Model Output Discussion:

[johnholmes]

thanks for the reply Kevin-no argument with that logic

[Jayces]

I don't know why but the models seem to have some bias in taking the energy NE in the +144 range and it isn't until this moves closer that this sometimes changes. Until this model bias is resolved then E,lys will continue to be a nightmare for models to get correct.

Do the folks who run these models correct them if they see a similar pattern in a particular scenario happen over and over?

ie, in the above example if they had data stretching back that showed 7 out of 10 times the low moving SE instead of NE wold they then consider changing the software to reflect this as the most likely outcome on future predictions?

Or is it a case of this winter being so different to previous ones that the models have these odd blips?

Or just too many variables to predict anything reliably beyond a few days.

Also do they only ever give one outcome publically? I would assume they run different outcomes in their offices and in the above example may have moved the low NE instead of SE, seen the colder solution but decided to publish the warmer sollution as they thought that was the most plausible?

[Frosty.]

Well at last the upcoming cold spell is a 100% nailed on certainty now, there is still quite a lot of variability in the 00z output though with the positions of the high and the scandi trough which makes a big difference to who gets snow or not. The GEM 00z is again my favourite model run this morning with less hp influence and more instability with a NE'ly which then turns into an E'ly and later a raging N'ly, retrogression is again a feature of the 00z runs with the ecm heading towards a potent Northerly later but generally it doesn't look too severe next week although there will be some snow showers in the east and south and widespread frosts everywhere, the really juicy charts are in FI though.

Edited February 6, 2010 by Frosty039

[derrylynne]

If this is not a place to learn then I will leave. My request simply reflects my frustration at posts (not just Mr Browns) that state the obvious (i.e. it could do something) without showing people who have been here a month (an awful lot longer before posting, but I forgive you for your incorrect assumption) without providing evidence to back it up. Science has never meant 'knowing' as you put it. Science has always been about testing theory with practical backup. If all scientists just went off on theory without the requirement to back it up with evidence then we'd still be drilling holes in peoples heads to cure headaches. Ian does generally back his theories up, but tonight he hasn't. Could remains 'could' until someone turns in into 'should' and backs that up. Apologies for being arrogant and rude in your opinion. But hey - as you point out I only have 21 posts so I clearly don't count. (edit - 22 now!)

Mr Brown is right though. 'It could'. That sums up every synoptic chart that appears. Nothing is ever set in stone as far as weather is concerned. Trends are easier to spot but even then their are times when the trend is wrong - as in the charts up to recently when they were insisting the Atlantic would once again become dominant...The cold spell that is coming is progged to last ten to 14 days at present - but that is only a 'could'. The charts are showing it 'could' snow in the middle of next week - and that the south east 'could' take the brunt'. But a slight shift in wind direction and anything could happen. nuff said....From my slant the week looks to be cold but dry for the west with high pressure - frosty but a lot of sunshine. Although this could change....

[TEITS]

Also do they only ever give one outcome publically? I would assume they run different outcomes in their offices and in the above example may have moved the low NE instead of SE, seen the colder solution but decided to publish the warmer sollution as they thought that was the most plausible?

The only access the Met O have that we don't see is the MOGREPS (short range ensembles) and a more detailed look at the ECM ensembles.

What I find interesting is when the ECM was projecting mild SW/S,lys their were very few cold ensembles at the time. However the Met O obviously disbelieved the mild ECM runs and continued to predict a cold spell. This to me is classic old skool forecasting because they didn't rely on a computer model for their forecast.

Whatever anyone says about the Met O you have to admit that their forecasting this week has been very impressive indeed.

[johnholmes]

The only access the Met O have that we don't see is the MOGREPS (short range ensembles) and a more detailed look at the ECM ensembles.

What I find interesting is when the ECM was projecting mild SW/S,lys their were very few cold ensembles at the time. However the Met O obviously disbelieved the mild ECM runs and continued to predict a cold spell. This to me is classic old skool forecasting because they didn't rely on a computer model for their forecast.

Whatever anyone says about the Met O you have to admit that their forecasting this week has been very impressive indeed.

I think Ian F may be able to give the actual situation with regard to just how much data UK Met have, both their own and other that we don't see. Might be an idea to ask him to show what is available without breaking any confidentiality?

From what I saw when I had access 6-12 months ago it was rather more than you suggest.

[Long haul to mild]

Well at last the upcoming cold spell is a 100% nailed on certainty now, there is still quite a lot of variability in the 00z output though with the positions of the high and the scandi trough which makes a big difference to who gets snow or not. The GEM 00z is again my favourite model run this morning with less hp influence and more instability with a NE'ly which then turns into an E'ly and later a raging N'ly, retrogression is again a feature of the 00z runs with the ecm heading towards a potent Northerly later but generally it doesn't look too severe next week although there will be some snow showers in the east and south and widespread frosts everywhere, the really juicy charts are in FI though.

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!!

Edited February 6, 2010 by Chalk Serpent

[TEITS]

I think Ian F may be able to give the actual situation with regard to just how much data UK Met have, both their own and other that we don't see. Might be an idea to ask him to show what is available without breaking any confidentiality?

From what I saw when I had access 6-12 months ago it was rather more than you suggest.

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?

[in the vale]

Mr Brown is right though. 'It could'. That sums up every synoptic chart that appears. Nothing is ever set in stone as far as weather is concerned. Trends are easier to spot but even then their are times when the trend is wrong - as in the charts up to recently when they were insisting the Atlantic would once again become dominant...The cold spell that is coming is progged to last ten to 14 days at present - but that is only a 'could'. The charts are showing it 'could' snow in the middle of next week - and that the south east 'could' take the brunt'. But a slight shift in wind direction and anything could happen. nuff said....From my slant the week looks to be cold but dry for the west with high pressure - frosty but a lot of sunshine. Although this could change....

I understand that, but is the point of forecasting not to look at many 'coulds' (i.e. ensembles) and try to determine the 'should' - i.e. the mean, or the most likely? I have read so many discussions leading up to this mornings runs that talk about outliers etc. but some people have given their reasons why one particular outcome is more likely to occur than others. In the case of the upcoming cold spell a good example was TEITS explaining why the Atlantic LP needed to track SE. That may or may not happen, but at least it was an explanation that taught me (and many others) something. This is OT so apologies, I'll shut up now!

[nick sussex]

Very good agreement this morning from the ECM and GFS in the mean height comparisons. What stands out is that longwave trough stretching all the way from the central USA to central Europe.

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

In this circumstance we can see now why it was crucial that the blocking was strong enough to keep the UK on the northern side of this. Its often quite a stable long lasting pattern, however the uncertainty lies more with the signal for a western based negative NAO, in a nutshell given the set up the more the high retrogresses towards the west the more likely an attack will come from the sw as the Atlantic finds the weaker point.

The only ECM ensembles out so far are for the Netherlands.

http://www.weerplaza.nl/15daagseverwachting/default_pluim.asp?r=midden

Very good support in this region for the cold to continue,I think the high moving nw towards Greenland looks a good bet after the easterly.

[Iceberg]

I think Ian F may be able to give the actual situation with regard to just how much data UK Met have, both their own and other that we don't see. Might be an idea to ask him to show what is available without breaking any confidentiality?

From what I saw when I had access 6-12 months ago it was rather more than you suggest.

Yep my understanding is that they have several more models, most notable the UKV which is run at a 1.5km resolution, rather than the 12Km resolution of the NAE model. Now the UKV I would like access to.

There is also the longer range monthly ECM.

[Tim Bland]

Fax charts for Mon night to midday Tues shows a trough to the NE Scotland sliping south ending over SE England. Could be the 1st of many significant snow events for the East?

http://www.wetterzentrale.de/pics/brack2.gif

http://www.wzkarten3.de/pics/brack2a.gif

[nick sussex]

Yes very solid looking models this morning for a cold spell with the key being that the energy continues to go South and not across Greenland. The GEM is a particular belter this morning, I would be interested to see if GP has changed his position with regard to where the High will end up.

With regards to the METO, full credit to them for never altering their cold outlook on their 6-15 dayer, despite the models chopping and changing wildly.

Yes they do look very good for a decent cold spell. The GEM i'm not really convinced about as it was very slow to pick up the easterly and perhaps its still lagging a bit behind. The interest later IMO comes from how far the block moves to the west, I remember before Xmas the GFS in particular was most keen of the major models to drive low pressure too far north towards the south as it overplayed how far west the block went. I think however all the models at that time initially wanted to transfer it further west than actually verified so it will be interesting to see if that same trend is repeated this time.

[Cloud 10]

Yep my understanding is that they have several more models, most notable the UKV which is run at a 1.5km resolution, rather than the 12Km resolution of the NAE model. Now the UKV I would like access to.

There is also the longer range monthly ECM.

Here is a link with some info on the ukv model as well as some other interesting stuff.

Physics_athens_250909_1.pdf (application/pdf Object)

[Iceberg]

Here is a link with some info on the ukv model as well as some other interesting stuff.

Physics_athens_250909_1.pdf (application/pdf Object)

Yep would be nice to have it for the convective stuff, streamers etc likely next week, as it should prove the most accurate at detailing exactly where.

Hint- Ian you don't want to post up a few shots do you come the interesting days. ? If you can of course.

[Lincs Observation]

The only access the Met O have that we don't see is the MOGREPS (short range ensembles) and a more detailed look at the ECM ensembles.

What I find interesting is when the ECM was projecting mild SW/S,lys their were very few cold ensembles at the time. However the Met O obviously disbelieved the mild ECM runs and continued to predict a cold spell. This to me is classic old skool forecasting because they didn't rely on a computer model for their forecast.

Whatever anyone says about the Met O you have to admit that their forecasting this week has been very impressive indeed.

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

[cooling climate]

I understand that, but is the point of forecasting not to look at many 'coulds' (i.e. ensembles) and try to determine the 'should' - i.e. the mean, or the most likely? I have read so many discussions leading up to this mornings runs that talk about outliers etc. but some people have given their reasons why one particular outcome is more likely to occur than others. In the case of the upcoming cold spell a good example was TEITS explaining why the Atlantic LP needed to track SE. That may or may not happen, but at least it was an explanation that taught me (and many others) something. This is OT so apologies, I'll shut up now!

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.

Edited February 6, 2010 by cooling climate

[Iceberg]

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.

I agree, but 850s are more progged at -7 to -8 for midday wed, maybe a little colder in the far SE. Still time for it to change, but I fully understand the temps being predicted.

A more progressive 06Z with lower pressure generally.

[john mac]

Nice 850's of -10 at the east coast by t+90

[TEITS]

Better 06Z compared to the 0Z for the simple reason the general pattern is slightly further NW.

http://www.wetterzentrale.de/pics/Rtavn1261.png

As for GFS temp predictions. Well based on our previous cold spells I personally found my temps were around 2C lower on average.

[SKYMAN]

Would appreciate an update on the 6z, I do not understand how to read them like most of you.

[Cecil Hogmanay Melchett]

Would appreciate an update on the 6z, I do not understand how to read them like most of you.

Its a cold run and anyone in Kent or the SE in general looking very good for snow through the week.

Ammounts very uncertain though.

[TEITS]

Would appreciate an update on the 6z, I do not understand how to read them like most of you.

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.

[SKYMAN]

Many thanks Happy Days and T.E.I.T.S

[Cecil Hogmanay Melchett]

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.

Yup,agree with all of that Dave.