Winter Model Discussion 12Z 15/1/13 onwards.

[manutdmatt1986]

BBC South have it snow free all day Saturday and yet the five day forecast shows it snowing here on saturday! I cannot believe that anywhere in the South (apart from perhaps Cornwall) will have rain over the weekend especially with temps dropping because of lying snow. I bet if you watched each region's forecasts side-by-side it would be a right mish-mash of information. In a nutshell - I agree with you!

BBC South East (which covers some of the same areas as BBC London) didn't mention snow turning to rain and they said it will be staying very cold.

[Methuselah]

I think the problem is that even BBC London no longer than 10 mins ago said that London and the SE will turn milder on Saturday and the snow will turn to rain. Lots of contradictions so reason for scepticism. Hard to know as all models are still not on the same hymn sheet even 36 hours out.

Aye, but even maxes of 4C would be milder than what we have now. Perhaps 'less cold' would be more apt?

[Lincs Observation]

BBC South have it snow free all day Saturday and yet the five day forecast shows it snowing here on saturday! I cannot believe that anywhere in the South (apart from perhaps Cornwall) will have rain over the weekend especially with temps dropping because of lying snow. I bet if you watched each region's forecasts side-by-side it would be a right mish-mash of information. In a nutshell - I agree with you!

I tend to agree with this post i watched the BBC who were going for the front to pass across to us in the east with the heaviest snow in mid Wales but with the rest of the country having snow issues, Then Look North were still been cagey about the front getting to us and the comment made " will firm up on details tomorrow"

I think this just goes to show how complicated the weather patterns have become over the past few years or is it just a case of too much information muddies the waters................i leave that one to the experts.

LO

[Long haul to mild]

Thanks for your reply .. I thought 528 dam air meant the air was cold up there, and if it was higher

than 528 dam, then it wasnt so cold higher up ?

sorry for the question.

Yes, basically you are right but lots of other factors come into play, like dew points, wet bulb freezing levels, and upper temperatures, which can mean the 528 DAM line is not so vital to get snow.

Don't worry about asking questions; I do it all the time and I have learnt so much from the many respected posters here.

[Cloud 10]

The 12z NOGAPS is very ecm-ish.

http://www.meteociel...apse_cartes.php

[OldMetMan]

Some very interesting days ahead!

However, a forecaster's nightmare for sure, as they agonise over the eastward extent of snow for Friday, and indeed beyond.

I said the other day that I thought the overall circulation pattern looked anomalous and there are features at 500mb that do, I think, favour a rather longer spell of cold that looked likely earlier in the week.

The most interesting feature I think is the building ridge heading up the Norwegian Sea, helping to solidify the surface HP, together with the amplifying upper trough extending further S into the Mediterranean. It has taken a while for the models to come into reasonable agreement that approaching fronts will occlude out or for triple-point LPs will form and slip away SE as that formation gradually developed.

The real dilemma lies in deciding how far E this process will happen, which quite unusually is causing the Met Office to be ambivalent only 48 hours out from the event. At 500mb, because of the above configuration, there is much more of a NW/SE component to the flow over the whole UK rather than a W/E one, at least for the next few days, so looking at the latest 12Z FAX charts, I'd say the placement of the frontal boundary for Friday's system looks pretty reasonable.

Beyond that, the uncertainty increases considerably. The strong jet out of the US/Canada is not showing much sign yet of propagating E as the GFS has been saying for some days and my feeling at this stage is that it will gradually do this but at a more southerly latitude. There have been strong hints in the GFS for more decisive pressure rises building further W to the N of us in the mid- to long-term, although today's 12Z has once again reverted to zonality as it so often does. The 500mb flow gives me the impression that heights will build significantly further W across Iceland and Greenland bringing about these pressure rises.

So, I think we face some very interesting conditions, perhaps a more vigorous LP early next week may warm things up slowly for a day or so but then rising pressure will bring back colder air once again as next week goes on. We have ideal conditions for some significant snow Friday - several very cold days preceding it so the ground pretty well frozen - that together with a slowing frontal system could well dump a fair amount of snow. Not to sure how coastal areas such as where I am will fare. I would have preferred a more SW approach than a W one as a wind off the sea could turn it all to rain.

Nevertheless, I am becoming convinced that we are going to see model output stretching the cold spell out longer as time goes by.

It's all going to be really interesting to watch!

[pages]

Experienced members which run would we prefer ECM BOM JMA I am not fussed. All 3 have numerous snow events and if anything they are heading towards even colder conditions at the end of the runs.

[atrow]

I am so confused trying to look at the models .people seem to be ramping up my area (hertfordshire) for snow then others say it wont make it to me. any tips on what models to look at and what is expected?

[DanDorsetUK]

Amazing points west forecast tonight if anyone missed it here it is

http://news.bbc.co.uk/weather/hi/news/newsid_7760000/7760862.stm

[Mini tiger]

BBC will likely still be working off previously supplied data that very had it for as a snow to rain event (for many in the West and South at least) as the front bulldozed it's way through. Things have evolved a bit since then and (I would guess) would filter to the BBC etc as time goes on.

After the near time-frame faxes earlier on, tonight's fax updates are going to be fascinating!

S4 you are not far along the coast from me. Where do you think the front will stall, and will the southerlies from France keep us cold enough ?

[IDO]

Aye, but even maxes of 4C would be milder than what we have now. Perhaps 'less cold' would be more apt?

Highs were only 2c which makes it even more surprising.

ECM precip for the 12z run only about 4-6cm for the SE:

The heavier snow in the NW (after moving from SW) and dies as it moves NE.

Monday's event on the ECM looks v. south centric and a weakening feature, snow wise:

[Frosty.]

What do the experienced members make of the latest faxes?

t48:

t60

t72:

EPIC for very cold and very snowy weather, bitter cold SEly winds from a frozen near continent and active fronts is a potent cocktail for blizzard conditions and snow showers to many northern and eastern areas away from the frontal zones.

Edited January 16, 2013 by Frosty039

[Tom Montalbano]

What strikes me from the last few days output from all models, up to about D6/7 or so, is each same time run seems to have backed the pattern further SW, each time. In fact, something the more technically minded suggested could well happen.

Wherever we go from here, has to be one of the most fascinating periods of model watching I've had the pleasure to witness.

Regards,

Tom.

[IDO]

WRF NMM model does not even get the snow to the SE. It stalls over Swindon way and turns to rain at its edges? Certainly a lot of confusion.

[ChartViewer]

CMA T96....and has been very consistant out to Sunday bar last last nites run

Edited January 16, 2013 by ChartViewer

[russell k]

Some very interesting days ahead!

However, a forecaster's nightmare for sure, as they agonise over the eastward extent of snow for Friday, and indeed beyond.

I said the other day that I thought the overall circulation pattern looked anomalous and there are features at 500mb that do, I think, favour a rather longer spell of cold that looked likely earlier in the week.

The most interesting feature I think is the building ridge heading up the Norwegian Sea, helping to solidify the surface HP, together with the amplifying upper trough extending further S into the Mediterranean. It has taken a while for the models to come into reasonable agreement that approaching fronts will occlude out or for triple-point LPs will form and slip away SE as that formation gradually developed.

The real dilemma lies in deciding how far E this process will happen, which quite unusually is causing the Met Office to be ambivalent only 48 hours out from the event. At 500mb, because of the above configuration, there is much more of a NW/SE component to the flow over the whole UK rather than a W/E one, at least for the next few days, so looking at the latest 12Z FAX charts, I'd say the placement of the frontal boundary for Friday's system looks pretty reasonable.

Beyond that, the uncertainty increases considerably. The strong jet out of the US/Canada is not showing much sign yet of propagating E as the GFS has been saying for some days and my feeling at this stage is that it will gradually do this but at a more southerly latitude. There have been strong hints in the GFS for more decisive pressure rises building further W to the N of us in the mid- to long-term, although today's 12Z has once again reverted to zonality as it so often does. The 500mb flow gives me the impression that heights will build significantly further W across Iceland and Greenland bringing about these pressure rises.

So, I think we face some very interesting conditions, perhaps a more vigorous LP early next week may warm things up slowly for a day or so but then rising pressure will bring back colder air once again as next week goes on. We have ideal conditions for some significant snow Friday - several very cold days preceding it so the ground pretty well frozen - that together with a slowing frontal system could well dump a fair amount of snow. Not to sure how coastal areas such as where I am will fare. I would have preferred a more SW approach than a W one as a wind off the sea could turn it all to rain.

Nevertheless, I am becoming convinced that we are going to see model output stretching the cold spell out longer as time goes by.

It's all going to be really interesting to watch!

thanks OLMM, can we please stop quoting BBC ITV C4 fotecasts

[Methuselah]

Highs were only 2c which makes it even more surprising.

ECM precip for the 12z run only about 4-6cm for the SE:

The heavier snow in the NW (after moving from SW) and dies as it moves NE.

Monday's event on the ECM looks v. south centric and a weakening feature, snow wise:

Could be one of those ghastly situations in which warmer air aloft causes rain to fall even with cold surface-temps? It's happened before...

[Mini tiger]

this evening..

So if I got that right, the latest fax chart shows the front that piles in from the west on Friday, stalls somewhere over the southeast and east, and then backtracks west

again bringing more snow back across the country from the east this time ?

[NorthNorfolkWeather]

Thank god for the 216 http://www.meteociel...H1-216.GIF?16-0!! I think by then we will all need a break dry but cold that chart, nice winter sunshine!

unfortunately, it's so deep in FI it could have changed to this

and it it's like that throughout the period, we may need some summer sunshine to recover from what would be the best winter since 1963

[ukpaul]

I am so confused trying to look at the models .people seem to be ramping up my area (hertfordshire) for snow then others say it wont make it to me. any tips on what models to look at and what is expected?

I just posted, in one post, a positive and a negative spin. Essentially, it depends on where you are looking as to how favoured your area will be.

To give an example for where I am from two very short range models - the NAE suggests 5cm up to midday Friday with the main area of snow still to come, the WRF suggests only 1cm by that point and, even by the end of the front giving us less than 5cm because the front decays. The varying totals for your area are very similar for that time frame.

Generally, the met office have issued an amber warning where they are sure of the reach of the snow, it's yellow where it could be disruptive or a non event.

Edited January 16, 2013 by ukpaul

[Frosty.]

It will just make a nice change for the M4 corridor not to be the deciding factor between rain and snow, friday shows the most widespread uk blizzards for a long, long time, and nothing can stop it now, the even better news is we won't have a thaw after, it will freeze and then form a solid base for the next snowfalls, I can see this spell of weather becoming a youtube senstation in the next few weeks.

[Weather of Mass Disruption]

Just put phone on to check the model forum and the time in big bold numbers was 19:47! How apt if not a little spooky! Apologies it's off topic :-)

[michail]

Can some1 PLEASE put me out of my misery! I've looked at the FAX T72, it shows the front moving west on Sat. Snow 4 ireland? Thanks!

[Duane S.]

S4 you are not far along the coast from me. Where do you think the front will stall, and will the southerlies from France keep us cold enough ?

Would take a very brave person to call where fronts stall at this juncture. The guys n girls at the MET have no choice, they have to draw the faxes daily but they will be far from confident about it!I have to say though, the faxes are just oozing potential for us though.

Just refering to the Friday event, I suspect the only rain/snow mix will occur literally right on the coast. The rest will be snow. Thereafter it may turn to back to sleet . But that a million miles away in snow forecasting terms yet.

The difference perhaps for us as opposed to others living more inland and more to the NE is that a decent snowfall is nearly nailed for them, they have an insurance policy, we don't, if it trends east it will be predominately rain here.

But what I like so much about what I'm seeing here is that, whilst there will be winners and losers, I can only see more potential snow events on the horizon. So miss out on one, cop for the next hopefully. That'll do me!

[cooling climate]

I have not seen any evidence from the ECM, UKMO or the GFS that it will be a

snow to rain event for London and the southeast.The temperature on Saturday

are unlikely to rise above freezing except maybe in cenral London but dew points

etc, all support snow.

Back to the models and you definitely get the feeling from the last couple of

ECM runs that something big is brewing for the UK and its likely to come from

the east/northeast in the form of cold and snow.

Just to clarify a couple of my previous posts may have confused some posters

when I said there is still no real sign of the SSW in the models. This was

misleading the SSW is responsible for the very cold spell we are in now but

what I expect to start showing up in the models at some point is a strong

blocking high to the north or northeast(yellow and orange on the charts)rather

than the shallower high that we have at present.