Winter Model Discussion - The Hunt For Cold - 12th Dec

[Kentish Snowman in Yorks]

Exactly, Still got charcoal in shed from that,

Lol how much did you buy?!

Things look bleak at the moment for cold weather fans I will admit but there is so much despondency in this thread with the 'zonal' looking charts and the mild long range forecasts that a cold snap may appear at relatively short notice and surprise us.

The ECM in particular was not the worst run in the world with heights dropping to the South towards the end of the run but what will be will be.

[Panayiotis]

So as the 18z is trickling out the main thing we should be looking at is the angle of the low to east of America at around 165hrs, this angle can change a lot in terms of cold!

Edited December 12, 2012 by panayiotis

[Pixel]

Hardly any jet in the top of our hemisphere ! except from the billy-no-mates model:

may I suggest that the kinks in the jet after this time frame will look quite different after our low (just west of us) has done its thing with our little island?

Once the low spoiler has passed/disolved/done what it wants to do it could open up new scenarios to ponder

Model watching has to yet to become a cure for insomnia (-: Looking forward to future runs.

[karlos1983]

So as the 18z is trickling out the main thing we should be looking at is the angle of the low to east of America at around 165hrs, this angle can change a lot in terms of cold!

Presume we want SE track?

[OldMetMan]

Once again, the models are providing a bewildering variety of solutions, even in the short to medium term to some extent.

I guess there is a certain amount of consistency between the different models up until around T144 with a LP dominated pattern but even here, the GFS in particular is changing run to run. I am finding it hard to believe that by T144 we will have yet another LP sat on us with its associated upper low.

Looking back through the 500mb charts so far this month, one feature that caught my attention was the flow over the US and Canada has shown a tendency, especially over the past few days, for the broad upper trough to slowly amplify further and further S with systems moving SE from the Pacific NW. Further upstream over the Pacific there has also been more noticeable amplification.

As a result of what's happening, it seems possible for this amplification to spread downstream. Already this has resulted in the southern jet over the US sinking well S before pushing out into the Atlantic, again on a low latitude. Further N, over N Canada all the way to Scandinavia, the jet is quite weak and fragmented. So, I would expect the main jet energy to remain well S for the foreseeable future.

The GFS shows a new LP forming as the one approaching now starts to fill and it seems very unsure what to do with it. With the deep vortex over N America one would expect a certain amount of ridging developing ahead of it as I mentioned before and another amplifying trough ahead of that in the W Atlantic. In other words, we could see the flow amplifying across the Atlantic to Europe.

With so much variation in the models beyond T144, I think we need to concentrate on changes in the runs only up until that point (even more than we usually do), especially around the T120 to T144 period because what happens with that 2nd LP will show, I think, whether there is going to be a significant change in the upper flow. If this amplification pattern develops, and blocking starts to develop, then I still believe this would give a real chance for pressure to build across to the N of us, as the remains of the LP near us sinks away to the SE.

Meanwhile, the large Russian HP does now look too far away to directly affect us, but its mere presence at this point in the winter signifies to me that it may well redevelop and quite soon. Only if and when it does, we could see its influence.

The critical thing as I see it at this stage is to watch for any amplifying trends upstream. I see the 18Z is coming out so it will be interesting to see what new variation it comes up with this time!

[Panayiotis]

Hardly any jet in the top of our hemisphere ! except from the billy-no-mates model:

may I suggest that the kinks in the jet after this time frame will look quite different after our low (just west of us) has done its thing with our little island?

Once the low spoiler has passed/disolved/done what it wants to do it could open up new scenarios to ponder

Model watching has to yet to become a cure for insomnia (-: Looking forward to future runs.

Managed to move it then!Lol main thing is that the jet is south or very south of the UK whereas last year at this time it was North of us, the jet being south this year though gives us much better possibilities of cold weather. Edited December 12, 2012 by panayiotis

[bluearmy]

Ah - but hang on.... I also (a) pointed out in my original post how we pay little attention operationally to the seasonal models, nor cite in wider public message (they're far too experimental.... EC32 is as far as we'll employ with better confidence, at least of sorts, and it's done well into early Dec) and also ( crucially, you can't compare the UKMO seasonal modelling of a few years back to what's being synthesised now. The new version, as explained in a fascinating recent (Sept. 2012) paper, has been 'retro-run' to re-evaluate the 09-10 winter predictions, with much better success versus the original, and it's worth reading the outcome of this work undertaken at Exeter - because it's important when making any reasoned assessment of their current seasonal forecast effort and offers some balanced insight into their eventual validity. Note also how the essentially average/zonal dominated winter this year was also signalled, broadly at least, in the EC & NCEP seasonal outlooks as well as the last ones from UKMO. Nonethless, the current suite of seasonal models remain very much embryonic in this area of science. Liz Bentley's comments in the BBC sidebar below say it all, really.

Anyway - for those interested, see - -

See: http://iopscience.io...326/7/3/034031/

And more accessible explanation at http://www.bbc.co.uk...onment-19584302

ian , do exeter create a seasonal forecast of any kind in a similar way to that done on here by stewart or is it simply done via a computer model ? i presume that they must have clients who pay for seasonal info, even if they dont issue anything publicly (or is that left to the independent forecasting companies to take care of ?).

[Summer Sun]

ECM ensembles

[Gary_R_Walker]

I'm just one of the many hundreds of people who have no idea how to read the weather models that are discussed in this forum, so all I'm looking for is an honest opinion of what the experts are seeing. I understand that due to some individuals extreme weather bias they might see these charts through snow covered goggles. One thing that seems to be missing is when some so called experts get their predictions so badly wrong they haven't got the courage to say "I messed up." Most reasonable people would accept this, so be brave, you got it wrong, so what.

[Panayiotis]

Presume we want SE track?

Yes we shall see...in the reliable though still uncertainties for this Saturday, 3 lows now formed from the initial low?!

http://cdn.nwstatic..../57/h500slp.png

Edited December 12, 2012 by panayiotis

[karlos1983]

Blimey, its the low pressure train

@ Panayiotis you beat me to it

Edited December 12, 2012 by karlos1983

[Panayiotis]

Blimey, its the low pressure train

Ive never seen it before (well im only 16) but i find it quite extraordinary!

[karlos1983]

Ive never seen it before (well im only 16) but i find it quite extraordinary!

Swallowed up by +66

[Bristawl Si]

Ive never seen it before (well im only 16) but i find it quite extraordinary!

Looks like the 18z has been on the sauce again!

[fergieweather]

ian , do exeter create a seasonal forecast of any kind in a similar way to that done on here by stewart or is it simply done via a computer model ? i presume that they must have clients who pay for seasonal info, even if they dont issue anything publicly (or is that left to the independent forecasting companies to take care of ?).

Yes - they create a printed version replete with all manner of probability charts and such-like.

[Panayiotis]

The area where i have drew around is interesting to me,it has filled up this area much quicker than the 12z and covers a much larger area, could these heights move to Greenland and as a result move the low to east of us giving us a northerly?

Edited December 12, 2012 by panayiotis

[Matty M]

I don't know why i am still sat here watching the 18z GFS roll out.

ECM EPS is fairly poor, hanging on a 10% for cold after Day 7.

The faux easterly has got me hooked.

Anyway steady as she goes at T120hrs, a bit more amplification in east US.

[lorenzo]

The glosea4 paper is an excellent read, would be interesting to know if it has seen any sign of an SSW, quoted fro conclusion..

Nevertheless, given the lead time of several weeks for the

SSW mechanism, the results described here are promising for

enhanced forecast skill for similar exceptional events, even

though average hindcast skill may be low.

Although this is strat orientated is certainly on topic in terms of the Winter Hunt for cold !

If GFS became sentient and could produce a chart in honour of itself and it's well know bias - I reckon it would serve us this.

mmmm...dartboards.

As Blast mentioned earlier would be interesting to know an all encompassing low has featured before anywhere or if this is another wildcard for this winter.

Edited December 12, 2012 by lorenzo

[BLAST FROM THE PAST]

ok

i only ever read this discussion never reply as i am not as clever as all of you who read the weather so well

.

few questions though

netwerther,s winter forcast was more on the cool/cold side rather than mild ....it seemed to me they were very confident about this are they still?

if these darn model,s were going to give us the cold we all ,well most of us want and then they go change so fast into well whats seemed like 2 cold days then back to a little milder .......can they change back to cold sooner than january .why do some people seem so sure its now going to be a wet mild or windy christmas?

do the pros at netweather reply much on this thread i thought maybe one or some of them would be on trying to explain to people why they think the winter will be a cold one and why we are not getting the cold right now

Its early days but you have made a fair few points. Re winter as a whole there's nothing to answer yet. Re models backtracking to major cold......very unlikely in neartime for Dec.....but the synoptic pattern is moving well away from what was/is anticipated.

BFTP

[cold snap]

Nothing to get over excited about but so far this is much better the lows look weak coming east

Edited December 12, 2012 by cold snap

[Gavin Hannah]

On any other day, this would undercut. I mean, look how flat this low is......

Very minute differences at t.144. This is getting old hat.

Edited December 12, 2012 by IBringTheHammer

[Matty M]

Some very mild weather progged for next week with a Iberian Euro ridge developing and pumping up some mild uppers.

[chionomaniac]

Yes - they create a printed version replete with all manner of probability charts and such-like.

Hi Ian,

You may or may not know the answer to this, but possibly since the last run of the longe range model forecast, the possibility and probability of a SSW is increasing. The GFS has consistently forecast this (warming not complete vortex breakdown) to start at 10 hpa between 11- 15 days as shown below.

Now, assuming that the GFS is not alone here in its long range forecast, will the GloSea4 model have picked this up yet and if so will this have had time to be factored into or will it be fed into the longer range outlooks?

Thanks

Ed

[Robbie Garrett]

The area where i have drew around is interesting to me,it has filled up this area much quicker than the 12z and covers a much larger area, could these heights move to Greenland and as a result move the low to east of us giving us a northerly?

Seems to already be happening, something to watch..

Now for the Azores to link up...

Edited December 12, 2012 by Robbie Garrett

[cold snap]

Some very mild weather progged for next week with a Iberian Euro ridge developing and pumping up some mild uppers.

Not going to last according to gfs another low coming in high sinks

Not sure what outcome I prefer