Model Output Discussion 29th December - Into mid-Winter.

[Mucka]

5 minutes ago, s4lancia said:

Great 18z to round off a very positive day all in all. The GFS hardly ever does a dramatic flip / backtrack, more edging towards / baby steps.

True, but here is a prelude to tomorrow's GFS 00z Op 

Edited January 8, 2017 by Mucka

[nick sussex]

1 minute ago, Catacol said:

An easterly is what I crave - and today we saw progress in the models. Yesterday the only Wheeler plot showing an active MJO phase was BOMM. Today you can add to that the GFS and to a lesser extent ECM. Something may be stirring at long last in the Pacific though the Ventrice charts I use have conked out for now... so Wheeler is all there is... but it's a good sign.

GLAAM also gently on the up according to the Schiraldi plots, and GEFS also has positive GLAAM for the first time since the end of December - also good news.

End result is in increase today in chances of higher lat blocking, though baby steps rather than a dramatic acceleration in amplification potential. Model watching this week might become interesting...

 

 

Yes the MJO seems to have woken up all of a sudden but I think we need a few more days to make sure this isn't another false dawn. My mood is better than it was a few days ago with that wretched Euro high out of the way and at long last lots of fresh snow forecast for the Pyrenees. I may yet get my husky ride after having to cancel this before Christmas. I'll be interested to see what NCEP say on their update, if we could see the MJO get its skates on then we could see even more interesting outputs.

[SMU]

1 hour ago, Mucka said:

 

Yeah makes a big difference over just a few hours in prolonging cold. I really mean the actual amplification though if we want an Easterly. 

I do see the significance of the changes you are outlining and same corrections we would have a nice ridge by tomorrorws 12z.

Do you fancy a continuation of slow corrections or a complete flip tomorrow?

The GFS ensembles just beginning to sniff out a different solution -

[Nick F]

22 minutes ago, nick sussex said:

The best fax charts of the winter so far, the T120hrs shows the 510 dam on its way south and the flow looks unstable and full of fun!

 

Friday the 13th will be unlucky for some but lucky for others, looking at the 12z UKMO-G, which is broadly similar, sub -6C T850s covering much of the UK and surface temps of below 4C for many too.

With regards to 850-1000 hPa (partial) thicknesses, generally need below 1290 dam for snow to low-levels

22 minutes ago, bluearmy said:

London temps reflect the anticyclonic nature of the latest eps with more than a a hint of continental flow I reckon

 

And note that exeter haven't seen fit to change the fax too much from raw ukmo at day 5

Wow, the 12z GFS op was a big outlier, though not surprising.

Edited January 8, 2017 by Nick F

[Mucka]

5 minutes ago, Steve Murr said:

The GFS ensembles just beginning to sniff out a different solution -

Bad form Steve, I think you missed p14

[Frosty.]

Well it's been great on here today, the highest number of members so far this winter which can only mean one thing..the models are indicating snow in the reliable timeframe and with a bit more fine tuning it could yet be even better but as things stand, the week ahead shows an Arctic blast on the way for the second half of the week with the best spell of this winter so far..looking forward to it immensely!..frost, ice and snow, even drifting snow, high wind chill factor too..Bliss

[Man With Beard]

Dare I say it - strong clustering towards locked in cold on the latest ECM ens

[karlos1983]

1 minute ago, Man With Beard said:

Dare I say it - strong clustering towards locked in cold on the latest ECM ens

I don't recall a better set of ensembles this winter.... 

things just got interesting! 

[Ice Day]

3 minutes ago, Man With Beard said:

Dare I say it - strong clustering towards locked in cold on the latest ECM ens

Now that is the best set of ensembles so far this winter. Momentum is going our (coldies) way.   Another couple of days to go before we can get really excited. 

[Summer Sun]

I make it around 1 week where the 850's stay below zero

Edited January 9, 2017 by Summer Sun

[The Enforcer]

1 hour ago, radiohead said:

A proper nowcast if that happened. Real knife-edge stuff there. Some happy people, some soaking wet people!

GFS still obsessed with 'rain day' Saturday, even at this juncture.☹️

[Scandinavian High.]

6 minutes ago, Summer Sun said:

I make it around 1 week where the 850'5 stay below zero

Yes the is cold is coming you better get your gloves out and a warm coat .

[Nouska]

It cannot be very often you see probabilities shading for parts of the UK to be sub -8C at 850 level.

First from the north....  

and then the continental influence shows its hand.

                                          

[nick sussex]

Another fun/nerve wracking/ emotionally draining day comes to an end in the model thread! All this over a bit of snow, are we mad?

Possibly but really deep down we think those that don't like snow are a bit weird!

Anyway its currently looking like some wintry weather is finally on the way, however snow chances this far out are difficult to pin down bar the usual favoured areas. The best chance for a more organized band of snow would be with a shortwave running south in the flow, aswell as this troughs this far out are subject to change so best advice is to keep a watch on those UKMO fax charts.

Where we go after this nw/n flow depends how much amplitude we can develop with that ridge in the Atlantic before the PV starts to work south towards the north Atlantic. The downstream response to that PV dropping south is normally a ridge being pushed ne ahead of it which is agreed on by the models, the uncertainty is more in relation to how far north we can get the ridge and how much cut back we see in the jet, this needs to loop back sw'wards towards the Low Countries. This is often the hardest part and the bit the models often have a lot of problems with.

The models are currently more in the slack continental flow view rather than the strong easterly with convection, whether this changes depends really on how far north the high can get and whether theres deepish low pressure developing over northern Italy or more generally to the south, this is really key to support the high and advect the coldest air in towards the UK.

We do have a possible curveball thrown into the mix with the MJO, if this gets a move on then we could see more amplification added to the set up. So far the MJO has been on holiday and not doing very much for the last month.

Overall then some colder weather on the way with some snow but a question mark after that, hopefully we can see the cold extended.

 

[Mucka]

UKMO 00z drives the trough much deeper than GFS by 96h

 

GFS has the cold spell over by mid day Saturday with rain moving in and Westerly winds.

UKMO would keep it cold a little longer with possibly a transient snow event with the breakdown but no ridge unfortunately.

Quite disappointing given last nights output but at least we have a cold snap to look forward to. Just hope it doesn't get watered down and is more like UKMO than GFS if we can't keep the cold and have a ridge.

Let's see how the GFS ensembles look and if ECM keeps the faith. 

If you are an ardent coldie and value your sanity then don't look at GFS past 144 and instead gaze upon GEM

A nice ridge maintaining any snowfall with cold surface temps by day and harsh frosts by night - quite preferable to GFS long fetch mild W/SWterlies.

 

Edited January 9, 2017 by Mucka

[Skyraker]

I'm just glad it's 4:30 am and the usual hysterics are soundly tucked up in bed.

Im surprised by the UkMet output, let's see what the ECM has for us.

[Cheshire Freeze]

2 minutes ago, Skyraker said:

I'm just glad it's 4:30 am and the usual hysterics are soundly tucked up in bed.

Im surprised by the UkMet output, let's see what the ECM has for us.

Advice: make the most of the end of the week. However, even the GFS introduces a mild sector making it marginal....

[Weathizard]

Typically just as it looks like a modicum of agreement is appearing the UKM backtracks towards a more GFS type solution - though not as bad! 

 

Sods bloody law!

[Cheshire Freeze]

 I said last week that the way this winter has gone I'll be happy with just seeing snow fall. 

Euro heights back firmly in command in FI...could be a long way back from here

Edited January 9, 2017 by Polar Maritime
To move discussion on.

[Seasonality]

2 minutes ago, Skyraker said:

I'm just glad it's 4:30 am and the usual hysterics are soundly tucked up in bed.

Im surprised by the UkMet output, let's see what the ECM has for us.

Indeed. At 192 we have a familiar picture. Cold feels like it is trolling the UK with the pleasant winter weather kept in Europe. ECM last night was still a variation on a theme of its recent output so it will be interesting to see where it sits today. Whatever happens expect more drama today, and also some model discussion.

[geordiekev]

On 1/6/2017 at 11:52, geordiekev said:

Something I've noticed over the last week is the 0z and 6z runs have been poor for cold following a decent previous run, only for the 12z's to be a lot more encouraging. As a result the threads have been downbeat in the mornings and more encouraging in the afternoons. What evolutions will win out is still anyone's guess for the next few runs but it's part of the chase I guess. 

 

Just thought I'd bump this, I know a few have mentioned the same since I posted,  but can't help feeling that different algorithms are run. Don't want to start another myth, but defo been a trend for well over a week. 

Hopefully the trend will continue with an uptick later in the day. 

[Mucka]

GFS ensembles

Quite a mixed bag by 144 so this has some running time yet. Many want to introduce milder air by Saturday but some want to have that come in off a warm sector from a low pushing SE across the UK and reintroduce colder air behind and ridging.

Perhaps most interestingly the control does not support the Op and does just that.

 

Overall I'd say a pretty good chance ECM stays with the ridge this morning.

Edited January 9, 2017 by Mucka

[knocker]

The GFS this morning in the ten day time frame is very much what one would expect looking at last night;s anomalies and this morning's GEFS. Which very roughly translate into an intense Aleutian trough, strong WAA Canada and eastern N. America with mid Atlantic trough and ridging over the UK. The surface high cell under this scenario will almost certainly be just to the south moving E/SE as the trough nudges in the same direction thus most of the UK in an anticyclonic flow becoming a southerly drift becoming a south westerly.

A little more detail. Most of the UK will experience a much cooler Pm north westerly at the beginning of this week with gales in N. Scotland and wintry showers more likely in the north. By Friday the Atlantic ridge has amplified which veers the wind northerly over the UK and sees a wave depression track down the eastern North Sea  Thus some quite wintry showers particularly in Scotland and along the east coast where it will also be very windy. This northerly regime rapidly gives way to fronts and warmer air encroaching from the west as the ridge collapses under pressure from the upstream energy which reinvigorates the jet.

From here it's all about renewed downstream amplification with ridging to the SE of the UK and a strong mid Atlantic trough and just about where we came in this morning

Edited January 9, 2017 by knocker

[Long haul to mild]

1 hour ago, geordiekev said:

Just thought I'd bump this, I know a few have mentioned the same since I posted,  but can't help feeling that different algorithms are run. Don't want to start another myth, but defo been a trend for well over a week. 

Hopefully the trend will continue with an uptick later in the day. 

Completely agree with this. I know it's only anecdotal but I've been following the winter model output for years and I can hardly ever recall a situation where the 0Z runs improved on the 12Z, especially when cold has been forecast. In fact, they usually go the other way.

Seems that most of the time folks go to bed happy only to be brought down to earth with a bump in the morning!

[terrier]

So the ukmo moves slightly towards the gfs this morning. Also the gfs brings in a milder sector making things marginal for some. Think I will enjoy Thursday-Friday cold snap. Because if the gfs proves correct it wil be all over by Saturday lunch time. Which did tie in with BBC forecast last night.