhill from this time on.

Is that light green showing rain though?

Gaoth Laidir

froog wrote: »

Anyone know what model the yr weather app uses? Its linked to norweigan met.

Norwegian HiRLAM for the immediate area and the ECMWF outside of that.

MJohnston

Gaoth Laidir wrote: »

09Z ICON Flash (hi-res ICON run at out to 24 hours at 03, 09, 15 & 21Z) shows some good snow for much of Munster tomorrow morning, even the south Cork coast, especially around 6-8 am. This is its last frame. The 15Z should be out at around 17Z.

Sadly I think you're reading it with the ECM's colour key — blue on this model is sleet.

DOCARCH

Larbre34 wrote: »

I used to run up the bill on the house phone ringing 1550 123 854 something wicked!!

I also rang a few times!

I also remember in the late 80s/early 90s BBC used to have news and weather on the hour on afternoon TV. I would be there every hour to see the very low resolution radar!

Gaoth Laidir

MJohnston wrote: »

Sadly I think you're reading it with the ECM's colour key — blue on this model is sleet.

It's snow or rain&snow

TTLF

Looking at the charts, Thursday night will be quite good for the SE, going off a nowcast the band might reach into dublin, with it heavier for SCD as there's more of a chance for us (lucky me :P) but I think my focus has shifted to the event that night :eek:

By the time the Thursday band gets into parts of E Leinster, it will probably be either late evening or even Friday morning, I'm not entirely sure but it would probably be bigger flakes as it's a SW band of precip, however for me anyway, I don't expect it to stick or accumulate all too well...

If the models are believed to be right, There could be two separate "snow systems" (snow storms kind of) for the E over a 12 hour period with a respite in-between! :eek:

A little less confident with the Thursday band reaching Dublin but my guess is, the SE wind will help it get here as we're not exposed if I'm correct Kermit?

Friday night however, could be truly epic. The low system looks to be rearing and really packs a punch with it's precip as it turns to snow from North Sligo down to Wicklow Eastwards. I do however, expect the precip from the West to downgrade a bit like this low tomorrow night.

Exciting times! I do hope we get a decent shower anyway like last night.

munsterlegend

Gaoth Laidir wrote: »

It's snow or rain&snow

Looks like rain though mostly on cork coast.

Gaoth Laidir

munsterlegend wrote: »

You have made my afternoon GL. It usually starts to go downhill from this time on.

Is that light green showing rain though?

Yes, but earlier runs had that green extending well inland through the southern half of Co. Cork.

kerrycork13

Larbre34 wrote: »

I used to run up the bill on the house phone ringing 1550 123 854 something wicked!!

Me too!!! Got killed over it. Ha

MJohnston

Gaoth Laidir wrote: »

It's snow or rain&snow

Right, it just seems to lack the orange hues of the ECM charts which more specifically indicate sleet vs snow.

munsterlegend

Gaoth Laidir wrote: »

Yes, but earlier runs had that green extending well inland through the southern half of Co. Cork.

I am about 30 miles inland of cork city so will be interesting to watch. Past experience tells me to expect rain/sleet.

Gaoth Laidir

munsterlegend wrote: »

Looks like rain though mostly on cork coast.

Yes, we all know that rain will follow behind, but earlier (around midday) that green is blue.

Donegal Ken

My own app which I released back last year uses the GFS model output to generate forecasts.

Screenshot_20210210_135517_com.donegalweatherchannel.DWCApp.jpg

Screenshot_20210210_135526_com.donegalweatherchannel.DWCApp.jpg

Screenshot_20210210_135538_com.donegalweatherchannel.DWCApp.jpg

Screenshot_20210210_135722_com.donegalweatherchannel.DWCApp.jpg

Kermit.de.frog

TTLF wrote: »

A little less confident with the Thursday band reaching Dublin but my guess is, the SE wind will help it get here as we're not exposed if I'm correct Kermit?

Friday night however, could be truly epic. The low system looks to be rearing and really packs a punch with it's precip as it turns to snow from North Sligo down to Wicklow Eastwards. I do however, expect the precip from the West to downgrade a bit like this low tomorrow night.

It should reach Dublin and further north than that up to Louth or north Meath. Most if not all models show that now. A question of timing and intensity.

Friday night looks very good indeed. Just a pity there is slightly milder air in behind. We may get Saturday morning out of snow on the ground but doubtful much beyond that.

Gaoth Laidir

Strangely the 11Z TAF for Cork Airport (valid up to midday tomorrow) makes no mention of any precipitation at all! The Harmonie must be seriously lagging the ICON Flash timewise.

TAF EICK 101100Z 1012/1112 09016KT 9999 FEW020 BKN030
TEMPO 1012/1016 10017G27KT
TEMPO 1020/1024 11017G27KT
BECMG 1100/1102 11022G32KT
BECMG 1107/1109 BKN008
TEMPO 1108/1112 12025G42KT=

Gaoth Laidir

Gaoth Laidir wrote: »

09Z ICON Flash (hi-res ICON run at out to 30 hours at 03, 09, 15 & 21Z) shows some good snow for much of Munster tomorrow morning, even the south Cork coast, especially around midday. This is its last frame. The 15Z should be out at around 17Z.

A lot of coastal snow showers ahead of ot in the east I see

MJohnston

I'm hoping that this Friday/Saturday band of precip can stay on the colder side of marginal. Especially the Saturday morning stuff, give the kids something to see, unlike these overnight dustings.

Kermit.de.frog

ICON has it as snow pretty much throughout for most

TTLF

Kermit.de.frog wrote: »

It should reach Dublin and further north than that up to Louth or north Meath. Most if not all models show that now. A question of timing and intensity.

Friday night looks very good indeed. Just a pity there is slightly milder air in behind. We may get Saturday morning out of snow on the ground but doubtful much beyond that.

It is a pity, however since I'm on midterm from Friday, I will be staying up all night and walking around my estate taking photos and videos in the heavier snow.

I will also be doing the same tomorrow night. That band going off model guidance for tomorrow seems to keep Dublin under the band for quite some time, maybe a few hours? depends on intensity though.

I'll get lots of photos just for you so don't worry! :P

Also just to add ; I'm guessing tomorrow/fridays low would be more inclined to stick because of the frigid DP/WB and temps, along with the more intense precipitation? Sort of what we saw last night here minus the snow grains?

davidsr20

I see a lot of chats for the 12/13th. I thought tomorrow is the big day for most snow. Kermit could u tell me how east Galway 20kms inland might fair out please tomorrow? And thanks.

Kermit.de.frog

davidsr20 wrote: »

I see a lot of chats for the 12/13th. I thought tomorrow is the big day for most snow. Kermit could u tell me how east Galway 20kms inland might fair out please tomorrow? And thanks.

You should get a good few hours out of it. 2 - 5 cm's seems to be the concensus in that part of the woods. That's model guff though. Could be more locally.

kerrycork13

munsterlegend wrote: »

Looks like rain though mostly on cork coast.

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.

redsteveireland

davidsr20 wrote: »

I see a lot of chats for the 12/13th. I thought tomorrow is the big day for most snow. Kermit could u tell me how east Galway 20kms inland might fair out please tomorrow? And thanks.

Looking like borderline snow /sleet at the moment, best to wait another while before planning your snowman design.

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.