Model Output Discussion 25/11/2012 12Z onwards

[Bristawl Si]

Time to bring out the NW 'Big Guns' to restore some calm and rationality, before this thread descends into model output anarchy!

Is GP about this eve?

IF some of the models have picked up on a pattern change before the previously forecasted one has even begun then it just goes to show this forecasting business is just as difficult now as it was in the days before super computers. And would represent one of the biggest model changes on here since i first started viewing.

BUT as the weekend and following week still hasnt even arrived, in real time, only time will tell.

[cyclonic happiness]

And there is still this to fall back on to, it's been hinting colder and colder over the last few days, if the models can flip this far this quickly, they can flip back again, more run needed

"UK Outlook for Friday 30 Nov 2012 to Sunday 9 Dec 2012:

A mixture of sunshine and wintry showers at first. The showers mostly affecting eastern areas, with the west tending to see the best of the drier conditions. The heaviest showers will be towards the northeast, falling as snow over higher ground. Windy at times, with the risk of gales in exposure. It will be rather cold with a risk of overnight frost and icy patches. Becoming cold as we continue into December, with widespread overnight frosts. Further wintry showers, especially in the north and east, where accumulations over high ground are likely with snow perhaps falling to low levels. Also the potential for some more widespread outbreaks of rain, sleet and hill snow, especially towards the southwest."

Updated: 1156 on Sun 25 Nov 2012

[chionomaniac]

It's game over - incredible how the weather can make fools of us. To be fair it was always possible that the Arctic High would not be able to make the link, so difficult is the modelling in that area.

Whenever an Arctic High link up has failed and there have been many over the years - you have had all the eggs in that basket because the jet has broken through at a Northern latitude and you are raising pressure from the South, so it is another 10 days at the very least before you can get another shot.

Interesting to see if Choino could shed some light on if it was the cooling of the Strat in the first third of November that has tilted this in the direction we are now seeing.

No, this has nothing to do with the cold upper/ mid strat - this is still disconnected from the lower strat and troposphere.

Ian you are acting like the ECM ouput is a fait accompli - it is not. However the modelling of how the vortex splits and reforms is always going to be problematical as we have segments of energy detached from their usual positions. I think the ECM is too quick in reforming these segments and that we are not going to enter a period of long term zonality as you suspect.

It is still likely that in the 10-15 day time range that we see a displacement of the vortex that is eventually likely to have a bearing tropospherically - leading to further blocking patterns - most likely somewhere over the Canadian sector - possibly leading to a west based -ve NAO. How we travel there is still up for negotiation with the output.

This isn't game over by a long stretch.

[jethro]

The time to say 'it's game over' is after the event, not before. You're all talking about weather a week away, a lot can happen in a week. There's a reason why people like JH say don't get hung up on every individual run, take note of that advice - it's probably the most important advice to take for all you model watchers.

It's going to be a long winter.....

[Mr Frost]

Ian if you really believe this then that is fine you are perfectly entitled to your opinion. However I would like some 'meat' so to speak to show your theory is sound, charts or more explanation please?

Great post John.

Ian, we all know you are an extremely intelligent guy and can read the charts as good as anyone on this forum and beyond so please don't revert back to using nonsense like game over and what not. I actually enjoy having you around, it takes me back to when I was a younger lad on the BBC weather forum! You are a pantomime villain but when you are honest and not looking to stir many folk learn from you're posts.

Don't let yourself down!

Edited November 25, 2012 by Paul

[Dexter29]

countryfile will save the day... or night even, we still have an excellent ukmo, thats 2 peachy ukmo runs today, as yesterday, and a good gfs 00z followed by an excellent 6z followed by a stonking gfs 12z. The ecm has been wobbling like a jelly in the last 2 or 3 days and apart from 1 mega run early in the week, has never really been fully onboard.

But the ECM does also have massive support, JMA now added to the list.

I agree with the previous post, we need to be prepared for a 'Crushing disappointment'

I'm very pleased I kept an open mind.

[SteveB]

Could it be that not as much data is fed in at the weekends, more especially Sunday. Things like weather balloons etc?

[bradymk]

Be interesting to see in the coming day or two when the greenland low comes into higher resolution models like the GME to see what these show. I will be happy if the fax goes with the raw output.

Countryfile Friday pressure chart forecast not with ECM.

Matthew

Edited November 25, 2012 by bradythemole

[Suburban Streamer]

Joe B is still on track with this twitter piccy

That's a gfs chart posted by Joe b, rather than a Joe b prediction. Imby its an upgrade from the last time he posted that chart, wen the whole se was unshaded

[dragan]

Some agreement for the AO and NAO been around -3 on saturday so I cant see the atlantic smashing through. I would love to have the will power not to look at the models and wake up in a week to see exactly what we have outside!!

[Harsh Climate]

For crying out loud people the charts have been all other the place in the last few days, if your going to get so dissapointed on 1 run out of a hundered and just one piece of the jigsaw this is going to be an awfully long winter...

The trend for cold weather and blocking is good, we have the NAO/AO on board which is the biggest key to future atlantic blocking and the fact there is vast disagreement in the models just shows the uncertainty which is a problem they have every year with predicting blocking or dare I say it an easterly.

Please do not get hang up on one run, especially when we haven't even seen the validaiton for it within it's own esembles..

[xioni]

as promised a pdf for the next 2 weeks about the overall weather pattern

Thanks for the reasonable analysis, but I think you were wrong to say this:

"In my view this pattern will undergo minor changes from time to time but there is NO sign of any genuinely mild air making into the UK for at least 2 weeks from the middle of this week, who knows it could be longer!"

Even if you wrote this before tonight's 12z runs, a 'small chance or unlikely to go mild' would be more appropriate.

And since I keep reading in this thread that the teleconnections are great for cold, they aren't exacly great: we got an impressive westerly wind burst at the equator near 160E (always good for downstream amplification) and a very good AAM spike, but there's been a lot of interference from other areas which has prevented a nice MJO phase 6-7-8 circuit. This meant a more zonal setup over N.America which can put pressure on our block (e.g. tonight's EC run) and it also meant that the N.Atlantic ridge is not that strong.

The AAM is likely to fall now in the next 2-3 weeks and we'll probably get tropical convection returning over the Indian Ocean in mid-Dec (phases 2-3 of the MJO), which is not a geat setup for high latitude blocking. That can still happen though if the base state still favours it.

[andy_leics22]

That is a massive difference between the UKMO and ECM at t144!

Don't the UKMO use both their own model and the ECM to make forecasts? Must be giving them a right headache at the moment! I'm surprised just how different both models are at t144.

Hopefully someone will save those pictures and post them here again at the end of the week to see what the outcome actually was, I might do that myself.

Edited November 25, 2012 by andy_leics22

[Zenarcher]

Here's a comparison between the ECM, UKMO and GFS at 96 hours we have the ECM showing this low differently here.

I've just looked at the 3 hour pressure charts of the ECM to see what's happening and compare it to the 00z run, it makes the low stronger and the ridging in the Atlantic slightly more flat. At 120 hours big changes occur everything is being pushed more East compared to it's 00z run. It may be a case of the ECM overdoing the low and getting it's positioning right which is really important. Is the ECM tonight a worry? It's not a great run and seeing the minor models agreeing is another worry but no reason to panic just yet and overall in the end it does bring the heights back over the Northern Hemisphere. Winter is not over yet.

Just seen the country file forecast there it will be cold at times during this week ahead and the pressure chart on Friday goes against the ECM.

[ribster]

Here's a comparison between the ECM, UKMO and GFS at 96 hours we have the ECM showing this low differently here.

I've just looked at the 3 hour pressure charts of the ECM to see what's happening and compare it to the 00z run, it makes the low stronger and the ridging in the Atlantic slightly more flat. At 120 hours big changes occur everything is being pushed more East compared to it's 00z run. It may be a case of the ECM overdoing the low and getting it's positioning right which is really important. Is the ECM tonight a worry? It's not a great run and seeing the minor models agreeing is another worry but no reason to panic just yet and overall in the end it does bring the heights back over the Northern Hemisphere. Winter is not over yet.

Just seen the country file forecast there it will be cold at times during this week ahead and the pressure chart on Friday goes against the ECM.

Indeed it does, showed the low pressure sliding away up to the west of Greenland.

[A.J]

It never ceases to amaze me how some data fed into a computer can cause such issues that would have a watching psychiatrist rubbing his hands with glee...at the end of the day, as a NW colleague recently mentioned, the model outputs do not control the weather, it;s the other way around and I think a few posters need to engage this dictum before posting knee-jerk reactions if a run doesn't suit their own weather preferences.

[SMU]

All-

its at times like this we cant all jump ship.

The reality is - No matter how many experts are on here- or monitoring the models at NOAA you cannot make a definitive forecast on that canadian low.

We are in the lap of the gods. end of story.

S

[I remember Atlantic 252]

Could it be that not as much data is fed in at the weekends, more especially Sunday. Things like weather balloons etc?

I thought that, but then again I thought it would be an excuse, but wasn't there some wild ECMWF runs on sundays befotre Dec 2010? had a feeling there was

[PubliusEnigma]

If the ECM is to be believed the break down from the current cold will begin from this coming Friday evening and be

complete by Saturday evening. I cant even see any frontal snow occurring from the breakdown on Saturday ?

Eagerly waiting on the 18z GFS run now for solace.

[Frosty.]

countryfile will save the day... or night even, we still have an excellent ukmo, thats 2 peachy ukmo runs today, as yesterday, and a good gfs 00z followed by an excellent 6z followed by a stonking gfs 12z. The ecm has been wobbling like a jelly in the last 2 or 3 days and apart from 1 mega run early in the week, has never really been fully onboard.

countryfile did save the day,,sigh of relief, the low out to the northwest which threatens the whole thing, is eventually pushed back west allowing the cold block to the northeast to push southwest towards the uk, wintry showers peppering eastern counties after midweek..phew, it looked like a more wintry weekend would follow.

Edited November 25, 2012 by Frosty039

[BLAST FROM THE PAST]

Can't post images but if one looks at UKMO T72 to T120, a quite deep low gets squeezed to nothing and the ATlantic ridge moves north getting absorbed into the arctic HP. I have to say it looks not right and thus makes the ECM plausible and a worry re depth of cold and longevity.

BFTP

[Zakos]

It has to be said, the latest ECM is ghastly.

However, there are two important things to note:

1.The ECM still has high pressure over the Arctic throughout the run, a continuing trend, a cold shot could be just around the corner as-long the AO remains negative.

2.Its just one run The high variability in the output recently illustrates the issue ~96 hours is FI. The models are all over the place right now, things will not become clear for a few days yet.

My view:

A wobble in the output. Things will be back on track tommorow. While the ECM does show a plausible evolution, I really doubt it will occur. Perhaps there will be a brief/full Atlantic breakthrough, but I cannot see it being as rapid as the ECM is predicting

[snowstorm445]

Its always interesting how we will always regard milder weather as somewhat more valid in terms of charts than colder weather. Yesterday we had the GFS vs the ECM and UKMO and the majority of minor models (even though it has been said many a time on here that these models are unreliable). And yet many cautioned people on "not ruling out" what this one chart was showing, despite its utter difference to the other models.

Skip forward to today and despite the fact that these same models are showing cold, and, particularly the UKMO, have been very consistent, many are happy to write off the cold spell and take the ECM as gospel. Now, I may have been looking at the wrong thread, but has the general trend over the past, oh I don't know, week or so been for colder than average weather? Why all of a sudden does an unprecedented switch that has emerged in the past number of hours mean it is undeniable fact and that all hopes of a nice cold spell, which is still on, btw, have evaporated?

Now, I know this might fall on deaf ears, but can we please not make overly sweeping statements like "bitter disappointment" and "its all over" BEFORE we see proper consistency from all models, you know, like the consistency that we have seen for cold weather in the last week or so.

Thanks.

[ribster]

But the ECM does also have massive support, JMA now added to the list.

I agree with the previous post, we need to be prepared for a 'Crushing disappointment'

I'm very pleased I kept an open mind.

Firstly nothing has occurred yet, so your comment may be slightly premature. Secondly - 'crushing disappointment', I might use that phrase for something rather more serious, like losing my job or god forbid something worse, certainly not something as unimportant as a possible lack of cold and snow!

[Severe Siberian icy blast]

Am sorry but the ECM this morning and last night had the same trend

Also a lot of the minor models back the ECM

Also the ensembles have been trending away from severe cold for several days now

So it's not one run its been building for sevral days and this is the climax of it.

You are right though we were all excited an hour ago so there is still hope the UKMO has it right

I suppose the reason there is disappointment is the odds of a cold spell currently stand around 30% at bext whereas 2 days ago they pbly stood at 85%

So disappointment is well founded, but this could easily swing back to cold again

Your doing it again, how can the cold spell have 30% of verifying when 2days ago it was nearer 85% ? Do the weather forecasters on bbc and on hear Base there thoughts on what comes out several times a day? This is one small part of a much bigger picture, yes the models have showed a step toward a more zonal pattern at times, but it goes against all teleconnections and other signals, they are putting too much strength in the low off Greenland and underestimating the blocking signals . You say there has been trends the last few days , but it was only 2hrs ago the gfs showed an amazing cold spell, it was only 8hours ago the 6z gfs gave us another brilliant cold spell, the ukmo is solid aswell, so your picking up on things such as ensembles and putting it all together to give your thoughts more weight but its things that you will always see on the models when we are on the crisp of a major pattern change, how many times do we see blocking signals getting underestimated??