Model Output Discussion - 5th December - 11th December

[Zakos]

Why does GFS always do this? It had the scenario of a northerly on friday days ago, then downgraded it many times, and has now latched back on to the idea! This could potentially be quite a noteworthy and severe cold snap. It will not be sustained, but, the high could topple in a position favouring cold weather. Fingers crossed!

[BLAST FROM THE PAST]

06 GFS does little to help clear up the confusion, bringing HP back in from the SW, albeit not as strong or as far north as during yesterday. Gotta say though the evolution being touted in the medium term (132-168hrs) looks much more plausable.... unfortunately!

Please explain Shedhead. Genuine question here and others may want to know too. It may be right so how is more plausible? Is it the 06z evolution? I assume so as different GFS runs have differed.

BFTP

[Coast]

I'm not sure what model(s) or data these snow forecast maps are based on, but they proved quite accurate last year in the time frame being discussed:

Snowfall for 12 hrs ending Fri 09 Dec at 12am GMT

http://www.snow-forecast.com/maps/dynamic/uk

[Thundery wintry showers]

The GFS is flopping about in successive runs at the moment- yesterday's runs showed a mid-latitude high over the UK, the 00Z kept zonal but not especially mild weather, and now the 06Z goes for a middle ground that would represent the worst case scenario for snow lovers, high pressure settling to the south bringing a mild tropical maritime westerly type. One of those situations where John Holmes's suggestion of comparing each run with the previous day's run at the medium-range could save quite a lot of bother, but at the same time suggesting that GFS is struggling.

With the ECMWF and UKMO continuing to suggest continued zonality and some colder polar maritime shots for the north, while milder at times in the south, and strong support from the ECMWF ensemble mean, I think this looks the more likely bet.

[kold weather]

Aside from the backedge snow on Friday and maybe some wintry stuff for Scotland on Thursday as well the 06z is a very bleak run. Pretty much the worst case from the 06z where we are once again stuck in no-man's land...

We do NOT want that type of run at all, hello to 2-3 weeks of mild weather if that happened!!

ECM is better but still not exactly great overall.

[weathe20]

Nothing to write home about in the 6z GFS, maybe the chance of something for the north at the end of week like we have had this weekend, appart from that just back to our W and SW winds. This pattern of the odd PM cold shot for the north this months seems like a good bet (would love to wrong), with mild inbetween. But a very mild end to the month is on the cards..??

Edited December 5, 2011 by weathe20

[shedhead]

Please explain Shedhead. Genuine question here and others may want to know too. It may be right so how is more plausible? Is it the 06z evolution? I assume so as different GFS runs have differed. BFTP

Throughout yesterday GFS built pressure strongly across the whole UK in the 120-168hr timeframe, which to most looked wrong because it was centered too far north. Todays 06 does similar, but keeps the center farther south and west, which given the overall set up with the strong PV looks more plausible - unpalatable as that is.

Edited December 5, 2011 by shedhead

[BLAST FROM THE PAST]

Throughout yesterday GFS built pressure strongly across the whole UK in the 120-168hr timeframe, which to most looked wrong because it was centered too far north. Todays 06 does similar, but keeps the center farther south and west, which given the overall set up with the strong PV looks more plausible - unpalatable as that is.

Ok, but hasn't GFS been poorest performer of late and so I assume that support would be needed from euros too? Wouldn't the strong PV have had us in that situation now if it was the controlling factor and the default set up? Or is the PV set to intensify further? For me we will need euros on board and a few more days of consistent runs.

Whilst the coldest of any weather is for the north I think over a period of ten days if this set continues I think for the south average is better description.

BFTP

Edited December 5, 2011 by BLAST FROM THE PAST

[Richie V]

Firstly, I'd like to apoligise to any members I upset with My lump of dissapointment comments In the last model thread. Went down like a lead baloon did that!.

As I said a few days back, expect the PV to remain the dominant force for some time to come, ECMWF shows this beautifully now. Looking like GFS is finally backing off the Idea of the uk high at the weekend.

Peace all

[Bobby]

Big difference at just +144 with the ensemble means of GFS/ECM.

GFS

ECM

Though even GFS turns more zonal later. My bet is on ECM/UKMO unsettled zonal outlook.

GEM looking very unsettled and zonal too

[TonyH]

Mine too.

[Timmytour]

At present the best the south can seem to hope for is a shower of snow that doesn't stick....and this might be a pattern for the winter. That woud still be a big improvement on some winters within recent memories.

But at his moment I'm happy to see the models act a little inconsistently.... it kind of reminds me of winters of old. While maybe not the kind of cold and snow that sticks around for weeks on end, it does provide hope for the little incursions of three or four days cold blasts. Personally I think the GFS is coming in for too much stick at the moment. To me it can sometimes be the first to pick up on something and then while it lets it go for a while, it can come back to it and drag al the other models there. I wouldn't be surprised to see a little cold spell for the weekend develop that is more potent than is currently being modelled.

On another subject...... I used to like a combination of chocolate, caramel, hazlenut and nougat.....but I don't anymore.

Sorry for going off topic!!!! :-)

[Paul_1978]

I have been looking at the world pressure charts on WeatherOnline. These give a wider picture than just looking at the Europe view.

In summary, too much high pressure to the south, and not enough to the north. I'm only an amateur model watcher, but that basically says to me we are in for a predominantly westerly regime, with perhaps the odd north westerly spell. Something drastic needs to happen to counter this set up, and that's where I look at the posts of the more knowledgable.

[Kentish Kiwi]

Ok, but hasn't GFS been poorest performer of late and so I assume that support would be needed from euros too? Wouldn't the strong PV have had us in that situation now if it was the controlling factor and the default set up? Or is the PV set to intensify further? For me we will need euros on board and a few more days of consistent runs.

Whilst the coldest of any weather is for the north I think over a period of ten days if this set continues I think for the south average is better description.

BFTP

Like it or not the stratospheric signal would provide reasonably strong support for an evolution akin to the GFS 06z. I get the feeling we've been pretty 'lucky' with the current cold snap and indeed we are fortunate to have the one forecast for later this week.

The stratosphere has been at record or near record levels of cold for a while now and it seems inevitable that we revert to such a pattern as illustrated on this mornings run eventually. This is particularly significant taking into account the usual lag time for the effects of the stratosphere to be felt in the lower levels of the troposphere.

[tinybill]

well if this comes on the 15 dec could make thinks interesting in the uk

Edited December 5, 2011 by tinybill

[Frosty.]

The Gfs 06z is a lot closer to what the Ecm 00z is showing for friday with an Arctic blast for friday and early saturday (especially for northeast britain) before a ridge pushes east through next weekend with widespread frosts, then the outlook is a mix of mild, average and rather cold with northern britain being colder at times with wintry showers. As for this week, becoming less cold for wed/thurs but some useful rain for the south and the far north at risk of hill snow even during the less cold sector on thursday before the arctic plunge, also for tonight and tomorrow, a small polar low looks like hitting the northern isles with gales and heavy snow possible before conditions slowly ease during tomorrow but with more snow for tues night and through wednesday in the very far north.

[Matty M]

A few GFS ensembles do show some potential for a Scandy high to develop.

And that is what i would bet on in the current set up.

[shedhead]

Ok, but hasn't GFS been poorest performer of late and so I assume that support would be needed from euros too? Wouldn't the strong PV have had us in that situation now if it was the controlling factor and the default set up? Or is the PV set to intensify further? For me we will need euros on board and a few more days of consistent runs.

Whilst the coldest of any weather is for the north I think over a period of ten days if this set continues I think for the south average is better description.

BFTP

To be fair no model has covered itself with glory across the last week or so. Lets put it this way, if I was paying to access them individually I'd be asking for a refund from all of them.

[cyclonic happiness]

Right at the end of the ECM run, it does show the polar vortex buggering off away from Greenland and then pressure does seem to be trying to rise in that area?

A good signal?

[Weather Boy]

I'm intrigued as to whether the ECM or GFS are going to back down. I see the ECM's low (in direct contrast to the GFS's high) is not progged a few hundred miles north, over northern England rather than Southern England as it was on Saturday. I am wondering whether this is a prelude to the ECM waving the white flag at the GFS.

Longer term, GFS is a bore-fest, as people are calling it with a flat jet right across the UK in the run up to Xmas - unsettled with regular fronts. That could well change, but it's being saying that for a while and it seems more consistent with the teleconnections.

In the shorter term looks chilly country-wide until at least Saturday, and I don't see that High giving much of a warm up, if that's what happens.

[Gavin Hannah]

Well, I have only been reading the models for a couple of months ago now. And from the depths of despair, we finally have a decent dumping of snow over the highlands. Even got a few inches outside my door! (South of glasgow)

What I will say is, expect the unexpected. Just a week or two ago, I don't think anyone saw this little cold snap. Lets hope the cold can dig in for the long haul and keep the unwanted mild air at bay.

[Bobby]

Right at the end of the ECM run, it does show the polar vortex buggering off away from Greenland and then pressure does seem to be trying to rise in that area?

A good signal?

It's one hint on one run on one model 10 days away... straw clutching unfortunately.

[karyo]

The met office 6-15 day outlook seems to expect cold zonality as it mentions temperatures on the cold side (apart from the southeast) and wintriness from Wales northwards. The further outlook goes average to mild but that's a long way from now.

Based on this, I would expect the GFS to be wrong with the mild outlook.

Karyo

[cyclonic happiness]

It's one hint on one run on one model 10 days away... straw clutching unfortunately.

A signal non the less!

I am a straw clutcher too, so it's perfectly relevant in this thread

[shedhead]

Gotta love the Reykavik pressure ensembles on GEFS... fair to say there a bit of disagreement after 13th... The 850mb ensembles do show a more consistent warming pattern after the 11th though, suggesting HP towards NW Europe and more of W-SW flow up there.

Edited December 5, 2011 by shedhead