Model Output Discussion

[Nick F]

I can't see any evidence of this polar low? I don't think it is a polar low. Am I mistaken?

I say this every winter I think, but I think weather fanatics can use the phenomenum of a 'Polar Low' too loosely to give to any low that drops down from within the polar circle.

A polar low has specific paramaeters, namely it is specifically a small organised circulation of convection created by a cold pool characterised by 500mb temps below -40C crossing off the icefields of greenland and other polar areas over the warmer SSTs (hence convection and low pressure circulation developing). These features are much smaller than the lows some are refering to - and tend not to be forecast until within 36hrs.

More swings and roundabouts on the 06z, but least some snow potential is there early next week and again later next week.

[Frosty.]

The deep low on the GFS 06z is further east than was shown on the 00z at the end of next week which I think is better news as we would get a pure arctic flow rather than a mixed atlantic/polar airmass although it could and probably will change again many times. Fantastic 1060mb Greenland High forming although it fades later in the run, the initial E'ly won't deliver much IMO but it will bring in some wintry showers after the weekend into many eastern and southern areas with a cutting ENE'ly flow, much colder across the low countries of course. The north probably missing most of the action from the initial burst but maybe making up for it later if the N'ly does occur which would be great news for the scottish ski industry. Signs of the jet pushing further north at the end, bringing milder air in just after christmas day but not before a snow event turning to rain scenario, it's too far out to be worth bothering about at this stage though as other runs have shown the cold block continuing for longer.

Edited December 11, 2009 by Frosty039

[Neilsouth]

It is true that the general setup is something we haven't seen for years , HOWEVER how many times has a northerly come across the uk in one form or another through the years. Yep nearly every year ! , northerlies unless it was the thundersnow type event are generally boring for us down south. Now a blasting north east/ east with snow is much more rare , if it ends up with more of a northerly event i'll not be pleased and for me that's a downgrade. However if we do end up with a 24+ hr ne blast with snow then a northerly i'll take that.

Still awhile yet to go though

[weather eater]

The parallel is of course looking rather good, keeping mild air away right through its output.

[Lewis]

It is true that the general setup is something we haven't seen for years , HOWEVER how many times has a northerly come across the uk in one form or another through the years. Yep nearly every year ! , northerlies unless it was the thundersnow type event are generally boring for us down south. Now a blasting north east/ east with snow is much more rare , if it ends up with more of a northerly event i'll not be pleased and for me that's a downgrade. However if we do end up with a 24+ hr ne blast with snow then a northerly i'll take that.

Still awhile yet to go though

Sorry Neil, but over the past few days you have concentrated on your area and south, you have thrown fits when there's been a downgrade etc. This is the model output thread and correct me if i'm wrong but the South is not the entire United Kingdom.

Look at it from the bigger picture, you will probably be better in the "Own model predictions" thread.

Lewis

[TEITS]

Just viewed the Parallel run and to be honest making a summary of the models is relatively simple.

A brief E,ly early next week with upper temps possibly as low as -8C in the SE. We then see a brief less cold N,ly (surface temp similiar though) followed by an even colder E,ly. At the moment the favoured locations for the E,ly from midweek onwards is definately SE/E Anglia for the simple reasons being coldest upper temps, duration. This E,ly could be followed by a N,ly as we see the HP retrogress NW.

Again subject to change!

[Geordiesnow]

It’s funny how attitudes change, when this was first programmed everybody was just happy to get the wet and windy weather out of the way and get something more seasonal. Now we are getting to the, it’s not good enough, where’s my snow stage. Please, let’s just let things develop, there is a lot more variations to come from model outputs, this 06z run is just another one. All in all, in my book this is about as good as it gets for mid-December and could bode well for the rest of the winter.

Yep but for me personally, i don't want to go through alot of model watching and posting on here, then finding out that snow will be quite limited because of last minute changes.

It's only one run though but there does seem to be a bit of agreement that the easterly will sink into europe however we all know that we probably should not take the models for granted at that stage.

The only thing i will say though is that Greenland blocks and low heights to the South won't stay forever so the quicker we can take advantage of them, the better.

At least it won't be mild whatever happens.

[WhiteXmas]

The easterly is looking very weak now I would say. However the Northerly looks a lot more potent however I am not naiive I know this is subject to change. It is promising though we cannot deny that and I for one couldn't be much happier with the start of this winter to be honest!

[Neilsouth]

Sorry Neil, but over the past few days you have concentrated on your area and south, you have thrown fits when there's been a downgrade etc. This is the model output thread and correct me if i'm wrong but the South is not the entire United Kingdom.

Look at it from the bigger picture, you will probably be better in the "Own model predictions" thread.

Lewis

But why should i care what happens in some distant county in the far reaches of the tip of scotland?. P.S you failed to mention that i have also mentioned the EAST & North East in my posts?. I'll say it again from a much earlier post , a north east or strong east wind would favour right down the eastern side , including east and south east. I would like regional forecasting threads HOWEVER that would be locked. If my posts are a problem with discussing all the eastern areas and south , put me on ignore. I'm still discussing the models and thus i'm breaking no rules!

[andy_leics22]

The easterly is looking very weak now I would say. However the Northerly looks a lot more potent however I am not naiive I know this is subject to change. It is promising though we cannot deny that and I for one couldn't be much happier with the start of this winter to be honest!

Hmmm I would have to agree. The 06z run has placed that high pressure further South and affecting most of the UK apart from Southern England. I much preffered the 00z but these things are going to chop and change right up to t00 so this is by no means a certainty at the moment.

[nick sussex]

The easterly is looking very weak now I would say. However the Northerly looks a lot more potent however I am not naiive I know this is subject to change. It is promising though we cannot deny that and I for one couldn't be much happier with the start of this winter to be honest!

The initial easterly was always likely to be it was only the gfs which progged this as anything more, again this is the problem with the gfs taking centre stage all the time in here.

It's like the Jordan of models, always seeking publicity and wanting to be centre of attention, although the gfs has alot more talent !

Edited December 11, 2009 by nick sussex

[FetchCB]

So much of the what the models are showing are based on fine tipping points. If the high pressure tilts a few degrees one way or another or is further north or south, If the low pressure that squeezes over the top of the Greenland black is less vigourous....so many ifs and buts.

I have a hunch ( not a scientific one) that with the first potential snow chance now just outside t72 that GFS is playing its usual downgrade game only for it to come back 24-48 hours later but where we will get a dumping may be down to looking to the fax charts for troughs on an E/NE wind

[Lewis]

But why should i care what happens in some distant county in the far reaches of the tip of scotland?. P.S you failed to mention that i have also mentioned the EAST & North East in my posts?. I'll say it again from a much earlier post , a north east or strong east wind would favour right down the eastern side , including east and south east. I would like regional forecasting threads HOWEVER that would be locked. If my posts are a problem with discussing all the eastern areas and south , put me on ignore. I'm still discussing the models and thus i'm breaking no rules!

I did not say your breaking the rules,

Just when your reading the model output thread and you get members like yourself constantly talking about your area and reflecting your area on the models, stops the true reflection of the models on a larger scale. Which makes it harder for other members especially intermediate members that rely on our posts to get some kind of wide-scale idea. I just think your posts are very biased and it would be great to see more members less bias with the outputs, and be more informative on a wider picture.

Lewis

Edited December 11, 2009 by Storm Force Lewis

[WhiteXmas]

Is the GFS cosmetically enhanced? No wonder it's runs can be so superificial At least it's not dating some cagefighter I guess then it would constantly be coming in late and making excuses about delaying our runs!

Have I gone too far?

PS I suppose you could call the ECM the Peter Andre of the models then :lol: Always keeping GFS in check!

Edited December 11, 2009 by WhiteXmas

[SMU]

Well I suppose the evolution looks as follows-

Weekend becoming progressivly colder- especially acorss England- Temps Maxing out sunday & Monday around 2;/3c- We do get a cold Easterly Monday & tues & I wouldnt surpised if there was a temporary covering in the Extreme SE-

Then it quietens down Tues + weds with the potential of frontal snow moving down from the North - this COULD happen - but it would be all about timings-

The air + dewpoints ahead of it would be fine, so the SE could start with snow, then sleety then back to snow-

The window for some heavy snow across England- espcially the East & SE opens up around Thursday with teh current progs having about 24/30 Hours for snowcover to build up-

In perfect synoptic situations like the one modelled here-

http://91.121.94.83/modeles/gfsp/run/gfs-0-138.png?6

There will always be a streamer-

Within a timeframe of 30 hours you have the scope for well over 8 inches of snow-

If you want snow then watch the next 10- 15 runs of the GFS & see how long your window slot is- if your in KENT/SUFFOLK in will be the longest of everyone-

S

[Thundery wintry showers]

The current outputs illustrate the main issues with the omega blocking situation- it either ends up very cold and snowy or moderately cold and dry, and the specifics are strongly dependent on where highest pressure ends up. January 1985 (which has often been mentioned recently) was, for most, a very snowy month, but looking over the synoptics there were many occasions when, had high pressure been a few hundred miles further south, only the southeast would have seen any significant snowfalls. Similarly if you look at February 1956, the synoptics for the first half strongly suggest a predominantly cold dry regime with snowfalls restricted to the SE, but with frequent snowy north-easterlies from around the 15th to 25th. This kind of pattern does not always guarantee precipitation.

Regarding the upcoming outputs, for once there is reasonable model agreement. Unless we see some upgrading to the two easterly outbreaks in the near future we will not see any widespread snow cover from them as the high pressure comes in too quickly before the coldest air reaches us- with the possible exception of the southeast. In both cases 36 hours of wintry showers (hail, sleet, snow) for eastern areas with limited accumulations are likely. However the second one in particular is open to some limited upgrading which could give a more widespread snow event for the E and SE.

Interesting post by Steve about possible frontal snowfall between the two events. It's not beyond the realms of possibility, though I fancy most areas (especially the north) will be too marginal.

The longer term looks increasingly likely to see highest pressure transfer to Greenland allowing in a northerly, which to my mind is fraught with danger for cold/snow lovers as the models are notorious for overdoing high pressure over Greenland, resulting in the T+72-T+120 "downgrade" as Atlantic systems crash through the block. Still, such northerly regimes have been far from unusual in mid to late December in recent years (Decembers 1993, 1995, 1999, 2000 and 2001 all had pretty potent northerlies late on), so we could get something out of that.

[TEITS]

GEFS ensemble mean at +138.

http://91.121.94.83/modeles/gens/run/gens-21-1-138.png?6

I've spent many a winter looking at charts like this at +384 and here we are at +138.

Fully expect Kent to have the coldest mean for this period in the ensembles.

[Neilsouth]

There will always be a streamer-

Within a timeframe of 30 hours you have the scope for well over 8 inches of snow-

If you want snow then watch the next 10- 15 runs of the GFS & see how long your window slot is- if your in KENT/SUFFOLK in will be the longest of everyone-

S

Thanks for your great posts SM!

Looking good for us ! , hope it stays that way. May the GFS bring us all a deep snow event lol

[kold weather]

Well very interesting runs again this morning, personally like the UKMO the least this morning simply becuase of a flabbier flow but all models have suddenly come into very good agreement about the eventual evolution of the set-up.

For an utter peach though, the 144hrs ECM is a beast for the SE, on a personal note, I would think my friend te snow streamer would set up quite happily from the ECM.

Ayway what we see from the 0z runs is something that has happened in the even larger teapot but you can count it on one hand and thats the southerly jet combined with the Scandinivian vortex keeps us locked in cold even after the block over Greenland has more or less totally decayed, its a classic 60s evolution and one that can really just lock for a long time, esp if you get another big block 7-10 days down the line from it.

No real exceptional cold anymore from the models, but very sustained cold.

[MisfitDog3]

Very entertaining reading on here at the moment. It always makes me smile the amount of pessimism which shines through on a lot of postings about the various models, always looking for an indication of the 'end' of a pattern!

The outlook over the next few days or so is an early gift to cold lovers and I can't remember seeing charts like we have at this stage in December for many years and I'm 43!Personally, the golden rule of not trusting anything much beyond 5 to 6 days in advance seems to be as valid during a cold block as it is during mobile patterns. I suspect we will see a zonal pattern re-assert before Christmas Day on past experience but I can hope, like many others, that it doesn't....

[Pennine Ten Foot Drifts]

The key period (Tuesday evening to Thursday) is firming up nicely now. Whilst it's true that flows are quite slack and pressure rises a bit to our east, (before decaying southwards), so the worry is that it'll 'just be cold', the uppers being pulled in over this period are still pretty cold and the airmass is not that stable, so I would have thought that there is very likely to be some reasonable shower activity given that the North Sea is still relatively warm as this cold air passes over it. And thats just the 'hors d'oeuvre' anyway, because over that same timespan a very impressive Greenland/Iceland block is forming, which by T168 stretches all the way from N.Canada down to the tip of S. Ireland (!), and thats not going to be shifted for quite a while, leaving us open to all sorts of fun and games from the north and east. Very impressive !

[bluearmy]

nice to see the models firming up on the pattern for next week. the blocking looks to be stronger than some of the output has shown and will supress the trough to our south which leaves us in a 50/50 type position as to whether we actually advect the cold over us when it comes in for a day or two. i would nt be too confident that we will get a frigid easterly - that bulge of higher heights looks to be keen to ridge further southeast as each run passes. by the time we get to monday, we may see all the cold pass to our south. of course, the jet to our south might be stronger and a bit more north than currently shown which would squeeze the flow and be fantastic for us. there are hints of a reload from the north but that is very uncertain as the block trends towards eastern canada and this may well allow the -NAO to set up too far west leaving nw europe in a sw flow. maybe, the favourite should be for the trough to end up over us again, as it did in much of november. that would give a possibly very snowy northern half of the country. (something i recall was quite common in winters thirtyish years ago).

patterns not seen in december for a good few years. remember, when anything decent arrives, its never as extreme as it appeared to be at a longer range. its just the way it is on the edge of the atlantic. as sm has often said, it does give us a chance of a much more snowy set up though.

[Frosty.]

There is always a SE IMBY bias going on here when a bit of snow is possible, most on here don't live in the SE and there is some interesting weather being shown for everyone in the british isles at some point during the next 7-10 days according to the GFS & ECM.

[Weather-history]

The longer term looks increasingly likely to see highest pressure transfer to Greenland allowing in a northerly, which to my mind is fraught with danger for cold/snow lovers as the models are notorious for overdoing high pressure over Greenland, resulting in the T+72-T+120 "downgrade" as Atlantic systems crash through the block. .

True but one could argue if you are a cold lover would you prefer to see those type of charts at this stage or ones where the block collapses quickly ie Jan 1972/Dec 1997 and no chance of sustained cold?

Edited December 11, 2009 by Mr_Data

[andy_leics22]

This term 'nailed' has come up several times in the last few days.

Yesterday T36 and T48 was 'nailed' then the ECM took the nail out (but that ECM run was suspect).

The only thing 'nailed' is the fog today.

Its clear that the models cant agree T48/T72.

If we 'nail' things say to T72 or T96 we then just post FI charts (because all the rest is 'nailed') and then get surprised when FI doesn't come of.

That easterly has had more nails in and out of it then a coffin in the last week !

Absolutely agree, I think even T120 at the moment is going to change quite a bit. None of the models are handling it that well, a difference of 300 miles further North with the high pressure and we could be seeing snow showers for the majority of the UK, 300 miles further South and it's cold and dry conditions. It's little changes like that that will make a massive difference come next week.

Edited December 11, 2009 by andy_leics22