Model Output Discussion 18z 30/09/15

[knocker]

That's not how I see the ECM extended knocks. remember we only see mean ECM output. mean slp over the south of the UK by day 14 is 1022 mb. Not too shabby with a decent positive anomoly still sitting to our west.

 

Well I did say hinting at.

Edited October 11, 2015 by knocker

[Singularity]

I made those composites a while back - will need to see how things pan out prior to winter, but a southwards displaced jet into Europe will be a common theme. In the meantime the Atlantic SST, wENSO pattern pretty much as expected for October. The increase in amplitude of the Atlantic ridge may be in response to the MJO forecast into phase 1 by day 10 so that figures and may contribute to some western Eurasia snow gains which will help with the SCE and SAI.

 

Interesting that this October seems to correspond better to wENSO in general rather than just those that have a westerly QBO as well. Or so it seems having just read this for example: http://www.weatherscientific.co.uk/2015/10/10/winter-2015-16-analogue-years-assessment/

 

It also looks like Arctic sea ice (and perhaps falling solar activity?) could change the game a bit in November... but not necessarily. I'm wondering what you make of the potential sea ice/solar flux influence, but of course that's best answered in the winter discussion thread!

 

. . . . . . . 

 

Some striking model output on offer so far today, which is a nice progression from the fairly uninspiring charts of the past couple of days. This is largely down to the high looking to have more of a chance of retrogression west of the UK for a time... but what are the odds that the changes to a more zonal regime not only manifest but do so at just the right time to topple the high before anything much comes out of it   

 

The GFS 06z det. still manages to finish on a fascinating note though. Imagine of the model was being under-progressive...!

 

ECM'z 00z det. may be a reflection of some over-amplification but you never know I suppose. That +240 sure is a teasing chart.

[snowking]

Be very wary of any overly amplified +240 ECM det. charts - we've been here a lot in the last 2-3 years and in around 90% of cases it was indeed overamplified, particularly around the Atlantic sector, vs the actual result.

SK

Edited October 11, 2015 by snowking

[johnholmes]

Some striking model output on offer so far today, which is a nice progression from the fairly uninspiring charts of the past couple of days. This is largely down to the high looking to have more of a chance of retrogression west of the UK for a time... but what are the odds that the changes to a more zonal regime not only manifest but do so at just the right time to topple the high before anything much comes out of it

 

not if the anomaly charts are anywhere near correct between 6 and 14 days!

[knocker]

Sam Lillo â€@splillo 15m15 minutes ago

Huge wavebreak over the N Atlantic sets up blocking ridge for week 2, directly over the coolest SST anoms

[IDO]

Be very wary of any overly amplified +240 ECM det. charts - we've been here a lot in the last 2-3 years and in around 90% of cases it was indeed overamplified, particularly around the Atlantic sector, vs the actual result.

SK

 

Not the only culprit, since the GFS upgrade the GFS op has been even more bias for HP. The following is D6 bias, so you can imagine at D10 how the HP cells are over egged on the daily runs:

 

 

Always worth taking this into account, and that is why I generally take more notice of the ensemble clusters after about D8. One to be wary of when we see some FI Scandi or Greenland Highs during the Winter!

 

Good agreement up to D8 from GEM and GFS, HP dominant:   

 

GFS builds a ridge from D8 to give a brief northerly around D10 before it topples, but GEM (probably more likely) just has the UK High fidgeting about till D10 and no northerly:

 

 

 

The GFS maintains the recent theme from then of the lowering of heights in our sector: 

[Mucka]

Some very interesting posts today, especially about the natural transition into something more zonal as we head into November. Certainly that is the historical "norm" and it may well happen but I will say that there is absolutely no sign of the pattern flattening in any of the output as yet which will take us into the final week of October.

 

We don't really need anomaly charts to be very confident in this because all models are predicting a strong Alaskan ridge and amplified upstream pattern which will not allow the Atlantic to establish itself downstream as long as it exists because the PV cannot organise around Greenland.

For example GFS 12z and ECM 00z

 

 

This essentially means the pattern must remain amplified out to deep FI unless the upstream is being modeled very badly right now.

This is why anomaly pressure charts are not really required to acknowledge the pattern will be amplified still in 10+ days time but they are useful for gauging where the blocking will most likely set up.

 

So for me we will head into the last week in October with an amplified pattern and by that time the models will be modeling November patterns which is where we will get to see the real developments and if the PV is going to ramp up as is tradition.

[Mucka]

Some striking model output on offer so far today, which is a nice progression from the fairly uninspiring charts of the past couple of days. This is largely down to the high looking to have more of a chance of retrogression west of the UK for a time... but what are the odds that the changes to a more zonal regime not only manifest but do so at just the right time to topple the high before anything much comes out of it

 

not if the anomaly charts are anywhere near correct between 6 and 14 days!

 

But the block wouldn't have to be much further West to allow a colder Northerly flow around its Eastern flank. this has been hinted at many times on various runs.

I wouldn't be surprised if the highlands see their first snow of the season final 3rd of October.

[Captain Shortwave]

At the moment still no consistent signal to pull a proper Arctic blast down from the north, though it remains a possibility with winds in general being northerly, albeit an anticyclonic one and hence not that cold by day (frosts possible at night).

The signal remains for heights situated just west of the UK, though close enough to keep most places dry (apart from an occasional weak front or showers down the east coast).

GFS anomalies

 

Maybe signs that the negative anomaly over Europe might intensify with heights pulling a little further north west. No it would be nice to see a consistent signal in the nearer timeframe.

[bluearmy]

Be very wary of any overly amplified +240 ECM det. charts - we've been here a lot in the last 2-3 years and in around 90% of cases it was indeed overamplified, particularly around the Atlantic sector, vs the actual result.

SK

Tbh Kriss, a Greenland block in October is nice to look at but serves little purpose re winter proper. The arctic high anomoly is well supported on the extended ECM ens mean so expect to see arctic blocking feature as we head into the final week of october

Incidentally, if sylvain is around, the meteociel parallel gefs mean and anomolys aren't updating since the 2nd october

Edited October 11, 2015 by bluearmy

[Cheshire Freeze]

Tbh Kriss, a Greenland block in October is nice to look at but serves little purpose re winter proper. The arctic high anomoly is well supported on the extended ECM ens mean so expect to see arctic blocking feature as we head into the final week of october

Incidentally, if sylvain is around, the meteociel parallel gefs mean and anomolys aren't updating since the 2nd October

 

True, but such extensive Arctic heights must surely have some impact going forward....this being allied with consistent FI charts like these-

 

[ANYWEATHER]

Evening Folks. Has anyone watch Paint Dry!!!    

[BlueHedgehog074]

A little look at the operational models this evening and it certainly looks as though the high heights will be acting as the UK's High Pressure defence system keeping guard on all the sneaky Lows and troughs that could try disarm that system.

 

The 500mb anomaly charts from the NOAA tonight maintain some kind of UK and Atlantic blocking thanks to the high anomalies and ridging over and to the West of the UK. Quite akin to what numerous operational models show.

 

There's chances for Lows and troughs to drop down to our East at times into the nearby continent. One or two of the Lows from the troughing to our East may drop down close enough to the UK to perhaps pull in more of a Northerly flow and maybe provide something a little more unsettled, otherwise it looks as though pressure will remain high over the UK with any real Northerly shot looking as though it will become concentrated a little too far East affect the UK. 

 

 

Would look as though there wouldn't be much wet weather around with Lows being no match for the UK and Atlantic High Pressure systems. 

 

A peak at the 12Z GEFS ensemble air pressure graphs for both London and Aberdeen and they both show that pressure should remain generally high for the next 10 days. However, despite the usual scatter that occurs towards the end of these charts, both do show hints of pressure slowly starting to fall beyond ten days (23rd October onwards) with a risk that Low Pressure could start becoming more influential, particularity for Aberdeen where the lines on the ensemble graph chart show bit more of a noticeable pressure drop. Perhaps something to watch and I know some of the GFS Fantasy Island charts have been hinting at some kind of breakdown from the West or North-West. Personally, though, unless the NOAA anomaly charts bring more of a Westward shift to the ridging and higher than average heights over Western UK, then would be weary about any breakdowns, especially the ones from the North that the operational models such as the GFS shows. Certainly not completely out of the question though since John mentioned that the anomaly charts could possibly lead to a setup to allow an Arctic blast from the North. Think as longs as High Pressure remains to the West of us, then it's not an entirely infeasible evolution. 

 

 

In the meantime, settled, dry and, at times, cool weather, more so during the night, looks apparent. A bit more milder/less cool at times in sunnier spells. Maybe a risk that High Pressure at first this week may drift far enough North to allow a cool, cloudy, conditions to spill in from the East to affect the South at times perhaps with the odd front from Low Pressure to the North brushing past the far North-West of the UK. Otherwise, these are the type of conditions to expect...

 

 

 

(Some sunny, misty and more cloudier conditions at times). 

 

While I was at it (for a bit of enjoyment), been flicking through all the 12Z GEFS Perturbations and this is the one I feel deserves the Cold Chart of the Evening award for the cold weather enthusiasts - Perturbation 20! 

 

[chionomaniac]

CFSv2 ensembles just showing the first signs of change come November - the change from the October ridge to the November trough:

 

 

[Cheshire Freeze]

CFSv2 ensembles just showing the first signs of change come November - the change from the October ridge to the November trough:

 

wk1.wk2_20151010.z500.gif

 

wk3.wk4_20151010.z500.gif

 

Retains some Arctic heights however- which is good heading into November and very reminiscent of '09/'10

[Paul]

Incidentally, if sylvain is around, the meteociel parallel gefs mean and anomolys aren't updating since the 2nd october

 

The new GEFS (which incidentally won't be going live this Tuesday as originally planned) doesn't contain mean data directly. We'll be creating it from the data, as I'm sure others will too, but it's not as simple as it was when it was an included data field.

[Mucka]

CFSv2 ensembles just showing the first signs of change come November - the change from the October ridge to the November trough:

 

wk1.wk2_20151010.z500.gif

 

wk3.wk4_20151010.z500.gif

 

Yes they do.

And that is what we would expect to see, the anomalous heights sinking SE as the Atlantic ramps up.

We should start to see that developed in the MO over the next few days if there is any veracity to it.

[SylvainTV]

Incidentally, if sylvain is around, the meteociel parallel gefs mean and anomolys aren't updating since the 2nd october

 

Thanks, I fixed it ! Indeed I have to compute Avg and Spread manually for the new 0.5° / 3h  datasets, and take Z500/T500 fields in another file. They made everything harder (if you want to use the more detailed version at least)  

Edited October 12, 2015 by SylvainTV

[IDO]

Sylvain TV.

Thanks, I fixed it ! Indeed I have to compute Avg and Spread manually for the new 0.5° / 3h datasets, and take Z500/T500 fields in another file. They made everything harder (if you want to use the more detailed version at least)

Thanks you do a great job.

Edited October 12, 2015 by IDO

[IDO]

All sorts of fun and games from the ensembles in FI as they muck around with the pattern change in late October:

 

 

The PV is still weak for the rest of October so plenty of chances for transient  high latitude blocks, though by D16 the PV is beginning to ramp up though still undefined:

 

 

The UK MLB still in place at D10 on GEM, ECM and GFS:

 

 

 

October looks great for finishing the harvest or for drivers like myself. Still no idea what happens after this but there should be signs by the end of the week.

Edited October 12, 2015 by IDO

[Ali1977]

Ian F on Twitter saying possibly unsettled later in the month - but forecast models showing mixture of Zonal and blocked. So a breakdown looks possible, from what direction to be decided. Still a long way out so keep enjoying the quietist autumn for now!!

[knocker]

By the end of the ext period the ecm has brought a weak mid Atlantic trough into play and although the UK is still under the influence of HP it's influence in the eastern Atlantic has weakened considerable.

 

EDIT

 

Ooops

Edited October 12, 2015 by knocker

[carinthian]

Signs of the upper flow disturbance taking hold in Central Europe. This is a fairly common pattern in a NEly flow when no dominate strong wind fields occur. The coldest upper are presently over Southern Poland and Slovakia and East Czech Repulic zone. Snowing on the higher ground. The disturbance likely to move towards Germany with its upper cold pool development and later move SW in the weak upper flow towards France by Thursday. Some showers and lowering of temps across SE Britain during this transition. Our models hold the high pressure zone to the west of Britain by next week with a cold plunge down the East side of N.America firing up the jet poleward a mid Atlantic blocking seems the favourable outcome in the 10 day forecast with a increasingly cold Eastern Europe/ Russia. We will see but the 5 day forecast turning colder for all.

C

[mountain shadow]

Interesting end to the GFS 6z...

 

http://max.nwstatic.co.uk/gfsimages/gfs.20151012/06/384/h500slp.png

 

Continued higher heights around NW Europe with colder and colder air moving down the Eastern flank of the high pressure zone. No sign of the Atlantic on this run.

[Ali1977]

Some very interesting outcomes amoungst the GEFS - upto 264 anyways. P14 looks about the most outrageous but a fair few would bring an early taste of Winter.

Edited October 12, 2015 by Ali1977