Model Output Discussion - The Start Of Winter

[Frosty.]

Hey guys the way I'm interpreting the models for the next few weeks has led me to reach this conclusion. There is no sign of mild benign conditions gaining a foothold whatsoever, we may well have a quieter interlude at the end of next week but not likely to last. I think the generally rather cold zonal pattern will persist with Atlantic depressions tracking east or southeast across the UK with mild weather at a premium. I think we will continue to have a risk of wintry precipitation, more especially across the north and in particular at elevation, also an ongoing risk of frost and ice during the many colder incursions. Uncle Barty won't be a Christmas / New year party pooper and there are signs of a colder pattern developing by the start of 2015. :>)

Edited December 12, 2014 by Frosty.

[Frank Trough]

The CFS is actually pretty good at picking up long term signals/trends if used correctly, Obviously looking at every run and picking out detail its useless.

 

is it really? i've heard this said before on here but never really given it much thought. Do the METO use it in their long range forecasts? If was that decent then surely they ought to?

[Polar Maritime]

is it really? i've heard this said before on here but never really given it much thought. Do the METO use it in their long range forecasts? If was that decent then surely they ought to?

 

I never said it was 'that decent', The Meto have much better in-house Models of there own (well ours realy) which they use for long range, As Ian expressed yesterday. 

 

Yes Frosty, Agree with your analysis there on the Models, Cold Zonal having/being the main driver over the UK so the theme continues as per Meto outlook - Just below average.

Edited December 12, 2014 by Polar Maritime

[Methuselah]

The CFS is actually pretty good at picking up long term signals/trends if used correctly, Obviously looking at every run and picking out detail its useless.

To be honest, PM, I've learned to pay it no attention at all...  

[Polar Maritime]

To be honest, PM, I've learned to pay it no attention at all...  

 

Me to Pete, To much like hard work 

[Tamara]

. We see the prospect of a weak poleward Hadley cell. This is supportive of poleward propagating (sub tropical) anticyclones to mid latitudes (i.e Azores High) combined with positive Atmosphere and Angular Momentum (+AAM). The energy budget deficit and then rebalancing in the atmosphere poleward is contributory to a spike in the AO.

 

Further likely re-enforcing of warming of the western Nino regions is likely to weaken the Hadley Cell, especially as the other hemisphere feedbacks tighten their grip in tandem. Why is this relevant?

 

Weaker eddy heat flux into the mid latitudes occurs as ENSO warming occurs in the region which reverses the Ferrel Cell circulation and meridional mass field/Polar vortex gradient and that, self evidently, leads in turn to enhanced opportunity for stratospheric wave attack to lead to higher latitude blocking.  The sub tropical ridging (think Azores High again) is weakened and retracted in this process as the higher sea temperatures supporting these anticyclones is weakened. This is a key to the +NAO spoiling conundrum appearing in seasonal forecasts. But we have to be patient and watch to see when this happens.....

 

 We are now starting to see early, but very real and evidential answers to that Azores High and +NAO conundrum (as previously discussed) and how this now might be broken towards, but most especially into the New Year.

 

Its simply a case of watching these signals grow and wait for the results to become palpably evident in the modelling with time. But is it really as easy as that?

 

As others have rightly commented on and illustrated, changes upstream to pressure and jet stream patterns are required to allow the atlantic sector to amplify properly and lead us towards something more meaningfully cold than half hearted topplers.....

 

....+AAM is now finally signalling an increasingly negative tendency and this should inevitably impact, with time, on the Pacific pattern - shifting the EPO ridge further westwards and northwards. The downstream response of this in the atlantic sector will be to retract the Azores High correspondingly westwards and weaken it. We should not therefore worry about any of the hints from some modelling of High pressure setting up shop to any extent over Europe to introduce a sustainably mild pattern.....

 

These developments also favour a reduction of the fast Pacific Jetstream strength over mid latitudes (again with time). It furthermore indicates the demise of the Ferrel cell signal, as discussed recently, with the NH atmospheric signal ending its aloof stance with the oceanic El Nino signal - which in turn teleconnects nicely to strengthening further still the Siberian High, Aleutian Low - and associated -AO feedbacks. More so, a path to those -AO feedbacks bearing productive fruits to mid latitudes towards our parish.

 

As posted previously, we already have in place a southward tendency/displaced Pacific Jetstream. With a retracted Pacific pattern evolving over the medium to longer term, we have the mechanism for weakened and split flow downstream in the atlantic over the medium and longer term. So, a very important part of the jigsaw to also breaking the stubborn +NAO stranglehold and turning it through neutral (as the altantic sector amplifies) and negative thereafter as the negative forcings over the pole turns the pattern much colder courtesy of a very likely SSW.

 

In the first instance (probably post xmas), cautious, but still good enough reasons for those long range G5 and ECM ensemble signals for greater northerly element to our weather to maybe verify (and just perhaps associated wider snow potential?) to end the year. The amplification in the atlantic will also provide us with the Greenland wave activity ammunition we need to help progress to the next stage and back the pattern even further west.

 

So, in summary:

 

Stage one is the retrograding Pacific pattern ( now indicated through second half of December) and leading thereafter to the proper amplification of the atlantic (late December reasonable estimate) that gives us a reasonable chance of a decent arctic maritime shot.

 

Stage two is the wave mechanism into the pole, courtesy of amplification. to hurt the vortex further and complete breaking up the stubborn lobe of vorticity to the NW (turn of the year and more especially early Jan)

 

Stage 3 is the in-tandem pincer effects both sides of the pole - as the Siberian High, primed by autumn SIA feedbacks, reacts to the ocean vs  atmospheric Nino coupling and in turn enables the pattern to back even further west

 

Stage 4 is very likely SSW territory.... with the Beast heading west towards NW Europe and UK in January as the NAO flips completely, undercutting the deep cold and marching it towards and hopefully right across the North Sea...

 

Simple innit

Edited December 12, 2014 by Tamara תָּמָר

[Barry12]

Potential for snow to lower levels at day 7 and 8-

 

 

One to watch out for.

Edited December 12, 2014 by Barry95

[Mucka]

"Simple innit  :wink:"

 

Yes, what could possibly go wrong?    (Great post BTW)

 

GFS and GFS (p) [currently stalled 132 at time of post] improve the chances of another shot of cold air end of next week somewhat and across the output the trend has been to slow down the East West progression of the next deep depression to affect our shores from around day 4/5 through to day 7/8.

 

 

 

 

GFS op flattens out thereafter and offers monotonous fare TBH  but we have seen it overplay the AH time after time so that is open to change.

 

GEM keeps things a little more interesting with a more amplified FI

 

Edited December 12, 2014 by Mucka

[Paul]

is it really? i've heard this said before on here but never really given it much thought. Do the METO use it in their long range forecasts? If was that decent then surely they ought to?

 

On the flipside, NOAA and the NCDC do appear to have faith in it, spend time/money running and updating the model so if there was no value in it, you'd think they wouldn't bother?

[karyo]

Thanks Karyo, as you say though, the run to run differences are quite marked. The blue dotted ensembles run from yesterday, must have been a cracker.

 

The link would seem to indicate no decent -NAO until mid to late January.

The worrying trend is that the - NAO is getting pushed back all the time. It is like chasing a rainbow...

 

At some point, December was the start of the -NAO but now we are looking at late January!

 

Karyo

[Summer Sun]

For a time it was looking like the NAO would go negative in early January but today's update has pushed it back to the end of January now

 

[Snowman.]

The worrying trend is that the - NAO is getting pushed back all the time. It is like chasing a rainbow...

 

At some point, December was the start of the -NAO but now we are looking at late January!

 

Karyo

Who said such thing?

[Mucka]

For a time it was looking like the NAO would go negative in early January but today's update has pushed it back to the end of January now

 

 

 

But open to large scale changes and the NAO is a measure not a driver so it will change with any pattern change that gets modeled. Not something to get hung up on anyway.

[Don]

The worrying trend is that the - NAO is getting pushed back all the time. It is like chasing a rainbow...

 

At some point, December was the start of the -NAO but now we are looking at late January!

 

Karyo

 

I thought not so long ago that forecast was showing a positive NAO throughout the whole of Winter?  Do correct me if I'm wrong!

[ukpaul]

Is the GFS run visible anywhere after 132h? Does someone needs to give the spanking new computer a kick or is it just Meteociel?

[karyo]

I thought not so long ago that forecast was showing a positive NAO throughout the whole of Winter?  Do correct me if I'm wrong!

That showed only for a day so I guess it was a glitch. In general, it was persistenly showing -NAO from mid December but then it got pushed back to early January and now later in January.

[fergieweather]

is it really? i've heard this said before on here but never really given it much thought. Do the METO use it in their long range forecasts? If was that decent then surely they ought to?

 

No, CFS never cited in any UKMO medium or longer-range analysis.

[johnholmes]

For a time it was looking like the NAO would go negative in early January but today's update has pushed it back to the end of January now

 

 

the NAO even when used in conjunction with other factors is very unreliable after about 7 days, best not to use it for anything beyond 7 days or so. It is not a driver anyway as I believe someone has already stated.

[The Post-modern Winter]

Agreed Nick. Noteworthy (as some others here have also spotted through different output) are the increasing EC and MOGREPS members offering ridged solutions towards latter stages of 10-15d trend period, which, in words of UKMO Dep. Chief, "...may be the first signs of a general change of type across northern Europe, with a slow-down in the predominantly W/WNW’ly jet – this in response to some signs from global teleconnectors of a move toward a negative NAO." There's no sign of meaningful change/cold pre-Christmas, but the period afterwards *might* offer broadscale change.

 

 

That showed only for a day so I guess it was a glitch. In general, it was persistenly showing -NAO from mid December but then it got pushed back to early January and now later in January.

 

As stated consistently by Ian, the above quote from the chief forecaster should be treated with caution however they are clearly seeing something we aren't. I wouldn't place too much focus on the CFS-derived outcome regarding the projected NAO.

[johnholmes]

There is certainly nothing I can see using whatever models cover the next 2 weeks to suggest any real change in the overall westerly pattern of weather. Possibly even a touch less cold (bit milder than the past few days) by Christmas?

Will do a summary of anomaly charts and other factors some time tomorrow along with links.

[Methuselah]

On the flipside, NOAA and the NCDC do appear to have faith in it, spend time/money running and updating the model so if there was no value in it, you'd think they wouldn't bother?

I've no doubt that, over time, the CFS model will gain more and more credibility, as a long-range forecasting tool...No-one can expect new models to be as reliable as the older ones. I do think that the CFS is the way of the future. I'll not trust in it yet, though...  

[ukpaul]

GFS now rolling onwards again on Meteociel, thank you to whoever put the money in the meter.....

[Cloud 10]

GFS now rolling onwards again on Meteociel, thank you to whoever put the money in the meter.....

 

Used to have a gas meter many years ago which  took 50p pieces,then they came and changed it

for a one that took £1 coins.

 

I may have drifted off topic....

Is the GFS run visible anywhere after 132h? Does someone needs to give the spanking new computer a kick or is it just Meteociel?

 

Someone must have heard you and given it a kick as its out to 180 hrs now.

Edited December 12, 2014 by Cloud 10

[Banbury]

The worrying trend is that the - NAO is getting pushed back all the time. It is like chasing a rainbow...

 

At some point, December was the start of the -NAO but now we are looking at late January!

 

Karyo

6 1/2  weeks , I doubt that

[Barry12]

GFS now rolling onwards again on Meteociel, thank you to whoever put the money in the meter.....

 

Thats the GFS P, GFS has been out ages.