Model Output Discussion

[TEITS]

Pretty good run so far for Wales/Midlands for the simple reason the band of snow arrives during the night. In these marginal situations you ideally need any fronts to arrive during the night if you want to see a good covering of snow. For E areas its interresting to see the colder pool just to the E.

[Tom D]

The 6z is clearly further west than the 00z, but there is still potential for a big snow event across most of England, Wales and particularly Scotland from the set up shown. Very cold uppers over France and to our east and cold uppers coming down with the low from the north. It's a recipe for a snow event, no matter where the low does eventually track.

The interesting thing about this run is that the low goes further south than it has been shown before, allowing an almost easterly flow over Scotland with a cold SErly over England.

http://91.121.94.83/modeles/gfs/run/gfs-0-138.png?6

Edited February 11, 2010 by Tommyd1258

[nick sussex]

A very uncertain and complex pattern in the models. Looking at this low heading south there does now seem a better chance of seeing some snow as on its eastern flank there seems to be a pull of continental air nw wards. Any flow from northern France is likely to be very cold with many parts of France snow covered and below freezing, you always know its cold when they're having snow ball fights in Biarritz! Although some moderation in temps is expected into the weekend there should still be enough cold air over France to draw on come the time.

Its quite an unusual set up seeing a low drop south through the UK, I think eastwards movement of the pattern is now very unlikely, more likely the pattern backs even further west, my thoughts yesterday regarding a possible Scandi high remain and dare I say it another possible easterly!

Edited February 11, 2010 by nick sussex

[Lewis]

Pretty good run so far for Wales/Midlands for the simple reason the band of snow arrives during the night. In these marginal situations you ideally need any fronts to arrive during the night if you want to see a good covering of snow. For E areas its interresting to see the colder pool just to the E.

Huge upgrade this, looking very good for me, dew points, 850's and isotherm, and the heavy precipitation.

Shows snowfest for areas North of the East midlands, only one run though so i'm next getting too excited.

[TEITS]

Very interesting developments on the 06z GFS run t120 with the low moving even further

southwest but with a continental feed into the southeast and higher pressure to the north.

If this is a new trend we could be looking at a east,northeasterly come next week.

Yes whilst we have been referring to the LP moving further E. What could be possible is that the LP backs even further W so it becomes favourable once again. The models are clearly struggling with this LP but I feel its whats happening to our N thats causing the problems. This in my opinion is down to the lack of observations within the Arctic region.

[cooling climate]

A very snowy day Tuesday for much of the country according to this run.

It looks like we may have been wishing in the wrong direction lol, an east

northeasterly would almost certainly result if this trend continued.

I think Nick Sussex mentioned this yesterday.

The trend to the north continues with heights further south and east lets

hope this continues.

[chionomaniac]

A very snowy day Tuesday for much of the country according to this run.

It looks like we may have been wishing in the wrong direction lol, an east

northeasterly would almost certainly result if this trend continued.

I think Nick Sussex mentioned this yesterday.

The trend to the north continues with heights further south and east lets

hope this continues.

I think that this trend is backed up stratospherically and by the MJO forecast returning into phase 7. Still early days and just one run, but I suspect that the ECM could possibly edge this way later. The trend will be for pressure to build behind the dropping low. Ironically the further southwest that this trough drops the easier it will be for pressure to rise behind it.

[TEITS]

I'm still learning how to read the models so what timeframe are you refering to here please?

Thanks

Kar999

Sorry about that I forgot to say what timeframe.

At the moment the 06Z suggests snow during Monday moving SE reaching the Midlands during the early hrs of Tues morning.

Alot of uncertainity remains however!

[bluearmy]

trends towards the end of the ecm run look most interesting to me with a hugely cold pool over scandi and signs of the cold sinking south again. given that the atlantic will make efforts to head northeast, we could well be looking at some significant snow events, even without taking the cold trough next week into account and whatever that will deliver. the extended dutch ens are definitely headed cooler again rather than atlantic driven.

[Lewis]

A lot of changes to come of course and its only one run, but if we do get the easterly, it's more of a ESE'rly, and all areas but Scotland will have a milder feed from the near continent and will be dragging in warmer air.

So, what we have if I understand correctly the conjecture of the last few days combined with the model variations is:

Low moves south on an eatserly track - good, but looking increasingly unlikely

Low moves south on a very westerly track - good, (but maybe not as good as above, certainly for more southern/eastern areas), and a reasonable bet now as this is the most recent trend

Low moves south pretty much down the western side of the UK - bad as causes too much mixing of warmer upper air, the worst option, and the one favoured by ECM/UKMO/GEM at present

Therefore what we want now is the other models to either come into line with the latest GFS predictions, or totally backtrack and pull the low back east again.

Hope I've got that right !

Good post, that's spot on mate.

Only one problem, i can't see any other models coming into line.

GFS has over taken the ECM in verification accuracy, although in FI we all know what the GFS does past say t96.

I think there's going to be a lot more changes to come. Personally, i think come Saturday it'll be showing us with S/SW'esterlies, and much milder.

lewis

Edited February 11, 2010 by Coast

[Pennine Ten Foot Drifts]

Yes whilst we have been referring to the LP moving further E. What could be possible is that the LP backs even further W so it becomes favourable once again. The models are clearly struggling with this LP but I feel its whats happening to our N thats causing the problems. This in my opinion is down to the lack of observations within the Arctic region.

So, what we have if I understand correctly the conjecture of the last few days combined with the model variations is:

Low moves south on an eatserly track - good, but looking increasingly unlikely

Low moves south on a very westerly track - good, (but maybe not as good as above, certainly for more southern/eastern areas), and a reasonable bet now as this is the most recent trend

Low moves south pretty much down the western side of the UK - bad as causes too much mixing of warmer upper air, the worst option, and the one favoured by ECM/UKMO/GEM at present

Therefore what we want now is the other models to either come into line with the latest GFS predictions, or totally backtrack and pull the low back east again.

Hope I've got that right !

[BLAST FROM THE PAST]

What we may be seeing by the models is a LP system from tha arctic developing into a significant feature for the UK for next week. The jetstream is way south of its 'norm' and the recent 'exposion' on the sun is going to see rapid and dynamic developments in the models for next week. LPs tracking W to E well south of the UK could well 'mix' with the LP diving SSE and suck it further south which 06z sems to want to do. Indeed the ECM plays with this idea and thus keeping cold/mild divide well south of the UK. The Alps are going to get battered and I think we are in the firing line for some juicy weather too. Eyes down for the continued southward movement of the arctic LP [sSE would be better in NE France.]

BFTP

[TEITS]

A lot of changes to come of course and its only one run, but if we do get the easterly, it's more of a ESE'rly, and all areas but Scotland will have a milder feed from the near continent and will be dragging in warmer air.

Any flow off the continent could be very cold with lower dewpoints.

Still a promising run and very good for your location Lewis.

Im always wary when the GFS suddenly changes like this. I feel the model output could be quiet volatile at the moment. Seems to me that their is some uncertainity how influencial the heights over the Arctic could be. Always be a nightmare to forecast these have due to the lack of observations like I said earlier. Remember CH did say yesterday the model output could change more favourably.

Overall im much happier after seeing the 06Z. However im just going to go with the flow on this one without posting my summaries. I feel the likes of CH, GP, Nick S & F will be able to comment better than I can.

Yep spot on PFTD.

Edited February 11, 2010 by THE EYE IN THE SKY

[Lewis]

Any flow off the continent could be very cold with lower dewpoints.

Still a promising run and very good for your location Lewis.

Im always wary when the GFS suddenly changes like this. I feel the model output could be quiet volatile at the moment. Seems to me that their is some uncertainity how influencial the heights over the Arctic could be. Always be a nightmare to forecast these have due to the lack of observations like I said earlier. Remember CH did say yesterday the model output could change more favourably.

Overall im much happier after seeing the 06Z. However im just going to go with the flow on this one without posting my summaries. I feel the likes of CH, GP, Nick S & F will be able to comment better than I can.

Hi mate,

I know how you feel with regards the GFS, it has a weird habbit of showing us something promising/nice and juicy for it only to put us out of our misery time and time again, then it will give us another little upgrade so we get excited again for it only next run to blast it away haha.

To be honest, if the GFS is ahead of the ECM for verification, yet the GFS now and during the last cold snap has continued to show different scenarios etc in FI, and also short term, for it to just back track. In all honesty i can't work out whats happening with the GFS recently.

The LP is looking good in terms of position. With low pressure's as it sits and pivots your always going to "for at least a small time" bring some warmer air in, it cannot be avoided tbh. It's what happens with regards the direction and flow we get when the LP wants to sink away.

lewis

Edited February 11, 2010 by Storm Force Lewis

[johnholmes]

putting a view for next Monday and Tuesday into the forecasters blog area.

[D KARLSON]

A very uncertain and complex pattern in the models. Looking at this low heading south there does now seem a better chance of seeing some snow as on its eastern flank there seems to be a pull of continental air nw wards. Any flow from northern France is likely to be very cold with many parts of France snow covered and below freezing, you always know its cold when they're having snow ball fights in Biarritz! Although some moderation in temps is expected into the weekend there should still be enough cold air over France to draw on come the time.

Its quite an unusual set up seeing a low drop south through the UK, I think eastwards movement of the pattern is now very unlikely, more likely the pattern backs even further west, my thoughts yesterday regarding a possible Scandi high remain and dare I say it another possible easterly!

Indeed a very wintry picture and certainly some disruptive snowfall especially the hilly areas but by no means exclusively a lot of low ground snowfall is likely i think its more a question of how much.

the details of synoptics will be hard to pin down and the GFS at 244 does hint at the return of a scandinavian high and this is a very plausable idea ,with high pressure having a habit of reforming over the very cold continent and this as you say could well initiate yet another easterly and as i said in other posts everything indicates a long winter going into March.

Although there has been know mention of the snowfall amounts to come next week i feel its only a mattwer of time before some severe warnings are issued as the synoptics although they do not appear particularly cold they are very snowy and with things being marginal in some areas this will only add to the disruption

[BLAST FROM THE PAST]

Not having a go guys, I am fasinated by the skill on here to read the charts, just confused why it stops when its within a solid reliable timeframe.

I suppose when something is nailed the conjecture and skill side is gone because what one sees is going to happen. I certainly do and I believe many others do too, enjoy the different interpretations and 'forecasts' made by individuals, and their reasons behind their interpretation...it seems more interesting that way especially awaiting to see what the outcome actually is. When the outcome is there, time to use ones skills/methods etc again.

I may be wrong, but that's how I see it.

Next week at a punt, more widespread wintriness than will be initially thought/forecast as LP bomb plunges southward. I think on a track pretty close to 06z with latitude rather than longitude being the main detail to resolve.

BFTP

Edited February 11, 2010 by BLAST FROM THE PAST

[chionomaniac]

Any flow off the continent could be very cold with lower dewpoints.

Still a promising run and very good for your location Lewis.

Im always wary when the GFS suddenly changes like this. I feel the model output could be quiet volatile at the moment. Seems to me that their is some uncertainity how influencial the heights over the Arctic could be. Always be a nightmare to forecast these have due to the lack of observations like I said earlier. Remember CH did say yesterday the model output could change more favourably.

Overall im much happier after seeing the 06Z. However im just going to go with the flow on this one without posting my summaries. I feel the likes of CH, GP, Nick S & F will be able to comment better than I can.

Yep spot on PFTD.

It is still a difficult call working out how things stratospherically will effect the troposphere. What has happened following the warming is that the displaced vortex has been split in two - this is rather akin to squeezing a balloon in the middle - there will still be a lot of pressure build up inside the balloon as it forced into two section. Rather than releasing the pressure on the balloon the next stage is akin to a slow release of air from inside the balloon with the grip remaining constant and trying to work out where the leak is and which half of the balloon reduces first. That is what is happening with the stratosphere presently and this is getting propagated down to the troposphere and that is where the difficulty lies in working out where the residual energy is likely to be . Today it looks like that the Scandinavia trough will reduce in energy allowing some height rises in the area. How much is difficult to work out but it is the start of a trend.

[snowmadchrisuk]

gefs is bad there really bad.

The 6z ensembles are not out yet are they ?

The Gfs OP programs this as Snow , Factors in Snow cover into it's temps and keeps it as Snow for the rest of the week . Next Thursday looks like some really Heavy Snow could be possible.

The Chart below is for +120 Tuesday Morning.

[Frosty.]

Agree 100% with you frosty!

Thanks

The GFS 6z is even better with less marginal situations for southern britain, once again the north and especially scotland is in a win/win position whether the 6z or 00z verifies because the cold air holds up there for the entire run. There could be the biggest snowfalls of the winter so far during next week with a potent mix of cold air and low pressure.

[Winter Monsoon]

Thanks for the reply Nick F. LOL no sooner do i say i think its marginal the 06z pops out with alot bettre run not just for the North West but most of the country too.

Mon,Tues and Weds looking good for IMBY. Hopefully the models will continue and upgrade the closer we get.

[Weathizard]

The 6z ensembles are not out yet are they ?

The Gfs OP programs this as Snow , Factors in Snow cover into it's temps and keeps it as Snow for the rest of the week . Next Thursday looks like some really Heavy Snow could be possible.

The Chart below is for +120 Tuesday Morning.

I'm with you on this, this shows widespread snow away from the SW where its probably a wintry mix. Not as marginal either for southern areas. (away from the SW)

[cooling climate]

According to the 06z GFS there is nothing marginal about the snow threat for Monday

night into Tuesday and Wednesday for much of England.

Dew points, 850's and temps all look good.

Certainly agree Chionomaniac I've been saying for a while I like what I see from

the stratosphere profiles. Even though the low may well trend west now, which looks

as though it could prove very benificial for us the block over Greenland will Join with the

Arctic high building pressure to our north and over Iceland, Scandinavia area allowing

what could turn out to be a very potent continental feed to develop.

These 30hpa temperature forcasts for various towns look very encouraging to me.

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=town&alert=1

[karyo]

The 6z is a tasty run despite moving the pattern west. It looks quite similar to the UKMO actually at 144 hours. However, I suspect it is overdoing the existing cold pool over the continent and the UK.

The ECM has much higher upper temperatures over us and over the continent.

I suppose if the pattern won't move east, it might as well move west/southwest, as it is the next best thing.

Still, a shame that we are probably going to miss the proper arctic blast!

Karyo

[Yeti]

Yes, ironically as some have said, it looks like the East may actually be in a better position for Monday/Tuesday's snow event than the West, because the low looks like tracking too far west for anywhere, in England/Wales at least, to pick up a northerly flow but at the same time this could draw a SE'ly flow off the continent up the eastern flank:

http://www.wetterzentrale.de/pics/Rtavn1202.png

http://www.wetterzentrale.de/pics/Rtavn12010.png

So the North and East currently look most likely to see snow from this event although this is obviously still subject to change. A small shift W may actually help keep DPs lower further W, but it requires a pretty big shift E now to get the full effects of the N'ly and this looks unlikely.