Model Output Discussion - The Start Of Winter

[johnholmes]

Guys & Gals.....

 

Many thanks for the responses....I appreciate them and how everyones viewpoint and take ont he outputs are interpretated individually... i am forever learning!!!!

 

keep up the fantatstic effort all....  it really makes this forum the best place to be for the likes of myself and other `wannabes` lol..

 

 

 

Marty, go to the Guides section as you will find lots of information on how to read charts and lots of other interesting articles, again if something is not clear then please ask.

[nick sussex]

The GFS P is the best solution in terms of trend from a cold perspective with low heights finally lifting away from Greenland and it develops that more amplified eastern USA troughing at T192hrs.

[Ali1977]

Agreed Nick, GFS P looks much more subject to a pattern change..Surely this is the better model isn't it?  Anyway, still no consistancy from the models.

[Backtrack]

Nothing like an Azores High for ruining your Christmas. 

 

There's still hope in the GFS though.

 

Should the jet stream move northwards, allowing the Azores High to build, it could well move north eastwards and give us a settled spell of weather.

Granted that there aren't many, if any solutions which bring this into play, but it's always a possibility. I don't know about you, but I'd take a cold, crisp & sunny Christmas over a rainy, Atlantic-driven Christmas any day of the week?

 

This being said, it's December 11th, Christmas day itself is two weeks away, and this is well beyond the reaches of high resolution, bringing it into the depths of FI. I think for now, attention should be drawn to the short term, especially as we have a frontal system bumping into some colder air tonight, in ADDITION to drawing colder air in with it. This will give many northern areas of the UK a snow event, for a short while at least.

 

I'd focus less on Christmas until it's within the 5-7 day range, where a general idea can be drawn as to what the weather may be like on that particular day.

Edited December 11, 2014 by Backtrack

[nick sussex]

Agreed Nick, GFS P looks much more subject to a pattern change..Surely this is the better model isn't it?  Anyway, still no consistancy from the models.

Yes in terms of verification compared to the normal GFS but you can see its vastly different at the T192hrs timeframe compared to the 00hrs run but if you add this to the mornings ECM operational run then some signs that the PV might relent from Greenland.

 

I certainly wouldn't be booking the Mariachi band yet though because we need to see that lifting of low heights at T144hrs. Overall though I'm a bit more optimistic for the Christmas period , I'd rather we suffered the underwhelming output now and saw this change in time for Christmas, theres nothing worse than mild dross at that time.

[Ali1977]

I wonder if the "interesting signs" are still showing within the METOs output today, they have been spot on not jumping on the occasional cold charts we have had in the last few weeks and stuck to their guns..These height rises over the pole and Greenland that are popping up might be something they are watching closely!!!

[Iceaxecrampon]

06Z

 

The utter turmoil of Model watching........

 

 

 

Ian

 

 

 

 

 

 

 

 

[IDO]

Looking at the latest JMA week 2 upper anomaly it ties in very strongly with the current GEFS output: 

 

A flat Asian/Pacific jet, heights to the south, US and Russia and the UK under the influence of lower heights. For week 3-4 it looks like the influence from the NW and the south shifts (Azores) and the zonal flow may favour a more N/S split:

 

 

Certainly no clear sign in the NH for anything remotely like a NH blocking pattern setting up.

 

Looking at the CFS MJO and it returns to phase 5 in January after a hint of the Circle of Death: 

 

Composites: 

 

Though whether the MJO is still the main driver by then is debatable. I still get the impression that the trop is not looking helpful for a HLB in our region so we are relying on an SSW and for that to favour us. Although the CFS is consistent with Northern blocking Feb-March and also Jan now going that way, it rarely favours the UK. Again the US and Russia/Siberia looks like getting the bitter cold:

 

 

The strat experts are more knowledgeable as to if this is likely when the SSW occurs or is CFS misreading the signals? So a waiting game for 3-4 weeks in the hope the SSW does indeed develop. 

 

 

[bluearmy]

06z gefs anomolys again provoke interest as we head through week 2.

Seen worse ways to end a year!

[Captain Shortwave]

I wonder if the "interesting signs" are still showing within the METOs output today, they have been spot on not jumping on the occasional cold charts we have had in the last few weeks and stuck to their guns..These height rises over the pole and Greenland that are popping up might be something they are watching closely!!!

Maybe just maybe some people should take a look at the GFS ensemble mean from Christmas onwards. That is not normal. Strong positive ridge over western side of north America with an amplifying pattern downstream (Atlantic ridge/scandi trough). I can't post charts as I'm at work so see for yourself. Unusually strong signal for the polar vortex to take a pounding at the lowest levels around and post Christmas.

Edited December 11, 2014 by Captain shortwave

[mountain shadow]

Is this a sign of change in the extended NAO forecasts?. Yes, all but one is positive, however, there is a marked dive towards the end across the suite. I would take any model output showing a strong Azores High in FI with a large pinch of salt at the moment.

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gif

 

 

Hopefully a potential cold spell beginning around New Year finally creeping into view.

[Jamesjane]

The much signposted upcoming pattern is entrenched in the D10 charts:

 

GEM gemnh-0-240 (3).png ECM: ECH1-240 (6).gif

 

GFS P: gfsnh-0-240 (2).png

 

A very Atlantic driven period for the next 10 days plus. Obviously ECM has potential but I always discard the amplification (from D8-10) and look at the overall flow, especially when it has little support. Down south surface wise it translates to average temps overall: 

 

graphe6_0000_306_141___Londres.gif

 

The GEFS at D16 show no signal for a MLB or HLB in our region and the mean remains similar to D10: gensnh-21-1-384 ( .png

 

So the most likely solution till the end of December (at the moment) is a westerly flow with a mix of PM and TM shots. The mean of the 850s matches the 30 year average for London so normal December fare:

 

MT8_London_ens.png

 

I would say 75% certainty for the next 10 days then dropping to about 50% in that pattern continuing till D16. The extra uncertainty is in how the Canadian PV lobe is dealt with. The overall consensus is that it will

The much signposted upcoming pattern is entrenched in the D10 charts:

 

GEM gemnh-0-240 (3).png ECM: ECH1-240 (6).gif

 

GFS P: gfsnh-0-240 (2).png

 

A very Atlantic driven period for the next 10 days plus. Obviously ECM has potential but I always discard the amplification (from D8-10) and look at the overall flow, especially when it has little support. Down south surface wise it translates to average temps overall: 

 

graphe6_0000_306_141___Londres.gif

 

The GEFS at D16 show no signal for a MLB or HLB in our region and the mean remains similar to D10: gensnh-21-1-384 ( .png

 

So the most likely solution till the end of December (at the moment) is a westerly flow with a mix of PM and TM shots. The mean of the 850s matches the 30 year average for London so normal December fare:

 

MT8_London_ens.png

 

I would say 75% certainty for the next 10 days then dropping to about 50% in that pattern continuing till D16. The extra uncertainty is in how the Canadian PV lobe is dealt with. The overall consensus is that it will move east in the first 10 days then return back towards Greenland/NE Canada afterwards.

move east in the first 10 days then return back towards Greenland/NE Canada afterwards.

I am very new to model watching and am trying to learn all the time but how can one be 75% certain for a whole 10 days..surely even the MO cant do this..

[No Balls Like Snow Balls]

Latest ECM Snow total charts from WSI via twitter.

UK daily snow totals (in centimeters) decreasing in drier, although still cold, air from the north-west.

[Gavin Hannah]

Just taking a look at the latest ensembles, very few members are going for a raging swerly jet and mild temps. Even out in FI. The majority of members are showing PM and LP to the north-ish. Think I even spotted the odd scandi HP appearing in one or two of them.  In a nutshell, I think it looks like the majority of the country is going to keep on getting normal winter weather with temps around average or slightly below. And with PM lows in the main feature/pattern, plenty of chances for snow the further north you go.

[IDO]

I am very new to model watching and am trying to learn all the time but how can one be 75% certain for a whole 10 days..surely even the MO cant do this..

 

I am no expert, but zonal weather has a very high confidence level. 75% was building some uncertainty in due to the weather always has the prospect of surprising you. However I am nearer to 100% with regard to the upcoming 10 days. Obviously surface conditions are a very different matter as these are variable dependant on how flat the pattern is and where the jet sets up.

 

The mean for the 15-20th is an example:

 

  WSI_EuroEnergy

Mostly windy N Europe and wetter NW persisting next week in association with persistent marked low pressure. http://t.co/pMx3oMYhkS

11/12/2014 13:18

 

The PV is on the move from west to east and there is little chance of anything other than a strong negative height anomaly to the north. ECM and GFS 8-10 day anomaly very closely matched:

 

 

That is a very flat upstream flow. 

Edited December 11, 2014 by i'm dreaming of...

[MR EXTREMES]

where?

 

1.gif 2.gif

 

3.gif 4.gif

 

5.gif

sorry karl old chap, but theres nothing wintry next week on these runs except for the far north. in fact its looking like the mild weather you and most others dont like looks like being pretty dominant IF these charts varify... of course they may well change, but i believe these charts

 

610day.03.gif 814day.03.gif

 

do support a gradual change from a north of west upper flow to a westerly with the flattend jet north of a strong azores high... and this is manifest in the current opperational runs.

And to be fair westerly flow can be cold.

[johnholmes]

I am very new to model watching and am trying to learn all the time but how can one be 75% certain for a whole 10 days..surely even the MO cant do this..

hi James

I use the 500mb anomaly charts as the best 'guide' to the upper air pattern in the 6-15 day time frame. Correct, with some provisos, about 70-75% of the time for the upper air pattern. It is the upper air pattern which largely governs what occurs at the surface. Mind you trying to work out the bottom 500mb (approx 18,000 ft) is the tricky bit. Ignore the anomaly parts, shown as - or +ve on those charts, just look at what direction the contours (isobars if you like at 500mb) are showing for an idea where the weather is going to come from. Please feel free to pm me for a chat about these if you wish. Also take a look at the Net Wx Guides for more help.

As a favour can you pop your nearest town in your avatar please then we all know where you are reporting your own weather from?

thanks

Edited December 11, 2014 by johnholmes

[mushymanrob]

And to be fair westerly flow can be cold.

 

yes it can, but the current ecm (i chose this as its the best performing model ) would not suggest next weeks a cold westerly. its even suggesting the +10 (upper) isotherm over the southwest! briefly... thought two things... one i accept that the ecm might be over amplifying the uppers next week, and two, when frosty made that comment the charts might well have been showing alot more polar maritime incursions. i dont know, im guessing he was too busy to post charts to support his post. im as guilty of that as anyone but it does highlight the need to.

[Mucka]

It is not so much those two posts were conflicting, they weren't, they were just describing different aspects of the MO.

 

What we see posted here are mainly Operational charts but they still come from 3 or 4 different models so will have differences among them but there are also the ensemble suites which contain dozens more runs between them and within these there are also variation so while an Operational GFS or ECM run may show one patterns setting up several members among the ensemble suite may show something else. This is what the ensembles are for, to test the plausibility of the operational output and so you will often read a different interpretation of what is being shown within the ensembles to that which is shown by the Operational output.

 

Of course a lot of people on here, as I, are constantly on the look out for where and how we can get some cold air over the UK both by tweaks to what the current output shows and where the models may err at larger timescales. So you have face value Op chart discussion, ensemble interpretation discussion and future pattern and probability discussion all within one thread which can be difficult for newcomers to separate if it is not well explained.

It is not that members try to be cryptic or obscure or send conflicting messages (except where there is direct disagreement on what one particular chart may show), it is more that is just difficult to always keep in mind the appropriate level of description and add caveats to their posts where necessary.

 

On top of all that even where there are two conflicting views on the same data there is often no right and wrong, just opinion, and which opinion you go with will be down to your personal taste and experience of the posters involved but bear in mind nobody is always right and those that are prone to seek to find upcoming pattern changes in longer range output will wrong more often than those that stick to the safety (or more sensible realms) of the current and 3 to 5 day output.

That is to say, the further we attempt to predict or discuss possibilities beyond the 5 day range more likely we will come a cropper. 

 

That is why questions are always welcome by newer members as you are very likely not only clarifying things for yourself but for many others too, as noted by the amount of up votes the question got. 

 

My interpretation of today's output.

Not good.

 

Actually nothing has changed except beyond 5 days where the models are beginning to firm up on the Azores high becoming more influential which essentially means any cold air will more likely be pinned to our North as low pressure is forced on a more Easterly rather than Southeasterly path giving a shallower trough or at least forcing it further East so that the UK only receives a "glancing blow" from any Northerly around day 6.

Below examples 144h by increasingly influential AH with the first showing it displaced West and then the next two showing it less so.

Thus,

 

GEM Northerly cold air pushing down across whole of UK. 

 

 

UKMO glancing northwesterly cold air getting quite far south but shorter lived and less cold further West. 

 

 

GFS 06z, shallow trough, no northerly, cold air pinned North.

 

 

Note how high pressure to our SW is increasingly forcing a flatter longwave pattern over our shores. We would describe the GEM as an amplified pattern and the GFS as a flatter pattern and it is always reasonable to assume we are talking about our region unless mentioned otherwise.

We might also describe them by as a deeper and shallower trough, there are often many ways to describe what is essentially the same thing.

So there you have 3 operational models for the same time-frame showing 3 different weather types for the UK yet the actual broad-scale differences in the pattern are tiny.

 

This is why it is a matter of opinion as to which is most likely correct but as noted by others, taking all the data into account the "trend" is for the Azores high to become more influential but that can easily change back the other way. As we get closer the models will come closer to consensus and we will be able to forecast with greater certainty.

We should have a very good idea by Tomorrow evenings runs but a said the trend is for a less cold flow to develop over that period.

 

Naturally it follows that this also affects the trends for later with this mornings GFS being a bit of no go for cold fans and those hoping for any chance of snow around Christmas with the Azores high pushing NE.

 

ECM offers some hope with the trough setting up to our NE which would likely keep the AH displaced West and the pattern more amplified (or about to be over UKm explained shortly) though any cold would be fairly transient so we would need to get lucky on the timing re any hope of snow for Christmas and the pattern generally favours those further North though it is possible to get a decent UK cold snap out of such a synoptic but we would need several improvements on the raw ECM 240 chart for that which I won't go into in this already over long post.

Below GFS and ECM 00z contrasting 10 day output which makes clear how the Azores high plays a big part in our weather. (Though confusingly the GFS is actually the more amplified pattern, it just has it setting up too far East for the UK to benefit. If it modeled the same 500/1000 miles West it would be cold. ECM is flatter but about to become more amplified as low pressure develops and moves SE displacing the AH back West. So even here we can see it is debatable which pattern is best even though as a snapshot ECM is the better chart for the UK re bringing in colder air over the next day or two from there)

What is certain that both will look different on this evenings run so we can only talk in general terms this far out.

 

 

 

Hope that helps some of newcomers decipher the discussion and understand why "conflicting" messages may appear.

I have only touched upon some of the basics but once you have these you can better understand some of the more technical discussions and add layers to your knowledge with anomaly charts and such, you may even feel brave enough to visit the brilliant Stratosphere thread and read some of the fantastic posts within which looks at longer term still and some of the teleconnections that affect the PV and what in turn that may mean for future HLB/MLB prospects which we need for sustained cold. 

 

Last word on long range prospects with the above two images in mind.

We can hope the GFS is correct and backs the pattern West which with a little more amplification upstream would be very good but if it is as far East as it is being modeled and any flatter it will be the opposite, very bad.

With ECM we could do with much stronger heights to our East to stop the trough just pushing through and again the pattern would benefit from being a little further West and more amplified.

Edited December 11, 2014 by Mucka

[No Balls Like Snow Balls]

From Mark Vogan Weather

N England snow event: Both GFS & ECMWF have coating to 1" for low levels, up 6" over the Pennines next 36 hrs.

Edited December 11, 2014 by No Balls Like Snow Balls

[TonyH]

From Mark Vogan Weather

N England snow event: Both GFS & ECMWF have coating to 1" for low levels, up 6" over the Pennines next 36 hrs.

B4lVaL4CAAARGcp.png large.png

He could be right but not a source I would rely on

[offerman]

Hi Mucka, can you help explain something for me please.

 

On those charts you posted above why is it that the Azores high never links with the Greenland high. Also how come the A.H just sits in that same location for weeks on end ?  

 

Is it something to do with earths internal magnetic differentials?

 

I once saw an amazing documentary on bbc with a very good , passionate , black lady presnter and in it she mentioned 6 very strong magnetic internal independent areas across the globe with Southern spain having one of these areas. Could it be that that stops the high moving very far afield, I.E retrogressing in to the central Atlantic  or North linking with Greenland high.

 

Your charts above clearly show everything shifting quite quickly accept the Azores high which only changes its shape not position.

 

Many Thanks.

[Mucka]

Hi Mucka, can you help explain something for me please.

 

On those charts you posted above why is it that the Azores high never links with the Greenland high. Also how come the A.H just sits in that same location for weeks on end ?  

 

Is it something to do with earths internal magnetic differentials?

 

I once saw an amazing documentary on bbc with a very good , passionate , black lady presnter and in it she mentioned 6 very strong magnetic internal independent areas across the globe with Southern spain having one of these areas. Could it be that that stops the high moving very far afield, I.E retrogressing in to the central Atlantic  or North linking with Greenland high.

 

Your charts above clearly show everything shifting quite quickly accept the Azores high which only changes its shape not position.

 

Many Thanks.

 

Hi, I will be brief because we are veering off topic and there are other threads people will be able to point you to that are more appropriate.

Essentially the Azores high is a semi permanent anticyclone (high pressure) so called because it is located around the Azores region. It tends to exist at around 30 degrees North latitude in Winter (just to our South) and move north in summer.

It is part of a belt of high pressure systems that dictate Northern latitude weather patterns.

 

On the charts I posted or on any chart a part of the PV naturally exists around the Greenland area which spawns low pressure systems which run across the belt of high pressure West to East (typical zonal winter pattern) this series of low pressure systems prevents high pressure ridging North.

When the jet is more southerly it can force low pressure further South "amplifying" the pattern and high pressure can be displaced from its usual home.

In such circumstances we can get a cold zonal flow such as we have now with the Azores high displaced West of its usual home.

If we can also get the PV weakened or moved from Western Greenland then we have the prospect of a ridge of high pressure building in the Atlantic but this also requires low pressure to dig into the Azores highs Western flank and push WAA polewards. When this occurs we can get high pressure into Greenland as low pressure undercuts the Atlantic ridge and forms a "cut off" high in that region. This not a typical pattern but such HLB can be very beneficial in dragging in very cold polar air from the NE.

 

When the jet is flatter the Azores high will ridge into Southern UK and Western Europe giving us milder unsettled weather (typical zonal). Where the PV is weak and low pressure system slow and weak to travel East to West then Azores high can build across the UK and form  a UK high.

There are many more variations too numerous to mention here.

 

At present there is no sign that we will build a strong Atlantic ridge within the next 10 to 12 days but looking at GFS 00z we can foresee how modification to that pattern might allow for it.

 

Hope that helps.

Edited December 11, 2014 by Mucka

[fergieweather]

I wonder if the "interesting signs" are still showing within the METOs output today, they have been spot on not jumping on the occasional cold charts we have had in the last few weeks and stuck to their guns..These height rises over the pole and Greenland that are popping up might be something they are watching closely!!!

Yes, albeit with the caveats of uncertainty previously expressed..

Expect the broadly W to NW flow bias to dominate through next 10-15 days with good broad confidence. Towards end of this trend period, both some MOGREPS and EC members (n.b. bear in mind we always follow postage stamps closely, rather than just ENS mean, as latter tends to become skewed by leaning towards the climatological more 'energetic' influence eventually, i.e. prevailing westerly/zonal) hinting at height rises initially to S / W / E (varied emphasis thereof) of the UK, with some recent longer-range NCEP-GFS members also suggestive of same signal. This may, or may not, prove to be an initial phase of a zonal relaxation or subsequent complete reversal but mechanism for this is enigmatic, noting a continued GloSea signal (post-d15) for some northerly blocking solutions appearing amongst members into end December-early Jan.

Edited December 11, 2014 by fergieweather

[SMU]

Afternoon all-

 

Just been keeping a watching view over the last 48 hours-

 

the GFS at 144 on the 12z has changed the orientation of the upper flow- from Sw to NW, so along the boundary places like London for example have had the +8 isotherm replaced with the -2c isotherm

 

that's a 10c swing!

 

Also reintroduced is the further potential for snow over Scotland- this time focussed more towards the NE-

 

S