Model output discussion - 5th December 2016 - Into Winter we go

[mulzy]

11 minutes ago, swilliam said:

Short ensembles look distinctly colder than previously - at least in Holland

Indicative of blocked conditions - if anything the pendulum maybe swinging away from mobility to a blocked scenario.

Edit: Extended eps confirms the swing away from mobility shown on this morning's run.

Edited December 7, 2016 by mulzy

[January Snowstorm]

I don't particularly buy into the line that the rest of December is gone cold wise.

We need to understand something here in that forecasting weather isn't an exact science and beyond 10 days is simply not possible. As long term forecasts often go by the wayside equally does the talk of a mild Winter now setting in...We simply don't know!!

For me it's quite simple, the arctic was unusually mild and that delayed the flood of cold air moving south in the atlantic...hence delaying the clash of airmass that drives the jet stream. Now the Arctic is cooling rapidly, cold air moves south and bingo!! Jet kicks off.

Longe range forecasts are great fun but whether they go well or not is pbly down to luck more than anything else. Equally writing off the rest of December is also folly. It's lottery and all we can do is buy a ticket!

My punt is things will pick up soon and with background signals the polar opposite to last year the lotto jackpot might get v high!

[winterof79]

Anyone's guess in the extended. A few colder options starting to feed in to the equation

 

Edited December 7, 2016 by winterof79

[Summer Sun]

 

[Ali1977]

Can we swing this back the other way I wonder - lets see at this time on Friday some of these better ENS are starting to show at day 10, and gain some back up from the Ops and further reaches of ECM. 

 

Edited December 7, 2016 by Ali1977

[Stravaiger]

7 hours ago, Steve Murr said:

So Why did I ( & the NW team perhaps ) go for a 'front loaded winter' - what does it mean ?

For 'ME' I dont really have any interest in the teleconnections per say, that is simply because they rarely deliver any success in terms of forecasting other that when the major player ENSO completely bulldozes the NH pattern with a super Nino-

What I do follow though is the zonal wind (u) @ 10 HPA across 60N - that gives us a real time framework of where the vortex is in terms of (u) zonal component & if its weak some guage of the meridional component- Its also the end result of all the trop forcing on the strat - 'the sum of all'

The ECMWF compiled a data file of All zonal wind speeds back to 1957 called ERA40 & then redid them at a better resolution called Interim ERA for 1979- 2015-

Whilst the data is not publicly available the key element from this is the climo line that this dataset produced to give us a steer from Nov-March where we should be on the zonal winds. ( I would love a breakdown though of the DJFM seasons though to correlate to our CET & AO/NAO couplet )

There are some key dates & info in climo ( see below ) that we should really get to know as well as records of peaks speeds & lowest speeds- for instance surprise surprise 2015 set many 'day' peak records & yesterday Dec 1981 was the lowest record - again think about that month in the context of blocking.

So key dates.. - all speeds are zonal (u) wind-

December 1st sees a climo ave of 30 M/S westerly ( propergating eastwards )

December 25th sees a climo ave 'peak' of 38 M/S - ironic that its xmas day - so from a winters perspective that period from about 20th -30th the NH is at a time that will have the least amount of blocking.

January 15th- Feb 1st is the biggest reduction of the zonal wind across winter as the PV starts to breakdown

Feb 20th onwards sees the windspeed at less than 50% of the December peak - Which is why traditionally our cold spells do come around & just after valentines day ...

Hi Steve,

Thanks for a highly informative and interesting post, just out of curiosity...has the mean zonal wind speed at 10hPa increased over the time frames of the ERA40 and Interim ERA? As in, are we likely to see higher W'ly wind speeds (on average) during winter than we were say 30 - 40 years ago, when the good old winters of yesteryear still brought frequent frost, snow and HLBing events?

I'm just wondering if climate change has affected the stratospheric wind patterns at all. I know that the surprising wQBO this year was unprecedented, for example, with most (if not all) experts believing the switch to an eQBO was a foregone conclusion. 

Also with the forecast increase in 10hPa zonal wind speeds, would you expect the polar vortex's coherence to increase and its segments to unify?

Cheers!

 

[Grimers]

The only hope for coldies is if the ECM's output shown below comes true. Cold and dry sums it up. Though, as you can see the uppers aren't anything special. But, due to a high being present, cloud breaks will allow for potentially some harsh frosts to develop especially over inland areas. However, I don't expect anything too special due to the lack of snow fields.

   

Edited December 7, 2016 by Grimers

[Cheshire Freeze]

2 minutes ago, Ali1977 said:

Can we swing this back the other way I wonder - lets see at this time on Friday some of these better ENS are starting to show at day 10, and gain some back up from the Ops and further reaches of ECM. 

 

Might be a few days yet IMO before we see the ECM op start to suggest something of interest at day 10. I think we're at the stage now where the GEFS are starting to sniff out a change but may be jumping the gun slightly. Christmas to New Year week is where the interest is for me RE cold & snow potential...transition period few days leading up to Christmas.

[Ali1977]

1 minute ago, CreweCold said:

Might be a few days yet IMO before we see the ECM op start to suggest something of interest at day 10. I think we're at the stage now where the GEFS are starting to sniff out a change but may be jumping the gun slightly. Christmas to New Year week is where the interest is for me RE cold & snow potential...transition period few days leading up to Christmas.

Well I always miss the cold, was away for both 9/10 cold spells, and 12/13, I'm away 1st week of Jan so I imagine it will be cold then !! Pub run special coming up I'm going for - it needs re named after the last few to knockers nightcap.

[Grimers]

5 minutes ago, CreweCold said:

Might be a few days yet IMO before we see the ECM op start to suggest something of interest at day 10. I think we're at the stage now where the GEFS are starting to sniff out a change but may be jumping the gun slightly. Christmas to New Year week is where the interest is for me RE cold & snow potential...transition period few days leading up to Christmas.

Understood, however it seems to me that we may be chasing the cold weather a little too much, and that the colder conditions seem to be being pushed deeper into Winter. It's possible that your guess from a few months ago of a cold January and February could come true, but again it's all potential. We really need the charts to verify before we can start getting our hopes up too much.

Edited December 7, 2016 by Grimers

[knocker]

Tonight's 6-10 anomalies show some slight differences upstream and with the precise orientation and shape of the Atlantic upper trough but the overall agreement remains fairly impressive as it has been recently. So confidence in the daily evolution within the pattern is pretty good.. The slight upstream changes involve the orientation of the Canadian vortex and the Aleutian HP.

I think everyone is familiar with the majors players so not to bore everyone by going through them all again, suffice it to concentrate briefly on the Atlantic arm of the vortex and the Azores high pressure The former will continue to dominate the western and mid Atlantic, and a fair way south, and continue to spawn surface systems that for the most part will track north east in the quite amplified pattern (a strong jet which on the whole tracks around the upper trough). This is ably abetted by the Azores high pressure which is still strongly influential ridging north east over SE England.

So in a nut shell, remaining unsettled with periods of rain and maybe strong winds, generally favouring the north west whilst the SE remains fairly dry..Temps above average. I'll substitute the EPS 850mb temp anomaly for a change but looking at more or less gives you the hPa anyway

Moving into the 10-15 period there still remains pretty good agreement all things considered, Not so amplified upstream although the Canadian vortex is still a player and the western Atlantic trough is not so influential. all this means a flatter Atlantic pattern with the Azores ridging adjacent to  the UK. Thus still an airflow from the westerly quadrant so still trending changeable bur still applying the previous qualification. Temps around average.

[Cheshire Freeze]

3 minutes ago, Ali1977 said:

Well I always miss the cold, was away for both 9/10 cold spells, and 12/13, I'm away 1st week of Jan so I imagine it will be cold then !! Pub run special coming up I'm going for - it needs re named after the last few to knockers nightcap.

Yep, certainly within my focus for early Jan cold. Don't think it'll be sustained throughout January though, potentially quite a marked drop off back to mid latitude heights expected further into Jan and a possibly wetter and more unsettled Feb.

I don't think anyone could really grumble if we had a 2-3 week window of proper winter potential TBH

Edited December 7, 2016 by CreweCold

[nick sussex]

I've been digging around for a few crumbs of positivity. At this rate I'll be hitting oil soon as my search is now heading towards the earths core!

Putting my obvious irritation at the outputs aside I have managed to locate some news. Now I advise members have a stiff drink before I deliver this earth shattering info.

So here it goes, cue drum roll!

This is from the NCEP New York state forecast:

In the mid levels, a fast quasi-zonal flow Friday through the
weekend will become more amplified next week.

 

[stewfox]

Another day and another 24 hrs of model watching.

Pub another quite affair The ECM and GFS were showing similar trends to T240 small uncertainties in  how far north the high will get 

However the  Gfs 18z! did show some interest at T384. Although that was many flip flops away.

This Morning

Flip flop back “ 0z is the most boring and mild run some folk have ever seen with endless southwesterlies.” (Get use that roller coaster) .

The theme started with  no point looking further than D10 today as we don't have the building blocks for cold in place at a reliable timeframe and  long range models are unclear

The GFS 06hrs run now ejects the shortwave near Iceland! (big flip flops)

Afternoon

Interesting discussions followed about back ground signals and why we have not seen a front loaded winter. Although its difficult to understand how we then can determine we wont get any cold/snow till min mid Jan if background signals have not been correct ??

While the 12z rolls out, with  a  Happy white Christmas awesome chart , by Xmas day we'd be cold with chance of snow for sure gfs gfs gfs

 GFS ensembles pick up some interest post T240 but we are talking about slight amplification only and perhaps a failed northerly (boo GFS)

Evening

Definitely a upgrade in GEFS, including control 

 T240 is FI so lots of nice xmas charts are posted.

JMA showing some interest in amplifying the pattern.

Some promise on the ECM at 192/216 materialises itself into nothing (boo)

But do we have right out in la la land pressure rise to the north west - just like the gfs 

When you see folk looking at ensembles in Holland it’s a bit of s straw clutch

Some great posts today but nothing really to get hold of, again we need a sign.

Cold 1/10 (Background signals 0.00002)

For those old enough to remember the famous pub run of 28 Nov how things change 

-----------------------

Pub was just about to close last night and we had a few big hitters GP, Fergie etc basically said drinks are on the house.

“”12z ECMWF ENS set against model climatology lean pretty firmly in median 2m temps towards below avg (at times quite markedly) out to at least 9 Dec. “”

“”.and a big intrusion if the N Pacific ridge into the Arctic towards the mid Atlantic ridge. Strongly negative AO latter stages of the EPS””

Tamara adds a few cheeky Christmas charts and it’s a lock in.

-----------------------

Prozac being ordered

 

 

Edited December 7, 2016 by stewfox

[Scandinavian High.]

looking dry and cold with frosts later December as we go on high pressure looks like it's pushing to the north west of U.K. 

[Cheshire Freeze]

13 minutes ago, Grimers said:

Understood, however it seems to me that we may be chasing the cold weather a little too much, and that the colder conditions seem to be being pushed deeper into Winter. It's possible that your guess from a few months ago of a cold January and February could come true, but again it's all potential. We really need the charts to verify before we can start getting our hopes up too much.

No, as I said a week or so back to you, I did not plump for a colder Jan and Feb per se...I was more trying to point out that the November update of the GLOSEA5 model did not, to me anyway, indicate a front loaded winter. Hence I was quite surprised this scenario was being plumped for with such vehemence. 

This winter, for me, falls into the 2012-2013 template...with perhaps a 1-2 week head start. Coldest period of winter from Christmas through to mid Jan (at the latest) followed by an average rest of winter. This followed by a colder than average March.

[winterof79]

3 minutes ago, abbie123 said:

looking dry and cold with frosts later December as we go on high pressure looks like it's pushing to the north west of U.K. 

The GEFS are sniffing at this prospect

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

[SMU]

46 minutes ago, North of North Yorkshire said:

Hi Steve,

Thanks for a highly informative and interesting post, just out of curiosity...has the mean zonal wind speed at 10hPa increased over the time frames of the ERA40 and Interim ERA? As in, are we likely to see higher W'ly wind speeds (on average) during winter than we were say 30 - 40 years ago, when the good old winters of yesteryear still brought frequent frost, snow and HLBing events?

I'm just wondering if climate change has affected the stratospheric wind patterns at all. I know that the surprising wQBO this year was unprecedented, for example, with most (if not all) experts believing the switch to an eQBO was a foregone conclusion. 

Also with the forecast increase in 10hPa zonal wind speeds, would you expect the polar vortex's coherence to increase and its segments to unify?

Cheers!

 

Hi mate -

There is no way of telling - i dont have access to the ERA data, however the MERRA / NCAR renanalysis is almost the same ( as you would expect )

you can pull a reanalysis chart from 1948 however where do you decide the cut off point it -

I think more importantly for me is looking at the base state 500 plots are for generally average decs, then the anomaly months 

A snippet of info though- the closest match for Nov 16 in terms of zonal mean anomaly is 2009- & whilst late Dec wasnt that great into Jan - we had a huge warming event late jan

heres the comparison

& the warming late jan

propergating to this 500 anomaly in Feb- ( downwelling of about ~10-14 days

& the zonal speeds showing the dramatic warming

S

PS yes I would expect to see some consolidation of the vortex over the next 10 days... very similar to the ECM...

 

 

 

 

Edited December 7, 2016 by Steve Murr

[nick sussex]

Following on from my previous " earth shattering" post. Whats expected to happen is a cross polar flow developing towards the east USA and the amplification they're talking about is really in relation to the jet diving south in the central/east USA.

This often drags the PV a bit further to the nw as the jet digs south in that region, unfortunately for us the deep cold heading quite a way south there fires up the jet. It's really at this point whether some of that energy can get under the high rather than just piling over the top. You'll see the JMA at T192hrs tries to do that, we haven't seen its later output yet but that chart is possible with the upstream pattern. Once you start raising heights over the top of that Atlantic low you can get some pressure on that to edge more se.

Heres the JMA at T192hrs, you can see that cross polar flow and the sign of some positive heights getting over the top of that low. I don't normally do paintjobs on the JMA but its desperate times I'm afraid!

 

Edited December 7, 2016 by nick sussex

[bradymk]

ECM EPS and GEFS at +360....

Both v similar hemispherically but differ in our locale with the above average heights located further to the north west of U.K (Iceland basically) on GEFS compared to further SE and more directly over or to the east of the UK on EPS.

JMA probably best output of evening as Nick explains above.

[supernova]

38 minutes ago, nick sussex said:

I've been digging around for a few crumbs of positivity. At this rate I'll be hitting oil soon as my search is now heading towards the earths core!

Putting my obvious irritation at the outputs aside I have managed to locate some news. Now I advise members have a stiff drink before I deliver this earth shattering info.

So here it goes, cue drum roll!

This is from the NCEP New York state forecast:

In the mid levels, a fast quasi-zonal flow Friday through the
weekend will become more amplified next week.

 

Glad that's cleared that up Nick. Presumably we can all now look forward to significant Atlantic troughing forcing the jet way south with a resulting Greenie high that ushers in a fortnight's cold spell starting Dec 12th and resulting in a significant nor'eastlerley soon afterwards? 

[Frosty.]

Tonight's Ecm 12z T+240 ensemble mean and operational have something in common, they both show high pressure firmly in charge.

Edited December 7, 2016 by Frosty.

[booferking]

The main low is held further west on the west tip of Greenland this run could well turn out more blocked later on.

Edited December 7, 2016 by booferking

[Gael_Force]

3 hours ago, nick sussex said:

Looks like the USA has stolen our cold and snow yet again! Their original NCEP monthly forecast had suggested a greater likelihood of milder conditions but as their fortunes improved ours went down the pan. Oh well at least we can console ourselves in Europe that we're less likely to get our head blown off going to buy a pint of milk.

Anyway after that mini tirade the ECM desperately tries to raise some interest but the jet stream is far too strong. It does look similar upstream to the GFS at day ten and we're left to chase some amplification. Another generally tragic evening for coldies bar the scraps thrown to us in some of the GEFS and the GFS  Pre-Xmas Special.

 

Somebody posted a NOAA discussion about this way back in the autumn; was it you? They were saying the models predicted mild but their take was that it might not be correct due to some other parameter. Trouble is, I cannot remember what it was causing them to doubt the seasonal output. Maybe you can .. might give some pointer as to what the problem has been.

[Man With Beard]

One of my key requirements for decent mid-range forecasting certainty is a 1030mb mean high. We have that until T216 on the GEFS mean - over Central Europe.

So high confidence in high pressure being centred very close to the Germany. I am confident enough to completely rule out a Scandi High or Atlantic High during the next 10 days.

NW areas likely, then, to remain in the mild SWly flow. But the high may get near enough to bring a continental influence into the SE in particular. A slight correction east, though, and we're in 2015 territory (check the archives if you don't believe me)

Edited December 7, 2016 by Man With Beard