Model Discussion And Chat 19th Feb.2012

[Polar Maritime]

The GFS have been hinting a cold start to March for weeks now, but this evening the ECM jumps on board. Very strong singals for blocking to take place giving a E/N/E flow.

The CFS is showing a cold March throughout.

Very interesting model waching over the coming days, much more interesting than the last 3 weeks...

[weather eater]

First chance to post in awhile, rather surprised that the thread is so quiet, especially as we have seen several days of interesting evolutions being throw up by the models. Personally I wouldn’t get carried away with the GFS 12z, if form is anything to go by its overcooking the intensity of the low at 120+. The ECM looks far more realistic to me, while still holding plenty of interest.

[Cheese Rice]

well there are 207 viewing atm mucher higher than the 70 we were always hovering around, could see over 500 if the 18Z is a belter

[Summer Sun]

The 12z shows the ideal snow setup for NE England really, -10 uppers for a short time early next week, and probably several inches of snow in NE England and E Scotland from snow showers (these don't usually show up on the models properly until +48). Post +192 would be cold and grey with a thaw of lying snow at sea level. I suspect its very unlikely to come off, but it shows that there is probably a 10% chance of a lucky NE'ly.

The 12z also shows cold 850s getting in via a W'ly later on Sunday, and this is much more likely to occur. It also shows the low moving over N'ern England with a blizzard in the Pennines. Interesting as I'm supposed to be travelling home from Cumbria on Monday.

A lot of snow in Scotland.

FWIW, the 6z ensembles showed 40-50% of members opting for the snowy NE'ly next week, so I wouldn't totally write off the 12z.

Thanks

[SMU]

Steve,

Do you think the low pressure is way over done on the GFS? Correct me if I'm wrong, but it seems to me the GFS is the most consistent model at over developing the low pressure systems, and not so "excellent" with the positioning/track.

The GFS 12z output screams shortwave spoilers/galore to me.

I think the GFS V ECM will end up further south with the depth somewhere in the middle of the two...

S

[Alex95]

First chance to post in awhile, rather surprised that the thread is so quiet, especially as we have seen several days of interesting evolutions being throw up by the models. Personally I wouldn’t get carried away with the GFS 12z, if form is anything to go by its overcooking the intensity of the low at 120+. The ECM looks far more realistic to me, while still holding plenty of interest.

I agree with you re. the ECM being more realistic; I just don't buy into the idea of the low stalling for a day or two then slipping south to allow a cold NE'ly in. The low looks too intense as well. I'm looking forward to tomorrow's 12z runs though.

[Summer Sun]

The 12z ensembles are out,

[johnholmes]

so on that one would suggest a coldish speel approx 5-8 March?

[suxer]

The 12z ensembles are out,

And what is your analysis ?

[Lewis]

so on that one would suggest a coldish speel approx 5-8 March?

Looks like it John.

We are at a stage of the season now though where if the colder uppers did not make it across, and it was uppers of -5 with a strong easterly/ north easterly wind, we would end up with rain/sleet more than snow, more particularly so for coastal areas.

IF and a big if, we get them colder pool of uppers across our shore from the East, it could prove to bring a memorable snowfall event to many eastern parts, and a majority of Northern England, and the East Midlands, Scotland would get a pasting too.

I still feel though as we head towards the period of the 6th-7th of March, it will be a somewhat watered down version than that of the current GFS eyecandy. I think Steve Murr has it nailed really, more of a "in the middle" between the ECMWF and the GFS. So with that I would expect less so colder uppers, and a much slacker flow, snow reserved for inland areas, and overnight/non day light hours, with heaviest of the falls across the highlands, and higher ground across much of England.

Lewis

Edited February 28, 2012 by Storm Force Lewis

[Alex95]

The 12z ensembles are out,

Plenty of cold options there - about 1/3 stay mild, 1/3 go chilly, and 1/3 go cold enough for snow. Probably leaning more towards the cold end tonight though.

Edited February 28, 2012 by Alza 2

[weather eater]

I think the GFS V ECM will end up further south with the depth somewhere in the middle of the two...

S

I doubt it, I’d put a fair wager on the ECM being much closer to the mark, rather than a half way house. The GFS has a rather long and inglorious record of seriously over cooking LP systems, mores the pity. You have to wonder if its not the major factor in why it scores consistently behind the ECM in the verification stats.

[bluearmy]

the gefs have been sniffing a 'snow chance for london' post march 5th for well over a week now. whilst originally only a couple of runs out the 20 members, todays 12z suite has a 25% and 30% chance 6th and 7th which is the highest yet. so this hasnt come 'out of the blue' but it certainly wasnt the favoured solution until we have come within higher resolution. ecm has been the main player on this thus far. it spotted the potential for dropping a trough into the blocking as soon as we hit its 10 day range. the ens were also on board to more of an extent than naefs have ever been. i think the gem ens are way behind on this one as the gefs have looked more bullish on a cooler interlude for a couple of days whilst naefs hasnt really embraced anything of note.

will be tough to get settling snow away from higher ground but not impossible. need a few upgrades as per nick's post. good to see the 12z make a correction in the right direction after the 00z were a little less enthused re the possibility of a cold snap.

Edited February 28, 2012 by bluearmy

[Thundery wintry showers]

I think we should bin the UKMO output as it was clueless during the run up to the February easterly and deserves to be ignored!

Not really- the UKMO turned out to be wrong on that occasion, overdoing the northern arm of the jet, but it was no worse than the GFS which erred too much on the cold side, sending continental air too far west too quickly. The ECMWF was generally the closest to the mark although it had a few minor wobbles. Tonight's UKMO output looks quite plausible and would still give slightly below-average temperatures across the northern two-thirds of the country with a rather chilly polar maritime airmass heading in from the west.

There is strong agreement that the weather will turn cooler and more changeable into March, with the possibility of some short-lived snowfalls especially in the north. I think the main battleground between the Atlantic air and the continental air will probably take place to our north-east like the ECMWF suggests but this time around there aren't any particularly warm options- it will either be cold (if the continental air wins) or average to fairly cold (if the Atlantic wins). The ECMWF at T+168 is very close to giving a pretty snowy north-easterly but I think the Atlantic weather systems will be too strong.

[johnholmes]

they are upside down lol.

for once Peter you made me smile

[Frank Trough]

the gefs have been sniffing a 'snow chance for london' post march 5th for well over a week now. whilst originally only a couple of runs out the 20 members, todays 12z suite has a 25% and 30% chance 6th and 7th which is the highest yet. so this hasnt come 'out of the blue' but it certainly wasnt the favoured solution until we have come within higher resolution. ecm has been the main player on this thus far. it spotted the potential for dropping a trough into the blocking as soon as we hit its 10 day range. the ens were also on board to more of an extent than naefs have ever been. i think the gem ens are way behind on this one as the gefs have looked more bullish on a cooler interlude for a couple of days whilst naefs hasnt really embraced anything of note.

will be tough to get settling snow away from higher ground but not impossible. need a few upgrades as per nick's post. good to see the 12z make a correction in the right direction after the 00z were a little less enthused re the possibility of a cold snap.

i love this - now the GFS is to be believed having been useless all winter (apart from when it didn't show cold just post christmas - although it got that wrong synoptically). Support of sorts from the ECM (not from the UKMO) but it's a blink and you'll miss it affair with the Atlantic crashing back in, albeit nowehere near what you would call mild.

i don't really see any reason to go against the METO forecast (which has been half decent this winter, lets be honest) except for the following reasons:

1). recently they said the south would be wetter than average - that hasn't happened

2). until recently the outlook was average/mild

i see no reason why the ECM isn't correct - brief easterly as the trough drops into southeast, then cool PM's with the heights to the south never really going anywhere for any length of time.

[nick sussex]

Not really- the UKMO turned out to be wrong on that occasion, overdoing the northern arm of the jet, but it was no worse than the GFS which erred too much on the cold side, sending continental air too far west too quickly. The ECMWF was generally the closest to the mark although it had a few minor wobbles. Tonight's UKMO output looks quite plausible and would still give slightly below-average temperatures across the northern two-thirds of the country with a rather chilly polar maritime airmass heading in from the west.

There is strong agreement that the weather will turn cooler and more changeable into March, with the possibility of some short-lived snowfalls especially in the north. I think the main battleground between the Atlantic air and the continental air will probably take place to our north-east like the ECMWF suggests but this time around there aren't any particularly warm options- it will either be cold (if the continental air wins) or average to fairly cold (if the Atlantic wins). The ECMWF at T+168 is very close to giving a pretty snowy north-easterly but I think the Atlantic weather systems will be too strong.

The ECM I often view as the sensible choice between the excesses of the GFS and the less than enthused UKMO.

If we just look at the main colder options that have been modelled across the big 3 at T-144hrs since the New Year then the UKMO has failed miserably, two northerlies that imploded and it didn't want to know about the early stages of the February easterly.

The GFS has been slightly better than the UKMO but still streets behind the ECM when it really mattered, of course outside of the winter months we don't really view the models with such a critical head.

As for next week marginality will be an issue, so I think we'd need the ECM to edge the pattern west, it has already done that this evening, can we squeeze a couple of hundred miles further west tomorrow?

That could make a big difference.

Edited February 28, 2012 by nick sussex

[Tim Bland]

Meteociel has crashed at 48hrs but from what I can see on wetter 18z is the same as 12z up to 120hrs

[damianslaw]

Some movement towards a much cooler spell of weather as we head into March. All models keen on heights transferring quickly into scandi and the trough dropping into the country introducing much colder uppers - compared to what we have now.

We are then likely to be left in a 'col' - no mans land with strong heights to our SW and NE and low heights to our NW and SE. Those heights to our NE are unlikely to be eroded by the atlantic any time soon - it does look a weak affair, so it will very much depend on how the azores high behaves. We may see a very similiar scenario to what we had in early Feb - albeit not as cold.

UKMO is quite interesting at the 144hr range - it shows the trough languishing over the country and with strong heights building to the NE could we see some undercutting?

The last couple of weeks have been exceptionally uninteresting weatherwise - but there are signs of a shift in the pattern to something perhaps more akin to winter than spring.

[Cheese Rice]

GFS is a downgrade somewhat, uppers aren't as cold and the low is further east, further west the better but this will still change till nearer the time. Still, I'm pleased with what is shown, there will be alot of percipitation around although snow is likely to be confined to inland areas only.

[J10]

IF we do get a col, some similarities to early Feb 2009, when we were under cold conditions and this allowed shortwaves to attack us from various directions which brought some snow.

However we are now in March (or at least the forecasted event is) and a lot of things have to fall into place.

But some sort of colder weather does seem likely, how cold and how long lasting is a completely different matter.

[nick sussex]

The GFS 18hrs run has the perfect sausage shaped high but the upper air isn't cold enough on this run to bring those convective snow showers in on that strong easterly flow until very much later.

Part of the problem is the original orientation of the Scandi high which doesn't have a deep cold pool ready to be ejected westwards into the welcoming arms of the many snow starved net weather members!

The cold uppers are held further to the east and only start edging west much later, in terms of snow chances it does look marginal regarding the shortwave, certainly though higher ground could do very well.

Still we can't even be sure of the shortwave heading south and thats still a big obstacle, it's incredibly difficult to overcome past history of these set ups. We all know the rule with shortwaves, don't bank on anything until thats modelled within T-96hrs.

[SP1986]

I recall the last two winters the models pulled up something similar, in my experience it tends to happen, then gets dropped, of course just from the past two year (in March), suggest an easterly, but it got dropped nearer the current timeframe, so I'm not sure about this.. no way am I saying it won't happen, but personally I'm not yet convinced of this spell of cold. Furthermore the oscillations don't scream unaminous cold spell, and without these showing their signal support, I tend to be a little sceptical.

So the GFS for me is overpiping this slightly. I'm sure someone will point out I'm talking rubbish, maybe I am, we'll see at the time.

[Lewis]

I recall the last two winters the models pulled up something similar, in my experience it tends to happen, then gets dropped, of course just from the past two year (in March), suggest an easterly, but it got dropped nearer the current timeframe, so I'm not sure about this.. no way am I saying it won't happen, but personally I'm not yet convinced of this spell of cold. Furthermore the oscillations don't scream unaminous cold spell, and without these showing their signal support, I tend to be a little sceptical.

So the GFS for me is overpiping this slightly. I'm sure someone will point out I'm talking rubbish, maybe I am, we'll see at the time.

Far from talking rubbish, the most sensible post of the night Stephen.

Already with the 18z the GFS has it further East, and the upper 850's are much more modified, with a slacker flow as the LP pulls away, give it another few days, and we'll see the initial blast from the LP system becoming modified out even more, GFS has a consistent tendency to over do LP systems, in depth, and sometimes track. Messy mid-range coming up, bust I suspect after the Atlantic making a continuing appearance, we may start to see pressure build, and bring some more settled weather around the 10-11th of March.

Lewis

[summersnow]

GFS 18z shows right good messy old dog fight between the air masses, with the Azores HP unwilling to go without a mother of all scraps, while cold HP builds to our NE. Agressive low pressure development the result & sandwiched in between, winds itself into a proper late winter storm. All looks very plausible for early/mid March, while GFS 12z was a colder outlier, both ECM 12z and GFS 18z look the more likely but different scenarios. Expect alot more change in the next few runs - nothing nailed at all! Azores HP might well yet have one final victory this winter but then again..... it's all ripe for a pattern change!

Edited February 28, 2012 by summersnow