Model output discussion - 5th December 2016 - Into Winter we go

[Hotspur62]

Well after alot of uncertainty over the last few days it seems that the potential for a cold spell has well and truly gone down the plughole and the sight of Uncle Barty and the pv seemingly wake up in the wrong place in the coming days is not a sight i wanted or had hoped for .On top of that no lowering of heights in the Med and it looks like we need snookers for any chance of a white xmas. As CC stated on here and has been banging the drum for a while(Fair play to him) he has never bought into a colder spell that so many others thought/hoped for.I know we are not mid-month yet but history tells me as well as the models that it would take the mother of all flip backs for a cold spell to arrive anytime soon.North America has once again nicked all the cold and looking at LRFs for that side of the pond it looks like many over there will be having a white xmas( either snow on ground or falling). 

Still enjoying this forum though even though it has been painful to watch this week and just hope that a "miracle" happens and the models suddenly flip to cold(I know-there"s a pig up there in the sky lol!!)

[carinthian]

1 minute ago, blizzard81 said:

Many thanks for posting this Carinthian. This is what I have been trying to stress as a real contender in about 7 to 8 days time from now. The trend today has been to strengthen those heights over scandi. I have also noticed over the years how good the ukmo is at forecasting scandi highs

Yes Blizzard, its now our only hope. Funny enough , just got our latest snow portal update ( Austria ) and they go for a major drop in temperature in 8 days time with snow in the forecast. So I would assume some sort of under cut under the high pressure , whether this affects the UK eventually will all depends if a Scandi high can be prolonged. Lets hope, will be watching closely.

 C

[fromey]

6 minutes ago, Hotspur61 said:

Well after alot of uncertainty over the last few days it seems that the potential for a cold spell has well and truly gone down the plughole and the sight of Uncle Barty and the pv seemingly wake up in the wrong place in the coming days is not a sight i wanted or had hoped for .On top of that no lowering of heights in the Med and it looks like we need snookers for any chance of a white xmas. As CC stated on here and has been banging the drum for a while(Fair play to him) he has never bought into a colder spell that so many others thought/hoped for.I know we are not mid-month yet but history tells me as well as the models that it would take the mother of all flip backs for a cold spell to arrive anytime soon.North America has once again nicked all the cold and looking at LRFs for that side of the pond it looks like many over there will be having a white xmas( either snow on ground or falling). 

Still enjoying this forum though even though it has been painful to watch this week and just hope that a "miracle" happens and the models suddenly flip to cold(I know-there"s a pig up there in the sky lol!!)

I am getting very confused because the post above yours from blizzard81 also quoting Carinthian says the opposite!

fromey 

[blizzard81]

7 minutes ago, carinthian said:

Yes Blizzard, its now our only hope. Funny enough , just got our latest snow portal update ( Austria ) and they go for a major drop in temperature in 8 days time with snow in the forecast. So I would assume some sort of under cut under the high pressure , whether this affects the UK eventually will all depends if a Scandi high can be prolonged. Lets hope, will be watching closely.

 C

I think this potential for approximately next weekend will be built upon over the next 24 to 48 hours. If I am reading the debilt ecm ensembles correctly, there is a cluster of easterlies starting from day 8. These were not showing on the 00z ensembles.

[blizzard81]

7 minutes ago, fromey said:

I am getting very confused because the post above yours from blizzard81 also quoting Carinthian says the opposite!

fromey 

Just differing opinions

[fromey]

Just now, blizzard81 said:

Just differing opinions

I know, it's just getting very confusing

i value every ones views and input, but boy it's one hell of a rollercoaster

fromey 

[Daniel*]

1 hour ago, Snowmut said:

What,Bob?..must be another war in the Pacific!!

No, quite the opposite. 

I don't understand the mass hysteria myself. Some folks don't like the background signals but this one I think is going to underpin our destiny. GEFS and jma MJO forecast takes us to phase 8 on the run up to xmas - which has a ripple effect, in the northern hemisphere, it could be the shake up we've been looking for. This is a high amplitude phase, known to help produce northern latitude blocking. I don't understand the dynamics. Therefore it's a v positive 'forcing' with the current state of low angular momentum being a thorn, spoken by the likes of Tamara, it may be the piece of the puzzle, we've been looking for, so a proper cold pattern can come about. I'm calling for a change of fortune in the model output in the coming days ahead, from late Dec into early January for UK to see a genuine cold spell from the E. Forsooth, I've cursed it well we'll just have to see.  

Edited December 9, 2016 by Changing Skies

[knocker]

This evening's anomalies are not a great deal of help in attempting to be definitive even in the 5-10 time frame. No big surprise that NOAA and GEFS seem to be nearer the same ball park with the EPS dissenting. The problem appears to arise with the precise orientation of the Aleutian HP and the Canadian Vortex. Certainly the EPS has a different angle on the former. Downstream slight variations on the angle and depth of the Atlantic trough which in combination with the different interpretation of the strength and orientation of the European HP lead to different levels of amplification in the Atlantic which will invariable lead to different day to day surface evolutions.

On the face of it NOAA (especially) and the GEFs with the ridging adjacent to the UK and fairly strong positive anomalies to the NE would incline to better weather as systems generated by the upper trough to the west will track NE in the strong thermal gradient. The EPS, with the HP further east is tending slightly flatter. Essentially this mainly variations by degree and made come out in the wash as we move forward

Well it doesn't come out in the wash in the 10-15 time frame. The EPS remains the lone wolf upstream and thus the amplification downstream with a negatively tilted trough to the north west. NOAA would certainly be the better outcome with quite a slack upper flow and the possibility of the surface HP being quite adjacent to the south east.

[Hotspur62]

2 minutes ago, fromey said:

I know, it's just getting very confusing

i value every ones views and input, but boy it's one hell of a rollercoaster

fromey 

That"s why i enjoy this forum as it is about opinions.I just feel that the UK has missed out on a potential cold spell but hope i am well and truly wrong 

[bluearmy]

9 minutes ago, blizzard81 said:

I think this potential for approximately next weekend will be built upon over the next 24 to 48 hours. If I am reading the debilt ecm ensembles correctly, there is a cluster of easterlies starting from day 8. These were not showing on the 00z ensembles.

 Very few ice days (3 or 4) showing over there. An easterly flow in december would deliver ice days in holland, especially further south east. 

The new eps keeps the Atlantic trough that bit further west compared to the 00z run and sinks the low anomoly to our west a tad more taking the jet a little further south. Sceuro ridge little more defined. The GEFS and eps perhaps beginning to come together?? 

Edited December 9, 2016 by bluearmy

[nick sussex]

18 minutes ago, blizzard81 said:

The ecm 10 day ensembles for debilt seems to show a cluster of easterlies at days 8 to 10

Yes theres a cluster which look like keeping the high further north, wind directions between east and se with much lower dew points. The much  bigger cluster though does look to have the high further south.

Generally in these situations with a strong signal in the GFS/ECM to become even flatter and drive the jet ene after day 7 then its the starting point re base position of the high earlier that's important, because once the topple happens any cold advection westwards is set at that point.

For that reason we should be looking quite early on for any small changes be it in either sharpness of upstream trough and slower more amplified shortwave exiting the ne USA to see whether we can get that high further north.

A crucial time is when that shortwave phases with the troughing to the west between T96 and T120hrs, at this point you'll get some energy thrown towards the high, how much goes se versus ne.

I'm doing my best here to turn an underwhelming rom com into something a bit more exciting!

[Summer Sun]

You couldn't make it up!!

 

Edited December 9, 2016 by Summer Sun

[bluearmy]

We saw the GEFS make a step towards the eps solution so why are we surprised to see the new eps make a step towards the GEFS? (Especially as we know glosea is in the GEFS court)

[northwestsnow]

Are coldies being trolled?

Bit of hope that theres some easterlies for de bilt, but im really not sure i can believe there is any 'legs' in them....

[damianslaw]

Some good posts in the past 30 minutes, yes eyes on whether we see a more sharpened trough feature exiting the NE USA seaboard at the 144hrs, which will induce a more pronounced amplified low, allowing the ridge to our east to become more north-south aligned rather than east-west aligned which in turn would force the jetstream on a more NE path, meaning the current progged deep low shown on today's models rather than taking a more east-west path, will be forced NE, and crucially enable heights to build in more strongly from the SE aided by the azores high which will be able to ridge north as well.

I'm not seeing an easy ride for the atlantic zonal train, the ridge to the east looks a strong feature. In time it could very easily anchor itself into a position that enable the UK to sit on the colder side of the jet, before December is out.

I suspect the models will be painting a very different outlook 240 hr timeframe this time next week than they are now.

[bobbydog]

Having had a busy day and only briefly had a chance to look at the models throughout the day, I was dreading coming on here.... however, despite the initial  ( only to be expected and probably justified ) doom-mongering, I'm pleasantly surprised by the positivity and objectivity tonight. Miserable "Winter's over" posts just add to the... well... misery! So it's nice to see optimism in the face of adversity. The models don't look great and it's difficult to find any positives at the moment but we've seen changes for the worse happen in the matter of a couple of days. There is always the possibility that in a couple of days time we see the opposite happen. There is still 2 weeks until xmas and that is a very long time in weather terms. After that there is still over 2 months of winter left. Keep the spirits up, look forward to xmas with the family and maybe we'll get a little bit of luck. 

Even just a couple of days of decent snow would do, just so my little Molly gets to build her first snowman. 

[nick sussex]

At T72hrs the GFS 18hrs run looks a small upgrade compared to the earlier 12hrs, the troughing to the west digging a bit further south and further west.

[gottolovethisweather]

The expected ECM operational D4 chart as posted on my post from Monday evening.

The actual reality is shown below, for 1300hrs Friday.

 

Regions highlighted in red were those which I believed we had to pay particular attention to. Well it turns out at a t+96 timescale, Monday's ECM 12z wasn't far off the mark (hence the UKMO give it more credence than the GFS for example in their analyses). If anything the Upper Air patterns have backed further to the West by a few hundred miles. This might explain why the USA has been plunged into Arctic type conditions and us in the UK remain at the other extreme. The temporary extension of WAA due NNE of the UK and positive heights anomalies over in the North Pacific were also well-forecasted at such a range.

Monday's D5 chart for this Saturday, was as indicated below.

The corresponding D1 chart for t+24hrs 1300hrs tomorrow is now predicted as follows.

Again the D5 range chart wasn't too far off the mark, although the regions highlighted in red have shifted, the Pacific Heights cover a larger area than expected and again are aligned further Westwards towards Canada and the USA. Sadly for coldies, the heights are stronger than forecast towards our South and across towards the Azores. However, the behaviour of Canadian vortex (trough?) incoming from the North Atlantic could yet force ever stronger heights ahead of it towards our North. This is where my prediction of more solid heights towards our NNE and NE (Scandinavia region) comes in and if we look at the D8 chart for the 13th December I threw in for a laugh on Monday's post; we can see how the ECM handled that aspect at the time.

 

Right now, said chart would be D4 so clearly within the reliable, yet did it look similar to current predictions? let's take a look.

Crazy differences over in the Pacific, almost 80mb differences in Air Pressure readings, for one thing, a deep trough where there were once forecast substantial heights. The WAA currently expected by D4 in the Eastern Pacific is what holds my interest, and I think it is this that will bring about some colder solutions post the 13th December. Conversely, the Eastern Seaboard Atlantic picture and the substantial heights to our South and Southwest are holding firm. As the NWP outputs have largely struggled past D4 as proven in this analysis of simply the ECM 12zs, I would take the following D5 and D8 ECM charts with a truckload of salt. Thankfully, we can likely discount the final chart which isn't at all kind to coldies, in the hope that the D5 example has say a 70 to 80 percent chance of verifying, so could be much nearer the eventual reality. Of course, it is where we go from here that counts and the GEFS and ENS ensembles will provide more guidance in such instances.

Once the models come to some sort of agreement on developments over in the Pacific with one eye on the depth of cold in the US, we can be a bit clearer as to what Christmas week itself might bring.

All the best.

gottolovethisweather

 

 

Edited December 9, 2016 by gottolovethisweather

[phil nw.]

29 minutes ago, knocker said:

This evening's anomalies are not a great deal of help in attempting to be definitive even in the 5-10 time frame. No big surprise that NOAA and GEFS seem to be nearer the same ball park with the EPS dissenting. The problem appears to arise with the precise orientation of the Aleutian HP and the Canadian Vortex. Certainly the EPS has a different angle on the former. Downstream slight variations on the angle and depth of the Atlantic trough which in combination with the different interpretation of the strength and orientation of the European HP lead to different levels of amplification in the Atlantic which will invariable lead to different day to day surface evolutions.

On the face of it NOAA (especially) and the GEFs with the ridging adjacent to the UK and fairly strong positive anomalies to the NE would incline to better weather as systems generated by the upper trough to the west will track NE in the strong thermal gradient. The EPS, with the HP further east is tending slightly flatter. Essentially this mainly variations by degree and made come out in the wash as we move forward

Well it doesn't come out in the wash in the 10-15 time frame. The EPS remains the lone wolf upstream and thus the amplification downstream with a negatively tilted trough to the north west. NOAA would certainly be the better outcome with quite a slack upper flow and the possibility of the surface HP being quite adjacent to the south east.

Yes Knocker the upstream modeling continue to create the differences with the GFS and ECM  with the lattershowing a flatter Atlantic pattern.

It may or may not be some comfort to coldies that the ECM ens at day 10 highlight the Aleutian area as the big spread in it's modeling solutions.

 

maybe related to the uncertainty in the tropical forecasts?

Anyway that uncertainty is shown to a lesser degree in the downstream Atlantic pattern right across towards Scandinavia.Maybe more changes in the models to come.

[Gael_Force]

2 hours ago, LRD said:

Evening all

First post. Been a long time lurker.

I wish my 1st post was able to talk about positives! The models look shocking and after all the expectation, the last few days, as realisation has started to sink in that cold was becoming an ever-distant prospect, have been a real disappointment to folk like me who like cold in winter. Got to say that I don't ever recall a winter where the longer term models have been proved so wrong (so far).

Don't think we should be giving up on longer term models though. GLOSEA has performed well in the past. Some have been calling to stop bothering with longer term models but that's defeatist. Got to keep learning and improving understanding. That's what science is about

 

 

Welcome! 

I'm afraid it is only the longer term models we cannot see which have built the idea of a cold early winter. Not one of the online (for all to see) models showed anything but a varying degree of positive for temperatures. The fact the UKMO had such confidence in their own products has allowed eyes to be taken off the ball and ignore the less palatable options from other forecast agencies.

[nick sussex]

Dramatic developments on the GFS 18hrs run! Almost, just needed some more energy going se but the high is orientated more favourably.

Edited December 9, 2016 by nick sussex

[Ravelin]

Definitely a more N/S aspect to the ridge to our west...

12Z   18Z 

Edited December 9, 2016 by Ravelin

[bluearmy]

18z Shows what might have been possible if the Atlantic jet wasn't so strong. Remember those GEFS run from last Saturday which showed winter coming this week. They had the Atlantic jet too weak. will be interesting to see fi if the picture remains very amplified at day 8.  Nearly all of the wacky cold fi runs have been on the back of a very amplified day 8 (not surprisingly)

[nick sussex]

Very frustrating GFS run, the cold air is much further north but just most of the energy going over the top. As BA just mentioned without that jet on steroids we'd see that cold air advected westwards. Last winter we hardly ever saw any pressure rises to the ne and so far in the last few weeks we've had several chances which look like being close but no cigar.

Edited December 9, 2016 by nick sussex

[Seasonality]

Talk about beast from the east from the 18z. Look at the cold pool! Proper cold for central and eastern Europe if it verifies.

Edited December 9, 2016 by Seasonality