Model Output Discussion; into 2015

[J10]

I know the charts are not looking good for a cold perspective .

 

But last week they forecast a Northerly which then turned into an Easterly.

 

In the end a watered down Northerly gave a little snow yesterday.

 

The Easterly which was promised to deliver some very cold weather into the new year is set to be a sinker.

 

The point I am making is that charts can go wrong, and what they might be showing in a few days time may well be different to what they are showing today.

[dragan]

You may well be right in your prediction but calling for zonal conditions in the British Isles is a bit like saying that Chelsea have a good chance of winning the League, therefore for me there is very little kudos attached to it!

Yes but it's the model output discussion. That's what I see so that's what I have commented on.

[Allseasons-Si]

And back to model posting and chat which i find this is the right thread-i think

 

quiet a difference there with a neg tilted trough out in the mid atlantic pushing hieghts a bit further north

 

18z@11412z@120

 

 

[johnholmes]

I am really pleased we have John Holmes posting on this forum, level-headed and full of weather wisdom.

However, having followed the NOAA anomaly charts avidly this year (and found them to pretty good in the summer), the last two weeks have got me concerned - it is able to cope with major pattern changes? Look at the following, the date produced and the forecast period - I have to say, we know that these charts are wrong / going to be wrong for our area of the globe - Royal.

see my post lower down rather than insert here

[Long haul to mild]

Yes but it's the model output discussion. That's what I see so that's what I have commented on.

That's fair enough but the "fantasists" you derided earlier are also doing the same, but they are looking into trends and ensemble members instead of the operationals alone.

Everyone is entitled to their view of the output be it optimistic or pessimistic but considering the best respected models don't go out beyond 7-10 days, then everything can be considered as FI after that so claims of whole months being lost to zonality are somewhat premature.

[Mucka]

It's a ridge, Jim.

 

 

But not as we know it.

Edited December 28, 2014 by Mucka

[johnholmes]

I am very flattered by that and my old eyes and head are not sure if you are saying they are correct or not. For the benefit of some who may be mystified by these charts. The 6-10 is the only one we can check on accuracy as the 8-14 is for the start of 2015

 

Below is the actual for today 28 December at 500mb from the Net Wx version of GFS.

What does it show?

A substantial upper ridge west of the UK with a marked trough just east of the country digging well into Europe.

 

http://www.netweather.tv/secure/cgi-bin/premium.pl?action=gfs;sess=089454bb1f0b196e4bd90e9745d72ad3

 

sorry it just shows the Extra link but my summary is fairly clear I hope?

 

This is what I wrote in my own huge files on these charts on that day

Noaa Noaa

6-10 and the anticipated pattern change in the main  wavelength looks to be getting under way; trough nw pacific/w of Alaska and ridge Alaska along with reasonable sized +ve anomaly, the Canadian trough is now way west of the predicted position 3 days or so ago (then s Greenland, now suggested to be towards gr lakes, ridge now shown as off ssw Greenland and largish +ve anomaly with it thus the flow into the uk is still w’ly over the uk but as trough-ridge and associated +ve with ridge edge east so the flow will turn n of west into the uk, also the flat trough e of the uk is likely to react to thses changes by extending south/sharpening into Europe. Not even looked at the 8-14 but that is what is needed to be seen there if the colder shot is to be more than a short spell?

8-14 is much as 6-10 over most of chart, indeed all of chart, with not that much change in the flow over and e of the uk showing so far but I suspect the flow will turn more n of west and extend more into Europe over the next 2-3 runs. IF the trough edges back west to be west of 10 e then it really would suggest a deep cold spell of at least a week but that is not yet predicted to happen.

Going back to the EC-GFS and only the gfs actually shows this idea in its time frame (6-10). Again if my previous comment is to occur then by 2 days from tomorrow they should both be showing this prediction.

So a colder shot for sure 6 days or so from now, after the colder shot in the run ip to Christmas perhaps or will it merge into one-we have to wait and see?

I backed this up the following day with, for me a mild ramp!

 

 

This was posted into Net Wx on, I think, 19 December

Below posted into net wx evening fri 19 dec

Noaa

6-10 from faw w and trough ridge along with -/+ve suggestions looks about same as last issue-canadian trough is looking about the same, re position/intensity-ridge/+ve heights and the +ve heights remains around 370dm + which is certainly a significant +ve height anomaly and it coincides with the ridge-this as before causes the 500mb flow to move towards the uk with a direction well n of west, with still quite a rounded trough over the uk along with some SLIGHT extension into Europe but NOT much.

Height over far s of uk=remains a touch over 546dm

The 8-14 an dit looks pretty similar to me in all aspects to the last issue; possibly the slightest ectension s of the uk trough, height far s of uk=546dm/touch above much as 6-10 so the pattern looks likely to be as shown on both these over the 6-15 day time scale.

For ski fans (like myself, we could do with the extension s of the trough into the uk to bring snow in decent quantities to lower levels than many resorts have had for a week maybe longer!

For the UK, remembering these are mean charts over the period given then the probability of sharper extensions is present. Small, relatively, upper troughs are best left to the synoptic models at shorter time scales.

Perhaps we can take a look at the 2 major synoptic outputs, maybe 3 if we use the UK model?

For some obscure reason folk want to know weeks in advance what it will do on the 25^th of this month, never any other month and some do get worked up when the models cannot do this, be it 240h or 96h out but never raise a murmur on 25^th of any other month. Scientifically this is totally illogical but never mind.

Link to NOAA output

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

for details on how this and EC-GFS were summed up from this morning please see the post with links in the technical thread. It is NOT technical.

A link to see how the EC and GFS models at 00 and 12z have coped with this from 240h down to today is below.

The GFS 12z version from 240h and it has some similarities, at least not showing any flow from the SW. The 00z  a little more consistency on most runs, again no SW flows shown

ECMWF 12z and 00z perhaps not quite the consistency of either GFS runs?

Anyway I will leave it to the reader to make their own mind up.

What I am trying to illustrate is that, to me if not you the reader, the anomaly charts have been more consistent than the synoptic charts in predicting this substantial build of pressure in the southern Greenland area for a number of days. Once the +ve heights began to show substantial numbers east of the Canadian trough, this partly the cause of the trough moving west, then the pattern they show for 6-14/15 days ahead looked fairly clear.

This build of heights and surface pressure below it is the cause of the lows/depressions running east not NE if you look at the Fax chart, link below

http://www.weathercharts.org/ukmomslp.htm#t0

If you look at their raw data below the Fax charts out, currently, to 25 December note how the 552dm line is pushed south with colder upper air pulling in behind it. Also the transfer south of the surface trough to cover most northern areas by Christmas Day. Still held up as it often is by the ‘lee’ low that often develops in Arctic flows over Iceland. This will not change much until/IF the upper flow turns north of west over the UK as the trough then extends into Europe. At the moment there is no sign of that happening.

Will it happen, sorry do not know. The next further out link I use is the MJO and that is currently and predicted to be in a very low orbit. This usually means that the weather patterns over the UK are likely to be much as they are for some time to come. How long? Again I do not know but the MJO change to a relatively reasonable orbit may signal a change. Again to what I have no idea. Perhaps the other links we read in the OPI or Stratosphere thread may give us more guidance there.

 

Finally how active is this incursion of colder air likely to be? That can only come from shorter time scale guidance using the synoptic models. Judging by the quite stron indication from UK Met, they are fairly convinced it is going to quite marked in one or more parameters, be it wind, rain or snow.

 

If things look to be changing I will post again over the next few days. Some look like having snow on the ground or falling over the Christmas period. Stay tuned as no doubt on here we will be treated to all manner of ups and downs before Christmas Day and after.

 

Don’t get me wrong, they can give bad guidance, I can at times not read them very well so the posts I make on here are not very good. They do pick up changes, they do give good guidance on upper patterns remaining the same. They do both these things when the signals from the synoptic outputs, 4x or 2x daily show different.

They are to me about the best upper air guidance available to us on the web IF used carefully. As with ANY output do NOT take too much notice of one ouput and DO look at everything else in the same time scale before trying to decide what is the answer.

 

I am not blowing my own trumpet, simply suggesting that they do give good guidance and are well worth trying to understand.

Not checked for spelling errors.

 

All based on trop charts and AO and Nao forcing which I suggest will change very soon ....The NOAA anomaly charts are just a deviant of all current gefs members ...they change as does the members dictated by upper patterns...AO And NAO only show positive as do anomaly charts showing Azores ridge west winds because they can't handle strat events surely.

 

I have no idea about that, they are mean charts models produce for the atmosphere at 500mb and having used them for the last 4-5 years they are as good a guide on the web as anything else. Indeed in my view in the 6-15, sometimes longer when used in conjunction with the MJO output(when that is relevant) proably the best we have available FOR 500mb. That is the easy bit, the more, much more difficult part is getting the surface correct or even nearly correct. But they will show, on a very simple basis, what airmass will predominate, Pm or Tm, remembering they are averages and day to day changes will occur.

Edited December 28, 2014 by johnholmes

[Allseasons-Si]

It's a ridge, Jim.

 

 

But not as we know it.

Yes Mucka better cross polar flow enhancing those hieghts in the Greenland area forcing that low to further undercut with better negativity tilt.

[LomondSnowstorm]

I know the charts are not looking good for a cold perspective .

 

But last week they forecast a Northerly which then turned into an Easterly.

 

In the end a watered down Northerly gave a little snow yesterday.

 

The Easterly which was promised to deliver some very cold weather into the new year is set to be a sinker.

 

The point I am making is that charts can go wrong, and what they might be showing in a few days time may well be different to what they are showing today.

 

Just to illustrate this point, some big changes on the GFS 18Z over the last 24 hours:

 

 

A rather typical zonal picture yesterday (albeit still with an Arctic High) compared to hints of some cross-polar ridging tonight. Interesting also to see both the GFS and GFS P placing a cut off low in the Atlantic around D5. This would certainly help with the amplification and potentially manage to carve out some sort of ridge to our north to deflect the jet southwards.

This is pretty close to what I mean:

Edited December 28, 2014 by LomondSnowstorm

[Allseasons-Si]

Boo,and the pv comes to our shores with her hand waving in the air lol

 

SMILE

[blizzard81]

But the question has to be asked is what you say true or a perception you and some others have about it. As Gibby posts the 10 days statistics, like the 6 day ones show it clearly in the lead even over the revamped GFS. That revamp was partly fed by guidance from ECMWF staff trying to get the GFS model to give better results. I find it hard to believe, until folk show me the predicted AND then the actual chart that ECMWF is as bad as some say. How can that be when the northern hemisphere statistics show otherwise. Do you feel it is west or east of the UK? Please show me actual instances.

I am not trying to cause a row but as a meteorologist and a bloke with a science training I do need factual evidence. So far the only charts I have seen are predicted charts which then folk do not remember when we get to T+00, much as I asked earlier today.

If I had time I would do just the same as I did with the anomaly charts, collect the data, post them for all to see, then comment how well or badly I felt they had been. I did this for 3 years so my view on them is a scientific one.

Let us have a discussion please but no name calling.

In answer to your question, it is many years of model watching that has exposed the ECM bias in over amplifying towards Greenland. This has more recently been cemented by some members highlighting this fact with bias verification maps. I am sure you will have seen these posted on here these last few weeks. I do not know where to access them so I can't attach them. They basically show height bias for each model.

[Frosty.]

I think if the UK was 750 / 1000 miles further north, the Gfs 18z op run would be very wintry indeed. Hopefully the 00z will be better.

[steelermark]

Don't post much at all on these forums but have been an avid reader for years now.

The standard of posting in here today from some has been diabolical. It spoils the whole thing. We all know that charts have been shown to be different within 12 hrs of the last one. So, anybody posting that winter is over or no cold in January is clearly looking for people to bite. It would be so much better if some decided to walk away from their keyboards, sit and think about what they are going to say, then be objective in their post. It would stop ruining this thread for the people that are trying to learn.

Sorry mods, not model related I know, but this thread is so poor right now.

[johnholmes]

In answer to your question, it is many years of model watching that has exposed the ECM bias in over amplifying towards Greenland. This has more recently been cemented by some members highlighting this fact with bias verification maps. I am sure you will have seen these posted on here these last few weeks. I do not know where to access them so I can't attach them. They basically show height bias for each model.

 

hi

I have missed them but would be grateful to see them if anyone can give me a link please?

[Carlrg]

This'd be a bit parky.   If it verfied that is.

 

 

Lala land as ever. 

 

 

 

[Long haul to mild]

Shocking chart for cold unless your an optimist re the Alaskan ridge

Thankfully it is a long way out into FI and given the GFS's seeming tendency to flatten almost any pattern after day 7, we can hope that it is just up to its usual tricks!

[Nick L]

This'd be a bit parky.   If it verfied that is.

 

gfs-0-372.png

 

Lala land as ever. 

 

That's just wet, windy with average temperatures.

[nick sussex]

Still a confused picture upstream with different handling of low pressure over the USA and Canada, the GFS teased a little but then the upstream pattern flattened out.

 

A chance still though of something a bit more wintry next weekend, its not the most exciting output we've seen from a cold perspective neither is it awful its just middle of the road really.

[Polar Maritime]

A very stormy period showing around the 7th for the North.. With a strong Jet over the UK.

 

Edited December 28, 2014 by Polar Maritime

[Carlrg]

That's just wet, windy with average temperatures.

I know but we live in hope. It's going to be zonal, mild and mushy.

 

And this chart don't look good either. Not a cat in hell's chance of an undercut followed by a beasterly.

 

[Polar Maritime]

Some heavy snow showing for the South out in the run.

 

[Tamara]

I love the posts from Tamara, Steve Murr, TEITS, Chiono, Phil and a few others - they always seem to give hope for great synoptics to, one day, deliver some fab cold and snow BUT............

for almost 100% reliability i take most notice of Big John Holmes - those anomaly charts he uses seem to be the best guidance. Plus......

the Meto.

For general trends, so far, this Winter the Meto have been pretty much spot on.

This guidance will somewhat limit emotional ups and downs.

A winter most of us crave for *may* truly start from mid-January.

PM incursions delivering cold rain (IMBY) just dont cut it, for me, despite the comparision to last Winter.

Even down here we would normally have seen snow, by now, even if it was just fleeting - that would be the hallmark of an average Winter.

So far OUR winter has been pants.

 

I am pleased that we have such a range of very valuable contributors on here. Including very much those you mention as reliable

 

In that respect preference is not an issue, and it shouldn't ever be  - otherwise what is the point of trying to contribute and learn. In doing so, you fool yourself before you fool anyone else.

 

My own winter preferences are very in tune with the majority on here - and some may not realise I was a very early SACRA member some 10 years back..when, although I had a good understanding from as early as school studies about weather types and including anecdotal memories, I joined netweather back in Jan 05 first time - and did not know what 'GFS' stood for... I was completely clueless about computer modelling and weather pattern forecasting studies. I owe the amount I have learnt (and still have a lot to learn !!) from many of the much more learned members that have been on this forum since I joined. A very few notable ones have sadly been lost and much missed. 

 

The point of all that O/T waffle? Simply that being objective and wanting to learn is more rewarding than getting frustrated with the fact that the weather doesn't fall in line with one's own preference. Such human emotions are never going to improve the mood of the models. The model mood thread is a suitable human invention on this forum for those who cannot control their emotions over mother nature. She ain't easily tamed afterall..   

 

So moving on, in line with objectivity and not hope, as you mention, and not telling people what they want to hear but trying to give some meat on the bones realistically...

 

Todays updated GEFS GWO forecasts have made much more sense of what has happened, as I posted yesterday, and what looks set to happen over the coming 10 days. It is a good illustration of the need to keep reading between the lines of these forecasts just as much as NWP output and any other type of forecast. It was Christmas (being my excuse) but still *a note to herself*

 

GWO is currently set in Phase 3/4, more progressively than earlier suggestions, and underpins the westerly momentum burst and the modelled extra atlantic jet energy. Positive frictional torgues created as a result of this westerly burst, and responding in turn with a positive Mountain torgue over Asia (extra tropospheric wave activity). This in turn set to balance itself out by driving momentum down again with a swift orbit return to Phase 1/2 once more

 

 

 

 

 Cue corresponding negative frictional torgue and negative mountain torgue over the US (cue renewed Wave 2 activity to follow up vortex split).

 

Frictional torque anomalies over the Pacific Ocean to the east of the convection line anomalies (MJO) are responsible for the exchange of angular momentum between the atmosphere and the ground. This exchange is manifested as a Mountain torque (as discussed above which provides strong trop wave activity). Therefore MJO phasing approaching the Eastern Pacific provides an extra forcing mechanism for Mountain Torque (and tropospheric wave activity) as well as over imprinting the atmospheric signal with the ocean El Nino signal

 

The MJO re-starting in Phase 3 with a fresh convective signal in the Indian Ocean is responsible for this poleward AAM momentum burst and accompanying movement of the GWO into phases 3/4. This is characteristic of a Nina atmospheric response. The problem with this cycle being rooted in the western hemsiphere is that cannot provide extra forcing on the pattern we need - as convection returns to the Indian Ocean before crossing the dateline. On that basis will predicted momentum through the Pacific of the MJO be sustained further than the last circuit?

 

This whole Indian Ocean rooted signal underpins the negative AAM tendency/ GWO Phase 3/4 and back to Phase 1/2 cycle and is also characteristic of the current Nina state of the atmosphere.

 

No surprise therefore that such a Nina type signal dogs us with a sub tropical ridge problem with a string of anomalous sub tropical ridges across the NH mid latitudes with the Azores High spoiling the pattern in our vicinity - and only becoming 'useful' when the Pacific pattern temporarily retracts in Phases 1/2 and provides us with some Atlantic amplification.

 

This is pretty much where the 'negative' news is derived form.

 

The continued MT events, as described, should continue to provide us with plenty of vortex ammunition to follow up the upcoming split on the vortex. It is true that these stratospheric forecasts might upgrade - however the pre-disposition of the atmospheric state and the Nina signal rooting in the Indian Ocean and Western Pacific continues to favour the -EPO ridge blocking the wrong side of the pole and not cross polar ridging to our side of the pole, whilst at the same time supporting return of the Canadian/Greenland vortex when tropospheric wave activity has split the vortex our side of the pole. The models currently support this scenario. As bluearmy said earlier today, we could do with a longer window of a split and fast further wave 2 activity bombardment. As discussed, this is expected vis GWO orbit return to Phase 2, but can it happen soon enough before the vortex has chance to reform once more across the pole?

 

Its great to have a weak vortex which is amenable to splitting quite easily this winter. However, it can be seen what the requirements are to take advantage of these splits. The unfavourable Pacific and sub tropical pattern is very much cancelling out (at the moment) the attempted cold pattern feedbacks over the polar field.

 

With regard to your own reference to reliable sources (and they are very reliable and impartial) : on the basis of what I have been discussing (not for the first time) understanding is becoming greater why the METO suggested a prevailing +NAO pattern into the winter with greater uncertainty into the second half of the winter.

 

There remains obviously plenty of time, and the watch is how we can break out of this atmospheric rut during January, to take advantage of a very weak and vulnerable vortex and transfer its goods to this side of the Northern Hemisphere.

 

Hope that helps clarify things somewhat  

Edited December 28, 2014 by Tamara תָּמָר

[Allseasons-Si]

Some heavy snow showing for the South out in the run.

 

Forgive me for saying this PM,but that's 300hrs away,can i have it @ 12hrs please :smiliz19:

[Nick F]

Arctic high showing face around t+150 on the 18z op, it even causes a temporary weak split between the deep cold vortices over Canada and northern Scandi/NW Russia allowing H500 rises over Greenland. But still a strong zonal jet in place to the south across the UK.

Don't think the models will have complete confidence in the Arctic high's cross polar spread, so we may see some interesting evolutions pop up from time to time in coming days, especially if the Arctic high drops this side to coincide with an amplifying mid-Atlantic ridge.

It seems as though the GFS op often re-organises and strengthens one big H500 vortex at higher latitudes into deep FI if there are signs of a temporary split, so not overly concerned until the models resolve the Arctic High's influence this side of the pole.

[Frosty.]

Roll on 10th Janvier, looks very wintry on 18z parallel universe run :-)