Model Output Discussion - The Start Of Winter

[SE Blizzards]

You don't get to see Boxing Day charts like this very often, so enjoy!

 

 

Of course, just for fun at this stage, but you just never know....

Edited December 15, 2014 by SE Blizzards

[johnholmes]

Now this is where I get confused. John says the anomaly charts show no change to the current pattern whereas others have posted anomaly charts showing expected HP into Greenland with resultant troughing to the East, which seems like a pattern change to me? Are different models showing different anomalies because I'm losing track!

Apologies if I'm just being slow on the uptake.

 

hi

I always use the NOAA and ECMWF-GFS anomaly charts, I do believe others use different ones.

hope that helps?

the links for me are below

NOAA

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

 

ECMWF-GFS

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[Long haul to mild]

hi

I always use the NOAA and ECMWF-GFS anomaly charts, I do believe others use different ones.

hope that helps?

the links for me are below

NOAA

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

 

ECMWF-GFS

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Thank you John, that helps my understanding. I suppose that, just like the operational output differs, so do the anomaly charts across different models and organisations.

[Mucka]

GFS being a terrible Scrooge this evening. Offering pressies  but they all turn out to be empty boxes with pretty ribbons.

 

10 days to Christmas though, let's enjoy the ride.

[Backtrack]

Parallel day 10

 

 

ECM day 10

 

 

I would take either of those at this stage.

 

 

Is that for the medium time-frame or the latter? For Christmas day they're great, a cold Christmas on the cards should either of those verify (which they won't). If it's the latter you're referring to, they're not so great, with the parallel at least, leading to a mild south westerly air flow by day 13.

 

For a quick, short-lived half-hearted cold spell, I'll take it. For an actual cold spell, something that some of us haven't seen for almost two years, I would bin the  GFS. The ECM COULD lead to something, but that's up in the air as of yet.

Edited December 15, 2014 by Backtrack

[Man With Beard]

Now this is where I get confused. John says the anomaly charts show no change to the current pattern whereas others have posted anomaly charts showing expected HP into Greenland with resultant Northerlies. Are different models showing different anomalies because I'm losing track!

Apologies if I'm just being slow on the uptake.

My take on the NOAA is somewhere in the middle - no MAJOR change that could be termed 'pattern change' (as I think JH's words were?), and not necessarily high pressure over Greenland but a raising of heights from what they are now over its southern portion. So potential for a slightly more amplified scenario?

But although the words "pattern change" are premature, a very small change in the North Atlantic could make all the difference for lowland areas of the UK - e.g. a more potent northerly, more penetration to the south, minus 8C uppers rather than minus 5C or 6C, snow falling in far more places, more convection via the Irish Sea etc. Because the northerlies we are currently experiencing are not a long way from producing this already - only a small increase in potency is needed.

I do wonder if we are going to see the odd op run going for something Armageddon-ish in the next 72 hours though - given its tendency to over-amplify Greenland highs, I'm almost expecting the ECM to split the vortex from Greenland through to the Aleutian High in a future run. To be taken with a pinch of salt unless it repeats it for 3 or 4 runs!

[nick sussex]

Now this is where I get confused. John says the anomaly charts show no change to the current pattern whereas others have posted anomaly charts showing expected HP into Greenland with resultant Northerlies. Are different models showing different anomalies because I'm losing track!

Apologies if I'm just being slow on the uptake.

You're not being slow at all. The problem with said CPC charts is that they lag behind any change especially when the models quickly start developing a trend. every single operational model output that goes upto T240hrs develops a more amplified wave working into the USA, the actual start is around the T168hrs timeframe.

 

The time when you're most likely to see big changes in the outputs is when you're moving from a flat upstream pattern to one more amplified.

 

The troughing which digs south into the USA is the catalyst for any cold for the UK around Christmas as this by its nature will help to lift low heights away from Greenland in tandem with a ridge pushing towards Alaska.

 

At this point it would be great to be able to say one way or another how this will fall for the UK, upstream troughing digging south normally correlates with ridge ahead of it in the Atlantic and a flow more nw/n into the UK , however the UK and cold is like England and penalty shoot outs!

 

I really hope the UK gets some luck here and the weather Gods deliver at least for the Christmas period, loads more outputs to get through before any certainty so its going to be a nerve shredding wait for the majority in this thread.

[Mucka]

Is that for the medium time-frame or the latter? For Christmas day they're great, a cold Christmas on the cards should either of those verify (which they won't). If it's the latter you're referring to, they're not so great, with the parallel at least, leading to a mild south westerly air flow by day 13.

 

For a quick, short-lived half-hearted cold spell, I'll take it. For an actual cold spell, something that some of us haven't seen for almost two years, I would bin the  GFS. The ECM COULD lead to something, but that's up in the air as of yet.

 

 

Hi,

yes I feel much the same way but reference chart is GFS (p) not GFS Op BTW.

 

I am talking longer term, 10 day+

I am talking in general terms and alluding to something Steve M explained earlier with the EPO and Atlantic ridge toward Greenland - that could form a formidable Greenland block if things fell right.

 

Of course at that range the details and outcomes will vary but that is definitely the sort of "big picture" potential pattern change we want to see setting up.

I am almost resigned to Christmas being snow free but know there is still enough wiggle room to see something more wintry develop.

Hand on heart I would say we are looking at transient cold if we are lucky at the moment on the big day and the real impact of any change in longwave patterns will be felt a few days later at the earliest (if 1st attempt successful)

 

All the detail is pure speculation though and as others have said it is more about the big picture (think anomaly charts and ensemble clusters etc) than pinning down the detail at this stage and in that regard we want things ro develop along the lines of ECM 12z, GFS (P) 18z.

Edited December 15, 2014 by Mucka

[Long haul to mild]

Thanks to rjbw and Nick for their views, I think I have a better handle on what to look for in the outputs.

I don't have a lot of scientific knowledge to add to the debate but what I will say is that many good cold spells and snow events that I can remember in recent times have appeared at around the T180 mark so I don't get too downhearted about model output 10 days plus ahead as things can and do change.

That is not to denigrate in any way longer range forecasts and output which I believe have much to offer too.

[Backtrack]

Hi,

yes I feel much the same way but reference chart is GFS (p) not GFS Op BTW.

 

I am talking longer term, 10 day+

I am talking in general terms and alluding to something Steve M explained earlier with the EPO and Atlantic ridge toward Greenland - that could form a formidable Greenland block if things fell right.

 

Of course at that range the details and outcomes will vary but that is definitely the sort of "big picture" potential pattern change we want to see setting up.

I am almost resigned to Christmas being snow free but know there is still enough wiggle room to see something more wintry develop.

Hand on heart I would say we are looking at transient cold if we are lucky at the moment on the big day and the real impact of any change in longwave patterns will be felt a few days later at the earliest (if 1st attempt successful)

 

All the detail is pure speculation though and as others have said it is more about the big picture (think anomaly charts and ensemble clusters etc) than pinning down the detail at this stage and in that regard we want things ro develop along the lines of ECM 12z, GFS (P) 18z.

 

Fantastic reply mate

 

I'm hoping that, even if the current pattern holds out until Christmas, we can squeeze a North Westerly out of it before the change, very up and down at the minute as you know, mild, cold, mild, cold, and despite the very up and down wave of things at the minute, it's been a reasonably balanced month with the CET running just 0.2C below the average.  Something has to give eventually, this being either the cold or the mild which wins out, after the warmest year on record, it only seems scientifically reasonable that we come to a stop eventually with a colder than average month, the charts at present not showing a month which is likely to come out below average (December). 

 

But as you say, I am hopeful of some kind of ridging developing in the Mid-Atlantic, holding to form a block. 

My favourite, and quite possibly most famous example of recent times being the below:

 

 

It's only a matter of time before we get a repeat, right?

One can't complain though at the current synoptics after last year's dismal performance. Promising times ahead!

Edited December 15, 2014 by Backtrack

[draztik]

Look out for an update from MattH on twitter regarding the updated EC32. The mean shows the UK and W Europe with a below average temp anom throughout & far from settled into January. 

Edited December 15, 2014 by draztik

[knocker]

Look out for an update from MattH on twitter regarding the updated EC32. The mean shows the UK and W Europe with a below average temp anom throughout & far from settled into January. 

And quite a significant trough north of the UK week 4.

[Frosty.]

All the effort put in on here in chasing cold weather is incredible and deserves some sort of reward. That reward will hopefully arrive in time for Christmas in the form of snow showers and frosts. There is certainly evidence in the output for a cold blast next week which will just be the appetizer for the main event in January..cheers

[Chris K]

Look out for an update from MattH on twitter regarding the updated EC32. The mean shows the UK and W Europe with a below average temp anom throughout & far from settled into January. 

 

And quite a significant trough north of the UK week 4.

 

If these are to coincide - it sounds like a pattern not too dissimilar from what we are just leaving? Perhaps a repeat NW'erly sourced PM flow being a dominant feature?

Edited December 15, 2014 by Chris K

[draztik]

And quite a significant trough north of the UK week 4.

I think the most notable charts were from the monthly control! Sending much of Europe into the freezer. Of course at that range..... but notable.

[Cloud 10]

Thank you John, that helps my understanding. I suppose that, just like the operational output differs, so do the anomaly charts across different models and organisations.

 

An important thing to remember when viewing the CPC charts,especially the 8-14 day,is that it shows the forecasted anomalies for a 6 day period,so can only really be useful at predicting the general pattern for that timescale,and not any real detail,which is where the daily ensemble mean and operational charts come in.

 

Nobody said it was easy though.

[Mucka]

In among all the uncertainty there are still some clearer signals emerging as we progress into this week.

It was less than 48 hours ago we were talking about a weak signal for some form of height rise either over the UK or to our West with only a handful of GFS ensemble members broadly illustrating such.

Now?

Now we have the majority going for strong height rises somewhere around the 26th and for those to be West of the UK (Atlantic ridge) - the signal IS building.

 

Where we are now it looks likely we will at least see some WAA up toward Greenland but as yet GFS still wants to override the signal and the topple the Atlantic ridge preventing any chance of a Greenland block but this is very typical of FI output - particularly with GFS.

Naturally we would rather see it modelling a Greenland high or at least more resilient Atlantic blocking at this stage but that we don't is not a clear signal the Atlantic will win out either.

With that in mind I hope to see the signal strengthen further within the ensembles and a more resilient ridge and/or Greenland block being modeled in the coming days.

It would also be nice to see the Operational output begin to lead the way with strong support from the control runs.

If this is a genuine signal and we are to have a sustained cold blocking pattern set up end of Dec we should see that come to fruition in the charts within the next few days.

 

18z ensembles

 

Edited December 16, 2014 by Mucka

[Jason M]

18z ensembles out. Not as good as 12z and best described as largely zonal. A few northerlies showing but mostly brief in nature.

Oh well, tommorows another day........

[Paul_1978]

18z ensembles out. Not as good as 12z and best described as largely zonal. A few northerlies showing but mostly brief in nature.

Oh well, tommorows another day........

The signals I'm getting from posts tonight are conflicting. From pattern changes to brief northerlies :-S

[Frosty.]

A Christmas Northerly would be just what the doctor ordered at this point..please make it so..snow :-)

The models are at least keeping coldies interested with a few carrots being dangled for sure. Let's hope for wintry upgrades in the days ahead.

[bluearmy]

Haven't posted today because not much to say beyond what I posted yesterday. a post Xmas day/pre new year northerly seems likely - much more potent than we've seen thus far due to better upstream amplification. how long the lower heights to our east and south hang around against the Atlantic ridge pushing in remains uncertain. Still believe a snow event across a fair chunk of the uk is a probability at this timescale.

Oh and the EC 32 must have some decent cold clusters at the same time period aswell. The mean anomolys more than decent with a mean upper ridge Iceland /Greenland which would deflect the jet far enough south to feed the nw euro trough at an advantageous angle for cold.

[Nick L]

The 00z GFS wants to give us very festive conditions on Christmas Day! A rather potent northerly on the table there. All fun and games at this stage though of course

[Mucka]

The 00z GFS wants to give us very festive conditions on Christmas Day! A rather potent northerly on the table there. All fun and games at this stage though of course

 

 

Yes a northerly outbreaks somewhere around Christmas/Boxing day looks likely but GFS 00z is rather poor if we want to see a signal growing for a strong Atlantic ridge.

GFS (P) somewhat better in that regard though it still goes on to flatten the ridge later.

 

 

The control also has a strong ridge.

 

 

GEM has the ridge but quickly topples it, even so it wants to try again a little upstream.

 

 

Hard to know what to make of gFS ensembles.

On the one hand their continued reluctance to build heights into Greenland still is duly noted but on the other at least one member does at last go someway toward setting up the real cold winter pattern change we are looking for.

 

 

It would be fair to call that cherry picking or eye candy given it is far from typical of most of the runs but worth posting as it at least shows the way to the promised land and it has been a long time since we have seen anything like that modeled - we just need to see a lot more of it.

Edited December 16, 2014 by Mucka

[Mucka]

With the troughs now looking to be shallower than initially modeled there will be a couple of very mild days for the South later this week and early next week especially.

I did say based on earlier output I doubted temps would get upto 13C for central/Southern England but I would certainly revise that now as it could briefly become very mild, especially in the SW.

 

Back to Cold prospects.

The Euros are much more amplified upstream than GFS Op or even GFS (p) so we will see how thta develops and how it affects later output (In ECM's case at least)

Below UKMO/ECM then GFS op/ GFS (p) 144h  for comparison.

 

 

[knocker]

Northerly blast over the Xmas period. Well the P has a depression nipping in from the SW. Agree in the short term temps could hit 14C in some places.

Charts weatherbell.

Edited December 16, 2014 by knocker