Model Output Discussion - The Start Of Winter

[MR EXTREMES]

isnt it? 1.gif a chilly couple of days, nothing too cold away from scotland 2.gif followed by three days of wet windy and mild 3.gif three days of 'average' cold before 4.gif mild mobile wet and windy weather returns throughout fi...if the gfs 00z is anything to go by, then the cold pm incursions have been reduced in their potency, and the general trend is for more mild weather as we progress into december. now that looks pretty dominant to me ! so the 00z looks average - above average.these arent cherry picked charts, i went through the gfs 00z and chose a chart to emphisise the ever changing outlook we have each mild/cold spell. there appears to be a tendancy here to play down milder options because its not what most appear top want. but denying their existance wont change the fact that there are milder options.

That's alright 1962 winter was rather mild wet and windy then Boxing Day it started to change and then rest of the winter 63 was written in the history books !

But by the charts around the start of winter 62 you would never of thought of any chance of a historic event weather wise.

Fine I'm sure some mild wet and windy weather would be fine more wave activity ect ect either way this winter already is much different to last.

[Mark Parsons]

isnt it?

 

1.gif a chilly couple of days, nothing too cold away from scotland

 

2.gif followed by three days of wet windy and mild

 

3.gif three days of 'average' cold before

 

4.gif mild mobile wet and windy weather returns throughout fi...

if the gfs 00z is anything to go by, then the cold pm incursions have been reduced in their potency, and the general trend is for more mild weather as we progress into december. now that looks pretty dominant to me ! so the 00z looks average - above average.

these arent cherry picked charts, i went through the gfs 00z and chose a chart to emphisise the ever changing outlook we have each mild/cold spell. there appears to be a tendancy here to play down milder options because its not what most appear top want. but denying their existance wont change the fact that there are milder options.

There has always been a bias towards colder options on this tread, I think most have a balanced opinion and a few do not except reality!

[bobbydog]

i'm constantly reading the word "mild" when referring to the output.

apparently, the last 2 weeks should have been "mild" especially for me in the balmy south. however, its alternated between light rain and cold and frosty and cold. -3c here last night, for example. the other night, the ice was over 1 inch thick in my wheelbarrow. on several days frost has lasted all day in the shade.

it might not be siberia but

its NOT mild!!!!

[bluearmy]

the extended ecm ens broadly agree with the gefs though i expect the gem mean to skew the naefs towards a less impressive euro low anomoly come the back end of the run.

 

early days but the signs for a snow event between xmas and new year are increasing each run.

[bluearmy]

i'm constantly reading the word "mild" when referring to the output.

apparently, the last 2 weeks should have been "mild" especially for me in the balmy south. however, its alternated between light rain and cold and frosty and cold. -3c here last night, for example. the other night, the ice was over 1 inch thick in my wheelbarrow. on several days frost has lasted all day in the shade.

it might not be siberia but

its NOT mild!!!!

 

agree totally bobby although the azores ridge is expected to make more inroads over the next 10 day period which should lift the overall perception of 'mild', however, as the spread chart i showed indicates, there may well be a continuation of warm sector/ cool period though perhaps more evenly spread than recently where the warm sectors were brief.

[IDO]

Good morning.

 

GFS like a Dog with a scent. It knows there is a bone buried somewhere but it is going to have to dig a few holes before it finds it. (we hope)

 

 

 

Still no cold being modeled at the moment though.

 

 GFS (p) a bit of a dogs dinner. (Maintaining the theme)

 

 

 

So still plenty of uncertainty on what Christmas day will bring or if we will get a more blocked pattern as we get into the last week of December.

If the models do latch onto blocking and experiment with it then we could suddenly be looking at exciting charts for coldies soon but of course there is also no guarantee this signal will come to anything.

 

It looks like a trop led NH mid-latitude cold shot is (possibly) on it's way and it appears to revolve around where the polar heights sink south after D12 and what happens to the US ridge in week 1. For example on the GFS P the polar heights move to Alaska and the Pacific ridge allows a HLB:

 

 So by D16:

 

The US ridge in week 1 pushes east:  and eventually end up in Scandi at D16.

 

The pattern is too far east for the UK to benefit from the upper cold flow. The core cold will then be diverted into the US (again): 

 

The resultant wave moves the UK into a warm sector. The GFS op sends the polar heights to Greenland along with the US heights:

 

and by D16: 

 

The Control sinks the US heights into the Azores and we remain flat upstream.

 

It is difficult to know if this will have any legs or will be a repeating theme or even if the polar heights will meet with a ridge to allow amplification. A good trend is that at D16 there is a downgrade in the number of members showing a more organised PV compared to recent runs, so even if we don't get the amplification, the polar heights keep the lower heights disjointed. I would say the trend continues for a transient meridional flow in the last few days of December due to the combined movement of the US ridge and polar heights, but no clear sign yet of the UK under very cold uppers, but a cooler theme looks likely.

 

No real change up to about D12 with alternating PM and TM shots. The last few runs suggest a TM flow in the two days before Christmas Day and a PM flow on the big Day. The ECM 12z on Christmas Eve:

 

 GEM: 

[snowsummer]

Rjbw. Thank you for reply. Made it very easy for me to understand. Sorry. On phone and not sure yet how to add direct reply.

[bobbydog]

agree totally bobby although the azores ridge is expected to make more inroads over the next 10 day period which should lift the overall perception of 'mild', however, as the spread chart i showed indicates, there may well be a continuation of warm sector/ cool period though perhaps more evenly spread than recently where the warm sectors were brief.

yes BA, 12c for the southern half on the GFS.

however, it seems that by the time we get to 00hrs any promised "mild" is a brief blip or doesnt happen at all

[Blessed Weather]

I'll sleep easy tonight then BW. Having said that I'm not sure there is any indication on that anomaly chart of any cold from the north. Agreed there may be northerlies for a time but that could easily revert to run of the mill NW then W.

 

Nice one Knocker!  I didn't mean to sound quite so condescending - apologies. I'm glad you are posting again - just look at the healthy debate you have generated in the last 12 hours alone! As long as people respond with a reasoned counter argument if they disagree, and keep personal digs out of it, then that's what a vibrant forum is all about!

 

Well following your "interesting" anomaly chart from last night, I have to say this morning's ECM-GFS 8 to 10 Day Mean Height Anomaly chart for the 3 days up to Christmas Eve leaves me very under-whelmed! Looks like a bog standard westerly flow off the Atlantic.

 

[knocker]

the extended ecm ens broadly agree with the gefs though i expect the gem mean to skew the naefs towards a less impressive euro low anomoly come the back end of the run.

 

early days but the signs for a snow event between xmas and new year are increasing each run.

 

Would more or less agree with that. The ecm perhaps a tad more emphasis on the Greenland ridge but at T360 that's a mere detail. So looking at a general area of low pressure over NW Europe with a weakening jet. On the other hand, fear not,  all is not lost.

Chart courtesy weatherbell

[knocker]

Nice one Knocker!  I didn't mean to sound quite so condescending - apologies. I'm glad you are posting again - just look at the healthy debate you have generated in the last 12 hours alone! As long as people respond with a reasoned counter argument if they disagree, and keep personal digs out of it, then that's what a vibrant forum is all about!

 

Well following your "interesting" anomaly chart from last night, I have to say this morning's ECM-GFS 8 to 10 Day Mean Height Anomaly chart for the 3 days up to Christmas Eve leaves me very under-whelmed! Looks like a bog standard westerly flow off the Atlantic.

 

ECM GFS 500 Height 8-10 Day Anom 24Dec14.gif

 

No probs BW. I agree with the above but it's in the extended period that's of interest I feel. Which way will the evolution jump?

[Tamara]

 We are now starting to see early, but very real and evidential answers to that Azores High and +NAO conundrum (as previously discussed) and how this now might be broken towards, but most especially into the New Year.

 

....+AAM is now finally signalling an increasingly negative tendency and this should inevitably impact, with time, on the Pacific pattern  .......

 

 

 

Signals for pattern change remain well on course

 

AAM tendency continues to suggest trending over the coming 10 to 15 days on an increasingly downward path - no surprise that this is a precursor to convection (MJO) returning to the Indian Ocean and shift in the GWO into a higher amplitude phases 1-2.

 

 

 

 

 

This signal keeps us increasingly on course for a retrogressed Pacific pattern and shift north westwards of the Azores High and a trough over NW Europe/Scandinavia. So, as stated the other day, the upstream pattern is counter intuitive to setting up any sustained eastward moving Azores/Euro mild pattern. Look west and think progressively colder to close out the year.

 

Best not get too hung up about precise timing arrival of proper amplification breakthrough...and signposting thereafter to a -NAO as we get into January. As long as the retrograde Pacific signal holds true, then we should expect the -EPO ridge to back north west and also allow in time the prohibitive polar vortex segment over Greenland and NE Canada to accordingly edge away from that spoiler zone into Hudsons Bay, with the more dominant lobe of vorticity transported east of the pole.

 

With renewed wave activity on the vortex to assist this process and the NH atmospheric signal more co-operative we also have, as snowking said, the prospect of renewed MJO activity heading eastwards through the Pacific in the New Year. This sets the stage for those chances of something more sustained during January .

 

Plenty going on as an antidote to intra day model watching vicissitude. This well accustomed seasonal MOD state of mind has also been apparent on a minor level in the stratosphere thread it seems  .

 

However, pardon the grammar, but if one can stay that infuriating word that starts with a P and ends with a T then *usual caution caveat and no dead cert guarantee of freeze disclaimer* we very much remain on the right track  

　

　

　

　

Edited December 14, 2014 by Tamara תָּמָר

[mushymanrob]

i'm constantly reading the word "mild" when referring to the output.

apparently, the last 2 weeks should have been "mild" especially for me in the balmy south. however, its alternated between light rain and cold and frosty and cold. -3c here last night, for example. the other night, the ice was over 1 inch thick in my wheelbarrow. on several days frost has lasted all day in the shade.

it might not be siberia but

its NOT mild!!!!

 

sorry old chap but that is simply not true! ive not seen ONE post here that suggested that the last two weeks were going to be mild, NO ONE has said its been mild .. please point me to these if im wrong .

there have been mild incursions, but the last two weeks after the very mild last weekend of november where 15c was reached, it has been mainly cold/below average.

but the facts are that there is alot of milder weather expected in the next two weeks, as we lose most of the colder pm air going off current gfs and ecm outputs.

[bluearmy]

Would more or less agree with that. The ecm perhaps a tad more emphasis on the Greenland ridge but at T360 that's a mere detail. So looking at a general area of low pressure over NW Europe with a weakening jet. On the other hand, fear not,  all is not lost.

Chart courtesy weatherbell

The gem mean too Far East with the ridge wrt to gefs and ECM.

[Captain Shortwave]

yes BA, 12c for the southern half on the GFS.

however, it seems that by the time we get to 00hrs any promised "mild" is a brief blip or doesnt happen at all

Double figure maxima predicted for this Wednesday and Thursday (even a 14C for Thursday from the BBC and Metoffice, that is flirting with very mild rather than mild). At the timeframe in hand, I don't think we will see this disappear.

We are having a very normal December overall (it feels strange as a normal winter month has been rarer than a total zonal-fest or severely cold month). A few cold days with snow coming down to low levels, a few very mild days and everything in between with no airmass getting the upper hand. 

 

Back to the models. The Eastern half of the US looks nailed to go into the freezer around Christmas, at this moment the resultant downstream pattern looks uncertain to me. A lot could come down to another cut off low sitting off the coast of Newfoundland and how this interacts with changing upstream pattern. This will determine the location and orientation of the resulting US trough.

Edited December 14, 2014 by Captain shortwave

[Summer Sun]

It looks like a mixed week coming up with a chilly start and end but mild mid week

 

 

By Wednesday away from Scotland temperatures are widely in double figures with parts of the south maybe hitting 13 or 14c

 

 

A mild night follows

 

 

Into Thursday and cooler air starts to push south into Northern England the south hangs onto another mild day

 

 

By Friday it turns chillier for all

 

 

So a mixed week with some rain and strong winds at times with some snow for higher parts of Scotland and northern England

[bobbydog]

sorry old chap but that is simply not true! ive not seen ONE post here that suggested that the last two weeks were going to be mild, NO ONE has said its been mild .. please point me to these if im wrong .there have been mild incursions, but the last two weeks after the very mild last weekend of november where 15c was reached, it has been mainly cold/below average.but the facts are that there is alot of milder weather expected in the next two weeks, as we lose most of the colder pm air going off current gfs and ecm outputs.

i think you missed my point mushy, i'm talking about people using the word "mild" to describe anything less than sub-zero. the output as a whole, would at any point over the last 2 weeks, have put us in this "milder" air.

anyway, we digress...

[carinthian]

Weather for the Christmas Period cannot yet be predicted. Forecast models for that period are far apart. Realistic predictions are possible only in the course of next week. Anyway that's our view over here. Any comfort for you cold fans, the charts for this same time in 1961 had a Barlett in place with warm temps over much of Western and Central Europe, then this high moved into Central Europe and by Christmas the block had moved to the NW of the UK and the weather over Christmas period then turned snowy in many countries including Britain. Innsbruck recored 96 inches of Lying snow on Christmas Day 1961, a record that still stands. 10 days prior to that date, people were still walking around with no winter coasts on ! So , the gist is not all is lost yet for cold weather fans, a lot a changes can evolve before the big day.

C

[johnholmes]

my take as promised

 

Looking at various model outputs for the next 2 weeks or so

Obviously first with the 500mb anomaly charts

Below is the last NOAA 6-10 and 8-14.along with my rough notes made last evening (12z issues)

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

 

NOAA

6-10 has larger +ve anomaly off California,

? shape of Canadian trough, otherwise chart as last issues

8-14 shows Canadian trough touch further west perhaps? Otherwise it looks as last issues really

No major changes showing in either time scale and not that different from ec-gfs

 

Below this morning from ECMWF-GFS (00z) again with notes

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

 

Sun 14dec

Ec-gfs

Fairly slight changes on both-ec increases w coast America ridge and also one in east-trough/ridge to e of UK is flatter and ridge remains more in charge than trough really

Gfs also increases American ridge/+ve but e’ern one not as much as ec  -for uk area trough ridge is such that flow into/over uk is from n of west whereas ec shows it s of west thus ec is more like flow shown on noaa both 6-10 and 8-14

 

The main comment to make is that there has been no major shift in the wavelengths over the northern hemisphere that I can see over the past week or more no has any been predicted over the past week or so. Thus the pattern has been and looks like remaining with much the same idea. That is a basically westerly upper flow, minor troughs and ridges running through this pattern but none look like being major enough to shift the position of the main troughs and ridges.

 

The synoptic models, ECMWF and GFS have, at times, run with the idea of some meridional type pattern giving a colder north west flow into the UK. But neither has shown this consistently which is hardly surprising given the consistency of the anomaly charts over the past 7-10 days.

The output this morning, GFS and ECMWF,(not sure if it is the 00 or 06z as I type this at 1005, and remember these links and the anomaly links will change as runs update-my comments are based on the times shown)

ECMWF

http://www.wetterzentrale.de/topkarten/fsecmeur.html

GFS (06z)

http://www.wetterzentrale.de/topkarten/fsavneur.html

 

Indeed they illustrate my comments about their variability at longer time scales but each time they have to revert back to the pattern suggested by the anomaly charts, a broad westerly upper flow with minor changes running through. Two main troughs, one in the eastern Pacific close to the western seaboard of N America and one close by the eastern coast. In between and over the Atlantic a fairly flat and fairly strong westerly flow. Sometimes south of and sometimes north of west giving our changeable weather with currently briefish milder shots and somewhat longer colder unsettled spells.

The current MJO is in phase as given below, getting close to little amplitude in phase 7

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/whindex.shtml

In such low orbit I find guidance is not very high. It has been giving prior to moving over the last week or so a 500mb pattern very similar to what we have been experiencing.

I use GFS for no other reason than it is convenient and do no muddy the waters looking at what other centres show and predict. Not very scientific but at least it gives me consistency.

The prediction is for it to move to reasonable amplitude in phase 3. This equates to what is shown in the link below. This suggests some kind of positive anomaly heights from NE America over the Atlantic, but with little intensity towards a new area over southern Europe. Negative heights anomalies are shown over Greenland into Scandinavia.

Perhaps it is this idea which we see quoted at times when Ian F refers to Met O briefings and also their hints at the end of their current further outlooks for cold. Tenuous at the moment.

http://www.americanwx.com/raleighwx/MJO/MJO/DecemberPhase4all500mb.gif

 

Other factors we can look at but they are really another version of what the synoptic patterns overall flow suggest=AO and NAO, see below

The NAO shown tending down but less so with the AO. I find they are not very reliable after about 7 days into the prediction.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml

 

So for 6- say 20 days ahead until the anomaly charts begin to show, consistently, the idea mooted in the MJO phase 4 I tend to side with no major change. If they do start to show this idea with some degree of meridional flow over the Atlantic over at least 2 and preferably 3 consecutive days, and all 3 show similar then I would flag this up as a very likely change in whatever time scale their charts indicate. So keep watching my anomaly updates.

 

By all means shoot holes in this post but please post charts and a reasoned explanation rather than a one liner.

Edited December 14, 2014 by johnholmes

[mushymanrob]

i think you missed my point mushy, i'm talking about people using the word "mild" to describe anything less than sub-zero. the output as a whole, would at any point over the last 2 weeks, have put us in this "milder" air.

anyway, we digress...

 

ok

[TEITS]

So yet another run that hints at a pattern change towards the end of the year with the interest starting from around the 28th Dec onwards.

 

As some of you know I like to look at the Iceland SLP ensembles when blocking to our N is hinted at. However keep an eye on the Madrid SLP mean also.

 

http://max.nwstatic.co.uk/ensimages/ens.20141214/00/prmslMadrid.png

 

Should blocking develop then you would expect low pressure systems to take a more S,ly route and the SLP mean will drop. A few 0Z GEFS members hint at this.

 

Finally as many know my forecasting is based on instinct. Until today I haven't seen anything of interest but my word my mind has now changed towards a mega cold spell arriving at the end of the year.

[Tim Bland]

Nice GFS (P) for Xmas eve!

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=234&code=0&mode=0&runpara=1

[95 Degrees]

 

 

 

 

  6z GFS post 240h teasing a possible northerly, but it still hasn't figured out what to do with it yet, still positive signs though, but needs more model support.

[bluearmy]

So yet another run that hints at a pattern change towards the end of the year with the interest starting from around the 28th Dec onwards.

 

As some of you know I like to look at the Iceland SLP ensembles when blocking to our N is hinted at. However keep an eye on the Madrid SLP mean also.

 

http://max.nwstatic.co.uk/ensimages/ens.20141214/00/prmslMadrid.png

 

Should blocking develop then you would expect low pressure systems to take a more S,ly route and the SLP mean will drop. A few 0Z GEFS members hint at this.

 

Finally as many know my forecasting is based on instinct. Until today I haven't seen anything of interest but my word my mind has now changed towards a mega cold spell arriving at the end of the year.

Bit early to go for 'mega' Dave! of course a ens mean won't pick up on low uppers yet but the ECM control looked pretty frigid on the 00z run

[Nick F]

Poked my head in briefly yesterday evening and this morning the mild vs cold debate for this coming week is still going on! Lol. Anyway, quite a useful new tool in Netwx extra for such occasions for expected temp anomalies over 3 day periods - so people can make up their own conclusions whether it'll be mild or cold in their back yards:

 

Mon 15th - Weds 17th:

 

Thurs 18th - Sat 20th:

 

Looking further ahead, 00z ECM H500/anomaly charts by day 10 picking up on a pattern change upstream over the NE Pacific with the +PNA / -EPO ridge building north towards the pole and retrogression of the Aleutian low. This would eventually change the pattern downstream by carving out a trough over eastern N America while amplifying a ridge toward Greenland, as there have been some hints at in the ops recently

 

From this pattern at T+120 - look at the NE Pac troughing:

 

... to this at day 10 - gain look at the ridge anomaly over the NE Pac

 

MJO looks like it could re-emerge form the COD into phase 2-3, the ECMWF Seasonal Prediction ENS has the MJO then motoring through at a reasonable amplitude towards phase 7 towards/into Jan ... so this could help drive change in the pattern too.

 

These are not just one off signals, the extended ENS have been hinting at this pattern change upstream for a while, and its drawing closer now in time, into the day 10 range. Though 00z GEFS anomaly charts seem less enthused than ECM this morning for the pattern change  until later in the month. So a way to go yet until we can firm up on any pattern change.

Edited December 14, 2014 by Nick F