Model Output Discussion 18/11/2012 12Z onwards

[Frosty.]

I found another hen for you steve.

Come on guys, it's only an op run, look at the bigger picture with the ensembles gaining support, Ian F with his snippets of met office data, i'm sure there were some model wobbles before the late nov 2010 freeze, the ecm at one point had the freeze hitting the mid atlantic instead of the uk, the rest is history. I think the models are having a wobble right now but will soon settle down and begin to firm up on how cold it will get, how long it will last and whether or not there will be any likelihood of snow, and it's snow most of us want, not just cold and dry..

[Grimsby Snow Lover]

From viewing the models over the past week I think we have a lot to be happy with at the minute if a colder outlook is your cup of tea. This time last year were were staring down the barrel of a very zonal weather type driven by a bullet proof PV over Greenland. Yes the currrent models aren't showing a December 2010 outlook at the minute but wasn't that a 1 in 100 year event? Colder, frosty weather with possible snow showers could be our weather type in around 10+days time which would be seasonal if nothing else. Everything seems to be heading in the right direction after the next 5 days if you are wanting colder temperatures, what happens then is anyones guess. Personally I would be mega relieved if we are not seeing a PV driven pattern if nothing else.

[OldMetMan]

I've been watching the longer term trends for cold conditions come and go in the model output in recent days, not just the GFS which seems to change from one run to the next, but today both the GEM and JMA are showing interesting possibilities:

Here's today's 12Z JMA:

Such a chart would be exciting indeed if it were Jan/Feb but it's a bit too soon. Nevertheless this type of easterly often changes to a N or NE flow as the main HP transfers to our N and NW.

At 500mb, once again there are signs of increasing amplification of the flow over the US and Canada.

The large vortex off W Canada seems likely to sink SE whilst further E to the NW of the UK, a weakish block exists in the sort of position that would favour what the JMA is saying. One other area of interest is the fact that W European blocking has finally collapsed, again this suggests to me that blocking will re-develop further W.

The strongest jet energy across the Atlantic is on quite a low latitude plus the sub-tropical jet across N Africa is also unusually strong. These factors which seem to indicate most of the LP activity in days to come will be well S of the UK, once the upcoming stormy spell this week dies down and the Atlantic vortex disrupts.

I think we will have some interesting weather to look forward to!

Edited November 18, 2012 by OldMetMan

[Liam J]

I don't think we're any nearer than we were 24 hours ago and the 24 before that.... Any decent looking charts are still being held out of reach, yes the evolution changes from run to run with the odd half decent looking chart, but, time is moving on and the said charts aren't getting any closer to the reliable time frame. Without trawling back over previous pages fishing out posts I've read over the last x amount of days, shouldn't we now be seeing agreement between the models and counting down to the 'cold spell' ?

I do agree that we'll be seeing a pattern change in the NH probably by the months end, but at this current time it feels like the all to familiar winter past time that many of us get sucked into each year - chasing FI cold synoptics, which then leads to hugely inflated expectations and equally large disappointment.

Apologies for the wet blanket on the fire type of post....

Edited November 18, 2012 by Liam J

[johnholmes]

Would I have said the same thing following the 12Z? I think not! A fine example of what can happen when one bases a forecast on a single run...

ah but there is perhaps the clue Pete, NEVER at long time scales go from run to run.

My suggestions of how and when the cold will arrive is based on watching the less volatile versions for over a week now.

[Cloud 10]

ah but there is perhaps the clue Pete, NEVER at long time scales go from run to run.

My suggestions of how and when the cold will arrive is based on watching the less volatile versions for over a week now.

Todays "less volatile versions" seem to be singing a similar tune to each other.

Climate Prediction Center - 8-14 Day 500mb Outlook

ECMWF/GFS DAY 8-10 MEAN 500MB HEIGHT COMPARISON

[phil nw.]

It does seem like we have been anticipating a cold pattern for some considerable time.

We have to remind ourselves that a pattern change to something less mobile was never expected untill near month end.

We have been teased a few times with some attempts by certain runs to bring this change closer but they have been dropped nearer to real time.

We are now starting to see that change being modeled within the next 10 days now-indeed the 12z ops were in quite good agreement at T240 that the persistent trough finally shows signs of warming out with pressure rising near the UK.

Pretty unanimous from the GEFs for this change too.

http://www.meteociel...&mode=6&ech=240

The 2m temps on the GFS ens also continue to show the cooling trend to month end.

We have to see where we go from there as to whether some deep cold comes our way.

If the vortex continue to be put under pressure as we go in December our chance will come when those blues(low heights)move further away from Greenland.This would enable the anticipated Atlantic blocking to push much further north diverting all the jet energy south and allow a more stable cold pattern to establish.

[Grimsby Snow Lover]

It does seem like we have been anticipating a cold pattern for some considerable time.

We have to remind ourselves that a pattern change to something less mobile was never expected untill near month end.

We have been teased a few times with some attempts by certain runs to bring this change closer but they have been dropped nearer to real time.

We are now starting to see that change being modeled within the next 10 days now-indeed the 12z ops were in quite good agreement at T240 that the persistent trough finally shows signs of warming out with pressure rising near the UK.

Pretty unanimous from the GEFs for this change too.

http://www.meteociel...&mode=6&ech=240

The 2m temps on the GFS ens also continue to show the cooling trend to month end.

We have to see where we go from there as to whether some deep cold comes our way.

If the vortex continue to be put under pressure as we go in December our chance will come when those blues(low heights)move further away from Greenland.This would enable the anticipated Atlantic blocking to push much further north diverting all the jet energy south and allow a more stable cold pattern to establish.

A quick question from me Phil. Why does the operational run on the 2m temps always seem to be an outlier compared with all the other runs? As soon as it gets to the low res sections it flat lines? Thanks GSL

[Frosty.]

Excellent post phil, I ran out of votes though. Cooling trend is key, op run model wobbles always happen before a cold spell. The week ahead of model watching will be thrilling I think.

[Liam J]

A definite trend towards cooler temps and higher pressure but the evolution remains very uncertain and messy indeed, I guess the key word here is patience. We may very well be heading towards a nice to start to winter proper...

Edited November 18, 2012 by Liam J

[Snowmadsam]

Really cant understand the negative thoughts on here for those who want a cold spell! The models are showing the weather getting colder from next weekend onwards, the trend is there, but how cold, how much snow, frost and the longevity of the cold spell remains uncertain. I would stick my neck out and say the computermodels are underestimating the projected cold. As ever time will tell, but for the coldies , there is alot to get excited about.....!

I agree, I did make up a phrase "C before S" basically meaning Cold before Snow...and also it is how I remember the alphabet...

PLENTY of potential....as always how long will it stay....will it snow...will there be frost...

Let's wait and see and get the cold air here first

[Harve]

I found another hen for you steve.

Come on guys, it's only an op run, look at the bigger picture with the ensembles gaining support, Ian F with his snippets of met office data, i'm sure there were some model wobbles before the late nov 2010 freeze, the ecm at one point had the freeze hitting the mid atlantic instead of the uk, the rest is history. I think the models are having a wobble right now but will soon settle down and begin to firm up on how cold it will get, how long it will last and whether or not there will be any likelihood of snow, and it's snow most of us want, not just cold and dry..

I think it's important to remember that for every November 2010, there are five 'almosts' which show promise but fizzle out to be nothing.

[phil nw.]

A quick question from me Phil. Why does the operational run on the 2m temps always seem to be an outlier compared with all the other runs? As soon as it gets to the low res sections it flat lines? Thanks GSL

Yes i noticed that and the honest answer is i don`t know GSL.Perhaps they don`t publish or calculate that data beyond HR?

Maybe someone else can help us on that as i would like to know.

[Frosty.]

I think it's important to remember that for every November 2010, there are five 'almosts' which show promise but fizzle out to be nothing.

Nov 2010 was an extreme example, I don't think anyone is expecting to reach close to those dizzy heights but I do believe we will continue to see a cooling trend and hopefully a warming stratosphere soon, december could see repeated attacks of arctic air, at least there is potential for it to happen as long as we don't get an anticyclone that then refuses to budge, I think retrogression will be a word used more and more in the weeks ahead, you make a very valid point though.

[weather eater]

Excellent post phil, I ran out of votes though. Cooling trend is key, op run model wobbles always happen before a cold spell. The week ahead of model watching will be thrilling I think.

I agree Frosty, as for chasing FI synoptics I really don’t think that’s the case this time round. It might be that one or two folks have been taken in by the odd eye-candy run, but I don’t think that’s happened too many of us this time round. In reality it’s more of a case of, we know a pattern change is going to happen and waiting patiently to see how that manifests itself, and I have to say having been away from the forum for a fair time that I’m really enjoying the will it won’t it tease of the whole thing. I’ve also been extremely impressed with the standard of posts, and not just from those with obvious good knowledge; even just a year ago the forum would already be starting to resemble a multi-car pile-up and that’s not the case at the moment.

Edited November 18, 2012 by weather eater

[Eskimo]

I know this is off topic but why do people always have to relate every winter to December 2010, we all know it's a rare event, we all know it may not happen again in our lifetimes so why are we comparing each run to that date? This winter will bring its OWN roller coaster.

Edited November 18, 2012 by PerfectStorm

[Frosty.]

I agree Frosty, as for chasing FI synoptics I really don’t think that’s the case this time round. It might be that one or two folks have been taken in by the odd eye-candy run, but I don’t think that’s happened too many of us this time round. In reality it’s more of a case of, we know a pattern change is going to happen and waiting patiently to see how that manifests itself, and I have to say having been away from the forum for a fair time that I’m really enjoying the will it won’t it tease of the whole thing. I’ve also been extremely impressed with the standard of posts, and not just from those with obvious good knowledge; even just a year ago the forum would already be starting to resemble a multi-car pile-up and that’s not the case at the moment.

Yes weather eater, we are going to get a much clearer picture emerging as the week goes on, very encouraging ensemble support for a cold spell to develop during last week of month but probably more especially throughout december.

[Timmytour]

Personally I'm hoping that 2010 is not a once in a lifetime event but closer to the new norm that the old norm :-)

I think my kids are growing up expecting to see it snow it winter....that's great but something I feared at one stage would not be the case. However each of the last four winters has delivered at least something and one of them in spectacular fashion.

But I'm also conscious of the fact that expectations have been raised as a result of the past four winters and perhaps that leads us to hanging our coat on the signs that show the potential of it being delivered. What I've seen so far has got me taking my coat off.....but I've not hung it up yet!

[Ice BIast]

They might not be the best models, but both the BOM and JMA 12Z's look decent.

[johnholmes]

Todays "less volatile versions" seem to be singing a similar tune to each other.

Climate Prediction Center - 8-14 Day 500mb Outlook

ECMWF/GFS DAY 8-10 MEAN 500MB HEIGHT COMPARISON

yes they are all, (3+NAEFS) giving stronger and stronger signals over the past 7 days, amidst all the volatility of the synoptic models, of heights rising from somewhere just south of Greenland, increasing in anomaly heights and extending towards Iceland then east and by then the Russian ridge at last begins to edge west. The 12z NAEFS this evening amalgamates them. Too early to be sure this will happen but the trend for height rises at 500mb NW-N of the UK by 26-28 November is as clear a signal as I've seen for a long time indicating a change of pattern is about to develop.

I would give it 85% with only 15% of it not happening.

But then the weather loves to make fools of us all at times so another 2-3 days of similar outputs and I would drop the 15% without increasing the 85% IF the trend continues.

After I have had a really good look at everything during tomorrow, IF all seems still to point towards the pattern change then I will do an update on my pdf from Friday. That was the idea when I first suggested doing this sort of thing to Paul. Once weekly Friday unless something warranted an additional output, change/wrong idea whatever.

Edited November 18, 2012 by johnholmes

[bluearmy]

John, the 12z gefs seemed different in trend to recent days re the pattern preceding the atlantic ridge and also re the subsequent trouging to our east. I would wait for tomrrows ens runs before takng too much notice of the 12z naefs. (Save the consistent week 2 greeny area height rise)

[SMU]

Once again the JMA comes up with the cleanest evolution & is exactly what I was expecting in terms of shape of high- That high has all the hallmarks of a retrograde to GH-

also a couple of STELLA runs in the ECM- sub zero maxima & snow-

S

[Methuselah]

ah but there is perhaps the clue Pete, NEVER at long time scales go from run to run.

My suggestions of how and when the cold will arrive is based on watching the less volatile versions for over a week now.

Indeed, John. I was using myself as an example...

[johnholmes]

John, the 12z gefs seemed different in trend to recent days re the pattern preceding the atlantic ridge and also re the subsequent trouging to our east. I would wait for tomrrows ens runs before takng too much notice of the 12z naefs. (Save the consistent week 2 greeny area height rise)

pretty much what I suggested ba I NEVER take one run from any model and only go for something using the 500mb anomaly charts when all 3 are showing similar ideas for at least several days. I use the NAEFS charts as it can sometimes look less complex to anyone new to trying to understand this part of meteorology.

Certainly no full on suggestion from me for snow/ice/low temperatures etc but a definite change of type.

[nick sussex]

Looks like the GFS is going on yet another route here!

Really the differences between GFS runs at only 120hrs are laughable,compare this to the earlier 12hrs over the eastern USA, unbelievable!

This does look closer to the UKMO so maybe this is a good sign! Here we see the phasing of those two lows upstream and we have a mini northern Scandi high popping up aswell!

Edited November 18, 2012 by nick sussex