Winter Model Discussion Thread 12Z onwards 5/1/13

[AWD]

EC postage stamps offer good support for a easterly scenario, especially across southern England. Varying degrees of how cold & unsettled however.

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009112700!!/

EC Reading ensembles again show support for the Op run.

Slightly unfavourable in terms of windspeed could mean the Op is too much on the unsettled side, so perhaps expect something a little less unsettled but a clear trend to cold conditions evident there.

Edited January 6, 2013 by AWD

[weather eater]

Just seen Snowkings posts, much better put than my musings and it does highlight potential pitfalls, my concern is that the GFS tends to deal with blocking patterns better than the ECM at least that’s my observation, so a turn round by the GFS 06z suite would be very welcome. It’s also true that the GFS sometimes has a blip for a few runs before settling back to its previous position hopefully thats all it is.

As for Joe B, rather like the express I wish he would stay off the case, you just know it will go pear shaped as soon as he starts talking it up. He’s very engaging but more often wrong than right

Edited January 6, 2013 by weather eater

[Snowman31]

BBC weather just said some of the UK could be seeing something wintry next weekend. Lets hope so :-)

[Ian Brown]

Promising outlook again from the models this morning.

The GFS ultimately doesn't deliver in terms of cold because it takes a piece of energy west of Greenland, blows it up and runs it through Iceland, right between the attempt from the Azores high to ridge into Greenland. This then topples the ridge over the UK.

http://cdn.nwstatic....192/h500slp.png

The subsequent powering up of the vortex in low res is entirely predictable but goes against the background signals, so will be surprised if it turns out as shown.

I've always trusted the GFS to handle the Greenland/Iceland area better than the ECM and we should continue to see the GFS outcome as the more likely until we see subsequent runs.

Perhaps a more middle ground solution for next weekend is likely with cold uppers clipping the SE, with the majority of the country under a ridge. Beyond that this is another run to fire up the jet to the NW in FI, and that has to be a major worry, Strat signals or not. We should in theory be seeing eye candy in FI or wild swings, but the GFS continues to show a lot of Northern arm energy.

[ChartViewer]

I've always trusted the GFS to handle the Greenland/Iceland area better than the ECM and we should continue to see the GFS outcome as the more likely until we see subsequent runs.

Perhaps a more middle ground solution for next weekend is likely with cold uppers clipping the SE, with the majority of the country under a ridge. Beyond that this is another run to fire up the jet to the NW in FI, and that has to be a major worry, Strat signals or not. We should in theory be seeing eye candy in FI or wild swings, but the GFS continues to show a lot of Northern arm energy.

Agree Ian re the jet energy around t192 on the gfs 00z. We really want that diving south allowing heights to build into Greenland asap and not hanging around NW of us.

Edited January 6, 2013 by ChartViewer

[IDO]

Agree Ian re the jet energy around t192 on the gfs 00z. We really want that diving south asap allowing heights to build into Greenland asap and not hanging around NW of us.

The GEFS mean jet does not follow the op: mean: Op:

So until we see the mean fall in line, the jet coming to our NW only remains an option.

[Kentish Snowman in Yorks]

Well if the 0z GFS verifying is the sum of all fears this morning, then I don't think we are doing too badly to be honest.

Even this run brings sub -5 air (and in SE areas sub -10 air) from this coming Friday for almost all of England and Wales (sorry Scotland and Ireland!) up until when the low res section of the output automatically powers up the jet. I'm not saying the GFS is incorrect, just that we should be suspicious of it given the continuing SSW event.

The ECM output is obviously much more favourable in terms of deeper cold and snow but is also not infallible at the 144/168 range, so it's just another case of more runs needed...

Regardless of the above, I do think we can now safely say that we are heading for a colder period of weather from the second half of this upcoming week onwards, as shown by the ensembles below but the longevity of this spell, and how cold and how 'white' remains open to conjecture at this stage;

What I would also say looking at those ensembles for my area is that even the extreme mild solutions in FI a la the control run do not quite reach the dizzy heights of the upper air temperatures forecast for this coming Tuesday, so the only way is down from there!

Edited January 6, 2013 by Kentish Snowman

[Cloud 10]

Cracking long range ECM ensembles this morning with the mean dropping to around

freezing and staying there.

ECM ensemble mean 850 anomalies at 240 hrs are pleasing!

Edited January 6, 2013 by Cloud 10

[ITSY]

Cracking long range ECM ensembles this morning with the mean dropping to around

freezing and staying there.

The best yet, which I also said last night. On that basis alone, expect the 06Z GFS FI to be wildly different. Those ens suggest initial Easterly then a slightly 'milder'/not so cold period while the building blocks fall into place for a greenie high, then a more pronounced cold period again. Now, if the GEFS ens can organise themselves similarly...

Upto +96 and no major changes. That's a start...

Edited January 6, 2013 by ITSY

[Cloud 10]

The best yet, which I also said last night. On that basis alone, expect the 06Z GFS FI to be wildly different. Those ens suggest initial Easterly then a slightly 'milder'/not so cold period while the building blocks fall into place for a greenie high, then a more pronounced cold period again. Now, if the GEFS ens can organise themselves similarly...

Yes indeed,looks like a classic easterly then northerly evolution.

[lorenzo]

Recalling December and playing around with the reanalysis tool for heights in the model verification suite, the GFS had a pre-disposition to deepening lows on approach to the South of Greenland tip, the area where much shredding was taking place earlier in the season. Net result was the block attempting to hold position there was invariably smashed down.

Here are a couple of images based on the Day 6 - 144hrs for 500mb heights using a re-analysis of the last 10 12z runs from ECM and GFS. To my eye looks like ECM deepening the east CONUS trough is the key difference. Both have a bulk of heights in orange to the North and similar pressure patterns over Europe looking east.

ECM > GFS

Also this chart shows the difference at 240hours between the 2 models as things look currently, GFS more positive on Iberian heights and restricting the heights to the North to directly North / North East, whereas ECM lowers the euro ridging and extends further North west. Hence the 2 markedly different solutions. The sensible prediction would be somewhere in between.

Final thought about those reworked model verification, these look at the last 10 days, and what is in front of us in the atmosphere is going to be decidedly different !

Edited January 6, 2013 by lorenzo

[lord stratus]

I've always trusted the GFS to handle the Greenland/Iceland area better than the ECM and we should continue to see the GFS outcome as the more likely until we see subsequent runs.

Perhaps a more middle ground solution for next weekend is likely with cold uppers clipping the SE, with the majority of the country under a ridge. Beyond that this is another run to fire up the jet to the NW in FI, and that has to be a major worry, Strat signals or not. We should in theory be seeing eye candy in FI or wild swings, but the GFS continues to show a lot of Northern arm energy.

Most cold weather fans are looking at trends and should be pleased with what the current outputs are showing. A bit pointless looking for a breakdown before the cold weather has even set in!

[Summer Sun]

GFS 00z shows the chance of some wintry showers by Friday evening

Into Late Saturday and early Sunday a more organized area of snow develops

[ITSY]

Setting up well for an ENEly next weeked. My potential worry is the low emerging in Canada, which could help prevent the building of heights into Greenland and sustain the Jet Stream (which is essentially one of the things that caused the 00Z run not to develop a Greenie high). Could be a red herring though.

EDIT: +126

That low in the middle of Canada is actually now less strong than the 00Z, with HP either side of the mid Atlantic stronger, as it is over Scandi, with a more potent looking ENE than the 00Z.

Edited January 6, 2013 by ITSY

[SMU]

GFS the real party pooper this morning- & dont expect any help from the 06z...

Its good to see a nice bit of consisency from the ECM, however the most pleasing sight is the ECM ensembles- nearly a full sweep of support heading to the longer term cold depicted by the 12z OP yesterday, also the 00z OP has the advection in nearly the same place as yesterday.

12's will be interesting...

S

[Panayiotis]

So with the 06z we have held back the -5C uppers compared to the 00z which had them over the SE at 120hrs.

[BARRY]

don't think the l;ow coming out of Canada is going to spoil the out come

[Paul White.]

I've always trusted the GFS to handle the Greenland/Iceland area better than the ECM and we should continue to see the GFS outcome as the more likely until we see subsequent runs.

Perhaps a more middle ground solution for next weekend is likely with cold uppers clipping the SE, with the majority of the country under a ridge. Beyond that this is another run to fire up the jet to the NW in FI, and that has to be a major worry, Strat signals or not. We should in theory be seeing eye candy in FI or wild swings, but the GFS continues to show a lot of Northern arm energy.

And conversely we see the ECM with inter run consistency showing a Greenland block 2 in a row. Ian if it was the other way around and we had the gfs showing showing the GL block and the ECM showing more of an Atlantic influence I bet your post would have been almost similar (swapping gfs for ECM ) to fit in with your winter theory at least that's how it looks IMHO. For me and someone posted earlier why wouldn't we trust the worlds best model at varifiyingl from d5 onwards. If the ECM had similar Synoptics to gfs at d6 onwards then I would be inclined to think its a none starter but its not and therefore from a cold perspective we certainly have more hope to colder conditions than what was shown a week ago.

Paul

[TEITS]

So with the 06z we have held back the -5C uppers compared to the 00z which had them over the SE at 120hrs.

Despite the cold being delayed on this run I actually prefer 06Z +138 to the 0Z.

[East Herts Snow]

Great run for cold weather coming up here, nicely shaped Scandinavian High at +120 advecting colder air into the UK.

Edited January 6, 2013 by East Herts Snow

[Panayiotis]

However what to me is looking better is the position of the high at 126hrs, ive labelled where the center of the high and where the isobars are for the 1024mb, as you can see the high is over Scandi, which is a much better place IMO to bring in those colder uppers.

It seems many have beat me to it

Edited January 6, 2013 by Panayiotis

[Iceaxecrampon]

Lancashire and Cheshire snowdome active and fully up and running

Hopefully a potent enough Easterly front to carry across the Pennines

Ian

Edited January 6, 2013 by Iceaxecrampon

[ITSY]

GFS the real party pooper this morning- & dont expect any help from the 06z...

Its good to see a nice bit of consisency from the ECM, however the most pleasing sight is the ECM ensembles- nearly a full sweep of support heading to the longer term cold depicted by the 12z OP yesterday, also the 00z OP has the advection in nearly the same place as yesterday.

12's will be interesting...

S

In the long run yes, but like you say, other models pointing more favourable outcomes. In the short term, our regions have snow potential by +126/132 on the 06Z as the Ely begins.

[Ice Day]

850 temps next Saturday.

Looking good so far on this run, angle of attack appears better (to my very much untrained eye!)

[TobyT]

GFS 00z shows the chance of some wintry showers by Friday evening

Into Late Saturday and early Sunday a more organized area of snow develops

Looks like I will be glad of my winter tyres come next weekend if this verifies