Model output discussion - 20th Feb onwards

[IDO]

57 minutes ago, Frosty. said:

As has already been said though, the GEFS 00z mean doesn't show a cold end to march, rather cool to average at worst. To be honest, if anyone is still trying to talk up the chances of significant cold weather occurring, it's just going to sound more and more ridiculous for that to happen at the end of March and first half of april and even though I'm a bitterly disappointed coldie with how winter turned out, I am looking forward to increasing spring warmth now the sun is getting higher and stronger with each passing day!

Yes spot on. And of course even the Met can get it wrong with temps. For my location this morning the max was forecast to be 6c, but it has just hit 10c, and feeling warmer in the sun.

The 06z mean suggests another 10 days of settled weather:  

With a potential for mild D8-11 though of course the usual caveats...

...but looking at the axis of cold the UK seems to draw the mild sectors in, so the conus and Siberia/E Europe remain the cold spots for uppers:

D10 

We have to rely on the spill from these anomalous cold regions, the story of the Winter.

[David Morse]

1 hour ago, Frosty. said:

To be honest, if anyone is still trying to talk up the chances of significant cold weather occurring, it's just going to sound more and more ridiculous for that to happen at the end of March and first half of april and even though I'm a bitterly disappointed coldie with how winter turned out, I am looking forward to increasing spring warmth now the sun is getting higher and stronger with each passing day!

I can clearly remember an early Easter in March in the 1970's with three foot of snow on the ground in Cornwall; it's not impossible.

One of the other things I've noticed and posted on is the total flip flopping of the models and particularly the apparent zonal bias of the GFS which shows the retrograding the HP only for it suddenly to be swamped by a dramatic return to zonal.

ECM 00z seems to be delivering a much more stable retrograding of the high with the continent getting colder every run, and more consistent than the 12z runs. Look at the set of runs below for Saturday March 19th, it certainly looks to me that the 00z runs are more consistent showing a retrograding of the high and encroachment of the cold?

 

 

 

Edited March 13, 2016 by David Morse

[Frosty.]

The GEFS 6z mean shows our UK based anticyclone lasting until around the middle of week 2 further south which is the same as the met office update today mentions, thereafter it becomes more unsettled with temperatures close to average, quite a flat looking pattern. I noticed the MO say unsettled with temps a little below average once the anticyclonic spell is over but the next 10 days or so are looking fine and in any sunshine, very pleasant.

[Chris.R]

Just on  15.0°C here. Was that even forecast?  Just shows the  strength of the sun now, and that combined with an offshore wind means locations like this can get warm very quickly.  Something to bear in mind. I expect the models to be underestimating temperatures for western areas this week. 

[IDO]

11 minutes ago, David Morse said:

 

ECM 00z seems to be delivering a much more stable retrograding of the high with the continent getting colder every run, and more consistent than the 12z runs. Look at the set of runs below for Saturday March 19th, it certainly looks to me that the 00z runs are more consistent showing a retrograding of the high and encroachment of the cold?

I would not worry about the ECM D8-10 op charts. Again the mean suggests 5-6c higher uppers at D9 compared to the op for the east of the UK. In fact the mean for GFS and ECM are not that far apart for 2m temps from D10-15 so I wouldn't expect any incoming cold on the current mean output:

Edited March 13, 2016 by IDO

[John Badrick]

2 hours ago, Frosty. said:

As has already been said though, the GEFS 00z mean doesn't show a cold end to march, rather cool to average at worst. To be honest, if anyone is still trying to talk up the chances of significant cold weather occurring, it's just going to sound more and more ridiculous for that to happen at the end of March and first half of april and even though I'm a bitterly disappointed coldie with how winter turned out, I am looking forward to increasing spring warmth now the sun is getting higher and stronger with each passing day!

I really don't understand, the whole winter you were searching for the cold and bigging up cold charts, just because it's past the 1st of march you say it's ridiculous looking out for cold. We all know there's every chance it can get bitterly cold and snowy even through April. You can't turn the weather on with flick offa switch and mother nature dosen't follow dates so remember Frosty, statistically it's more likely to snow at easter than Christmas!!!

[Milhouse]

If theres no cold and snowy spell on the horizon then people arent going to discuss it. Same goes for a warm spell, which in the next 10-15 days looks equally as unlikely. What we have is a very dry and settled spell with temps not straying too much from average.

 

[Nouska]

28 minutes ago, John Badrick said:

I really don't understand, the whole winter you were searching for the cold and bigging up cold charts, just because it's past the 1st of march you say it's ridiculous looking out for cold. We all know there's every chance it can get bitterly cold and snowy even through April. You can't turn the weather on with flick offa switch and mother nature dosen't follow dates so remember Frosty, statistically it's more likely to snow at easter than Christmas!!!

This will be the statistical Easter snow, ...

now, .... what's the statistical chart verification at that range?  .... hmmm

[Frosty.]

27 minutes ago, John Badrick said:

I really don't understand, the whole winter you were searching for the cold and bigging up cold charts, just because it's past the 1st of march you say it's ridiculous looking out for cold. We all know there's every chance it can get bitterly cold and snowy even through April. You can't turn the weather on with flick offa switch and mother nature dosen't follow dates so remember Frosty, statistically it's more likely to snow at easter than Christmas!!!

I think that's unfair, if there was something wintry showing on the models I would still be bigging up the cold charts but there isn't and the MO don't see anything wintry either. I just call it as I see it, if you don't like that, fair enough but I'm enjoying this settled spell now which looks like lasting for almost the next few weeks further south.

[David Morse]

1 hour ago, IDO said:

I would not worry about the ECM D8-10 op charts. Again the mean suggests 5-6c higher uppers at D9 compared to the op for the east of the UK. In fact the mean for GFS and ECM are not that far apart for 2m temps from D10-15 so I wouldn't expect any incoming cold on the current mean output:

 

LOL thanks for the re-assurance; but I'm really not interested in the UK at the mo its the Alps I'm looking at. As regards the surface temps, wouldn't they be massively influenced by the increasing insolation? Therefore the average is bound to rise. In the graph you've posted its clear that on the 18th March there could be a diurnal difference of 14C so the average is a bit mute. I still think this early spring has a kick in the butt for many in the next two weeks and I'm just looking for great Ski conditions in the north western Alps.

[TomDav]

12z GEFS clusters generally cooler than the 6z at D16 with a number showing the -5c isotherm close to or over the UK & roughly half the members with a continental flow, the other with a trough of low pressure sitting over NW Europe.

 

[feb1991blizzard]

The ECM 240 is a cracker but unfortunately unless it suddenly garnishes a massive support from a swinging ensemble suite and repeats on a good few op runs, I cant actually see it happening.

Edited March 13, 2016 by feb1991blizzard

[Cloud 10]

ECM teeing up a proper northerly at day 10 which has been a rare sight in recent winters.

 

 

 

Edited March 13, 2016 by Cloud 10

[Frosty.]

The Ecm 12z shows an anticyclonic week ahead but later in the run the high pulls westwards into the atlantic with all eyes then to the north, I agree the day 10 chart is setting up a potent Arctic blast soon after. As I said earlier, the models have not been showing much wintry potential but this run certainly does!

[knocker]

The GEFS anomaly on the 23rd is similar to the 00z ecm in that it retrogresses the HP (thus a NW airflow and temps not too bad) and activates the Canadian vortex. In the ext period it does differ somewhat as, although it plays around with ridging in the Atlantic it doesn't develop the Atlantic trough so the upper flow remains in a westerly quadrant. This portends the probability of more unsettled weather towards the end of the run although temps will be in general around average. The colder trough to the east continues to weaken and move south into central Europe.

Edited March 13, 2016 by knocker

[Singularity]

 

That's two troughs extending well south in the Atlantic on the 12z ECM run.

Just the one is enough to shift the high so that we have a northerly flow across much of the UK - potentially good for CS and SW England and Wales in terms of pleasant conditions. The second sets up for a 'proper' incursion of Arctic air from the north, but given the lack of inter-and-intra-model consistency of late, this is best placed on the side for now. Slight MJO activity in phase 4 for a time does increase the odds, but I'd need to see stronger activity being called for (as per UKME) in order to consider a major northerly more seriously.

       

Of course, some degree of SSW impact can't be ruled out - the models may yet have been wrong to block it off in the lower stratosphere so resolutely.

[ANYWEATHER]

Good Evening All.....! The old saying that March comes in like a Lion and out like a Lamb maybe a little bit tweeked this year as March came in like a lion a bit like a lamb during the middle and models suggest in one shape or form out like a lion!

[Guest]

MY LATEST REPORT UPDATED WITH MARCH 13TH 2016 INPUT

Please note that most of the charts that I refer to in this post are through “live” links which update periodically. So, if you are reading this a few hours after I publication, the charts may already have updated. My comments relate to what the charts showed at the time of this posting.

There is better news for the coldies tonight - not just on some of my rather "crude" trackers but look at the latest ECM! I include details of this below.

Does Anyone Know What is Really Going on Up There in the Stratosphere?

While most of us are probably enjoying the current “spring-like” conditions, there remains the “possibility” of a broad pattern change with a colder outlook. The crunch point seems likely to come within the next 10 days. We are currently in the middle of a major stratospheric warming event with a very strong reversal within the Arctic stratosphere (and in high latitudes just beyond the Arctic Circle). There seems to have been “something” slowing down or stopping this reversal from propagating through the troposphere to the surface. Whether this is due to another major “competing” influence like the very strong El Nino or a combination of other factors does not seem to be known. It has baffled many of the experts in this field and the uncertainties have been reflected on the strat thread with a distinct lack of posting there in recent days. This area of science goes way beyond my very limited level of understanding. It seems that when this current SSW event has concluded it will have provided a huge learning curve for the analysts and how the models should be programmed to take account of it in the future.

We still might see some major surface impacts from this SSW and perhaps we have merely seen a delay in these manifesting themselves. I shall be very keen to see Dr Judah Cohen’s latest take on this. His next weekly AO report is due out later tomorrow and I shall be posting a summary of his thoughts on this thread “late” tomorrow (Monday) evening. Will he accept that we will not see any surface impacts? Will he stick to his recent thoughts that we shall see some major impacts by around March 20th? Perhaps he will say that there has simply been a further delay. We need to remember that the very unusual atmospheric set-up is just as much of a challenge to him and his models as anyone else.

We might still see a wholesale change in the surface patterns with some highly unusual synoptics and weather episodes. The further that we go into the Spring season would probably reduce the effects of any pattern changes. “Long fetch easterlies” would be far less potent and less cold in April than even now. I would think that any really cold airstream reaching the UK would need to be either directly from the high Arctic or from a truly polar continental source from northern Siberia.

So, another week to 10 days of patience and then we should have a much better idea of what mother nature has in store for us here in the UK. My obsession with this subject has really dominated my life during last few weeks and I need to re-focus on running my online business! In the meantime, I will continue, for the next week or so, to look for any signs of SSW surface impacts, broad pressure pattern changes, HLB, developing cold pools and any indications in the models’ output consistent with these changes.

The Models Today:

Most of the runs continue to be completely inconsistent. For example, the GFS 6z run showed rather more HLB, particularly in the second half of the run but the 12z reverted to a much flatter pattern with very little HLB. These are clear signs that they cannot decide whether we shall see any surface impacts from the SSW in a week to 10 days’ time.

I continue to post all the T+144 Northern Hemisphere pressure charts (now showing for next Saturday, March 19th. This is so that I can include all the main models, as UKMO end their run at 6 days out. March 19th is getting to within 2 to 3 days of when some of the analysts (like Judah Cohen) feel that the current SSW should finally impact at the surface (this may change of course). So, let us see over the next few days how these charts progress. 6 days out should be in the more reliable period but the uncertainties of the SSW surface impacts and how the models assess the possible pattern changes may show even greater confusion and wild swings in the next 2 to 3 days!

I will update these at T+144 for the next couple of days. If the impact signs are starting to show and the timing remains similar, I shall start to home in on that date with increasingly shorter term charts until (if/when) it arrives.

The main changes that I will be looking at over the next few days is to see if (any of) the models are showing whether there is any movement of low heights out of NE Canada and transferring across to Europe and Siberia and also signs of HLB. This would reflect part of the possible pattern changes which might have a greater impact of the UK later this month and into April. Of course, the changes might move the other way. It is another, perhaps rather crude way, of monitoring these possible impacts. I note that the strat thread has remained extremely quiet in the last few days. Will this major SSW with its strong stratospheric reverse propagate down to the surface?

Here are the charts. Once you have used any of the links and have located a model, you can look at earlier and later charts. I hope that the T+144s show properly. If anyone can suggest a better way of making this comparison (which I shall update daily for the next few days) please feel free to say so.

Northern Hemisphere Pressure Charts for T+144 on Saturday, March 19th:

GFS:   http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=144&mode=0&carte=1

UKMO:   http://www.meteociel.fr/modeles/ukmo2.php?nh=1&ech=144&carte=1021

ECM:   http://www.meteociel.fr/modeles/ecmwf.php?ech=144&mode=1&map=1&type=0&archive=0

NAVGEM:  http://www.meteociel.fr/modeles/navgeme_cartes.php?&ech=144&mode=0&carte=1

GEM:  http://www.meteociel.fr/modeles/geme_cartes.php?&ech=144&mode=0&carte=1

JMA:  http://www.meteociel.fr/modeles/jma.php?ech=168&mode=1

Please note that the JMA update their T+84 12z charts overnight and their T+144 was published at 12z yesterday. So I show the T+168 chart for the correct time comparison.

GFS have definitely trended to rather colder looking charts on their 12z run but there is no consistency at all in their recent runs. Judging by Gibby’s comments this morning, it seems that their ensemble clusters remain very mixed. Surely, they will pick up a stronger signal for their current 6 days+ outlook within the next 2 to 3 days and will be more decisive one way or the other.

UKMO, on their 12z run, develop the European lobe by T+120 but then move away from it by T+144 and always keep the cold across Eastern Europe.

ECM have just finished their output for their 12z run. They also transfer the north-east Canada low heights across to north-west Siberia and north-east Europe by T+120. All the time they strongly build heights right across the pole and over an increasing part of the high Arctic. By T+144 they have changed the axis of the north-east Europe lobe so that it has veered from north-north-west to north-north-east across northern Scandinavia. In fact by T+168 it really looks like they are picking up a signal for SSW surface impacts. Their last few runs have moved decidedly colder and now are showing signs of a long fetch north-north-easterly making it very close to our shores and at least to central and much of continental western Europe. Between T+192 and T+216 they temporarily seem to back track a little but then several small break away lows around Iceland and western Scandinavia look like they will back the pattern temporarily before helping to bring the long fetch north-north-easterly closer to the UK. Note that the much colder air is still a fair way to our east at this stage but much closer to our north. Then by T+240 it has just about moved into north Scotland with -8c uppers there and -16c just east of Iceland. We will need to see consistency from them over the next few runs and with other models joining the party.

I am sure that other posters will be filling this thread with some of these charts but here are links to the T+240 northern hemisphere pressure and 850s charts:

http://www.meteociel.fr/modeles/ecmwf.php?ech=240&mode=1&map=1&type=0&archive=0

http://www.meteociel.fr/modeles/ecmwf.php?ech=240&mode=0&map=1&type=0&archive=0

Although some will agrue “not the dreaded ECM T240 promise again” but this time they get there gradually step by step and it would be consistent with the suggested timing (by some) of the SSW surface impacts. There is one downside. By T+240 they have rebuilt the North-east Canada low heights and the European uppers look like -8c to -12c and perhaps not quite low enough for late March should winds veer more into the east. The Siberian low heights and uppers look rather less potent than I would have anticipated with this pattern change. So, still plenty of room for improvement (from an SSW cold impact point of view).

GEM have also trended (slightly) colder again at 12z after several warmer runs. They transfer the lobe and low heights across from north-east Canada to north-east Europe and north-west Russia by T+102. Then they swivel it around between north-east Europe and northern Siberia by T+180. At the same time they gradually redevelop lower heights in north-east Canada. By T+240 they keep strong low heights over north-east Europe and northern Siberia and have high pressure strongly established over almost all of the high Arctic. In fact GEM may be the closest to building in some surface impact from the SSW. The main area of cold is about 500 to 1,000 miles to our east and the UK might stay on its periphery.

NAVGEM move the low heights from northern Canada across to northern Siberia and north-west Russia by T+120. but re-build the Canadian low heights later in their run.

JMA move low heights into northern Siberia by T+96 and then also to north-east Europe by T+180 but always maintain some low heights in north-east Canada with strongest heights over Greenland and Alaska. The east European low heights then weaken and dissipate by T+228 but they building increasingly high pressure over the pole and maintain the strong Greenland heights. Right out at T+264, although they deepen the Canadian low heights, it looks like they might take a break away low pressure across from our north-west to our north-east, perhaps across northern Scotland. This could well introduce an Arctic airstream in its wake but at 11 days out is really pure F1 speculation!

AO Ensemble Charts: 

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

Most of the 10 ensemble members move back from being temporarily positive to neutral around March 17th. From there, 3 members go positive again, 1 strongly positive by March 23rd. 2 members end more or less neutral. The other 5 members all end negative, 2 quite strongly negative. Overall, this is slightly more mixed again but with rather more emphasis on the AO index trending negative from the middle of this week.

This continues to reflect the extreme uncertainty of how strongly the SSW will impact in the lower troposphere and at the surface with only a moderate or mixed signal for more HLB. Just as with NOAA’s other charts (showing the 500mb pressure anomalies) we may need to wait another 2 to 3 days to see anything more decisive one way or the other.

MJO Ensemble charts:

Here are todays MJO ensemble charts for the big 4 and Kyle MacRitchie’s for March 13th. 

UKMO:  http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ukme.shtml

ECM: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml

NCEP/GEFS:  http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml

JMA: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/jman.shtml

Kyle MacRitchie: http://www.kylemacritchie.com/real-time-maps/realtime-mjo/

UKMO: Very little change again today. They moved out of the circle of death into phase 3 today and then gradually progress into phase 4 and on towards phase 5 by March 23rd but with a narrower or tighter spread of ensemble members but a slightly increased amplitude.

ECM:  They have really changed and sprung to life in the last couple of days and are no longer similar to UKMO. They moved out of the circle of death today but straight into phase 4. Then they progress quickly to phase 5 by March 16th and on to phase 6 by March 22nd at steadily increasing amplitude. They reach the important phase 7 by around March 27th with are wider spread of ensemble members but mostly at quite high amplitude and a couple of members re-entering the circle of death. 3 members have progressed at greater speed, just about reaching phase 8.

NCEP/GEFS: yet again take quite a different view and their chart seems to reflect the great uncertainty shown across almost all their other output. They generally nudge the circle of death as they progress through phases 3 and 4 and on into phase 5 during the next 5 days at marginally increased amplitude by around March 18th. Then they mostly stall with most members returning to the circle of death. A few ensemble members reach phases 6, 7 and 8 later on but at low amplitude.

JMA:  have changed their pattern very little with all ensemble members inside the circle of death but have moved them from the phase 2/3 boundary further across the phase 3 boundary. Several stray ensemble members try to break free before returning to hibernation!

Kyle MacRitchie:  Continues his consistently bullish approach. He shows the MJO progressing through all the phases from 1 right through to 8 by April 12th. He has increased amplitude even further with member almost breaking out of the chart!!!

Well today we see a few changes with 2 of the big 3 moving slightly further towards Kyle MacRitchie’s predictions. Perhaps he really is on to something and not completely wrong! The MJO is not in the important phases 7, 8 and 1 for several weeks and would not contribute to HLB in our part of the Arctic. We would need to rely on the SSW impacts and perhaps less directly from the El Nino or other factors.

What does GloSea5 show now? Please can Fergie provide another update.

Current Surface Arctic Temperatures:

GFS – Northern Hemisphere Current Temperatures:

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=6&code=0&mode=9&carte=1

The link to this chart updates 6 hourly with each GFS run. At the time of writing it is showing a chart for 1900 today (13th March***). As this is T0 to T6 hours, it should be pretty accurate. 

In the Arctic, temperatures close to the North Pole are around -28c to -32c (-20c to -24c yesterday). In “our” part of the high Arctic (around the Barents Sea) temperatures have fallen to around -8c to -16c (around  -4c to -12c yesterday). Most of Scandinavia is slightly warmer at around 0c to -4c today (-4c to -12c yesterday). Much of northern Siberia remains around -32c to -40c (similar to yesterday) but with an even wider area below  -40c. There is a cold wedge developing through north-west Russia (around -20c) with -8c  to -12c extending over a wider area south of this and into north-east Europe.

So overall, apart from Scandinavia, things have turned decidedly colder our side of the North Pole and through Siberia, Russian and into north-east Europe.

*** Please note:   At the time of posting this link it was showing 1900 on Sunday, March 13th. The charts are automatically updated 4 times a day, so the temperatures shown will be different to those I just mentioned above. We can follow the trends by looking at the latest data at any time from now on. It is vital to note the time of day to take account of daytime/nighttime variations. So for like for like comparisons, for example the 1900 charts for each day should be available to view from the 12z (T+6) updates which are published around 1600 or about 4 hours later. This also applies to some of the other charts I link to in this post.

Svalbard Daily “Maximum” Temperature Forecast for 10 Days:

Here are the links to the 3 Svalbard stations that I am monitoring.

Central Svalbard – Longyearbyen 28 m asl:   

http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf

March 16th  -11c;   March 19th  -12c;    March 22nd  -10c.

West Svalbard – Ny-Alesund:                                                            

http://www.yr.no/place/Norway/Svalbard/Ny-%C3%85lesund/forecast.pdf

March 16th  -14c;   March 19th  -17c;    March 22nd  -15c.

South Svalbard – Sveagruva:                                          

http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf

March 16th  -12c;   March 19th  -19c;    March 22nd  -17c.

The general trend is for the “maximum” temperatures to fall during the next 6 days and then to level out at the much lower values after that.

These links will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at short range. 

To put the above figures into context, here is a link to the main Longyearbyen site:  

http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html

This shows monthly means, and actual highest/lowest temperatures recorded during this winter and goes back further. Apart from a couple of days in December, Svalbard is likely to see “maximum” temperatures falling to well below average, for the first time since Winter 2014/15

Final Comment:

So, after several uncertain days, there is definitely more of a colder trend showing. The ECM seems to have picked up on this far more than the other models. This trend may only be temporary and perhaps not even related to any SSW surface impacts. I have a hunch, however, that we might see some very interesting developments for coldies during this week. I cannot wait to see what Judah Cohen has to say in his update tomorrow.

My report tomorrow will include a summary of his latest report. I have a business commitment that I cannot wriggle out of late tomorrow afternoon and into the early evening. So my next update might be posted very late tomorrow evening. If the headlines are worthy of more immediate attention – I may post a “quick link” to Judah’s report and then comment on it later on.

Lastly, although I am a “coldie”, I accept that some of you are not and I understand that a prolonged cold period in late March and early April might be devastating for sheep farmers, arable farmers and gardeners.  This is simply mother nature playing tricks on us. In any case, it still might not happen!

 

Edited March 13, 2016 by Guest
checked that links are working + grammar, spelling

[Frosty.]

The Ecm is such a tease, would love to have seen a T+264 chart...would love to see an ecm run verify at that range just for once, there were quite a few cracking wintry T+240 charts through the winter but ...there's a first time for everything!

[Weather Observer]

Not the first time, you only have to go back 115 years. To quote the Beach Boys "wouldn't that be nice"

[Frosty.]

26 minutes ago, Weathervane said:

Not the first time, you only have to go back 115 years. To quote the Beach Boys "wouldn't that be nice"

Now that would be worthy of a cold ramp

Anyway, back to reality...Nice and settled for another week or two according to the latest models.

[knocker]

The ecm continues the theme of retrogressing the HP by the 23 rd. As mentioned previously this does introduce the possibility of some more unsettled weather from the NW if systems swing around the HP tracking SE into Scandinavia. Could even produce a transient northerly.

Needless to say the NOAA 5-10 has the HP further east but that may be down to the five day average.

Moving forward into ext EPS range it loses the trough to the east and the ridging in the Atlantic and introduces a cool unsettled zonal flow not dissimilar to the GEFS by the 29th giving temps around the average. The NOAA 8-14 does actually keep some semblance of ridging.

Edited March 13, 2016 by knocker

[feb1991blizzard]

1 hour ago, feb1991blizzard said:

The ECM 240 is a cracker but unfortunately unless it suddenly garnishes a massive support from a swinging ensemble suite and repeats on a good few op runs, I cant actually see it happening.

But it does have some support!!

[TomDav]

GFS going blocked in later stages as high retrogresses, perhaps SSW effects filtering into the model output ? 

[Guest]

DR JUDAH COHEN'S AO REPORT UPDATED ON SUNDAY, MARCH 13TH:

STOP PRESS:  bryan629 has just informed me that Dr Judah Cohen's latest Arctic Oscillation Report has been updated a day earlier than usual. So, here is the link:

http://www.aer.com/science-research/climate-weather/arctic-oscillation

As this is so important, I shall copy his Summary and the Impacts below:

March 13, 2016

Summary

The Arctic Oscillation (AO) is currently neutral and will remain near neutral most of the week before trending negative next week following the peak in the sudden stratospheric warming (SSW) over the weekend.  The peak in the SSW will challenge the greatest stratospheric warming ever observed (as measured by the strength of the polar jet). 

The current neutral AO trend is reflective of mixed pressure/geopotential height anomalies both across the Arctic and the mid-latitudes of the Northern Hemisphere.

The neutral AO atmospheric state is likely a combination of offsetting or compensating influences.  The SSW in February favors a negative tropospheric AO (and since the SSW in February the tropospheric polar cap heights have been predominately warm) while the still active vertical energy transfer favors a positive tropospheric AO.

As has been the story all winter the still active vertical energy transfer predicted for this week will lead to yet another round of mild weather for Europe and eastern North America.  So while this latest pulse is leading to extreme negative AO values in the stratosphere it is delaying similar negative AO values in the troposphere.

The polar vortex (PV) is currently split over the Eurasian continent with one lobe over Siberia and the other over Western Europe.  With the main PV located over Siberia that is where the greatest negative temperature departures are located. 

Currently with the lack of any direct influence from the PV and with the vertical energy transfer still active, temperatures remain well above normal for much of North America.  However, the PV lobe over Europe is predicted to drift westwards and eventually over eastern North America.  With the eastern North American lobe of the PV predicted to become the dominant PV lobe coupled with northerly flow should allow temperatures to first cool over Canada and eventually the Eastern United States (US) starting next week.

Impacts

The weak PV is already one of the two weakest ever observed as reflected by the strongly negative stratospheric AO (Figure 1) and may still become the weakest.  The tropospheric AO is neutral (Figure 1) likely due to competing influences.  The SSW in February favors a negative AO but the yet still active energy transfer favors a positive AO (Figure 8).  The positive AO forcing is reflected in negative geopotential height anomalies near the North Pole and on the North American side of the Arctic (Figure 2).

The region of the Northern Hemisphere with the strongest relationship with the strength of the PV is Siberia.  With the PV at record weak, all of northern Siberia and southeastern Siberia are currently experiencing temperatures that are well below normal (Figure 3).  The stratospheric PV is split into two pieces with the main lobe over Siberia and a secondary lobe over Western Europe (Figure 9). It is likely that because the main lobe of the PV is over Siberia is also contributing to cold temperatures in the region as the cold air follows the PV.

With the lack of any direct influence from the PV and with the vertical energy transfer still active, temperatures remain very mild for much of North America (Figure 3).  However, the secondary PV lobe currently over Europe is predicted to be carried in the strong easterly flow, created by the SSW, westward across the North Atlantic and eventually over eastern North America.  With time this is predicted to become the dominant lobe of the PV (Figure 9).  The pattern in the stratosphere should descend with time into the troposphere with positive geopotential height anomalies across the Arctic and western North America and negative geopotential height anomalies across eastern North America (Figure 4).  This will lead to colder temperatures first across Canada and then eventually the eastern US (Figure 5 and 6).

The stratospheric negative AO is predicted to finally peak over the weekend.  Based on our best understanding, the tropospheric AO is favored in the negative phase following the peak of the stratospheric negative AO.  And as seen in Figure 1, the probability of a negative tropospheric AO is favored next week and beyond.  Also the polar cap geopotential height anomaly (PCH) plot shows the classic “dripping paint” signature of the warm geopotential height anomalies/negative AO descending with time from the stratosphere to the troposphere (Figure 7).  Therefore, the negative phase of the AO should be favored well into April as well.  However, given the lateness of the PV disruption, I remain uncertain how well the current PV disruption will follow the paradigm established for mid-winter.  Also a negative AO in April does not have the same impact across the mid-latitudes as it does in January and a snowstorm in January becomes a cold rain in April.  Another uncertainty is the temperature anomaly pattern predicted by the latest Global Forecast System (GFS) ensembles.  The GFS is predicting for next week and even into the following week for the cold temperatures to be mostly confined to North America.  If the AO becomes increasingly negative as suggested by Figures 1 and 7, then the eastern US/southeastern Canada, Europe and East Asia are all favored for relatively cold temperatures but Siberia has the strongest relationship with the AO of all the land regions.  Therefore, if the negative tropospheric AO does materialize the temperature anomalies may not be as asymmetric as depicted in Figures 5 and 6 (cold North America/warm Eurasia) with temperatures possibly warmer than predicted for North America but colder for Eurasia.  Though if the dominant PV lobe is over eastern North America as predicted this does favor cold in eastern North America as well.

If you wish to view Judah's charts you'll need to use the link above and go to his site.

My Very Brief Assessment:

So Judah Cohen tells us that the SSW has been peaking this weekend and is very close to the strongest one ever recorded (if not the strongest).  He expects the AO to trend negative by the end of this week. He gives his reasons for the delay (throughout February and early March)  in the propagation to the surface (which seem highly complex and not completely understood).

In recent weeks, the Polar Vortex (PV) has already become one of the “weakest” known and Judah expects it may become the weakest ever (quite a turnaround from mid-Winter!).  The PV is split with main lobe over Siberia (where the lowest temperatures are with the greatest anomalies) and a secondary lobe over Europe (much as he has been predicting for a few weeks now). Again as last week, he expects the very strong stratospheric easterlies to carry the European lobe all the way across the North Atlantic and into eastern North America and eventually becoming the dominant  PV (by mid April).

He still expects the stratospheric pattern to propagate to the surface and this still seems to be indicated for around next weekend – so probably no further delay on his predictions from last week (around March 20th/21st). He states that this follows the normal pattern following the stratospheric peak – a few days later. He says there are already the classic signs of this happening through the troposphere. Once established he expects the negative state to “last through well into April”. He still adds the caveat of the lateness of the event and whether the outcomes would be similar to those following a mid-Winter event. He re-states “January snow = cold rain in April”.

He then states that eastern USA/Canada, Europe and East Asia are all favoured for relatively cold conditions with the greatest cold in Siberia. He says that “if the negative tropospheric  AO does materialise, then Europe may be colder than the charts (he refers to) show”.

Overall, there is still much uncertainty. I would say still a small “if” but a bigger “when”. I detect that the cold in Europe will not be as intense as he previously suggested (although it still might be).  He seems to have dropped the “long fetch easterlies from eastern Siberia to the UK”. It is late and I am very tired and I might have misinterpreted some of this. I just wanted to get this out as quickly as possible.

Edited March 14, 2016 by Guest