Model output discussion - 1st December onwards

[Singularity]

I think that given what the 5/6 MJO progression ties in with (a very westerly pattern with blocks blown away), emphasis for the 7-14 day evolution should be one of moving away from a Scandi high and toward a UK/Euro trough with high pressure ridging poleward from the vicinity of Siberia. For that, the westerly push is okay as long as it doesn't go too far... ECM takes it a bit too far for my liking while GFS is very decent.

ECM's use of more than one bombing low to get where it does automatically lowers confidence in its solution, but it can't be discounted given the background signals.

 

In the nearer term, the hope is that the transient ridge through Scandinavia can push far enough north to give the vortex something to think about while we wait for the next attack. I had hoped that the vortex wouldn't be quite so strong as it's turned out to be, so as to allow for a bit of distortion and a spell of more interesting patterns around the turn of the new year, but unfortunately it looks like we'll have to settle for chinking away at the vortex's armour to leave it more vulnerable to the next period of wave breaking, which if the MJO makes it to phase 7/8 ought to be considerably greater in magnitude than the one coming up for the closing days of 2015.

We were always going to up against it this winter. As for the GEM 12z det. run... whaat 

[Daniel*]

5 minutes ago, chrisbell-nottheweatherman said:

 

Two posts saying two completely different things.  I don't know which model MS is referring to, but the ECM seems to show a continuation of recent conditions as nailed-on to me.

There's a large divergence in outlooks between the ECM and GFS the GFS giving seasonal weather the ECM giving blowtorch southwesterly winds, implying much uncertainty. It is not a done deal in the slightest. 

Edited December 22, 2015 by Daniel*

[tight isobar]

On Wednesday, December 16, 2015 at 3:57 PM, nick sussex said:

The MJO update sees the ECM monthly increasing the amplitude and now a majority of members manage to get this into phase 7. Theres still a divergence though between the ECM/UKMO and GEFS. The UKMO in particular increases the amplitude strongly .

Looking at the trend of the last few days the models have under estimated the strength, lets hope this continues.

Rhere does appear to be NS.

I be

19 minutes ago, nick sussex said:

I spent hours today doing a lot more reading about the MJO. For a second I thought I was back at University and having one of those last minute OMG its exam time tomorrow moments.

Well maybe they had a Christmas party at NCEP and too much bourbon caused him to download the wrong file. If its not sorted out by tomorrow I'm going to email them!

At this point I think its a case of us coldies going down to the casino and placing all our bets on red, red in this case being the MJO.

It could well end in tears but given events in the strat the MJO is at the moment looking like the last throw of the dice in terms of seeing some changes within the next two weeks.

 

Im lead to be

 

[tight isobar]

On Wednesday, December 16, 2015 at 3:57 PM, nick sussex said:

The MJO update sees the ECM monthly increasing the amplitude and now a majority of members manage to get this into phase 7. Theres still a divergence though between the ECM/UKMO and GEFS. The UKMO in particular increases the amplitude strongly .

Looking at the trend of the last few days the models have under estimated the strength, lets hope this continues.

Rhere does appear to be NS.

I be

22 minutes ago, nick sussex said:

I spent hours today doing a lot more reading about the MJO. For a second I thought I was back at University and having one of those last minute OMG its exam time tomorrow moments.

Well maybe they had a Christmas party at NCEP and too much bourbon caused him to download the wrong file. If its not sorted out by tomorrow I'm going to email them!

At this point I think its a case of us coldies going down to the casino and placing all our bets on red, red in this case being the MJO.

It could well end in tears but given events in the strat the MJO is at the moment looking like the last throw of the dice in terms of seeing some changes within the next two weeks.

 

Im lead to be

 

 

 

 

 

 

Having afew technical hitches

Atm...excuse me

[Vorticity0123]

 

Today the Astronomic winter has officially begun! Or well, winter… in the Netherlands we have yet reached another all-time record daily high. We have seen so many daily temperature records here that people barely notice them anymore. However, there is of course much more going on behind the scene!

Most importantly, a significant pattern change is bound to take place the next couple of days. Will it bring significant winter weather? Or are we going to see a continuation of this extreme mildness? Of course much will change over the next few days regarding the outcome, but still we can definitely say some specific things about the weather to expect. Before doing that, I would like to take you through a tour showing just how unique the warmth is we are experiencing.  Time to dive into the Spring month called December!

A crushing month

A record-warm December month is what this month will certainly be. But this December monthly record is not going to be broken, it is going to be literally crushed. And that is something we can say 9 days before the closure of the month. The previous December record high mean temperature stood at 7.3*C, set in 1974. Currently, December 2015 has a mean temperature of 9.6*C, a whopping 2.3*C above the previous record. And this is not going to change much, judging from the latest ECMWF ensemble:

ECMWF temperature ensemble for De Bilt, the Netherlands from the 00Z run of 22-12. Source: Weerplaza. The blue line denotes the average temperature for December.

The black line indicates the mean temperature that one can roughly expect averaging all the members. This temperature equals about 9*C. Applying a rough calculation, this would mean that the final temperature will reach 9.4*C, which is more than 2 (!) degrees above the previous all-time mean temperature high for December.

South-westerlies “ohne ende”

It has been windy during most of December, but most impressive is the prevailing wind direction. The image below shows this:

Wind direction and -strength for De Bilt, the Netherlands for December 2015. Source: KNMI.

It will not get much more south-westerly-dominating than this. About 90% of the time the wind has had a southerly component. Roughly speaking, the source location of the air has been’ tropical’ most of the time, originating from the seas near the Azores. These locations aren’t standing out for their cold winters weather to say the least.

Given all this, it seems clear that lots will be written in the media about the unpreceded warmth in the coming days. I’ll provide a short update once this record-breaking December has come to a close.

Polar vortex on the move

From looking to the past we are now going to turn our eyes to the future. As Nick alluded to in the previous post, one of the most significant changes taking place is the position of the (lower stratospheric) polar vortex.

100 hPa heights for today 00 UTC as analysed by ECMWF. Roughly, the center of the low pressure area indicates the location of the polar vortex.. Source: FU Berlin.

For now, the Stratospheric polar vortex looks to be rather circular. However, things are going to change a lot, as we can see 8 days later:

100 hPa heights for T+192 (8 days out) as forecasted by ECMWF 00Z run of 22-12. Source: FU Berlin.

The first thing that shows up is that the polar vortex will be by far not as circular as it is now. In fact, its main centre has moved southwestward towards Greenland. It needs to be stressed that this is all is not caused by a SSW.

From zonal to blocked?

Often, such pattern changes in the stratosphere result in amplification of the flow near the surface as well. This means that the flow starts to be more north-south or south-north oriented instead of east-west. In other words, the Jetstream starts to meander a lot. This is also what we are going to see happening as well.

For us, the most important ‘consequence’ of this all is that ahead of the polar vortex, high heights start to build at this level giving credits to believe that this will also lead to a significant blockade at the surface in the proximity of Scandinavia.  So far, December has represented high pressure over Central Europe. So what are the differences compared to what we have seen during the first parts of December?

1)      Low pressure activity is more active near Greenland and to the south.

2)      High pressure activity over central Europe is anchored slightly more to the north (though the exact location remains to be seen).

A setup to winter weather?

With such a setup forecast, a high pressure area at the surface near Scandinavia is a distinct possibility. Does that also mean that winter weather is on the way? The answer is most likely not. But why?

For the reason why it is useful to look at the ECMWF and GFS for 10 days out:

ECMWF (left) and GFS (right) 500 hPa heights (colours) and surface pressure (black contours) 12Z T+240. Source: Wetterzentrale.

The plots given above are for 2.5 days further out than the stratospheric charts of the ECMWF presented above.

In both cases we see the polar vortex nicely represented at 500 hPa as well by the purple colours (very low heights, so intense troughing). Both charts also show something of a Scandinavian/European high pressure area. But both charts are definitely not suggesting anything wintry. These charts would result in a continuation of south-westerlies instead. Why is that the case?

The ‘block’ is in both the ECMWF and GFS located too far to the east to be of much influence on the weather in Western Europe. It only tends to hold up approaching low pressure systems from entering Europe, instead sending them northward towards Iceland. The troughing over the Central Atlantic, on the other hand, is able to exert its influence over Western Europe. As we are going to be located in the upper branch of the troughing, the consequence is again mild southwesterlies.

Back to where we started: southwesterlies “ohne ende”

What we can conclude is that, despite the pattern change occurring in the upper levels of the atmosphere, the result is only a continuation of the same theme. With blocking in the upper atmosphere to be set firmly in place, the southwesterlies could last for quite some time, making after a record warm end of December also a very mild start of January a very distinct possibility. The best evidence for this can be found in the ensemble forecast for the wind direction.

ECMWF ensemble of wind direction for De Bilt, the Netherlands from the 00Z run of 22-12. Source: Weerplaza.

180 degrees indicate southerlies whereas 225 degrees denote south-westerlies. The black line is drawn to emphasize the ‘location’ of south-westerlies.

Even past the start of January, most ensemble members show a domination of south-westerlies.  For example, at January 5, the chances on a southerly to south-westerly wind direction still seems to be about 80%.

This, in combination with the ‘stuck’ upper pattern and the very mild ensemble temperature forecasts given at the very start of this post, lead me to believe that for the next 2 weeks or so, the weather will be most likely on the mild side. The question is only by how much.

Concluding note

I hope with this post I have shown just how extraordinary this December has been. And that even when the ultimate weather near the surface does not change, the developments taking place aloft can still be very interesting to follow! If you have any questions, do not hesitate to ask! And finally, a nice Christmas and best wishes to 2016 to all. Hoping for an interesting 2016 weather-wise!

Other sources

For the daily records, the following sources were used as well:

Weergegevens

MSCHA

Edited December 22, 2015 by Vorticity0123

[egret]

.....HIC? too long in the Iso Bar?

 

Edited December 22, 2015 by egret
off topic - still but its christmas!

[Catacol]

11 hours ago, IDO said:

I still believe there is no MJO signal and that the amplification is from a standing Kelvin Wave, so therefore I am still not expecting the 7-10 days composites of a MJO phase 7 to materialise (Scandi block). The ECM seems to be where I have suspected the pattern to be, a block of amplification moves into our region, that is mobile and flows within the positive AO signature. CFS weeklies are now correcting the signal and week 3 and 4 are now suggesting a return to our default Winter synoptic, with the Azores feeding into the UK from the SW. 

 

Cor blimey - it is depressing in here today. But I think some meat on the bones above is due - and also strat junkies need to get their radar right.

Firstly - all 13 of the MJO models available over at the CPC are today forecasting  move into a decent phase 6 in the next few days. Firs thing to note there is that this has taken the models by surprise - if you check the verification stats for the MJO GFS you will see that the last 2 weeks has seen a constant undermodelling of the strength of the convective pattern out in the Pacific, and I would hazard a guess that the models may continue to do this. And yet - the ECM MJO forecast today is much more vigorous than it was yesterday... and the forecast today from our own MoGreps model - highly regarded I believe - shows a clear signal for continued strong MJO activity heading towards phase 7:

 

 

It is a pity Mogreps does not go much further out... but both ECM and GFS today are singing to the same tune.

If we get to phase 7 - and to be clear this is still obviously an if - then the January composite is much better viewing for those who like their winter cold:

 

Secondly I think people need to start viewing the Strat with a sense of perspective. A full vortex breakdown is obviously the holy grail for cold lovers.... but in reality total breakdowns do not occur every year... and many cold spells from the past have not materialised from total breakdown scenarios. A weakening of the vortex combined with a favourable pacific MJO may well be all we need to get blocking in the right place, and so it irritates me to see tweets from those like Ventrice used as though they are proof of the end of winter. That is total nonsense.

Our current setup has a little way to go yet, and then as GP stated the other day it looks odd on that the pattern will shift to the east and the trough drop over the UK. Temps back down to somewhere near normal with the chance of height rises in mid atlantic as well as in western Russia. What happens after that will be hugely dependent on correct MJO modelling as well as trop led disturbance to the vortex - both of which many of us are pleased to see aligning in the right direction. Just how well the convection will hold together in the pacific, and just how great an impact wave breaking is going to have on the vortex is up for grabs. Both may fail. Both may succeed. We may get partial joy from one or both.

BUT for sure the pattern is at the peak of its dreadfulness, and statistically we all know that front loaded El Nino winters get less zonal and more blocked as time passes.

So let's keep a bit of perspective. We need to ride out 2015 and see what occurs in the first week or so of January. If the MJO begins to camp in the COD and wave breaking simply bounces off the vortex then by mid January perhaps we can start to worry.

But not yet.

[Allseasons-Si]

Ok ,i will have a stab at explaining the situation @ 144hrs from ECM,UKMO,GFS,JMA and of cause the GEM

the ecm and ukmo both have a positively tilted trough in the atlantic with no shortwave/low in europe to prop up the high preasure

the gfs has a slightly negatively tilted trough in the atlantic with a shortwave/low in europe so a bit better than the ecm and ukmo at that stage,the jma is a bit poorer than the gfs with the positively tilted trough but with the shortwave/low in europe

Now the gem,with a perfect neg tilted trough in the atlantic with a shortwave/low in the prime position to prop up those hight's to the north

this feature is amungst some of the gefs ens and we need to see this continue in subsequent runs

oh!,did i mention shortwaves in my post just then

fantastic posts by Vorticity and Catacol there,very sensible and understandable

Edited December 22, 2015 by Allseasons-si

[Frosty.]

LOL this winter is an absolute joke, daffodils everywhere, blossom on the trees and the models, don't get me started on the models..But at least it's Christmas!!

[Timmytour]

5 hours ago, No Balls Like Snow Balls said:

From Twitter

Michael Ventrice ‏@MJVentrice  2 hrs2 hours ago

We are running out of time for any impactful changes to the Winter pattern by the stratosphere.

 

 

 

 

 

 

 

Is that Professor Mole I see?

[Yarmy]

While I share the general lack of confidence in proper cold anytime soon, it's worth noting that the ECM appears to have modelled Nick's Atlantic shortwave badly even in the reliable time frame.

Yesterday's 12Z:

 

Today's 12z:

 

It's now showing more or less what the GFS was yesterday. The ECM is King, but it doesn't mean it's always right.

 

 

[Man With Beard]

Well I'm going to stick my neck out and predict a change in the Northern Hemispheric pattern after the turn of the year is quite likely. Whether that makes the UK colder, don't want to comment on that but at the very least I think we're going to see a lot more variability in our weather. Why my confidence? Well, compare the T168 mean with the T0:

There's no quick route to cold from this. Nothing to block the spinning of the vortex from west to east - cold locked up. But T168:

Now the PV has a bit of resistance to get through. It's harder for the vortex to get from the Atlantic through Siberia and back round. And this is the consequence on model certainty by T240:

Look at that giant area of uncertainty over Scandinavia. This means lots of possibilities between T168 and T240. The low in the Atlantic could be forced south by the Scandi heights - meaning heights over Europe dissipate, leading to a certain downturn in temperatures here whatever the weather. Or, perhaps a Scandi High may develop and lows are forced north - not impossible that the flow over the UK will turn S or SE - colder, no Feb 1991 scenario at that point but possibly a building block. Or maybe the Atlantic will smash through the block and back to square one - but this is no more likely than the other options, is my guess from that spread on the T240.

This ensemble member, for instance, is not an unrealistic outlier but a serious possibility, IMO - not freezing, but much closer to a freeze:

[PolarWarsaw]

Well this is as painful modelling as....oh last winter. Is it me or have the models provided virtually nothing but pure frustration for most of 2015 - in all seasons?

Obviously it's only the first day of winter officially today - but if there's no change at some point in the next 2 and a half months or so, the last 2-3 winters will have provided literally 2 attempts at snow in low lying England - utterly pathetic for those of us wanting seasonal and proper weather for each quarter of the year. For those that counter that with 'its rarely hot in summer either' - at least it's sunny and dry some of the time - us winter folk can't even get a bloody frost. 

Obviously there are factors against this part of the earth getting cold spells for prolonged or frequent periods, but to me, it just feels like the entire swathe of charts, the analysis, the strat, 5 different models etc that we have available these days are taking away the 'over night' flip ability, or the 'catch you by surprise element' of the models away and affecting/dampening the mood of the thread. It certainly feels like everytime someone has a positive comment to make, they have a chart, or a link, or a piece of writing thrown back in their face. For sure, everything we have these days are brillant for educational purposes and they do definetely enhance the technical ability of our forecasts - which can only be a plus, however, for me, it takes away some of the fun. 

I liken it to the good old days of being a wrestling fan as a child... no internet, no spoilers...everything that happened felt 'real' - these days we are bombarded by taped programming, spoilers and the internet...taking away the fun, even though you can't help but 'see' the spoilers you know will ruin your fun? (Or would have 15 years ago). 

 

Reading this thread tonight, you could/would effectively as a novice, come in and go away with the notion that you can effectively write off the next 2-3 weeks for cold weather and then come back to see if things changed. That wouldn't have happened a decade ago...AND YET..we are no further ahead now than we were 10 years ago in producing a 2 week forecast..says it all really..

 

Still, plenty of turkey, alcohol and family to enjoy in the next week or so folks. 

 

Enjoy - and have a good one. 

[Allseasons-Si]

2 hours ago, blizzard81 said:

I know which model my money is on and it doesn't begin with G

Is that gfs or gem

18z coming out soon,i will be keeping tabs on neg tilts and shortwaves in europe(in the right place of course)

Edited December 22, 2015 by Allseasons-si

[snowrye]

Some posters are running out of the mod thread,they think its all over,it is now

[Allseasons-Si]

1 minute ago, snowrye said:

Some posters are running out of the mod thread

Plenty of room in here for warm hearted people i would say

[bluearmy]

There is a new ECM tool currently running (in pre operational mode) which is the 45 day ens. I don't have the details on the resolution of this model but note that it currently predicts the status quo to be maintained through January apart from a period of Scandi trough  late in the month where temps wil drop a bit below average. certainly nothing to get excited about and broadly fits in with the EC 32 output we saw this morning

EDIT:

just checked ecmwf and the following :

New 45 day ens are 18km to day 16 and 36 km days 17 to 45.  Impressive!

also, the new eps when they come out will be same resolution out to the end of the run at day 15. No longer a drop off at day 11.  Also, impressive. I think implementation for all this will be March 2016.

Edited December 22, 2015 by bluearmy

[Carlrg]

They're all different at T144 the maximum UKMO goes to. What will play out is anybodies guess including the models. 

 

Edited December 22, 2015 by Carlrg

[Allseasons-Si]

6 minutes ago, Carlrg said:

They're all different at T144 the maximum UKMO goes to. What will play out is anybodies guess including the models. 

 

 

 

 

 

Of course they are all different @ 144hhrs away,until we resolve this shortwave at 96 hrs we won't know what will happen,i have explained in my previous post above about the posibilities out to that time,hope that helps   

[Carlrg]

Well at T96 the GFS has the Scandi High retrogressing and the shortwave losing its oomph.

[Mucka]

Well the shortwave didn't make it through but slightly compensated for by a deeper trough and more amplified ridge intially, certainly won't be GEM good but won't ECM bad either.

 

[Geordiesnow]

With a temporary area of high pressure just to the north of the Shetland Isles it means the rain on xmas day is likely to stall over somewhere over Northern England during xmas night and into Boxing day so its one to keep a close eye on for those flood affected areas. Also the models are not yet fully certain whether it be a shallow area of low pressure or something a little deeper although the 18Z has dropped the idea of previous runs that it could be a shallow area of low pressure. That said, I think more runs is needed to firm on this though.

Whilst it looks like height rises will develop, at this stage its unlikely they will have much affect on our weather regarding cold weather and instead it will be a battleground which will result in the UK having mild to very mild south to south westerly winds. 

After that will be uncertain of course but I think the main message the models are indicating is that after a brief cooler period with some actual PM air coming into the UK, the return of the very mild conditions will return more widely and the weather front which is leading for all that very mild air could well cause yet more flooding problems, especially if it stalls in the areas where flooding is still a high possibility.

[Nick F]

41 minutes ago, Carlrg said:

They're all different at T144 the maximum UKMO goes to. What will play out is anybodies guess including the models. 

Those charts you show look very similar at the 500mb level (the coloured contours), the positions of surface lows may often be different between models even at that range., but the 500mb is stable and more predictable. However, there are increasing differences further on in the 8-10 day period between ECM and GFS with regards to maintaing the ridge. But the end result with either solution is that the UK stays mild much of next week.

The extended 12z EPS in the means suggests T850 temperatures returning more to average from the west  later next week and to start the new year for most, even perhaps slightly below across Scotland. This is in response to a more westerly flow developing as the Sceuro ridge anomaly disappears and a low height anomaly develops centred over the Norwegian Sea and nudging into Scandi by day 15.

 

Edited December 22, 2015 by Nick F

[Allseasons-Si]

10 minutes ago, Nick F said:

Those charts you show look very similar at the 500mb level (the coloured contours), the positions of surface lows may often be different between models even at that range., but the 500mb is stable and more predictable. However, there are increasing differences further on in the 8-10 day period between ECM and GFS with regards to maintaing the ridge. But the end result with either solution is that the UK stays mild much of next week.

The extended 12z EPS in the means suggests T850 temperatures returning more to average from the west  later next week and to start the new year for most, even perhaps slightly below across Scotland. This is in response to a more westerly flow developing as the Sceuro ridge anomaly disappears and a low height anomaly develops centred over the Norwegian Sea and nudging into Scandi by day 15.

 

Just a question Nick,this low height anomaly you suggest pushing into Scandi at day 15,does the 12z eps show a poss height anomaly into the atlantic at that time,some 12z gefs members do show this?

Edited December 22, 2015 by Allseasons-si

[Carlrg]

Thanks for the insight Nick, looks like the rut is well and truly stuck then.