Model Output Discussion - 31/10/2014 and Beyond

[carinthian]

I think what Tamara highlighted in her post in the shorter term is the cause for some concern in the amount of rainfall likely , particularly early next week in the SW. Not exactly Ana front set up, but with plenty of warmth wrapped above from the continent and some cold surface undercut from the Atlantic, the SW looks prime for some heavy rainfall totals from a combination of frontal activity and squalls. This could also affect the SE later.

C

[Banbury]

Far too early to be hoping for anything severe IMO let's get into December .

 

It certainly seems more promising that last year, that's for sure

[Barry12]

Some good blocking developing on the ECM

 

[stodge]

Evening all

 

We often get a colder spell just after mid-November and then a return to milder conditions at the turn of the month and the first week of December. The only thing concerning me from the GFS output was the evolution of the Parallel into deepest FI as the PV seemed to be re-organising in the NE Canada area.

 

Apart from that, some interesting weather ahead for all.

[Snowman.]

Some good blocking developing on the ECM

 

Cross-Polar flow looking nice there.

[Captain Shortwave]

A little better from the ECM

That trough digging into Western Russia is the first shoots of an approaching cold spell, the high will start to beat back Atlantic fronts and bring a sunnier spell with a chilly south east wind. Still a long way to go and at day 10 then there is little chance of verification.

[Cloud 10]

Just looking at the day 10 ECM anomalies and its more of the same with more blocking than you can shake a stick at and cold air being forced to lower latitudes which is the sure sign of a tanking AO.

 

 

 

Fascinating model watching at the moment.

 

[seabreeze86]

Some interesting model watching at the moment. Building blocks in place for a shot at cold for the final third of November.

 

This is what the ECM was predicting for the 11th of November a year ago.

 

http://www.meteociel.fr/modeles/ecmwf/archives/2013110400/ECH1-168.GIF?00

 

Vortex becoming established, AO and NAO going positive. Yuk

 

Now look what it predicts on todays 12z run.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2014110412/ECH1-168.GIF?04-0

 

AO going negative,Polar Votex looking very sorry for its self,cross polar blocking over the pole not in the right place for cold to come our way just yet. Patience required as i said looking very interesting.Good to have interesting model watching so early in the winter season.

Edited November 4, 2014 by seabreeze86

[BLAST FROM THE PAST]

What I'm looking at currently in the charts is very encouraging.  Look, the cold switch I'm looking for backend of the month is the NW/SE movement of LP [Jetstream favourably angled] across us which brings in a N to E quadrant airflow.  We are seeing plenty of signs already of such movement early on but we still get anomalous mild pumped over us interspersed with chilly shots and as Tamara said the trough disruption actually stalls such systems that could bring some very wet conditions.  However, that will if it continues eventually pump pretty cold air towards us and its about the building pattern.  I'm going to ramp a bit here, such movement reminds me of how Feb 86 started where we got stuck in one hell of a rut...a real cold rut.  The trough just moved N to S as it could not move east and we know the rest.  I'm not forecasting a Dec 10 but I'm saying the hemisphere is really loading itself here and I am utterly convinced of a very interesting 'wintry' season ahead.  For me Dec has some decent cold periods in it disrupted by westerly breakthroughs.....but there might be more to come than that.

Right enough ramping, but we are so in  abetter place for chances of cold this approaching winter.

 

BFTP

Edited November 4, 2014 by BLAST FROM THE PAST

[ANYWEATHER]

Is the Gfs the Pioneering model in picking out cold spells?   This time last week the gfs was hinting on something much colder . It dropped the idea , but ,hey presto its becoming reality, although probably tempered down to its original version. Anyway business as usual for November, although Bonfire night tomorrow looks unusually cold and frosty, for most of the nation, a classic Bonfire night!. Wet ,windy and generally cold looks the outlook, gfs has the potential for much colder weather later at day 10   ecm is not sure where its going....

Edited November 4, 2014 by ANYWEATHER

[SMU]

Evening All-

 

We are really gathering pace now, with the NH pattern really becoming LOADED towards a Negative AO, but not just a normal run of the mill joe Average AO, nope. A super duper negative AO - Index Ranges from the 12z suite at day 10 is probably low end of -3 from the GFS & heading past -5 on the GEM.

 

To put this into Perspective theres 3 offerings I bring to the table tonight.

 

1)

EXTREME Negative AO ( Sub -4) is RARE. - some might say as rare as hens teeth.... ( hence my Avatar )

What is even more rare is Sub -4 values in November, this is because the AO index should by rights according to the long term mean have a positive value.

 

There are 5 Novembers since 1950 with a sub -4 value in the month.

 

1959  -5.9 18th Nov  

1968  -4.2 14th Nov   

1985  -4.5 25th Nov  

1998  -4.1 16th Nov  

2010  -4.1 26th Nov

 

Interesting Nov 62 just missed with a 3.8 

 

Why is that important- well of the 15 Winter months after these Novembers the AO was negative for 11.

This is only half the story as theres not much difference between -4 & -3.

 

2)

So lets cherry pick Winters with our Negative (below freezing ) CETS since 1950 & highlight the lowest -AO value in the preceding November-

 

Dec 2010             -4.1      

Feb 1986             -4.5

Jan 1979              NONE.( however December had a -4.2)

Jan & Feb 1963   -3.8

Feb 56                 -3.4

 

Again a high Correlation -  to Low November Values. - Interesting November is just a calendar date- 1979 is interesting as the Winter started late in December however still saw low index values.

 

3)

November AO V Winter AO Correlation inc OPI - This is the BEST statistic of them ALL-

 

In the AO dataset there is 63 years. 1950-2013.

There are 12 Novembers with a Negative Sub -1 AO for the month.

 

1952,55,57,59,62,65,68,80,85,98,00,03  -

 

that = 36 Months. - the Winter AO for those was 30/36 Negative which is around 85%.

Now remove the 1 positive OPI year- 1998 > 1999 & you get.

 

30/33 NEGATIVE AO months. that's over 90% chance of a negative winter.

 

 

So why are SOME of us happy today.

 

This

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif   MEAN high -3's

+ this

http://www.meteociel.fr/modeles/ecmwf/runs/2014110412/EDH1-168.GIF?04-0             MEAN high -3s to -4

+ This

http://modeles.meteociel.fr/modeles/gem/runs/2014110412/gemnh-0-240.png?12        -6  BOOM chart

 

Is putting us on the cusp of something Big.....

 

ITS COMING, & based on the AO mapping & the early timing of the drop the probability suggests before December, then again in December related to Wave 1 activity...

 

Cheers

S

 

PS

The ALL TIME  64 year record Winter -AO chart is the 19th of Jan 1985 @ -6.22

http://modeles.meteociel.fr/modeles/reana/1985/archivesnh-1985-1-19-12-0.png

 

Now look at the GEM AGAIN

http://modeles.meteociel.fr/modeles/gem/runs/2014110412/gemnh-0-240.png?12 

Edited November 4, 2014 by Steve Murr

[legritter]

Great model output discussion tonight gang ,and its nice to see member numbers increasing on our forum .I dont want to seem a bore but get the right pressure charts and it does not take long for that cold to build ,lets take present conditions as apposed to 5 days ago ,but keep reminding ourselves its only early November and already the cold in northern Hemisphere high latitudes is well and truly showing its hand .I,m finding the new GFS  Model interesting and some Tasty charts on ECM  ,hopefully some building blocks appearing ,Ps dont wish for an ice age ,no power no Forum ,cheers gang ,  

[knocker]

Not a huge change in the D10 anomalies and NOAA tonight. NOAA doesn't make as much of the mid Atlantic ridge as the GEFS and ECM. Briefly troughs eastern and western Atlantic with HP Alaska through to Scandinavia. Sound familiar. The jet still meridional and looping south of the UK but pretty weak,

 

Further afield not a lot that appears significant apart from the suppression of the mid Atlantic ridge and a more zonal flow. Perhaps later more ingress from the Scandinavian HP but very speculative otherwise much of the same with the temps above average.

[phil nw.]

Not wishing to stifle discussion but let us remember this thread is about current models and what they are showing.

One or two posts seem to be drifting into the realms of Winter forecasting/hopes.

Those views can be expressed in the many other threads that we have running.

OK thanks and on we go.

[MR EXTREMES]

Not a huge change in the D10 anomalies and NOAA tonight. NOAA doesn't make as much of the mid Atlantic ridge as the GEFS and ECM. Briefly troughs eastern and western Atlantic with HP Alaska through to Scandinavia. Sound familiar. The jet still meridional and looping south of the UK but pretty weak,

 

Further afield not a lot that appears significant apart from the suppression of the mid Atlantic ridge and a more zonal flow. Perhaps later more ingress from the Scandinavian HP but very speculative otherwise much of the same with the temps above average.

Certainly don't see the above average your seeing.

Pretty much average to slightly below judging by all the big 3!.

Still analogue year 09/10 type set up.

Once frost fog becomes a feature then the projected above average temps you see will soon get mixed out.

Once that cold stagnant air gets in place it will take a lot to replace as we see in 09/10.

The signals are unanimous in favour of blocking.

And as Steve has suggested December could be pretty cold.

But I really do think some of the uk will get something pretty cold towards the end of November.

And the ao going negative.

[summer blizzard]

Fantastic Euro tonight once again undercutting as far as Italy tempting the block west and creating an opening for the Arctic Trough to sink south which would eventually show us a route to cold.

 

GEM is just wow, needs a stronger undercut but those heights are stellar.

 

GFS backs my thoughts of the last few days, a quite wet period potentially upcoming..

 

[Nick F]

My latest synoptic outlook for the next 14 days can be found here: http://www.netweather.tv/index.cgi?action=news;storyid=6272;sess=

 

Mention of the cross polar +ve height anomaly developing with the -ve AO signal. No signs of any deep cold getting anywhere near the UK over next 14 days, though potential for higher pressure across northern and eastern areas 10-14 day period, with an increasing risk of frosts and temps falling slightly below average overall here.

[Purga]

Similar?

Not exact but interesting maybe - at least it's not raging zonality!

[bluearmy]

Nah purga - that second chart is naff. Look at the p/v over Greenland. Gonna be a rubbish winter to follow ...........

[Yarmy]

Some eyebrow-raising synoptics again on both the old-fangled and new-fangled pub runs. Just one frame amongst many:

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=180&mode=0&runpara=1&carte=1

Just wet and average for the UK of course, but, it does look...um...interesting.

[East_England_Stormchaser91]

I can't believe how shredded the PV is, especially for November! Normally by now it is ramping up big time. 

Latest charts show increasing signs that the AO will go into a more negative phase too, which promotes the chances of a -NAO. What a time to be seeing this happen too. 

[Duane S.]

It's probably worth mentioning to those fairly new to all of this that a fairly deeply neg AO set up often leads to long unsettled spells initially for the UK but, if it persists (likely to IMO), sooner or later, with the NH loaded favourably, a cold spell is often just around the corner.

 

Steve's example earlier of that very -AO period in November of 1959 is a good case of sometimes having to wait for the goodies. Whilst the Nov/Dec period as a whole averaged out as a fairly moderately negative -AO and the UK struggled for a slice of the cold action happening elsewhere, it would seem that the NH cold dice were simply getting more and more loaded and it was only a matter of when not if... The following JFM remains the lowest averaged -AO ever recorded and we went on to have our share of very cold spells during that time. Yes it was interspersed with cool unsettled periods as we endured Westerly NAO conditions at times but if ever there was a winter where the pv was ripped from pillar to post and retrogression was rife, that was surely one of the best of them!

[Man With Beard]

Some eyebrow-raising synoptics again on both the old-fangled and new-fangled pub runs. Just one frame amongst many:

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=180&mode=0&runpara=1&carte=1

Just wet and average for the UK of course, but, it does look...um...interesting.

Seems to me that all that's stopping us having a chance of getting cold in the short term is a persistent East European high

[summer blizzard]

GFS18z is stronger but a little further south sparing us the washout of the past few runs but in turn the stronger low never sinks so no route to cold.

 

 

Parallel is better but does not undercut far enough east to drag that warm air to us (we want the flow to remain so we drag it to us and then the cooler air behind)..

 

 

I tried to illustrate what we want if the pattern is stagnant enough, only the Euro has tried to undercut enough.

 

[Met4Cast]

GFS P goes crazy with developing a -AO