Big Freeze Discussion [Happy New Year]

Snowaddict

Gonzo wrote: »

things have downgraded somewhat since yesterday, perhaps more to what was shown on new years eve. Tomorrow looks milder than today, any showers should be rain or sleet. Turning colder from Monday with some chances of very cold and possibly snowy weather from Tuesday onwards. Cold snap looks like coming to an end next weekend.

Again this could read totally different by this time tomorrow.

I am afraid Gonzo that you are misguided in your interpretation of the current NWP Guidance, as indicated by Black Briar, Min, Weathercheck & others.

Firstly, with reference to tomorrow. Tomorrow will be & will feel bitterly cold. 850mb temperatures across the country will range from -7 to quite possibly -11 in Eastern districts, as a pool of cold air moves down across the country. This is indicated quite nicely on the 06Z GFS Output. A complex undercutting area of low pressure will continue to be centred to the south/southwest of the country, generating enhanced Easterly winds, making for a windchill that will make it feel well below 0C in many parts of the country, particularly in exposed Eastern areas.



At this stage now, this is more than just a cold snap, it is quite clearly a prolonged and sustained cold spell, being very close to a severe wintry outbreak in many respects. You are correct in that the risk of snowfall really does increase from Tuesday onwards. Very cold air will filter down across the country, in a brisk, at times strong Northeasterly airflow. Apart from embedded frontal troughs, there is also the risk of an area of shallow low pressure being centred to the Southeast towards mid-week, generating enhanced snow showers over the Irish Sea. In addition, convective developments should occur widely across the Irish Sea out to Wednesday, with very decent inland penetration of shower activity in rather strong winds. Again, it will feel bitterly cold & temperatures will struggle to rise above freezing in many areas.

This was indicated earlier from the ECMWF 00Z output:





Longer term, there are no signs on any guidance of a breakdown in the bitterly cold conditions, event out to T+240. Of course, that could very well change and anything past T+120 is subject to vast change, however at the moment the outlook is for discontinuous cold, severe at times with the risk of snowfall.

ECMWF 00Z - T+168 - 09th January



GFS 06Z Ensembles - Air Temperatures - Dublin

http://charts.netweather.tv/ensimages/ens.20100102/06/t2mDublin.png

In light of all of the above and several background factors, I would be very confident in a persistence of the very cold conditions until this coming Thursday at least. There is a small risk that if the formation of the High over Scandinavia does not take place rapidly enough, then we might lose out the westward advection of the very cold air. However, ECMWF does not indicate anything as such at the moment - although it's a risk. If this does occur correctly however, we are looking at another 5+ Days of further very cold, even severely conditions and snowfall potential.

Cold weather, with an increasing risk of snowfall is guaranteed until this coming Wednesday at least.

Also, note that ECMWF verifies the best in the Northern Hemisphere out to Day 5 & Day 6.

SA

lucernarian

nacho libre wrote: »

are you getting the impression that everything is being pushed back? originally today was supposed to be bitterly cold with no talk of milder air in the mix. can we just take it as red that anytime there is precipitation in the form of troughs coming from the north that conditions become marginal, given the very nature of a trough's formation this is likely the way it will always be. don't correct me if i'm wrong, but it seems unless we get a polar low, there is always a greater risk that we will see sleet falling by day rather than snow.

I don't think stuff is being pushed back. In fact I agree 100% with your post. I want to bring a bit more reality back into this, and not be clutching at straws and poorly verifying model forecasts. Unless the models make it clear that all the ingredients are in place for my part of the world (ENE winds greater than 15 kts, -9 850hPa air, highish SSTs and falling, not increasing 2m air pressure, I will not be too excited by this. And even then, general shower trains almost never lead to more than 10 cm or so of snow even at higher levels. Organised precip is needed for more than that IMO. And that sort of event is very rare. Nothing like that in the Pale since Shrove Tuesday, 2001.

lucernarian

One thing that got me annoyed on this forum is this. No forecast is guaranteed. EVER.

Snowaddict, to be at least fair to Gonzo in this regard, he mentioned the BBC forecasts. And met eireann too. Weren't the BBC predictive sequences meant to be taken more seriously than model output, as they had human input? Black Briar and others have also said this.

I'm going to point out here that I still do expect very cold conditions to prevail over Ireland in the coming week. I just want to avoid the assumption that snow *has* to follow cold air wherever it goes. The risks of this have already been illustrated by recent weeks and days.

Drapper

snowing in Carpenterstown in Castleknock, very light but it is snow but was only a little flurry

spadder

To_be_confirmed wrote: »

One thing that got me annoyed on this forum is this. No forecast is guaranteed. EVER.

Nothing in life is Guaranteed, except death and taxes of course

Winger_PL

A light rain shower has just clipped Maynooth, no real signs of thaw on the ground but the trees started to loose their white pretty quick.

Snowaddict

To_be_confirmed wrote: »

One thing that got me annoyed on this forum is this. No forecast is guaranteed. EVER.

Snowaddict, to be at least fair to Gonzo in this regard, he mentioned the BBC forecasts. And met eireann too. Weren't the BBC predictive sequences meant to be taken more seriously than model output, as they had human input? Black Briar and others have also said this.

The following is the latest Met Eireann forecast for tomorrow:

Frost and ice clearing only slowly tomorrow Sunday, and persisting in central and northern areas for much of the day. Some sunny spells, with many places dry, but a few wintry showers are possible along parts of the south and east coasts. Top temperatures zero to plus 5 C., but feeling even colder in the stiff easterly breeze.

The BBC Graphics/Guidance are a direct feed from the raw input from the UKMO's NAE Hi Resolution Model, however temperatures can sometimes be modified etc. Initially, during the week, it was looking like Sunday could get up to +7C, as some output indicated the area of low pressure to the south making northward progress. In fact, Sunday's outlook has turned progressively colder over the past two days.

I'm not being unfair at all, I'm just pointing out the facts that are available to us in terms of model guidance & forecasts. Met Eireann mention a ''chilling'' Easterly wind tomorrow, that's going to feel pretty cold.

As regards to forecasts not being guaranteed, it's impossible. Ireland is an island surrounded by maritime influences, chiefly that of the Atlantic - a 3,000 mile long sea track that enables significant modification of the airflow. Within T+24, anything can change, the exact track of a frontal fetaure will have significant implications for precipitation distribution etc. There are far too many variable in the mix, it's just not possible. 75%-80% accuracy at around T+36 to T+24 is quite possible, any higher is generally not.

SA

:oHi all. Im a bit confused now reading over the last few pages of posts.

Could someone tell me, if, Dublin is due to get snow tonight or not?
My head got lost somewhere in amonst it all. Sorry.:o

Doyler1981

Just rained here! The roads are going to be even more dangerous later this evening. It always seems to be a case that threat of snow gets pushed back 24 hours, no doubt the charts will be showing the snow threat for Wednesday tomorrow instead of Tuesday!

lucernarian

That is being discussed here among other things. I am of the opinion that there won't be any significant amounts tonight. i.e. 3 cm at the very max in very localised spots. 1 cm generally. A bit like new year's eve perhaps.

Snowaddict wrote:

Cold weather, with an increasing risk of snowfall is guaranteed until this coming Wednesday at least

As likely as it is, what makes you claim that this is guaranteed? Surely that's knowledge that no mortal can know? Even if it is 99% likely, it's not guaranteed.

And why are you talking about Fantasy Island (charts that are unrealistic, and almost fantastical, which predict weather in a few days or even further out) charts when they are so unlikely to verify as you rightly point out? Given the percentages, I could quite rightly point out that in my opinion, the Greenland high will not link up with the Scandi high but will sink southwards and leave us with cold foggy days. But why does no one talk about that outcome, if it's a possibility?

Snowaddict

To_be_confirmed wrote: »

That is being discussed here among other things. I am of the opinion that there won't be any significant amounts tonight. i.e. 3 cm at the very max in very localised spots. 1 cm generally. A bit like new year's eve perhaps.


As likely as it is, what makes you claim that this is guaranteed? Surely that's knowledge that no mortal can know? Even if it is 99% likely, it's not guaranteed.

And why are you talking about Fantasy Island (charts that are unrealistic, and almost fantastical, which predict weather in a few days or even further out) charts when they are so unlikely to verify as you rightly point out? Given the percentages, I could quite rightly point out that in my opinion, the Greenland high will not link up with the Scandi high but will sink southwards and leave us with cold foggy days. But why does no one talk about that outcome, if it's a possibility?

Cold weather is guaranteed out until Wednesday, with an increasing risk of snowfall. Now I didn't say that snowfall is guaranteed by any means, the cold weather is, there is just an increasing risk of snowfall. It is guaranteed because we already have all of the Key elements in place. A significant area of blocking high pressure centred over Greenland, with the Jet Stream displaced very far to the south, relative to other winters of late. In addition, we already have the beginning of the formation of an area of low pressure to the North of Scandinavia. The general theme of very cold conditions up until Wednesday is guaranteed, because all of the large scale features are already in place to support this.

With regard to the snowfall, yes that could well happen. Even at T+24, snowfall is one of the most difficult elements to predict. As I said & many others have said, it's only an increasing risk, because of the formation of an unstable northeasterly flow.

I would think that T+120 is the beginning of the FI/More Reliable boundary, the majority of what has been discussed above is within T+120. T+168 was shown because I was stating how guidance was not showing a mild incursion towards the end of the week, as was being suggested.

Regarding the Greenland/Scandi High, what percentages are these? The evolution is based solely upon a favourable Jet Axis. A large portion of the GLH will actually decline, sink southwards and become absorbed into an area of HP centred in the central southern North Atlantic. It is the motion of the Jet Stream that allows the Scandi High to form and back westwards & continue to strengthen. Again, I have clearly stated the risk of this not happening above, so I do think it is being discussed.

SA

Doyler1981

Rain mixed with snow here now!

dedon

Is there any chance we will get some snow in Limerick this evening or tonight? Is that band of showers due to push down?

G-Money

I haven't a clue what most of the posts are saying. I just want to know when this bloody cold weather will f**k off.

I'm in the Stillorgan area of Dublin and there *seems to be a thaw on. All of the trees and houses are back to their normal colour and the snow seems to be evaporating.

Hopefully if the temp gets up to +5c tomorrow, it will help move things along too.

To_be_confirmed

To_be_confirmed wrote: »

Weren't the BBC predictive sequences meant to be taken more seriously than model output, as they had human input? Black Briar and others have also said this.

No.They are sometimes quite wrong
They don't pay much heed to Ireland.
This was true even in the 80's when they'd stick a symbol on Eastern Ireland with one flake on it and put 3 flakes on the ones in Eastern England even though Dublin might be having heavy sea effect showers.
They give a broad national picture for the UK.
Their local broadcasts are much more specefic for regions and often say a lot more on snow than the national ones.

I'm going to point out here that I still do expect very cold conditions to prevail over Ireland in the coming week. I just want to avoid the assumption that snow *has* to follow cold air wherever it goes. The risks of this have already been illustrated by recent weeks and days.

One point I've always made on this forum since it started nearly 6 years ago is the following and it's worth repeating.

Easterlies are useless unless they are sustained for at least 4 or 5 days.It's only after that that we see real excitement.
We are staring down the barrel of those kind of synoptics regardless of whether it's East or North east.
Jan '87 brought little features down from the north east with increasingly cold air behind and in fact as I've said many times here sea level river freezing cold despite the wind coming off the sea.
Feb '91 and it was a sustained Easterly.I recall features reaching these shores all the way from the Baltic.

Bear in mind it's cold already.
Here in strong sunshine and even in a westerly , we were hard set to peak at 4c in coastal wicklow-so cold features have less work on their hands.

Now of course from a snow loving point of view the whole thing could go tits up...however a little leverage to people who have experienced what these types of synoptics can do would be nice.

These synoptics are very very difficult to forecast but NOTICE the trend in the Met Eireann forecasts.
They are increasingly using the word snow and expect to hear those glorious words "outbreaks of snow" next week.

Philcan

Hi,

I have been following these threads since mid December and feel I am becoming addicted. At times I have got dangerously close to actually learning about the weather, thanks to great posts from Su, WC and others.

Anyhow I now feel I am ready to make forecasts. My forecast is as follows:

Mid next Week: some snow showers on the east coast....nothing to get too excited about.

Next Saturday (approx 2pm): Heavy and prolonged snow for most of the country leading to the biggest snow event ever seen in modern Ireland. (The only place to miss out on the snow will be Coleraine in NI.)

March 3rd (approx 10am): A thaw sets in.

My forecast is based on the tea leaves from a split tea bag from my morning cup of tea.

The leaves also predict that Ipswich will win today in the FA cup and England will win the World Cup this summer.

Thanks

MayoForSam

Raining here in Galway - last thing we wanted, it will freeze on the roads tonight and they will be lethal in the morning.

If its going to snow, then I would prefer a good dumping (not too much likelihood there) - freezing rain is the worst possible outcome from this weather spell :mad:.

knoximus

Sat 2 January

All parts of Britain and Ireland are in for a lot of increasingly cold and snowy weather as we go through the next week with some potentially severe winter weather developing across our shores. We would advise people to prepare themselves for a spell of winter weather that's not been seen for many years as severe frosts and heavy snowfalls become the main feature during next week.
http://www.metcheck.com/V40/UK/HOME/

lucernarian

With respect BB, we have both stared down the barrel of these synoptics before, to come away empty-handed. I remember the 05/06 winter as an example of just how frustrating forecasting can be. Exceptional cold is still only being forecast in FI. A more "normal" cold is what we can at least expect for the first half of this week. The sort of cold that could just as likely give hail or sleet showers as snow for much of that period. (the -10 850hPa air is not always around) Or more likely, that convection is stifled by ridging or unfavourable wind directions. I haven't seen any fax charts yet that show troughs approaching from the east.

So only unorganised precipitation is being forecast by the UKMO in the next couple of days or so, for the Pale anyway and southwards of that. That can deliver, I remember 3rd January 08 as a great example. But it wasn't the sort of snow that made people abandon cars or anything like that! Serious events are rare by their nature.

Finally, these NE winds are still forecasts. After what's happened in recent weeks, I'll have to believe it when I see it. The true easterly winds are still dependent on the Scandi HP being born and being positioned right.

Lumi

MayoForSam wrote: »

Raining here in Galway - last thing we wanted, it will freeze on the roads tonight and they will be lethal in the morning.

If its going to snow, then I would prefer a good dumping (not too much likelihood there) - freezing rain is the worst possible outcome from this weather spell :mad:.

There are some angry looking clouds to the north of here but skies are clear over the city. There's been a slight thaw but frost remains in the shade

Su Campu

Just had a rain shower briefly turn to wet snow. Casement reported snow at 2pm.

Currently in Celbridge T0.6°C, DP -0.3°C

Supercell

Light snow flurries on and off here, definate drip drip of a slow thaw too but temp already dropping so expect the snow to turn hard and icy again soon.

Mothman

10 second rain shower, but temp has cooled 1C since and sun has appeared again.
A good thaw today except for the cold ground in shade. A lot of wet surfaces that'll probably freeze tonight
3.7/0.5C atm

To_be_confirmed

To_be_confirmed wrote: »

With respect BB, we have both stared down the barrel of these synoptics before, to come away empty-handed.

I've experienced them in real life so feel I have a licence to talk about what they can do and what I think they will do.
Previously on boards I've said that a particular projected Easterly is no good and such and such but now we appear to be getting a sustained blast from both the East and NE at times and I don't see that ending before next week end.
I've a higher confidence in that by far than I do in having any stab at what next weekends weather is.
So in a nutshell it would appear that one vital missing ingredient to previous continental flows is being at least fulfilled for the next 5 days and thats exciting.

On a side note,I got a call from some friends who I couldn't join because I'm working today.
They are up on a mountain at about 1800ft asl at the moment in south wicklow a few miles from me and report level snow [not drifts] of over 2 feet in depth.

inabina

Supercell wrote: »

Light snow flurries on and off here, definate drip drip of a slow thaw too but temp already dropping so expect the snow to turn hard and icy again soon.

sandyford, temp has dropped from 3.8 to 2.0 in last 50 mins:D

JonnyM

any chance of snow in the east south east next few days??

inabina

JonnyM wrote: »

any chance of snow in the east south east next few days??

you will find all the answers in previous posts today! yes in short.

Supercell

JonnyM wrote: »

any chance of snow in the east south east next few days??

I live in the South East, it is snowing here now, so I'll go with an affirmative.

Tabnabs

A few quick light/moderate snow showers in Dublin 24, as they clear south towards Kippure(/Everest )

JonnyM

inabina wrote: »

you will find all the answers in previous posts today! yes in short.

cheers just didnt want to thral through 28 pages of it :pac::P