Model output discussion - proper cold spell inbound?

[Summer Sun]

Control looks to have gone a bit mad at the end it goes from +7 to -11 in around 24hrs

[Man With Beard]

Looked at the ECM ensembles and the clusters - and as I suspected, the clusters (or should I say cluster as there's only one again) are for the bin after D10. 

When checking all the ECM ensemble members at D15, I'd say there's a 50/50 split between substantial northern blocking, and a more normal winter pattern of Azores High / low to the NW.

[chionomaniac]

2 hours ago, Nick F said:

Looks like the Polar Vortex over Greenland wants to have one last laugh this winter before perhaps succumbing to downwelling of the SSW later in the month. No getting away from it, but looks like a more zonal / mobile spell of weather  off the Atlantic is on the cards from the weekend, albeit cold zonal. Just hope the trop PV blows itself out quicker than the GFS operationals have shown this morning.

Still, we have a week of cold weather ahead, not particularly noteworthy or memorable for the cold or snow, but most should see some snow this week, as band of snow moves SE tomorrow across most parts, then another Atlantic front moving SE on Thursday/Friday should bring snow for some, though looking more marginal for this late week event, with a rain/sleet/snow mix at lower levels.

It's no surprise that the vortex wants to have one last laugh. It's a bit like putting pressure on a balloon, as it distorts the strain builds until the moment it bursts.The wave two displaces each daughter vortex which stay strong, until the warming weakens them.

Edited February 5, 2018 by chionomaniac

[Frosty.]

The GEFS 6z mean looks generally zonal with alternating colder showery / milder wet and windy phases with short-lived calmer interludes but eventually the flow veers meridional towards the end with arctic air drawn south as we see a large scandi trough and mid atlantic high / ridge.

[metrosnow]

2 hours ago, stodge said:

Morning all

One or two excellent comments last night to counterbalance the trolls. No one ever said the coming week was going to produce "feet of disruptive snow" and while my part of lowland East London is dry, very cold and clear currently, who knows what the day and the Thames Estuary might bring ?

• This is somewhat incorrect in my view. Perhaps best to take some peoples posts with a pinch of salt. I see certain peoples names now and quickly scroll down to the next before one of my fuses blows due to over ramping, but it saddens me that as soon as anyone has recently posted views similar to what I've also been seeing, that they are immediately set upon and are subjected to the kind of treatment seen in the closing scenes of The Wicker Man. A lot of us want snow, but we've been here so many times over the years people have a right to be cautious. I haven't the time to scroll though all of last weeks over the top posts, but I've included just one example of many below. it might be good to remember some of us have differing views, despite wanting the same end result, and to call people trolls just because they don't see what you see really isn't on. The exact opposite could be said about some over the top snow trolls on here, who see one good run and then head straight to Mountain Warehouse for a thermal ski jacket which in all likelihood will end up on Ebay a week later. This is supposed to be a model discussion forum. A few people tried to be level headed and were ridiculed and it now seems they were right. It might be an idea to hold back before ripping them to shreds in future. Just a thought......

On ‎01‎/‎02‎/‎2018 at 06:34, snowfish1 said:

I'm a very excited Boy this morning Mucka shall I go find my new toboggan ?

If ECM is right you had better hurry and find it before it gets buried. 

 

[sebastiaan1973]

24 minutes ago, chionomaniac said:

It's no surprise that the vortex wants to have one last laugh. It's a bit like putting pressure on a balloon, as it distorts the strain builds until the moment it bursts.The wave two displaces each daughter vortex which stay strong, until the warming weakens them.

Hi Chio, so this signal is so strong, it overrules the MJO phase 7 Scandihigh which we 'would' see in 7-10 days time?

Edited February 5, 2018 by sebastiaan1973

[karyo]

Speaking of the MJO, the gfs keeps it at phase 7 with a notable weakening.

[karlos1983]

8 minutes ago, karyo said:

Speaking of the MJO, the gfs keeps it at phase 7 with a notable weakening.

I can only see the Feb 3rd one on the noaa website 

Is there an updated version somewhere else @karyo

TIA

Edited February 5, 2018 by karlos1983

[chionomaniac]

20 minutes ago, sebastiaan1973 said:

Hi Chio, so this signal is so strong, it overrules the MJO phase 7 Scandihigh which we 'would' see in 7-10 days time?

Not necessarily so, as the main daughter vortex is very much Atlantic based which still allows some type of Scandi block - but it may be a type of stand off situation with the UK temporarily held in no mans land until the vortex veakens

[karyo]

8 minutes ago, karlos1983 said:

I can only see the Feb 3rd one on the noaa website 

Is there an updated version somewhere else @karyo

TIA

Yes, try this link http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

[karlos1983]

1 minute ago, karyo said:

Yes, try this link http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

Interesting. So the GFS takes it to Phase8 heading to phase 1 but the GEFS dies of in Phase7.

confused.com although I'm no expert when it comes to the MJO, far from it.

[tight isobar]

2 minutes ago, karlos1983 said:

Interesting. So the GFS takes it to Phase8 heading to phase 1 but the GEFS dies of in Phase7.

confused.com although I'm no expert when it comes to the MJO, far from it.

Variations but all heading in the right-direction!1

Edited February 5, 2018 by tight isobar

[Duane S.]

The ECM, Japanese and Canadian ens models have all now updated as well (within the last half hour). All going into P8. Nice.

[swebby]

3 hours ago, Yarmy said:

Insolation? 

The red line is roughly suitable for the UK. Of course the actual Watts hitting the surface will depend on cloud cover.

Edit: Image is from here:

http://www.physicalgeography.net/fundamentals/6i.html

 

Many thanks Yarmy, the thing that surprised me about that chart is that higher latitudes actually record a yearly peak that is higher than anything managed at the equator.  Obviously related to length of day at whatever lat (24hr daylight at the pole) but even with this, the fact the poles have, for a short period, a greater energy input than managed at the equator is a surprise.

[Derecho]

1 hour ago, metrosnow said:

• This is somewhat incorrect in my view. Perhaps best to take some peoples posts with a pinch of salt. I see certain peoples names now and quickly scroll down to the next before one of my fuses blows due to over ramping, but it saddens me that as soon as anyone has recently posted views similar to what I've also been seeing, that they are immediately set upon and are subjected to the kind of treatment seen in the closing scenes of The Wicker Man. A lot of us want snow, but we've been here so many times over the years people have a right to be cautious. I haven't the time to scroll though all of last weeks over the top posts, but I've included just one example of many below. it might be good to remember some of us have differing views, despite wanting the same end result, and to call people trolls just because they don't see what you see really isn't on. The exact opposite could be said about some over the top snow trolls on here, who see one good run and then head straight to Mountain Warehouse for a thermal ski jacket which in all likelihood will end up on Ebay a week later. This is supposed to be a model discussion forum. A few people tried to be level headed and were ridiculed and it now seems they were right. It might be an idea to hold back before ripping them to shreds in future. Just a thought......

If ECM is right you had better hurry and find it before it gets buried. 

 

Top post and I remember when I suggested the Scandi high and cold pool retreating wasn't good news for medium term prospects and was a distinct possibility. As a result the cold air to our east is being whisked away. I got trolled with a lot of confused reactions but that is what has transpired. I think some people just post what they would like to see rather then discuss valid developments in model output.

This may come across as negative but I've been looking at the GFS, ECM and UKMO models for many years and I've always learnt to be cautious until cross model agreement is apparent. I always find it interesting to read the more in depth posts on here and interest in the weather is what has led me to become a PhD student.

I do think that the MJO and stratosphere are important, look at the build of pressure towards Scandi for example of this. Consistent with a phase 7 MJO but not quite the giant scandi high that occurred in February 1956 or 2012. I also think people underestimate the importance of having a strong cold pool over Europe (especially over Scandinavia) as this often slows down or disrupts an Atlantic charge. Unfortunately this has been absent during the last 5 years. 2012/13 was the last winter with good cold pooling during the winter (though January 2017 saw a bit as well). With the MJO its often worth noting the thick uncertainty bars (grey areas on the plots) so a certain scenario is often far from nailed on. Though we have at least managed a very amplified phase at the moment so its a win for the models there.

Things in the stratosphere are interesting too. Though lets not forget that increased northern blocking is not always a ticket for cold here but it very much increases our chances.

Two things I have noticed about this winter so far though that have interested me:

1) La Nina appears to be developing differently. Usually a La Nina will peak in December and then move towards the central Pacific later on in the winter. This one however is going pretty well and is remaining clearly defined in the eastern Pacific. To see the same La Nina persist past Spring is rare. As I said usually the La Nina will move to the central Pacific and then fade out but sometimes it will re-emerge in Spring. An example below:

 2008 La Nina moves to Central Pacific during February

 2008 La Nina weakens a couple of months later in May

 February 1955 - La Nina just as strong in Eastern Pacific

 May 1955 - La Nina gets even stronger in the Pacific

 February 2018 - La Nina still doing pretty well in the East Pacific

Second thing I've noticed is that the Atlantic cold blob, the bane of our recent winters weakened a lot during January and that region actually had milder then average SSTs. It has been a feature during the last few years coinciding with more frequent then average westerlies. I hope temperatures will remain above average in these areas as the late February/March SST footprint emerges during the following year when deep water is mixed back to the surface. Some colder anomalies are starting to appear, probably due to cold weather and increased cold air outbreaks in this region.

          2013/14 - Awful winter                                                     2014/15 - Boring             2015/16- Wake me up when February ends
        

                     2016/17 meh...

Contrast this to 2010 and 2012...

 
      2010 - Pretty awesome winter period                     2013 - Not a bad winter eh?

I think the importance of SSTs and the ocean in general are really underplayed on this forum. Does the ocean lead the atmosphere? or does the atmosphere lead the ocean? hmmmmm

Ideally we would want the cold air pouring into the North Atlantic to stop and have a cold February/March period with a negative NAO. Of course it doesn't mean the next winter will automatically be cold (other factors overwhelm) but it would make a good change.

As for longer term prospects I think there is a fair chance of colder then average conditions continuing, especially if the stratosphere plays ball. Though in this warming world maybe it takes a lot more for cold spells to develop, hence we see cold spells downgraded quite often as the atmosphere acts differently compared to what it used to. Although a rather cold week this week it looks rather boring... was hoping the Scandi high would inflate.

Anyway we shall see. I hope we get one last hurrah before I start looking for the first warm spell of Spring and then thunderstorms.

Edited February 5, 2018 by Quicksilver1989

[Chesil View]

Just now, s4lancia said:

The ECM, Japanese and Canadian ens models have all now updated as well (within the last half hour). All going into P8. Nice.

Sounds like things are continuing to fall into place for our secondhalf of feb first half of march cold/snowy spell S4L

[John Michael How]

4 hours ago, Yarmy said:

Insolation? 

The red line is roughly suitable for the UK. Of course the actual Watts hitting the surface will depend on cloud cover.

Edit: Image is from here:

http://www.physicalgeography.net/fundamentals/6i.html

 

Just a question regarding this model& solar cycle- Does the solar cycle also have an effect on the strength of sun? as were heading for solar minimum would it be lower in the next year or 2 or has that nothing to do with this model?

[Yarmy]

Just now, John Michael How said:

Just a question regarding this model& solar cycle- Does the solar cycle also have an effect on the strength of sun? as were heading for solar minimum would it be lower in the next year or 2 or has that nothing to do with this model?

Yes, but it's been calculated to be something of the order of 0.1C in terms of impact on the Earth's climate, so presumably inconsequential. There are secondary impacts that are the subject of study and debate, but that belongs on the Solar thread.

[Yarmy]

44 minutes ago, swebby said:

Many thanks Yarmy, the thing that surprised me about that chart is that higher latitudes actually record a yearly peak that is higher than anything managed at the equator.  Obviously related to length of day at whatever lat (24hr daylight at the pole) but even with this, the fact the poles have, for a short period, a greater energy input than managed at the equator is a surprise.

Yes. You need to integrate the functions to find the total energy supplied though (i.e. find the area under each curve). So you can see that, overall, the equator receives massively more energy over the course of a year.

Edited February 5, 2018 by Yarmy

[ZK099]

Now I'm not an expert by any means, but I think people are paying far too much attention to the models. There are numerous changes in the atmosphere currently underway and the model output in a week's time will be vastly different to the output we're getting today, that's for sure. 

It's more important to look at the teleconnections at this stage. There are three main big factors for me. 1) Massive MJO pulse in a blocking-favourable phase. 2) A very clean SSW with a split. One look at Judah Cohen's tweets and it's evident that this really is significant. Likens it to 1985, which was one of the coldest in history for the US and was bloody cold here too.  3) Low sunspot activity- correlates with colder winters here in the UK.

The teleconnections are aligning so to speak. Have patience and in 7 days the models will hopefully have clocked on. Until then, expect some bizarre output! 

Edited February 5, 2018 by ZK099

[ghoneym]

Many times in the past week since the start of the mentioned SSW there has conflicting opinions and even arguments on occasion regarding NWP output and whether or not a certain model has a grasp on the background signals at starting conditions. I think it is worth remembering that the 3 big guns ECM, GFS, UKMO ( in the majority of opinion ) are considered low resolution models focusing horizontal grid spacing at 9-27km. (ECMWF 9km grid spacing, UKMO 10km and GFS 13km for the first 10 days) The GFS resolution moves out to 27km for days 10 to 16! These models are good at grasping "general patterns" and we must remember that pinpoint accuracy and detail of IMBY events is impossible for these models alone to predict. The same should be said for ensemble use as their resolution is even lower.

All that being said it is important to look at the ensembles of each model (where available) and interperate them correctly.  (ECM ensemble horizontal grid spacing 18km up to day 15 &36km thereafter, UKMO 20km & GEFS similair).

note- all resolution figures are ballpark and may not be 100% correct, up to date but you get the idea.

Looking at the Ensemble mean first, this typically verifies better than the control forecast by most standard verification scores because it smoothes out unpredictable detail & simply presents the more predictable elements of the forecast. It can provide a good guide to the element of the forecast but should not be relied upon on its own, as it will rarely capture the extreme events. (SSW surely being one of these extremes)

Postage stamp maps. These allow us to take in the individual ensemble member contoured plots and asses the possible risk of extreme events. Cherry picking an individual pertubation is good for eye candy but rarely will it be correct. 

An EPS best represents the uncertainty in resolved variables, upper air forecasts are generally more accurate than surface conditions at most ranges and for short range specifics thats why some on here use more convective models such as Arpege, Euro4 etc as their resolotion is of much lower range (0-2km )and detail.

An EPS is only as good as the model it uses. If a model is unable to represent an certain phenomena, the EPS will also be unable to represent it. (a good example would be that most models cannot represent properly convective storms, which is one of the reasons we have convective scale models)

An EPS will share any systematic bias that the model uses. A list of the models and their Bias from you guys would be appreciated.

A common thought when looking at an ensemble chart would be to ignore certain members or cherry pick a "best" member but is this realistic? Perhaps for certain aspects of the forecast over very short period forecasts and for local forecasts over a small area. Over a large area or the full model suite, the control run will always be the most skilful. 

To decide on your forecast , and therefore the comments you carefully select to input on to the MOD thread  have a look at the ensemble and if there is a lot of uncertainty try and describe a small number of possible scenarios and outcomes based on the evidence, and try to highlight your thoughts on the most likely scenario plus a single alternative scenario.

Some of the more seasoned posters in the MOD thread can quite rightly use there experience to sniff out certain outcomes and alternatives and these points should also be closely and carefully considered when thinking about you own forecast or model output interpretation. 

I Have been guilty recently of one liners, posting nonsense in the MOD thread and I can see why people get frustrated and the forum team have a hard time moderating. If we all try and think a little more before we post and analyse the data hopefully with a few of the pointers in this post it will make for a much more pleasant experience and informative thread for everyone.

 

[Daniel*]

1 hour ago, s4lancia said:

The ECM, Japanese and Canadian ens models have all now updated as well (within the last half hour). All going into P8. Nice.

CFS was the first to actually pick that phase 8 up last Tuesday I spotted it. It got something right?

[karlos1983]

By Saturday things up top are beginning to get toasty!! That's this Saturday! Nice to see this getting ever closer! 

[Ice Day]

Model volatility being seen at 144.  Can't see the uppers for UKMO yet, but I would imagine they are around -6's if not a bit lower by 144.  Corking run for Scotland and our NW contingent (edit - the UKMO output I should have said)!

GFS  UKMO 

Edited February 5, 2018 by Ice Day

[weirpig]

7 minutes ago, Ice Day said:

Model volatility being seen at 144.  Can't see the uppers for UKMO yet, but I would imagine they are around -6's if not a bit lower by 144.  Corking run for Scotland and our NW contingent (edit - the UKMO output I should have said)!

GFS  UKMO 

Yes that does look alot better  more of a North West South East axis on the UKMO    some showers of the wintry type of would have imagined 

Edited February 5, 2018 by weirpig