Model Output Discussion 18th Nov.2013-12z onwards.

[Mucka]

Much improved GFS Op run this morning for coldies though given how dire yesterdays output was that isn't saying much.

Basically it has shifted the pattern West and we get a couple of glancing blows of Arctic air but it is not hard to see how something more significant could develop with a few tweaks.

 

GFS 00z day 8

 

 

and day 10

 

 

This is not just a variation though, it is a trend for the pattern to be shifted West (By GFS at least) and this shows up on the ensembles as the first ridge (around day 5/6) is now shown as introducing colder air around the 29th than previous ensemble suits. (previously the high was to far  East to allow the cold air to push South down its Eastern flank into the UK .

 

http://www.meteociel.fr/cartes_obs/gens_display.php?x=262&y=62&ext=1&run=0&runpara=0&type=0

 

Still no real sign of a sustained Wintry spell thought it has to be said but at least there is the prospect of some more interesting output from GFS than what we have seen recently and who knows maybe the output will continue to upgrade the cold prospects as we gom into next week.

Edited November 24, 2013 by Mucka

[Frosty.]

No sign of the GEM backing down with it's more wintry, windy outlook, if anything, the 00z has upgraded compared to the 12z and is now on a par with the 00z yesterday, I would not take the gem lightly, it's performing to a high standard in recent times so the chances of a strong cold blast through early December are growing, synoptically it's a robust looking set up that the gem is constructing.

Edited November 24, 2013 by Frosty.

[MPG]

The settle spell ends at 120 on this mornings GFS. A very N/NW flow sets in throughout the rest of the run with a PV smashed all over the place. Interesting cross polar flow too.

[SLEETY]

ecm beginning to back the gem as well. this morning.

 

the gem the form leader now

[bluearmy]

looks like the questions are:

How strong will the east Canadian block be and can it keep the jet to its south, thus drawing our block wnw towards it.

How much vortex will be left over Greenland.

Once these become clearer, we can get an idea where we're going.

The week 2 gefs are interesting wrt the p/v. The trend is to break it into smaller fragments from the 00z run but we've not seen this before so should hold judgement on it.

[winterof79]

No sign of the GEM backing down with it's more wintry, windy outlook, if anything, the 00z has upgraded compared to the 12z and is now on a par with the 00z yesterday, I would not take the gem lightly, it's performing to a high standard in recent times so the chances of a strong cold blast through early December are growing, synoptically it's a robust looking set up that the gem is constructing.

Many options on the table.

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

Seasonal model output for the foreseeable.

The development of the low off the eastern seaboard is the key difference at  present

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-180.png?0

The lack of it on the GEM allows our high to migrate somewhat

http://modeles.meteociel.fr/modeles/gem/runs/2013112400/gemnh-0-180.png?00

[dragan]

Question. Would severe coldfrom usa and canada not keep jet pushed far south coming off eastern usa canada??

[Frosty.]

The GEFS 00z mean seems to be increasing the risk of a cold blast, at least for the north of the uk but it could become more widespread depending on what impact the lowering heights from the northwest / north / northeast will have on the pesky atlantic high.

[bluearmy]

the 00z naefs continues to indicate that the colder spell around the 5/7th dec will be short lived. the ridge amplification that brings the colder uppers south will not manage to hang on in mid atlantic as the siberian p/v begins to lose the upper hand aganist the canadian segment. this transfer of lower heights across the pole generally brings mobility to the atlantic. we may end up with the ridge close to us (again). the mean trough remaining over scandi and shallower to our se.

[Ian Brown]

The GEFS 00z mean seems to be increasing the risk of a cold blast, at least for the north of the uk but it could become more widespread depending on what impact the lowering heights from the northwest / north / northeast will have on the pesky atlantic high.

Frosty, I wouldn't pay much to the attention to the GEM. there is nothing really to suggest a transfer of the core of heights from the Atlantic to Greenland. North Westerlies at times for sure, but nothing to suggest any HLB. The ECM T240 chart would be particular poor for cold fans going forward.

[Summer Sun]

UKMO has the high furthest east this morning

 

 

ECM has the high a lot further west

 

 

And GFS still isn't interested at t144

 

 

t168 it gets close

 

 

But thats all overall the high on GFS never goes that far away from the south

 

Edited November 24, 2013 by Summer Sun

[Summer Sun]

Latest from Gibby on the 00z models

 

All models show little change tonight with High pressure remaining in control of the weather over the UK with just variations on cloud amounts day to day which also bears an influence over how much frost and fog is allowed to form overnight. In addition the weather becomes a little more breezy with more cloud streaming SE across the UK with even a little rain for a time across the North and East.

 

GFS today shows High pressure never far away from the South of the UK with day to day variations on the amounts of cloud and wind across the UK. The North remains favoured for what there is of rainfall over the period with very little reaching the SW Temperatures will vary somewhat day to day as some injection of colder air to the North occurs at times.

 

UKMO closes it's run with High pressure over the Eastern Atlantic with winds blowing down from the NW, quite lightly overall but a little stronger over far Northern and Eastern areas where a front crosses SE late in the week with a little rain possible for a time. It may feel rather cold at times in the NW flow.

 

GEM tonight shows a similar pattern to the other models with High Pressure in the Eastern Atlantic with a NW flow over the UK gradually strengthening and eventually allowing some rain to move through at times in the flow as well as turning things rather cold and fresher by the end of the run with some wintry showers towards the North and East.

 

NAVGEM shows High pressure gradually being squeezed away South in a week or so with the increasing threat of a fresher Westerly breeze ushering relatively mild but more unsettled weather with rain at times, chiefly in the North.

 

ECM shows a flow of NW winds and rather cloudy skies later next week before towards the end of its run it shows High pressure relaxing South over France as a trough of Low pressure moves in towards the West with freshening SW winds and rain moving East over Britain on Day 10.

 

The GFS Ensembles show there is a huge range between the members with some rain highlighted to develop over Northern areas especially later. There is nothing particularly wintry shown within the spread this morning despite some colder members shown at times.

 

The Jet Stream tonight shows an arching flow around areas well North of the UK and down into Europe as High pressure near the UK  keeps in control, especially over Southern Britain.

 

In Summary today there looks a growing trend for High pressure to loosen it's grip very slowly from next weekend as Low pressure to the North and NW gradually extends it's influence down across from the North to affect all areas eventually. There still looks unlikely to be any particularly eventful weather likely with all the changes being slow and arduous.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[Cold Winter]

High pressure dominating the weather over the next week, either directly over the UK or down to the southwest, bringing variable amounts of cloud and fog with frost possible in clearer areas at times.

 

After next week the GEM shows high pressure slipping away west while building pressure over Greenland, leading to a northerly over the UK:

 

ECM agrees on the general consensus of high pressure away to the west of the UK with a fairly brief north/northwesterly flow. Lower pressure over Greenland:

 

High pressure much closer to the UK on the 00z GFS with a northwesterly flow for a time:

 

 

In summary a quiet week of weather to come over the UK with high pressure dominating conditions leading to variable amounts of cloud and fog, with some frost when clearer spells develop. Towards the end of next week the possibility of high pressure moving west allowing a brief north/northwesterly flow.

[Jason M]

Having been looking through the opp and ensemble runs for the last few days it seems to me that the medium to long range form horse is for pressure to rise to our SE and south over Spain. More and more of the ensemble runs have been pushing this solution over the last few days. A couple of ensembles have Greenland height rises but I'd discount these as I think GFS ensemble suite tends to over push that idea and we also saw that a lot last winter.

Things can and do change but it looks to me like it may be a Bartlett style few weeks in early December at this point (or something similar). Not saying we are looking at this for months or anything like that (though like some others on here I recall 1988 and am still traumatised by that winter :-) ).

06z run rolling out though so as always waiting to be proved wrong.

Jason

[Frosty.]

Much better Ecm 00z ensemble mean compared to recent times, actually it has strong similarities to the GEM 00z now and for longer term prospects of reloading wintry blasts from the northwest / north with more amplification...the core of the atlantic high gets shunted much further west/sw and is not stuck limpet like just to the west/sw like it was previously. So I think the door is being kicked open now for polar maritime incursions through early December which could veer towards a draw of arctic air southwards and increasing the risk of snow in the process.

Edited November 24, 2013 by Frosty.

[cooling climate]

Frosty, I wouldn't pay much to the attention to the GEM. there is nothing really to suggest a transfer of the core of heights from the Atlantic to Greenland. North Westerlies at times for sure, but nothing to suggest any HLB. The ECM T240 chart would be particular poor for cold fans going forward.

Strange as soon as I saw the ECM t240 chart I thought WOW. Its probably one of the

best charts this autumn for a proper cold pattern to lock in IF it verified of course.

Northwest - southeast flow with amplified pattern over Canada and large pressure (amplification)

rise over eastern and northeastern Canada. 850 temps of -8c already starting to push into

northern Scotland by t240 and by say t288 the whole country would be under -8c air at least.

Very good chart in my opinion.

[draztik]

the 00z naefs continues to indicate that the colder spell around the 5/7th dec will be short lived. the ridge amplification that brings the colder uppers south will not manage to hang on in mid atlantic as the siberian p/v begins to lose the upper hand aganist the canadian segment. this transfer of lower heights across the pole generally brings mobility to the atlantic. we may end up with the ridge close to us (again). the mean trough remaining over scandi and shallower to our se.

the ext ecm ensembles show a similar evolution, with heights building by day 11 to our NW, but by day 15, the troughing is still over Scandinavia but further East. Looking as tho we will have 3 or 4 days of cooler uppers, before we trend to more average conditions overall.

Day 12

Day 15

[cyclonic happiness]

The ECM is very good this morning, it's showing cold zonality with the chance of snow from the north west, like we had a few years ago.

 

I'm happy non of the charts are showing raging easterlies, it usually means there is something brewing, especially when they throw out weirdness in the mid range.

[cooling climate]

A significant development on the models this morning is the development of low pressure

over the gulf of Alaska which all three models agree on in the 120 to 168 time frame.

This will help stop any more energy from circling around the vortex especially if as the

ECM run shows this low runs down the western seaboard of north America and allows

pressure to build in front and behind it.

Exciting times ahead I feel.

[nick sussex]

A rather mixed picture this morning, I think this movement of the PV is liable to cause some variability especially as it seems to go east to Siberia and then bounces back west again.

 

We don't mind the bounce back as long as it splits after this or the entire chunk ends up much further to the west. All the models agree on a ridge in the Pacific desperately trying to land a few punches on the PV, the question going forward is how resilient the PV is versus this attempt to split it.

 

Even with a split I think realistically at the moment the best we could see at the moment is a colder snap rather than spell, a northerly toppler is possible with the PV being pushed away from Greenland as long as the upstream pattern is sufficiently amplified.

 

I would sum up todays models simply as all a bit average and neither inspiring or deflating,from a cold perspective a few opportunities but nothing concrete. Lets hope that Pacific Ridge  can help out and at least deliver something of interest in the  outlook.

 

Putting aside the GFS lower resolution past 240hrs you can see here how that Pacific ridge has helped split the PV and upstream a bit more amplification leads to some interest but even here we have the wrongly tilted upstream troughing, in this type of set up you need a negative tilt upstream because this will correlate with the jet downstream, a negative tilt there ie running nw/se then means in western Europe the jet cuts back more ne/sw funnelling the cold into the UK rather than directing it into mainland Europe.

 

I've done a few paint jobs here for newbies to see why you'll often see us discussing the tilt of any low/troughing upstream, just think of what goes up has to come down! lol The angle upstream effects the angle downstream.

 

In the first you'll see the negative tilt to low pressure in the eastern USA as the warmer southerly flow heads north ahead of this this develops something known as WAA warm air advection, this basically helps build high pressure to the east of the low. The high develops in a different way, the energy runs over the top and into Scandi but heads southwest rather than se as shown in the next picture.

 

 

 

 

 

 

Generally with this type of set up you want to see a stretched low or phased lows, think oval or sausage rather than football shaped, the shape of this gives you an indication of how much energy is being sheared away so if its round the whole energy is moving east if its more oval or begins to stretch nw/se you can deduce that some of its ooomp is  being drained away, in this situation some of its energy will head se rather than just east or ne.

Edited November 24, 2013 by nick sussex

[Cloud 10]

Quite notable how poorly the 06z GFS has verified for today from its prediction

 five days ago.

 

 

today..  5 days ago..

 

 

Way to much energy to the north flattening the ridge as usual.

 

 

Could be worth bearing in mind when viewing it over the next couple of

weeks given the predicted ridging in the atlantic...

 

 

edit..i was wrong to single out the 06z. The other GFS runs were equally poor.

 

http://modeles.meteociel.fr/modeles/gfs/archives/gfs-2013111900-0-120.png?0

 

http://modeles.meteociel.fr/modeles/gfs/archives/gfs-2013111912-0-120.png?12

 

http://modeles.meteociel.fr/modeles/gfs/archives/gfs-2013111918-0-120.png?18

Edited November 24, 2013 by Cloud 10

[Frosty.]

The Ecm 00z thickness charts show an incursion of 528 dam into next weekend and then further on, 522 dam spreading into scotland with the likelihood of colder weather then spreading to the rest of the uk, so I think we have taken a step closer to some type of cold blast during early next month with reload potential with the jet tilting more towards nw / se which is supported by the ens mean.

[bluearmy]

the ext ecm ensembles show a similar evolution, with heights building by day 11 to our NW, but by day 15, the troughing is still over Scandinavia but further East. Looking as tho we will have 3 or 4 days of cooler uppers, before we trend to more average conditions overall.

Day 12

Day 15

what is possible is that the scandi trough, stuck between the displaced azores block and downstream sw Russian ridge, may have to exert itself further south. I note the ECM control dives a depression to our sw and into France and we have seen extended modelling that builds heights to our ne as we head through dec.

not likely but there are some hints of that solution.

The London ECM ens, which create those anomaly charts are very split by the 8th. I'd say 50% are v cold by then whilst the remainder are clustered average or spread from average through to mild. A few more days before we can see where the ecm ens are going post this colder few days (5/7th) which seem to be pretty well agreed upon by the models.

Edited November 24, 2013 by bluearmy

[cooling climate]

So in a nutshell you have the GEM and the ECM which show the formation in the

extended range of low pressure forming over the Gulf of Alaska and then running

south which allows pressure to build in front and behind it pushing all the energy

over the pole towards the east and a cold pattern setting up for UK and Europe.

The GFS run is half way there but splits the energy over the pole and also loses  

the low over west coast of north America in low res (post t192) hence no cold  

pattern.

[bluearmy]

So in a nutshell you have the GEM and the ECM which show the formation in theextended range of low pressure forming over the Gulf of Alaska and then runningsouth which allows pressure to build in front and behind it pushing all the energyover the pole towards the east and a cold pattern setting up for UK and Europe.The GFS run is half way there but splits the energy over the pole and also loses  the low over west coast of north America in low res (post t192) hence no cold  pattern.

But at the moment cc, the extended ECM ens and gefs/naefs all take that transferred energy back towards Canada in two weeks, spreading the vortex across the pole.