Model Discussion January 18th

[Isolated Frost]

This is not exactly the perfect match for a situation- but a southern russian high, vortex with sub 492 dam over the pole (currently we have the vortex around the western side of the pole, but stratospheric warming in the area should end this for the most part) , all we'd need is a more meridional trough suggestion stateside, some tweaks to the vortex strength and positioning and of course these factors could in turn produce a more s'ly tracking jet... this is an example that could well verify if we make the most out of the potential situation. Jan 30-Feb 20 seems the best 3wk period for optimised cold... if we see the ep-flux tend more northerly, mean zonal winds reduce, especially at tropospheric level and we generally see a more optimistic strat outlook, then things are definitely on a la GP- his thoughts on angular momentum remain very relevant as we move into a predicted phase 1 of the GWO.

The NWP reaction will take time, just wait and relax for the time being.

[Zakos]

About 5 out of 20 GEFS members suggest a strong scandinavian block with uppers cold enough for a deep cold spell being advected into Britain, and when you consider that 10 of the 20 members are tweaked towards a colder outcome, hardly compelling evidence, the fact is the Met office mentioned it but said its not the favoured outcome, but you would think some OP runs would have looked better by now, at least in FI, after all FI charts usually bring in phantom Easterlies even when there is no decent background signals, which there is at themoment.

the number currently showing cold is irellevant. I compared todays to yesterdays, and there is clearly an increase in colder ensembles. I see your point, but the way the models have been lately im siding with gp and others because the models have been so unreliable lately.

[weathe20]

As GP said earlier the AO and NAO are forecast to drop from +2 values to -1 in the space of 4 days and this is why the models are struggling so much with the current pattern change.

I know its hard and its been frusrating but we just need to be a little more patient. GP speaks with alot of confidence in his posts and i for one am convinced that we are going to see a decent prolonged cold spell very soon.

Also don't forget, he said expect the unexpected lol!!!

Ive posted the NAO and AO charst a few times here, I dont think the charts are a FORECAST its a chart of the ensembles? Correct me if im wrong.

[Backtrack]

This is not exactly the perfect match for a situation- but a southern russian high, vortex with sub 492 dam over the pole (currently we have the vortex around the western side of the pole, but stratospheric warming in the area should end this for the most part) , all we'd need is a more meridional trough suggestion stateside, some tweaks to the vortex strength and positioning and of course these factors could in turn produce a more s'ly tracking jet... this is an example that could well verify if we make the most out of the potential situation. Jan 30-Feb 20 seems the best 3wk period for optimised cold... if we see the ep-flux tend more northerly, mean zonal winds reduce, especially at tropospheric level and we generally see a more optimistic strat outlook, then things are definitely on a la GP- his thoughts on angular momentum remain very relevant as we move into a predicted phase 1 of the GWO.

The NWP reaction will take time, just wait and relax for the time being.

Not strictly model discussion, but for those wanting to know the difference between zonal and meridional air flows, here's a fantastic explanation:

http://www.theweatherprediction.com/habyhints/159/

Will benefit those less experienced model watchers.

Thanks.

[john mac]

Ive posted the NAO and AO charst a few times here, I dont think the charts are a FORECAST its a chart of the ensembles? Correct me if im wrong.

Not to sure myself mate just really going by what GP has posted.

[Stuie]

Ok, up until the 23rd (T138) we have the GFS showing a zonal flow of the stream, then meridional flow until the 26th. Maybe this is why FI is pretty short. Thanks for the link and I have learnt something again today.

[bluearmy]

Not to sure myself mate just really going by what GP has posted.

The AO/nao forecasts are merely representations of the gefs. They are, a forecast, but they are a graphical representation of the ensembles. As the ens change, so will the forecast of the AO/ nao

Some colder runs showing up on the ECM short ens which werent there on the 00z run. The spreads do show a propensity to drive troughing to our south though not a cluster as yet.

Edited January 18, 2012 by bluearmy

[ICETAB]

Anyone have a link for the extended ECM ensembles? Someone gave me one the other day but lost it

[summersnow]

Hi folks! I'm new to this forum but not particularly new to chart watching and model output. I don't claim to be any sort of expert but I have noticed a few key ingredients required for prolonged winter weather. I'm sure many here will agree that some of the key ingredients are simply not in place for prolonged cold and have'nt been all winter.

The 3 main components IMO are cold SSTs, a cold continent and strong northern blocking somewhere directly (and not too far) north, northeast or northwest of the UK - none of which is (or has been) in place tis winter. If none of these variable is evident by this stage in the winter, prolonged cold will always be elusive. Different models will (as we've seen) often show promise, but will be continually scuppered by surrounding warmth. Pattern change, while not unlikely, will also be more likely to set up in such a way as to avoid bringing entrenched cold air across the UK.

Unfortunately, the North Atlantic is mostly warmer than average as is the North Sea, the Norwegian Sea, the Baltic and the Barents Seas. There is a small cold anomoly east of Iceland but it is swamped by the warmth around it. The continent has been cooling recently but is still far from cold. As a result of all of this, Azores and near continent HPs are likely to prevail in the short term. Meanwhile any northern blocking will probably set up in such a way as to plunge cold air into or close to regions that are already cold and most likely therefore skirt around northwest Europe.

This is not to suggest, cold air won't get a look in, but I think our best shot at this is a prolonged spell of cool/cold zonality as some have already pointed out. Northern areas are more favoured for this and I suspect the south is unlikely to see significant snow for at least 10 days to 2 weeks. Even then, it will be reliant on a very favouable set up.

So far, the MET O long range forecasts have been spot on and their 3 month forecast particularly good in predicting the dominance of the Azores HP. I would tend to favour this winter MET O related medium to long range forecasts as they have done well to date. The MET O has of course recently put out a probability forecast for 2 very different scenarios but I think recent runs by the main models have started to fall into line with a more zonal outcome.

Of course, I hope I am wrong as I am as obsessed by snow as anyone else so here's hoping!

[sebastiaan1973]

http://www.weerplaza.nl/15daagseverwachting/default.asp?r=midden&type=eps_pluim

[ICETAB]

http://www.weerplaza...&type=eps_pluim

Thanks. Looks like the temperature is set to fall. Mean failing to 0 at the end. Some cold members in there.

[Glacier Point]

You know it's odd when inter run and inter model agreement drops people seem to put more not less faith in operational outcomes at the extended range. Strange.

Ensemble mean and spread products however continue to evolve relatively smoothly.

Following on from the last few days, we have ECM ensemble mean for day 10 and CPC 8-14 day mean height anomalies agreeing on a sharpening ridge over the NE Canadian maritimes and ridge edging its way towards Scandinavia (if anything ECM more keen on the ridge over Canada).

Not many operationals have been able to pin this pattern, so therein lies your dilemma.

I like the trend here. That upper trough is further south than anything the GFS op has been able to muster and two things are likely to come of it.

As shortwaves run into the back of the trough, they will pull its mean axis backwards further strengthening the block to the east. Also, as energy is ejected south-east off the trough, that will strengthen the blocking to the north. Easterly anyone ?

[feb1991blizzard]

Thanks. Looks like the temperature is set to fall. Mean failing to 0 at the end. Some cold members in there.

Here is a link for the London ECM ens as well, but bare in mind that they havent updated yet.

http://www.meteogroup.co.uk/services/ensemble-forecast.html

[The Northern Ramper]

I don't think i have seen GP as confident as this before over an outcome.

[Zakos]

You know it's odd when inter run and inter model agreement drops people seem to put more not less faith in operational outcomes at the extended range. Strange.

. Excellent post GP, thanks for the update. This is exactly what ive been saying yet some people continue to but so much faith in the op outputs. As you say, the ensembles continue to evolve to a colder evolution. Edited January 18, 2012 by Zakos

[Radiating Dendrite]

You know it's odd when inter run and inter model agreement drops people seem to put more not less faith in operational outcomes at the extended range. Strange.

Ensemble mean and spread products however continue to evolve relatively smoothly.

Following on from the last few days, we have ECM ensemble mean for day 10 and CPC 8-14 day mean height anomalies agreeing on a sharpening ridge over the NE Canadian maritimes and ridge edging its way towards Scandinavia (if anything ECM more keen on the ridge over Canada).

Not many operationals have been able to pin this pattern, so therein lies your dilemma.

I like the trend here. That upper trough is further south than anything the GFS op has been able to muster and two things are likely to come of it.

As shortwaves run into the back of the trough, they will pull its mean axis backwards further strengthening the block to the east. Also, as energy is ejected south-east off the trough, that will strengthen the blocking to the north. Easterly anyone ?

When can we expect this to start showing in the models GP?

[bluearmy]

When can we expect this to start showing in the models GP?

it sort of is but as soon as a run starts to dig trough energy se, the upstream pattern intervenes and drives the azores ridge ne again which prevents a second burst of energy heading se which would, in the end undercut a developing block. some of the ens members have managed to do it and we have seen some cold peturbations. its a slow process although there is always a chance that everything could fall together and manage it by the middle of next week. that looks doubtful for the time being. of course, there is no guarantee that it will happen like this but with the blocking al around us beginning to sink south in fi, we would be unlucky to avoid a cold solution of some kind.

[Jason M]

Whilst my feeling (more from years of watching the weather than anything massively technical) is that were headed for a nearly but no cigar situation, I've got to say that I hope GP is right. He's stuck to his winter view and has backed it up all the way down the line with facts and figures. If ever a winter forecast deserves to be right its his. No hopecasting involved, just the facts as he see's them.

[on the coast]

it sort of is but as soon as a run starts to dig trough energy se, the upstream pattern intervenes and drives the azores ridge ne again which prevents a second burst of energy heading se which would, in the end undercut a developing block. some of the ens members have managed to do it and we have seen some cold peturbations. its a slow process although there is always a chance that everything could fall together and manage it by the middle of next week. that looks doubtful for the time being. of course, there is no guarantee that it will happen like this but with the blocking al around us beginning to sink south in fi, we would be unlucky to avoid a cold solution of some kind.

Excellent post. How cold is the question? This weekends model runs may well have a few answers.

[TEITS]

Just want to say that i've been through the GEFS ensembles again and I counted 9 out of 20 members showing an E,ly. Fair enough some were shortlived but still an E,ly. Also 3 members showed a N,ly via blocking over Greenland. So thats 12 out of 20 members showing decent cold synoptics.

Lets see how many the 18Z delivers.

[Cloud 10]

Quite a difference between gfs and ecm regarding their 500mb outlooks,with the ecm looking much

more promising for northern blocking than gfs,and looking very similar to the CPC chart that GP posted.

Personally i've got no real faith in any operational run at the moment past 96hrs.

Then again if the pub run was to throw out a belter............ :lol:

[Zakos]

Just want to say that i've been through the GEFS ensembles again and I counted 9 out of 20 members showing an E,ly. Fair enough some were shortlived but still an E,ly. Also 3 members showed a N,ly via blocking over Greenland. So thats 12 out of 20 members showing decent cold synoptics.

Lets see how many the 18Z delivers.

. Yes, i posted something like this earlier. When comparing the 12z ensembles to todays, ( i cant post the link right now) there is a significant increase in cold ensembles. Im looking forward to the 18z, particularty its ensembles, as if they upgrade aswell that would make 4 upgrades in succession, definately a trend there.

[john mac]

I don't think i have seen GP as confident as this before over an outcome.

Ahem!!. I've been saying this for a few days. He has stuck to his guns and has not waivered so fair play to him. If he was unsure then i wouldnt be so confident and he sees to know more about all the background signals than anyone else onthis thread with respect.

[chionomaniac]

You know it's odd when inter run and inter model agreement drops people seem to put more not less faith in operational outcomes at the extended range. Strange.

Ensemble mean and spread products however continue to evolve relatively smoothly.

Following on from the last few days, we have ECM ensemble mean for day 10 and CPC 8-14 day mean height anomalies agreeing on a sharpening ridge over the NE Canadian maritimes and ridge edging its way towards Scandinavia (if anything ECM more keen on the ridge over Canada).

Not many operationals have been able to pin this pattern, so therein lies your dilemma.

I like the trend here. That upper trough is further south than anything the GFS op has been able to muster and two things are likely to come of it.

As shortwaves run into the back of the trough, they will pull its mean axis backwards further strengthening the block to the east. Also, as energy is ejected south-east off the trough, that will strengthen the blocking to the north. Easterly anyone ?

Agree with this.

I think that we are lining up for a cold spell in 10-15 days time starting from the east. This is for a number of reasons.

Firstly we are seeing a considerable warming at 30hPa which will take a little time to affect tropospherically but not as long as if the warming was higher up. We then have the vortex shape lower down which wool be more conducive to blocking to our NE.

Next we have an increase in frictional torque starting to occur which is likely to be followed by a positive mountain torque. The net affect will be removal of westerly winds north of 35°N. With the GWO likely to be around phase 1 then.

I suspect after this any longevity will be determined on the strength of the block and positioning of the PV following this.

On the look out for signs in the FI output in the coming days now.

[Jason M]

Just want to say that i've been through the GEFS ensembles again and I counted 9 out of 20 members showing an E,ly. Fair enough some were shortlived but still an E,ly. Also 3 members showed a N,ly via blocking over Greenland. So thats 12 out of 20 members showing decent cold synoptics.

Lets see how many the 18Z delivers.

Quite a few seemed to be more of the 'mid lat' variety though. When looking at the 850s they were often quite poor despite the fact that they looked synaptically very good. By the time the correct synaptics appear the cold pool has been displaced. In a sense there is a danger that we miss our window and end up with something akin to the dreaded 'faux cold' (really hate that phrase but needs must ).

Its a fair point re the 18Z though. Will be interesting.

Edit: where is IB? its his job to be negative, not mine

Edited January 18, 2012 by Jason M