Model Output Discussion:

[Lewis]

Morning everyone,

Thanks TEIT'S for fantastic and informed posts once again, i enjoy waking up to them. I always read your posts on here before i look at the model runs. I'm going to take a look at the gfs now . Slightly off topic mods, but since it was suppose to warm up doing this period of atlantic systems over the past few days, my max temp has been 5.1c, i got down to 0.9c last night with a little freezing fog before it lifted and temps rose to 2.1c

Lewis

[Guest North Sea Snow Convection]

I suppose you should always suggest that the key to the outlook is how the models balance the energy distribution between pressure systems (because that is an essence of the science behind it) but for the last seven days I have been constantly repeating how the models have been especially struggling with the weightings of energy flow. And struggled they cetainly have.

Firstly, wrt to the low pressure in the central/western atlantic and the makings of the high pressure to the N and E. The suggestion was how they might be miscalculating the spin off energy from the main low and pushing this too far east beyond the t120 to t144 frame (as was early this week) and suggesting that by now we would be in vigourous south westerlies. That clearly is not the case!

Thereafter, secondly, the energy equation in the modelling has centred around the position of the high pressure to our north and whether an initial Icelandic high would hold its position more or less or whether it would drift southwards towards the BI. The key element behind this has been the models trying to gauge the progress of downwelling negative zonal wind anomalies from the warm stratosphere and thereby determining the net energy that might go over the top of the high and the amount that goes under the high courtesy of the dominant sub tropical jet stream.

That has been the juncture that has been the centre of the debate (18z argument!) of the last couple of days. But in answer to that, the timing of the downwelling is coming right to support a cold pattern, and the high holding at a high enough latitude, and the models agree on the polar easterlies delivering some extra fuel to the shallow high just to the NW of the UK midweek in the form of a retrogression through Iceland and towards Greenland in the extended period.

The final strength of these reverse zonal winds isn't known yet, so predicting how much retrogression there might be is difficult to gauge. On that basis the exact placement of the high by t168 and beyond is still open to question in the modelling. However there seems to be plenty of agreement that an extended cold period is likely with snow showers becoming more of a feature towards midweek and beyond .

Edited February 6, 2010 by North Sea Snow Convection

[noggin]

Well a simple summary would be this.

Becoming colder during the week with snow showers becoming more widespread from midweek onwards. During Thurs/Fri temps during the day wll struggle to rise above freezing with snow showers breaking out more widely especially across E Anglia/SE but not exclusively.

I will suggest to members to start using the NAE now. Look at the SLP charts on the NAE at +48 and compare to other models.

Some regular summaries like that would be great for those of us who, after many years, still cannot grasp model-reading!

Thank you, TEITS.

[Lewis]

After looking at the GFS 06Z, it appears that a lot of us will see some action.

Monday - Wednesday; A more N/NNE flow, snow showers affecting Eastern parts of Scotland, NE England, Yorkshire and Lincolnshire coast line. With some snow showers about in the SE.

Wednesday onwards; The risk shifts a little further South, with the South East and EA getting plenty of snow showers. Yorkshire and Lincs will still see plenty of snow showers, although they become less frequent and widespread I would say just North of the North Yorkshire Moors.

Day time temps of around -1 to 2c for eastern areas Wednesday onwards.

Stupid i know, but becoming marginal from the East come friday night/saturday as warm sectors push in off the N Sea. With places further inland continuing to see snow, some very heavy especially for central areas, and southern central areas (M4 Corridor).

Things can still change of course but that's my take on things.

[sandstorm2]

Would somebody be good enough to give me a link to the NAE model, thanks.

SS2

[BLAST FROM THE PAST]

. The models have made a mug of a lot of people this past week.

They sure have Kev, I agree with that.

ECM after initial movement of HP towards UK seems to be getting keener and keener on retrograde of the HP to Greenland. That of course would elongate the cold spell to beyond 10 days to possibly 2 weeks or more. I still suspect that it is being too keen...but nice if its right.

BFTP

[Frosty.]

Yes, cracking set of charts from the GEM. However, it seems to me that that model is playing "catch up"; only a few days ago it was still showing an Atlantic dominated scene for this coming week, long after the big 3 models had ditched that and latched on to the forthcoming cold spell. Now it seems to be showing what the GFS/UKMO was on Thursday with the low pressure close to the SE and widespread snow for a big portion of the UK. However, now the major models have moved on to the HP having more influence, which I suspect the GEM will cotton onto come Monday!!

You could be right about the GEM model playing catch up but on the other hand it might be leading the way but that is probably wishful thinking on my part. There is still some significant differences in the modelling of the scandi trough and the high pressure cell between the models which will have a big impact on which areas are lucky enough to get snow showers. The 6z shows more ppn across the uk, even ireland might catch a few flurries but to be honest the models don't look anything like as severe as december and the first half of january but still a cold spell ahead with some surprises along the way i'm sure.

[492]

I think you make a very valid point. What was annoying (including myself) many posters was this

constant talk of the high sinking as there was never one single chart from any of the big three models

that I can remember anyway that showed this, which was very misleading to any newbies trying to learn.

Anyway onto the models and another excellent set of runs this morning. As far as temperatures go I think

the GFS for some reason is 2-3c to high for the middle of the week with Monday showing a max of 2c but

then Tuesday and Wednesday up to 5c. Also with 850's at -10 to -11c I would have thought a Max return

of 0 to +1c would be about right in sunshine and lower if cloudy.

Unlike the GFS I think the ECM looks more plausible in the medium to long range in moving the low to the

southeast of the UK westwards allowing a northeasterly to develop.

This upcoming spell certainly in my eyes has the makings of being the longest and most severe of the winter.

It is starting to look like it might turn severe especially with the snow cover to our east mostly intact.

[SP1986]

It is starting to look like it might turn severe especially with the snow cover to our east mostly intact.

I think perhaps if there is a word that is overused on this forum it is 'severe', nothing on the outlook looks severe. To be severe you would literally need something on the level of 1963 or 1947 - nothing on the chat is anywhere near that harsh.

[lorenzo]

Would somebody be good enough to give me a link to the NAE model, thanks.

SS2

Was on the thread earlier I think..

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&VAR=pslv&HH=0&BASE=-&WMO=&ZOOM=0

[SnowBallz]

Would somebody be good enough to give me a link to the NAE model, thanks.

SS2

NAE

[Totoro]

I think perhaps if there is a word that is overused on this forum it is 'severe', nothing on the outlook looks severe. To be severe you would literally need something on the level of 1963 or 1947 - nothing on the chat is anywhere near that harsh.

Agreed. Plus, assuming that the current GFS output verifies (unlikely as it's a week away!) there is some less cold air being mixed up into the flow in a week's time so a cold easterly would then turn into a less cold easterly. Didn't the same thing happen around Christmas 2009 ?

[sandstorm2]

NAE

Thank you SnowBallz for the link.

SS2

[D KARLSON]

After looking at the GFS 06Z, it appears that a lot of us will see some action.

Monday - Wednesday; A more N/NNE flow, snow showers affecting Eastern parts of Scotland, NE England, Yorkshire and Lincolnshire coast line. With some snow showers about in the SE.

Wednesday onwards; The risk shifts a little further South, with the South East and EA getting plenty of snow showers. Yorkshire and Lincs will still see plenty of snow showers, although they become less frequent and widespread I would say just North of the North Yorkshire Moors.

Day time temps of around -1 to 2c for eastern areas Wednesday onwards.

Stupid i know, but becoming marginal from the East come friday night/saturday as warm sectors push in off the N Sea. With places further inland continuing to see snow, some very heavy especially for central areas, and southern central areas (M4 Corridor).

Things can still change of course but that's my take on things.

Thats a pretty good appraisal and as you say with these synoptics souteastern england could well be in for a pasting with some disruptive snowfall likely as the snow accumulates.

Its crucial though that we wait till monday to get a better idea as to where that low pressure systenm sits to the south ,at the moment the southeast is on the cusp of severe weather with the winds just clipping se corner but this is likely to change.

I think even south east scotland will see snowfall as with the winds still coming off the sea, it will still drag cloud in and light snow even though the are close to the centre of the high.

As for snowfall amounts we can only speculate at this early stage ,but i think the persistance of snow showers will be the problem so say after a couple of days places in the east and particularly higher ground such as the wolds ,kent etc could have as much as 4 inches or more and low gound at least a good covering

[TEITS]

Based on all the models I would currently say the potential is there for this cold spell to be more prolonged and severe than our previous cold spells. At the moment I see this coming in 3 stages although of course subject to change.

Stage 1.

Sun-Wed a slack NNE/NE,ly flow bringing max temps between 2-4C with snow showers especially for NE parts.

Stage 2.

Wed-Sunday Winds veering E,ly and turning colder with max temps around 0C. Snow showers becoming more frequent and widespread. During this period the HP starting to back NW.

Stage 3.

HP over Greenland bringing a renewed surge of cold N/NE,lys. However at the same time LP may move across the S.

The potential is there for week 2 to be more wintry than week 1.

Again this is all subject to change!

Thanks for the kind comments Lewis.

Edited February 6, 2010 by THE EYE IN THE SKY

[johnholmes]

I think this post hits the nail on the head.

1. with the models struggling with the different scenarios for quite a long time now, I wonder if a case of a general Pattern change globally has been the catalyst for pre set values on the super computers that churn them out, to show a weakness in the way computer models handle input information. After all said and done all computer information starts as human input code. Now if that code is based on a long term average its only natural that the computers will be bias to certain information. Now what a computer struggles to do is work out a variable if the variable is not thought of or is of an unusual situation. Dont forget that computers are a modern thing and Input data is based on the information from the past, Now it is my view that the people who programme data for number crunching will have learned a lot from the past few years global weather patterns and in future computer models will have the data added to come to a more informed conclusion in the future Computers are a work in progress and like us they need the variables to learn and become accurate.

2. My second point is that sometimes when in complicated situations like above i always find that a back to basics approach is a good start, I think that sometimes to much information for most of us mortals is too much to handle. Any followers of the weather in my view on any site are spoiled by to much information (Models and Data) and unless you are very well educated or informed sometimes its hard to see the wood for the trees. However when all is crashing down around our ears synoptically the met office on the face of it have just gone back to straight forward forecasting using as little information but years of experience as possible. Over the last few years as more and more information has been allowed to come into the public domain, I have noticed a rise in misinformed posts and explanations. Noone can blame or point the finger at anyone individual because its human nature to make the best of the information before them and unfortunately that is the very problem we have.....just too much information to make a informed decision.

LO

not disagreeing with most of your post Lincs just one small point

Weather models are NOT given 'long term averages'. They are all 'fed' current data as available no averages or whatever else. They then, in somewhat different ways, GFS, UK Met, ECMWF, depending on how their programme has been set up, then work out for every grid point at 1 sec upwards to whatever end of time scale they are set to the basic formulae for thermodynamics-hugely complex that they are. No averages that I am aware of are fed in on any model. programmers do at times 'tweak' the models if they seem not to be responding to events very well. too little or too much moisture, not enough notice of topography, etc.

Edited February 6, 2010 by johnholmes

[MR EXTREMES]

They sure have Kev, I agree with that.

ECM after initial movement of HP towards UK seems to be getting keener and keener on retrograde of the HP to Greenland. That of course would elongate the cold spell to beyond 10 days to possibly 2 weeks or more. I still suspect that it is being too keen...but nice if its right.

BFTP

well all i can say its great to see after lastnights gfs 18z and lastnight ecm mayhem,

the changes i expected to come this morning have come.

and blast theres no reason why this cant be a lengthly cold spell.

its rather exciting to see our cold and the cold in the usa that crippled them out there,

this truely is a really exciting winter with a sting in its tail.

a retrograde towards greenland would really help things along nicely im hoping for the sausage special which was being shown lastnight but ofcoarse that was deep fi but exciting to see.

meto update will be exciting aswell today and i must add my two pennies worth,

they have performed fantastic.

[Frosty.]

I think perhaps if there is a word that is overused on this forum it is 'severe', nothing on the outlook looks severe. To be severe you would literally need something on the level of 1963 or 1947 - nothing on the chat is anywhere near that harsh.

I agree, there is nothing severe about the output for next week, no comparison with dec & early to mid jan, some snow showers and frost but nowhere near as cold as last time.

[johnholmes]

Cheers for the reply John.

I would be interested to read what models the Met O do have access to that we don't see. I would find this especially interesting considering the model output of the last 7 days and the Met O forecasts.

P.S do you remember someone called Ralph Hardy?

the name rings a bell, I rather think he was one of the senior forecasters at CFO (Central Forecasting Office) during my time in the Met Office, co author of at least one weather book?

[Duane S.]

Thankfully I missed the 18z and I'm not saying that because of the model output!

I have just spent the last hour 'catching up' and have to say it all looks excellent for the next week. I have been saying for a while that people should stop obsessing with the block sinking (by which I mean properly sinking down over us and beyond), it won't, it can't. Yes, It will later on but that won't be for quite a while.

The ens are now showing very firm agreement on the cold 'spell', which is now nailed.

I still favour retrogression as the most likely outcome in just over a week's time. The recent warming of the stratosphere can only help in this repect and may have occured at just the right time!

Obviously the SE, INITIALLY, is going to be more likely to cop for snow than, say, the NW. Chances for everyone will occur as the cold spell progresses though.

Speaking for my location and I'm not badly placed for once in terms of reaping the benefits of a full-on Easterly later on although the South West will be where the first Atlantic incursions will likely hit but... that's not for now.

[Guest North Sea Snow Convection]

I think it is too early to say whether the cold spell is going to be more severe than the last one. Personally I think this is unlikely at this time.

The heinz 57 variety of GFS outputs each day seem to be showing a pattern of a couple of drier one's and a couple of more unstable and colder one's. The ECM appears to be more measured on a more even and continuous basis than the GFS, whilst the UKMO has been somewhere in between.

The January cold spell featured widespread and in many places very deep snow. The snow cover coupled with very short days and weak solar output contributed albedo feedback into the intense freeze of the first 10 to 14 days especially. That widespread pattern doesn't look as likely this time around - although of course featues can crop up at short term notice on the models as we know and these might impact less obviously favoured areas.

I think the assessment of temperature that I read from Iceberg this morning is a reasonable one. Solar energy is more of a factor during the day now - we are a good month on from the coldest of the weather in the early to mid part of January and this will be a factor. Nonetheless, any areas where snow showers become persistent, then some interesting situations could crop up. This spell doesn't have the look of a Feb 91 about it - and it is something of that order that we would need to make this cold spell more severe than the earlier winter.

This cold spell is going to have to work harder than the last one - and I am not sure that the *peak* of the cold from earlier is going to be achieved. Much as I have said a litttle while back.

However, not to over downplay by any means - it does look an increasingly prolonged spell and quite probably will eclipse most of the relatively tame Feb cold spells we have seen in recent years

It could be that my signature, which would normally apply in the case of many traditional Feb cold spells that often occur more frequently in the latter part of winter, is not strictly speaking going to be true this time around! On the basis of the intense cold of a month ago - quite a target to beat!

Edited February 6, 2010 by North Sea Snow Convection

[damianslaw]

Longer term upstream signals as we get towards the middle of the month as they have been for a while now suggest retrogression of heights to Greenland - a very negative AO and NAO is developing and energy in the northern arm of the jet will be very weak indeed.

Next week will be predominantly easterly. NE flow becoming E flow, by next weekend retrogression occuring and we being to see a N-NE flow.

The third week of Feb is looking a potential severe wintry spell of weather with widespread snow. Whereas next week no real severe conditions, greatest chance of snow in eastern coastal parts, but the week after elsewhere will join in, a very good chance of a sustained very cold 2 week spell is on the cards. Mid-Late Feb traditionally sees the atlantic in late winter slumber and high pressure dominant, in 2005, 2006, 2008, 2009 this particular period has seen a very quiet atlantic. A very blocked outlook.

Edited February 6, 2010 by damianslaw

[cooling climate]

Based on all the models I would currently say the potential is there for this cold spell to be more prolonged and severe than our previous cold spells. At the moment I see this coming in 3 stages although of course subject to change.

Stage 1.

Sun-Wed a slack NNE/NE,ly flow bringing max temps between 2-4C with snow showers especially for NE parts.

Stage 2.

Wed-Sunday Winds veering E,ly and turning colder with max temps around 0C. Snow showers becoming more frequent and widespread. During this period the HP starting to back NW.

Stage 3.

HP over Greenland bringing a renewed surge of cold N/NE,lys. However at the same time LP may move across the S.

The potential is there for week 2 to be more wintry than week 1.

Again this is all subject to change!

Thanks for the kind comments Lewis.

Have to say thats pretty much the way I see it panning out as well. There is a real possibility what

with the tanking AO and SSW (sudden stratospheric warming)etc that we could very well be looking

at a third week as well.

I know though there is plenty to concentrate on this upcoming week without thinking about the

twilight zone.

[Frosty.]

There is no guarantee of retrogression occuring, the gfs 06z doesn't end up with a Northerly, in fact, the 6z tended to become less cold in the later stages, especially in the south.

[Snowangel-MK]

Based on all the models I would currently say the potential is there for this cold spell to be more prolonged and severe than our previous cold spells. At the moment I see this coming in 3 stages although of course subject to change.

Stage 1.

Sun-Wed a slack NNE/NE,ly flow bringing max temps between 2-4C with snow showers especially for NE parts.

Stage 2.

Wed-Sunday Winds veering E,ly and turning colder with max temps around 0C. Snow showers becoming more frequent and widespread. During this period the HP starting to back NW.

Stage 3.

HP over Greenland bringing a renewed surge of cold N/NE,lys. However at the same time LP may move across the S.

The potential is there for week 2 to be more wintry than week 1.

Again this is all subject to change!

Would someone please be kind enough to put this excellent post by TEITS on the 3 Counties & EA regional thread please ! (Sorry Mods OT I know but I'm sure there are people who don't come on Model Dis. that would like to read this)