Model output discussion - 16th Nov onwards

[Frosty.]

The Gfs 6z op run shows a strong polar maritime blast towards the end of the week ahead with sleet and snow not just confined to northern hills, quite a wintry flavour to the weather next weekend with icy patches and overnight frosts. It's a very unsettled run with bouts of wet and very windy weather and there are fleeting milder blips but nothing like we had recently and they are soon swept away by chilly polar sourced air so it's an action packed outlook and a lot of trough disruption over the uk at the end of the run which is also rather cold, it's so much better than the very mild, benign euro high dross we had earlier in november, in my opinion!    

[Nouska]

Anybody fretting about the last three frames of the 00Z ECM, would do well to take notice of the ensemble mean.

 

It is a huge outlier; NB - does not preclude it being right!   

I'm not a fan of extended ensemble means but when it is all we have to look at, better than nowt.

 

T+ 216 means for 850 temp and Z500 heights.

 

  

[Mucka]

ECM 00z London ensembles

 

 

Still a brief cold dip for around 27th/28th before turning milder and then settling back to around average, some slight milder/cooler days as low pressure passes through.

As would be expected large scatter into first week of December but no extremes of mild or cold showing.

I still believe we will have a chance of something better into 2nd week of Dec but it is just a case of patience for now and seeing how things progress through next week.

[Mucka]

UKMO has gone from most amplified to flat as a pancake but it has been abysmal of late so who knows.

Here is what it is showing today (left) for 26th compared with two days agao (right)

 

 

 

 

Unfortunately GFS has also been getting flatter though not quite so dramatically while ECM looks to have been pretty much on target.

While any faint hope of the pattern backing West over time has been squashed,,the Siberian high should still be strong enough to influence things further down the line and for me the best prospects of any cold spell in first half of Dec come from an Atlantic ridge reforming rather than any Easterly influence of which prospects should improve later in Winter.

 

Cold prospects over the next two weeks look to be a case of eking out any brief cold from transient Northwesterlies

 

GFS 12z interesting...

 

 

Strong Canadian ridge and Arctic high, that wouldn't be a bad thing as far as looking for upstream amplification later.

Edited November 22, 2015 by Mucka

[Ali1977]

Not much cold showing in the reliable timeframes, Scottish ski resorts may do ok though. I don't think the Siberian high looks like migrating our way any time soon.

[bradymk]

GEM best of the bunch so far tonight...

Still do not think any model has got the heights to the north east and Siberia high quite right yet. Not that I think the high will move west enough to bring a cold spell but it may have more effect than currently shown on some models.

Edited November 22, 2015 by bradythemole

[Summer Sun]

Looking at UKMO we could see further strong winds and possible gales next weekend

 

[gottolovethisweather]

 

However, the trop Polar Vortex appears to be too resistant against any poleward wave propagation from the Siberian High for now, so there appears to be no impetus from the medium to long range NWP guidance to dislodge the PV from its limpet hold on Greenland for now.

 

But, dare I say, none particularly potent or sustained with the set-up looking likely to persist into early December.

 

And the latest operational 12z run from the GFS seems to back these thoughts of yours up too. Tis early days yet though but not much on offer for coldies yet in mainland England bar Frosty spells and perhaps a few wintry showers in between the passage lows. Next weekend does appear be our next best chance for something similar to what has just been, a few more runs needed to confirm this latter aspect.

 

Overall, the bigger picture NH wise and those stratospheric signals remain of interest though, according to those in the know, so let's see how things unfold as head deeper still into month end. I reckon after these usual weekend wobbles within the various NWP outputs, they might yet pick up on an entirely different evolving trend again as we head into the midweek period.

Edited November 22, 2015 by gottolovethisweather

[Singularity]

We've almost lost the -ve AAM cycle from the GEFS outlook now, and it's getting close to a classic Nino state (phase 5/6). The 00z GFS det. seemed to respond by going crazy with the Euro High, with the balance of power shifting a long way toward that as a result of increased mobility from the Atlantic eating away at the Siberian High - it wasn't a pretty sight wrt long term prospects. Thankfully, the following two runs have stepped away from this, with the 12z det. keeping the Siberian High ridging poleward pretty much without pause during the 4 to 16 day period. 

 

Despite this, the 30 hpa warming is still not as pronounced as it was yesterday - hinting at the longer game that I mentioned yesterday; for me mid-Jan remains a reasonable target for a major warming event. We could do with a bit more wave breaking than the 12z det. has, though. IIRC, it underestimated warming events in late January this year so something more substantial could easily occur.

 

With the more Nino-like background state favouring displacement of the Azores High to Europe (usually more late Dec-Jan but as I've said before I feel we're ahead of schedule with this particular event), waves of unusually mild air are likely to feature intermittently over the coming fortnight or so, which may bring temps as high as 15*C. Incursions of polar air are relatively restricted but still very much within the range of possibilities and capable of producing a below average (temp-wise) day here or there.

 

 

Wind and rain events look to be the main focus on most days but with some wintry weather on offer too for more northern parts. Those in the south will struggle to see much more than a wintry shower or two but that's far from unusual between mid-Nov and mid-Dec.

[bobbydog]

those who are worrying about the output from the models should take some comfort from this-

November 22nd 2015 (today)

November 22nd 1962

it could happen....

[MR EXTREMES]

Was just looking at the current Nino there's most certainly been cooling in the eastern Pacific area I would not like to call December either way very close to either warm wet or colder take your pick.

Is modoki pattern a possibility?

[fergieweather]

I'm not a fan of extended ensemble means but when it is all we have to look at, better than nowt.

Yes, an important point: nothing can beat inspection of individual stamps, especially as the mean fields will always lean more towards the default type (zonal) and thus skew interpretation if based solely on them alone. Nonetheless, be it via means or stamps/clusters, both EC and GloSea5 remain in firm agreement on the varied/changeable theme between SW/WSW to WNW/NW zonality right through to late December; ie a relentless oscillation between milder windy/wet spells and chillier showery phases. So far, all in keeping with previous seasonal model expectations. We await the trend to be bucked...!

[BLAST FROM THE PAST]

To my eyes we see a slight upgrading to a more cool pattern coming back.  Was going to post further re BBC week ahead forecast ...Suggestion of not 'in the bag'

 

BFTP 

[Ali1977]

Yes, an important point: nothing can beat inspection of individual stamps, especially as the mean fields will always lean more towards the default type (zonal) and thus skew interpretation if based solely on them alone. Nonetheless, be it via means or stamps/clusters, both EC and GloSea5 remain in firm agreement on the varied/changeable theme between SW/WSW to WNW/NW zonality right through to late December; ie a relentless oscillation between milder windy/wet spells and chillier showery phases. So far, all in keeping with previous seasonal model expectations. We await the trend to be bucked...!

Did previous seasonal models show cold after Dec?

[phil nw.]

As we say goodbye to that crisp Arctic air the pattern is now reverting to a more typical westerly type as the Atlantic high flattens out later in the week.

Those low heights modeled to sit over Greenland is never a great sign if looking for prolonged cold but with the jet running across our latitude we will sit on the cold side from time to time.

What we don't want is to see the Atlantic high becoming a Euro high such as shown in later frames as this will mean milder air becoming more dominant from the sw as the jet realignes to a more sw-ne angle.

[blizzard81]

As we say goodbye to that crisp Arctic air the pattern is now reverting to a more typical westerly type as the Atlantic high flattens out later in the week.

Those low heights modeled to sit over Greenland is never a great sign if looking for prolonged cold but with the jet running across our latitude we will sit on the cold side from time to time.

What we don't want is to see the Atlantic high becoming a Euro high such as shown in later frames as this will mean milder air becoming more dominant from the sw as the jet realignes to a more sw-ne angle.

Yes, the azores high easing towards spain and france has been the unmistakable trend on todays modelling post week one. I want to see this trend obliterated on tomorrow mornings runs

[fergieweather]

Did previous seasonal models show cold after Dec?

Some.

Whilst ALL deterministic output agrees the zonal theme next 7 days at least... how much faith on the continuation thereafter all December? Discuss. My own view is one falling in the ranks of the unconvinced...I think too much faith being put in some medium range modelling. Time will tell.

[Sperrin]

Slightly off topic here but I'm new to this whole game. Are there any good links out there that summarize the model build up to the big freezes of '09 and '10? It would be nteresting to gain an understand of how they developed and were maintained. Cheers.

[bobbydog]

Some.

Whilst ALL deterministic output agrees the zonal theme next 7 days at least... how much faith on the continuation thereafter all December? Discuss. My own view is one falling in the ranks of the unconvinced...I think too much faith being put in some medium range modelling. Time will tell.

same here. i'm putting my faith in the charts i posted earlier...

dare we ask your personal view?...

[Yarmy]

Slightly off topic here but I'm new to this whole game. Are there any good links out there that summarize the model build up to the big freezes of '09 and '10? It would be nteresting to gain an understand of how they developed and were maintained. Cheers.

 

The Strat thread for 2009 is a good read:

 

https://forum.netweather.tv/topic/57364-stratosphere-temperature-watch/

 

Also, you can trawl through the pages from here onwards:

 

https://forum.netweather.tv/forum/1-weather-discussion-and-chat/page-115?prune_day=100&sort_by=Z-A&sort_key=last_post&topicfilter=all

 

(The model output thread used to be in the Weather Discussion and Chat subforum).

[phil nw.]

Slightly off topic here but I'm new to this whole game. Are there any good links out there that summarize the model build up to the big freezes of '09 and '10? It would be nteresting to gain an understand of how they developed and were maintained. Cheers.

Hi Sperrin,

I can't find any archived model discussions on here as far back but we do have the historical charts- link

http://www.netweather.tv/index.cgi?action=gfs;sess=5f7650265f163f4dbf62a0a1a69ff246

 

just type in the dates at the top of the chart window that you want and click Retreive chart below the dates.

 

The met office site have summaries on that period link here

http://www.metoffice.gov.uk/about-us/who/how/case-studies/winter09-10

 

there are some other links to found by using google- such as Wiki.- typing in those Winter years in your search.

Maybe some other members can help further?

 

I hope that at least gives you a start anyway.

[phil nw.]

The Strat thread for 2009 is a good read:

 

https://forum.netweather.tv/topic/57364-stratosphere-temperature-watch/

 

Also, you can trawl through the pages from here onwards:

 

https://forum.netweather.tv/forum/1-weather-discussion-and-chat/page-115?prune_day=100&sort_by=Z-A&sort_key=last_post&topicfilter=all

 

(The model output thread used to be in the Weather Discussion and Chat subforum).

Nice one Yarmy i overlooked those!

[Duane S.]

Hi Sperrin,

I can't find any archived model discussions on here as far back but we do have the historical charts- link

http://www.netweather.tv/index.cgi?action=gfs;sess=5f7650265f163f4dbf62a0a1a69ff246

 

just type in the dates at the top of the chart window that you want and click Retreive chart below the dates.

 

The met office site have summaries on that period link here

http://www.metoffice.gov.uk/about-us/who/how/case-studies/winter09-10

 

there are some other links to found by using google- such as Wiki.- typing in those Winter years in your search.

Maybe some other members can help further?

 

I hope that at least gives you a start anyway.

Interesting (and not in a good way), the difference between the likes of 09 and now at mid Strat level, a veritable world of difference in vortex strength. I do struggle to see any meaningful HLB manifesting for the next 3 weeks plus looking at the NH hemisphere state etc.

However I say let the vortex continue to wind itself up into a frenzy (and it will), the bigger and the more spectacular the fall. Still plumping for strong Wave 1 displacement followed by continued wave 2 activity to spell the start of the end of its dominance late in December, with some fun along the way.

[Steve C]

same here. i'm putting my faith in the charts i posted earlier...

 

 

Really? Are you asking the guy to forecast a similar winter to the coldest one in the best part of 300 years here (and the World has warmed in the last 50 years too, for whatever reason)

 

I look forward to your prediction coming off...

[lorenzo]

Some.

Whilst ALL deterministic output agrees the zonal theme next 7 days at least... how much faith on the continuation thereafter all December? Discuss. My own view is one falling in the ranks of the unconvinced...I think too much faith being put in some medium range modelling. Time will tell.

 

Time will tell is a very good statement - except some of us have to stick out necks out and have a guess !! Trust me we are working very hard on getting that 'best guess together as I write!'.

 

Well, it's a challenge worth doing. As I wrote last year to those writing off analogs, seasonal forecasts of any sort etc.

 

To me furthering understanding in what determines our weather is the greatest challenge there is, and never going to hold back on using all the information and academic research at our disposal to do that.

 

In previous posts have mentioned why last year went the way it did, with many positive signs falling, have also mentioned why the much maligned OPI caused great excitement then failed to deliver.

 

Ultimately, the academic paper that underpinned where the flaws in OPI were to be observed is highly technical, and in saying that the dataset for OPI from even before winter 2014-15 featured the very same flaws, most of which were entirely unpredictable and fundamentally unprecedented - this I think explains where new learning can create a negative view of any seasonal forecast.

 

Couple of charts from this evening that generate interest are from the ECM as Blue and GP mentioned overnight quite a significant trend on the GEFS is supported on ECM for action in West Eurasia.

7

 

One hopes this waveguide for EP Flux ( the stuff that annoys that beastly vortex) can be supported.

Basically arrows pointing further right and up annoy it if you are used to this thread and not the stratospheric stuff.

 

A whole lot of concentration of discussion lies around Siberia and the Siberian high this winter so far, and this in itself raises an interesting dynamic.

 

1) Q If people are so certain to discredit the OPI then - Why did Judah Cohen authour of the SCE and SAI ( Snow Cover Extent and Snow Advance Index) and student of atmospheric feedbacks feel it relative enough or credible enough  to get 'onboard' with their work? Would he have done so if it were an unconvincing model likely to bust?

 

Yes, it's a shame we don't have the 'hype' of the OPI, and also it's of credit to everyone here that we are now more aware of the larger scale impacts informing our weather.

 

Remember an SSW is not a guarantee of cold, and we can still have seasonable outbreaks that are trop led. I am not diminishing the stratospheric influence, just some thoughts recently that due to our higher awareness has taken the fun out of winter predictions on the model thread. This you could argue all day. #norwegian shortwaves

 

So no forecast stuff saving that for within the next week but some thoughts on context.

 

ECM looking like fun again let's see where the pub run goes - goodness knows !!