Model Output Discussion

[January Snowstorm]

If the models continue to trend colder as they have been doing we will be in a major freeze by this Friday. Severe deep cold 200 miles away to our North.

For once I think JH and GP have/are calling it wrong

After seeing the 18z im convinced a bitterly cold spell is a certainty by this wkd with snow for all

[conor123]

18z a snowfest Saturday Night, would dump inches of snow over us though unfortunately it will get pushed south.

[reef]

A further upgrade in the near-term in the cold on the GFS 18z. The model is now showing a significant snow event to Northern Wales, Midlands and parts of Northern England on Saturday night into Sunday:

Much less messy aswell with some extremely cold nights under stagnant cold air and low thicknesses.

http://www.wetterzentrale.de/pics/Rtavn10817.png

Much more than meets the eye on these charts.

[gottolovethisweather]

Hello.

Please forgive me as I've not read much of this thread just recently but is there not a battle developing above our heads right now between cold and a slightly milder airmass. I say this as when listening to the shipping forecast on R4 at 5.55 and subsequently a ramping up Nick Miller BBC forecast, they both mention a mixture of rain or snow even over Thames/Portland etc. sea areas in the case of R4 and a look out Thursday development from NM. This is I suppose an IMBY type post but when areas in the south and southwest are potentially going to be effected within the reliable say >72hrs ahead I start getting excited. I don't expect settling snow in my location but the downs locally could well get lucky with a good covering. Also, to prove I have been looking at the latest output the Thursday/Friday GFS 18z output looks really good for SNOW but maybe some more experienced posters will temper my enthusiasm and drop me back down to earth. Whatever, no 10c maxes anywhere real soon so 70+ days of sub 10's and more snow falling days iin the offing keep me and i'm sure others entertained.

Snowy Regards

STORMBOY

Edited February 16, 2010 by STORMBOY

[03jtrickey]

Looking at this chart here:

I'm thinking what is stopping that deep cold air to the NE from breaking through?

In the short term there seems to be a lot of potential for marginal heavy snowfall in places, starting tomorrow, then Thursday. A very unsettled week ahead and a true forecaster's nightmare.

[andymusic]

18z a snowfest Saturday Night, would dump inches of snow over us though unfortunately it will get pushed south.

not sure what you mean - it moves through wales from south to north and onwards up north

[Ben_Cambs]

This week has certainly becoming more progged to being colder and more snowier than was first thought, as Reef says above a possible snow event for the central swathe of the country on Saturday night, and with the Uppers at -6C or so in many places by the weekend, I think at this time some widespread snow is a possibility. Im sure other features/troughs would also form in this sort of set up which the 18z is showing....

[January Snowstorm]

A great chart to look at is 150hrs thickness on the 18z

The 510dam line is draped across just to our North.

Deep deep cold within touching distance, awesome!!

[conor123]

not sure what you mean - it moves through wales from south to north and onwards up north

I mean these features end up zipping through the channel in the end, well 95% of the time anyway.

[Tom D]

What do other people think about the way the 18z removes the ridge of high pressure over Scandinavia after t+108? I'm wondering whether maybe this ridge has been underdone, and just a small increase in this blocking would put the low in a better position for the setting up of a possible north easterly air flow which could bring those cold uppers towards us.

The only thing against this theory is the time between now and when the ridge if pushed out; GFS seems pretty adamant that this ridge/block won't hold and allows the trough to set up over the region.

18z is an improvement in the reliable timeframe in my opinion, t+96, and after that is still subject to minor yet important changes run on run.

EDIT: 18Zz FI is stunning.

Edited February 16, 2010 by Tommyd1258

[mountain shadow]

A great chart to look at is 150hrs thickness on the 18z

The 510dam line is draped across just to our North.

Deep deep cold within touching distance, awesome!!

It might be up to westerners and northerners to keep this thread going if the 18Z gets anywhere near happening. Seems to want to ditch the west based -NAO for a more neutral one bringing in a northerly. Would be very very good for here.

However ECM not on board so not to excited yet.

[cooling climate]

You may well turn out to be right CC but more by luck than judgement, your statement sad to say shows your bias and reveals your lack of objectivity, shame really because you would be worth paying attention to, if you eliminated the bias and gained the objectivity. The models really are struggling and the evolution being show by the ECM is as likely as any other, you may just as well say that all recent model runs lose their way at T96hrs and the errors just get worse. You may well say that events further afield, teleconnection evidence, etc, supports an evolution to colder conditions for the UK, but that is no guarantee. February last year was a case in point, plenty of signs for a cold spell then, that didn't come off. You may say it's ok to criticise, how about you put your cards on the table, what's your opinion. well to be honest I haven't got a clue for a week's time, in the longer range the models are as much use at the moment as the seagulls or Mystic Mathew. Not mild SWlys, but near or just under average temps, with a possibility of a change to colder conditions towards the end of the month would be my punt but thats a guess and support from the models is patchy at the moment.

I have said all along that during this week we will see the lows take a more southerly

and easterly track which the models have been showing. l am hardly likely to say different to

that if I do not believe it to be the case.

In my opinion into next week and beyond we are likely to see a more east based -NAO due to

heights building further east over Svalbard and Scandinavia and a very cold continental airflow

will become established over the UK. The GFS model has started to show such synoptics far out

in FI land, I think we will see this blocking starting to manifest itself next week.

Timing wise I may be off but imo it is going to turn very cold and wintry.

Now why don't you spend less time criticizing other peoples posts and try and add something to

the model thread.

[January Snowstorm]

Latest faxes back up the idea of a spell of sleet and snow across the South on Saturday.

Followed by a freeze up in very light winds for early Sunday

[kold weather]

Once again the 18z shows how we could evolve into yet another -ve NAO set-up, though this time it fails to reach it and instead becomes a Scandi high. I actually really like the 18z runb overall, several good chances for snow in the Midlands and places northwards, then slack low pressure and probably some nice and low mins followed by high pressure building in close to the UK and bringing in a SE airflow, very frosty and cold by night but maxes would probably reach 8-10C in such a set-up which would feel quite nice.

[Nick F]

Well, if you live in the Midlands, east Wales and parts of N England, I would be relishing the coming days wrt to snow. Tomorrow, thursday and again on Sunday looks to see some snow events for these areas, looking at 18z GFS.

Milder air trying to push up from the SW will have a real hard time to infiltrate these isles over the coming days, with a large upper trough with a cold vortex within it extending down across the UK from the arctic continually draining cold air southwards. Earlier ECM does try to turn it less cold in the south next week, so there is some uncertainties into next week on the position and shape of the vortex between models and how this affects the direction of flow over the UK - particularly the southern half. But always remaining cold in the north looks more certain!

[ribster]

You may well turn out to be right CC but more by luck than judgement, your statement sad to say shows your bias and reveals your lack of objectivity, shame really because you would be worth paying attention to, if you eliminated the bias and gained the objectivity. The models really are struggling and the evolution being show by the ECM is as likely as any other, you may just as well say that all recent model runs lose their way at T96hrs and the errors just get worse. You may well say that events further afield, teleconnection evidence, etc, supports an evolution to colder conditions for the UK, but that is no guarantee. February last year was a case in point, plenty of signs for a cold spell then, that didn’t come off. You may say it’s ok to criticise, how about you put your cards on the table, what’s your opinion. well to be honest I haven’t got a clue for a week’s time, in the longer range the models are as much use at the moment as the seagulls or Mystic Mathew. Not mild SWlys, but near or just under average temps, with a possibility of a change to colder conditions towards the end of the month would be my punt but thats a guess and support from the models is patchy at the moment.

The thing is WE, I cannot recall a single post from you with any real analysis of the models (yes before it is said, nor have I, I'm simply not clever enough). What I have seen is plenty of posts about how others should not look too far ahead and anything beyond 96 hours is hogwash. Then I hear people say that the models are struggling, only to be chastised with something along the lines of ' they are struggling no more than computer based weather models do beyond x hours', you really can't have it both ways. Same could be said that you might be worth paying attention to if you provided some real analysis of the models, rather than policing the thread for anyone that dares to discuss FI. If only up to T96 was discussed it wouldn't be worth reading the thread, we all know the caveats of charts becoming reality the further out that they go...

[LomondSnowstorm]

Well, if you live in the Midlands, east Wales and parts of N England, I would be relishing the coming days wrt to snow. Tomorrow, thursday and again on Sunday looks to see some snow events for these areas, looking at 18z GFS.

Milder air trying to push up from the SW will have a real hard time to infiltrate these isles over the coming days, with a large upper trough with a cold vortex within it extending down across the UK from the arctic continually draining cold air southwards. Earlier ECM does try to turn it less cold in the south next week, so there is some uncertainties into next week on the position and shape of the vortex between models and how this affects the direction of flow over the UK. But always remaining cold in the north looks more certain!

What are your thoughts on the chance of snow in eastern Scotland on Thursday as the band picks up again over the North Sea? http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/16/basis18/ukuk/prty/10021812_1618.gif

[arnott]

according to the latest bbc forecast on 2,jay wyn said tht thursday night could be very wintry for nothern england as rain pushes up turning to snow!whts happening here??

[damianslaw]

The overall tred for the foreseeable future is cold and unsettled with low pressure dominating. Forecasting where fronts and troughs will likely track in such a synoptic pattern is very difficult. As we are seeing now with the front to the south east now being forecast to swing deeper into the country than first expected..

It looks like the current low pressure will gradually ease into the east North Sea which will pull down some colder uppers into Scotland and much of north west england and northern ireland, however, another shallow low feature from the west looks like taking its place over the weekend which will kill the chance of those proper deep cold uppers just tentatively out of reach to the north east advecting our way, still the chances of widespread low level snowfall especially in the north look high for the weekend, any fronts or troughs that do develop will likely give snow away from the coast.

Looking into next week, low pressure over the country still and cold uppers every chance that we will see the NAO switch more easterly, I can see a northerly for the end of the month with strong heights over Greenland, potential for a very cold end to the month as we tap into the frigid air to our north east.

[Nick F]

What are your thoughts on the chance of snow in eastern Scotland on Thursday as the band picks up again over the North Sea? http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/16/basis18/ukuk/prty/10021812_1618.gif

Certainly chances have increased on the 18z NAE compared to 12z NAE, also 18z GFS shows snow potential for eastern Scotland as the occluded front clears NE from the UK. Situation for snow keeps changing though, as areas across Midlands and E Wales and N England are in the frame for snow tomorrow from the front, when it was looking like it would be areas further SE. The weather across UK developing around this low to the west is quite dynamic at the moment in terms of modelling exact positions of fronts, so expect more short-range changes!

[Guest North Sea Snow Convection]

I'm not going to make any more comment about further upper cold pool spell potential (ie how cold etc) but I think that care is needed imo not to make too many assumptions about the pattern for this week, weekend and into next week staying stuck much further beyond that. This winter has been a 'fool guy' for most of us and with embedded feedbacks and extremely cold air (-20 850's) just a nose width away in Scandinavia (with generally embedded cold over a wider area too) and with a very strong southerly jet, plus further negative zonal anomalies to filter through then I would prefer to suggest to expect the unexpected instead.

Tonights ECM was one output, and it may come to nought, but I saw further retrogression of the west based -NAO pattern, wherby we could come full circle to seeing pressure rise to the east, and then link up to the north east, whilst the scattered remains of the already disintegrated vortex retrogresses (courtesy of further downwelling polar easterlies) and the result is raised heights over Russia/Scandinavia that then back some of that impressive cold south west to us. That translates to cold unsettled weather for the next week or so, and then a temporary milder spell with southerly winds (in the south mainly) before a north easterly plunge as heights from the arctic into Scandinavia give winter into Spring a fanfare. Not comenting on how cold that would be obviously - suffice to say, with the time of year it wouldn't be 'day after tommorow'.

The composite fitting of patterns has stood us in remarkably good stead and outstanding accuracy for the early part of the winter, but they are a guide and in the curent situation (in my very humble opinion lol!) I think theory goes out of the window now to a certain degree, to be completely honest.

Things may pan as out the experts suggest, but I see a lot of minefields ahead in the next couple of weeks that might make things different. We will see

Edited February 16, 2010 by North Sea Snow Convection

[LomondSnowstorm]

Certainly chances have increased on the 18z NAE compared to 12z NAE, also 18z GFS shows snow potential for eastern Scotland as the occluded front clears NE from the UK. Situation for snow keeps changing though, as areas across Midlands and E Wales and N England are in the frame for snow tomorrow form the front, when it was looking like it would be areas further SE. The weather around this low to the west is quite dynamic at the moment in terms of modelling exact positions of fronts, so expect more short-range changes!

Thanks. In that respect it reminds me a lot of what the December spell was here at least, which was of course less marginal due to snow cover and cold surface temperatures meaning uppers of -3 delivered snowfall but with similarities of continually changing fronts and troughs sometimes popping out of nowhere - that was an incredible spell though, and I doubt as a period rather than in terms of one off events many winters, if any, could deliver a similar spell with both very cold uppers, significant snowfalls and lying snow for a sustained period.

Anyway, what I'm trying to say is that it must be pretty hard to keep up to date with these developments as short range forecaster - keep up the good work!

LS

[mackerel sky]

Thanks. In that respect it reminds me a lot of what the December spell was here at least, which was of course less marginal due to snow cover and cold surface temperatures meaning uppers of -3 delivered snowfall

In February last year on consecutive days a cumulative total of 15 inches of snow fell in uppers of -3/-4... the following week 4 inches of snow fell in even more marginal uppers of -2C, probably because of the existing cover. However, some people who will remain nameless told me in no uncertain terms that existing (and potentially quite deep) snow cover has no influence whatsoever in marginal situations. I still consider this to be rubbish. It alters the soundings, you can see it - if the temperature profile to ground level is below freezing, irrespective of the standard requirements, it'll be snow.

[TEITS]

The weather across UK developing around this low to the west is quite dynamic at the moment in terms of modelling exact positions of fronts, so expect more short-range changes!

I would strongly urge members to take on board what Nick F says because hes spot on.

Due to the current pattern we're in I would be wary of the exact details at the moment even if the BBC/Met O have warnings out for your areas. Even the NAE model is subject to changes between each runs. This is the sort of situation where I could be experiencing rain and yet 30 miles W of Peterborough they have 15cm of lying snow!

The reason for this is the snow events that the 18Z shows would only require slight changes that could mean the difference between rain/snow. I would strongly urge members to resist getting excited until the event is only hrs away and even then it would be worth tracking on the radar.

The locations that look least favoured are E Anglia/SE but like I say I want to see more runs before being certain.

In February last year on consecutive days a cumulative total of 15 inches of snow fell in uppers of -3/-4... the following week 4 inches of snow fell in even more marginal uppers of -2C, probably because of the existing cover. However, some people who will remain nameless told me in no uncertain terms that existing (and potentially quite deep) snow cover has no influence whatsoever in marginal situations. I still consider this to be rubbish. It alters the soundings, you can see it - if the temperature profile to ground level is below freezing, irrespective of the standard requirements, it'll be snow.

Absolutely spot on.

The Feb 09 snowfalls in our region still remain some of the best since the 1980s. However after the initial 8 inch snowfall on the 5th the conditions didn't favour anymore snowfalls. However I agree with you the following snowfalls occured due to deep snow cover having an effect.

Edited February 17, 2010 by THE EYE IN THE SKY

[mackerel sky]

I would strongly urge members to take on board what Nick F says because hes spot on.

Due to the current pattern we're in I would be wary of the exact details at the moment even if the BBC/Met O have warnings out for your areas. Even the NAE model is subject to changes between each runs. This is the sort of situation where I could be experiencing rain and yet 30 miles W of Peterborough they have 15cm of lying snow!

I agree Dave and quite honestly I think even looking at the GFS precipitation charts are going to change massively even in the +24hr range on individual runs upto the weekend. I do think there is enough scope there for spells of heavy snow for the Home Counties northwards at some point, but trying to pinpoint detail even at +48hrs is difficult. This is probably why the Met Office aren't bothering with advanced warnings out for the remainder of the week, because I don't honestly think they have a clue. Whats the point if you are just going to move them about constantly.

Having said that, they put out the advisories for today on Sunday consistently for the same counties, only to completely change it a few hours ago. If I was an end user of their forecasts, I'd be a bit cheesed off, had I made any preparations that might have financial consequences.

Edited February 17, 2010 by mackerel sky