Model output discussions pm 31/12/15

[Carlrg]

Back end of that system producing some snow.

 

[Eskimo]

Last couple of runs have shows that deep area of low pressure from the GFS. It it tracked 50-100 miles further south, a lot of people would see something wintry. 

Dew Points are very marginal for the North Midlands. 

Edited January 1, 2016 by PerfectStorm

[Mucka]

1 minute ago, Carlrg said:

Back end of that system producing some snow.

 

Not just the back end, check the two previous charts. Taken on face value (which is no value at all) that would 12+ hours heavy snow for some parts

 

[Man With Beard]

Hello, hello ... no-one was talking about snow from this feature, were they??

And in the south east, gusts over 100mph up the straits of Dover

Would be one of the stories of the winter.

Too far out to get worried/excited about yet, though?

[Carlrg]

T156 looks like a mess.

 

 

[Polar Maritime]

12 minutes ago, PerfectStorm said:

Last couple of runs have shows that deep area of low pressure from the GFS. It it tracked 50-100 miles further south, a lot of people would see something wintry. 

Yes most seeing snowfall out of that system as -3c/-4c 850's get dragged into the mix, And Knockers shed roof could be at risk as severe gales cross the channel. A very unsettled outlook for the next 10 days with a cold Westerly flow giving cooler more avg temps more often than not with a greater risk of snow especially with elevation.

 

Edited January 1, 2016 by Polar Maritime

[bradymk]

5 minutes ago, Carlrg said:

Back end of that system producing some snow.

 

Higher Res not quite as widespread. Higher ground mainly but either way,  it's a nasty little system if it were to occur. 

[TSNWK]

anyone think that these incremental small trends today, might be enough to flick the long wave pattern into something more conducive to cold...

[Jason M]

I'm sure most people are already well aware, but for any newbies GFS is renowned for over cooking snow. Away from the Scotland and high ground in the north, rain will be the order of the day based on tonights output (just my humble opinion of course ).

Some of the output today is bringing back memories of 2013 - 2014 in my mind. Of course no two winters are the ever the same, but plenty of rain, wind to come. Hopefully it will change!

 

[Nick F]

Well Happy New Year all, new year but same old Atlantic fire hose pointing us but a colder element across northern areas which could spring a few snow events. The man flu that I've developed these last few days kind of mirrors the damp rot that has set in on the model output.

Echoing Chino's comments earlier, the WAA/ridge route this past few days was never following the empirical route to bring a deep cold and snowy easterly because the ridge built north too far east and the WAA punched too far north -aided by some very deep depressions like Frank. Don't think I've ever seen a cold and snowy spell develop this way. Normally we would see a ridge build NE over the UK towards Scandi and a cold vortex dropping SW into Central Europe bringing low pressure for a better chance at an easterly. Or, another route would be a chunk of the trop vortex dropping SE via N Sea into mainland Europe from Iceland/Greenland bringing an initial Nly followed by height rises over NE Atlantic and winds turning NEly then Ely.

So where do we look to next for potential cold spell for all the UK? A SSW is more likely during El Niño and La Niña events, but this looks unlikely to occur until February now. But, the troposphere pattern may flip before any responses working down from the strat. The MJO is still forecast to track into phase 7 at decent amplitude before losing a coherent signal through phase 8/1 as per ECM which seems to perform best out all of them

 So, if El Niño isn't interfering too much with this signal, then we may expect some changes in the wave patterns and more in the way of high latitude blocking later this month. Though I'm not a great fan of the composites used for the 8 phases for the different months - particularly as coherent MJO waves and strong El Nino is rare so would not expect the same tropospheric response as those composites.

the most persistent and unchanged  +height signal from NWP out to day 15 thus far is across western Canada/Alaska (EPO ridge) on north into the Arctic - which is forcing the -AO signal. We see the +height anomaly over Kara Sea initially but this tends to fade unlike the EPO ridge. The NAO drops slightly -ve next few days before recovering to more neutral values then dipping more negative again. But, despite higher heights pushing east into Greenland, EPS and GEFS days 10-15 mean indicate a more west-based -NAO, thanks to a strong STJ emerging over southern US combined with eastern US trough as per CPC prognostic chart below.

Our best hope going forward, IMO, would be to get a break mid Atlantic via some amplification upstream to allow an Atlantic ridge into Greenland. Bit like the CPC analog chart made today shows below:

not totally out the realms of possibility if you rolled forward tonight's 12z ECM det.

Edited January 1, 2016 by Nick F

[Mucka]

Just now, TSNWK said:

anyone think that these incremental small trends today, might be enough to flick the long wave pattern into something more conducive to cold...

 

Personally I think we are going to need more amplification upstream to have any chance.

Tonight's GFS doesn't show any sign of a worthwhile Atlantic ridge by day 10 but ECM is better.

Also tonight's GFS has the PV break down the Arctic ridge/high and reform killing and height rises over Greenland

Although it looked quite good earlier.

 

I will be looking for improvements across the Arctic in the medium term and and better amplification in the Atlantic sector in the slightly longer term. If those two factor combine together we could be in with a decent shot of something from the North around mid month. If either one fails, especially Atlantic ridge then it becomes much less likely, Only other route is a diving low and cut off heights somewhere just N of UK but that would likely only occur a little further out and is just hope casting for now.

[Carlrg]

I'm sure I recall someone mention snow with uppers as warm as 0c  and these uppers are around and stay at -4c. May be possible to get a bit of the white stuff.

 

 

Edited January 1, 2016 by Carlrg

[TSNWK]

2 minutes ago, Mucka said:

 

Personally I think we are going to need more amplification upstream to have any chance.

Tonight's GFS doesn't show any sign of a worthwhile Atlantic ridge by day 10 but ECM is better.

Also tonight's GFS has the PV break down the Arctic ridge/high and reform killing and height rises over Greenland

Although it looked quite good earlier.

 

I will be looking for improvements across the Arctic in the medium term and and better amplification in the Atlantic sector in the slightly longer term. If those two factor combine together we could be in with a decent shot of something from the North around mid month. If either one fails, especially Atlantic ridge then it becomes much less likely, Only other route is a diving low and cut off heights somewhere just N of UK but that would likely only occur a little further out and is just hope casting for now.

Many thanks Mucka.. For your thoughts and detailed response.. Fingers crossed! I would say that certainly for short term ( sub 144 ) it has not been a bad day... We just don't seem able to tip those scales into a colder longer wave pattern.. Be it greenie high or something from the east.

[Mucka]

11 minutes ago, Carlrg said:

I'm sure I recall someone mention snow with uppers as warm as 0c  and these uppers are around and stay at -4c. May be possible to get a bit of the white stuff.

 

 

 

They were likely referring to dry air sourced from the continent which is less modified. with a situation like the one described evaporative cooling can become an important factor if we want snow to lower levels with less than ideal upper air values.

Edited January 1, 2016 by Mucka

[Paul]

Dunno if some people are maybe feeling under the weather due to a heavy night last night, but since there's been a bit of it already tonight, if you're planning to  post in here to point score, or create a confrontation just for the sake of it, please don't. 

 

[Mucka]

4 minutes ago, TSNWK said:

Many thanks Mucka.. For your thoughts and detailed response.. Fingers crossed! I would say that certainly for short term ( sub 144 ) it has not been a bad day... We just don't seem able to tip those scales into a colder longer wave pattern.. Be it greenie high or something from the east.

You're welcome and who knows what can happen in deepest FI?

Funny enough 18z goes on to produce some WAA and weak cut off high over Greenland similar to my hope cast thoughts. 

[nick sussex]

I think the differences between the GFS 12 and 18hrs runs highlight my long held view that trying to make sense of trends with the GFS in the dark reaches of FI is a pointless affair.

I really wish NCEP would just ditch the GFS past T240hrs and stick to improving the model within that range, this is a continual gripe of mine which surfaces every year!

Anyway after my annual GFS moan in terms of next week it looks a bit of a dogs dinner weatherwise, more seasonal temps  still a chance of some snow amidst the monsoon.

The PV chunk dropping south seems to be an issue in terms of how sharp the troughing associated with that will be, the angle of Atlantic attack still open for revision which will effect any snow chances before the deluge arrives.

Given my utter detestation of the Euro high at least that has shot its bolt finally!

 

[Mucka]

8 minutes ago, nick sussex said:

I think the differences between the GFS 12 and 18hrs runs highlight my long held view that trying to make sense of trends with the GFS in the dark reaches of FI is a pointless affair.

I really wish NCEP would just ditch the GFS past T240hrs and stick to improving the model within that range, this is a continual gripe of mine which surfaces every year!

Anyway after my annual GFS moan in terms of next week it looks a bit of a dogs dinner weatherwise, more seasonal temps  still a chance of some snow amidst the monsoon.

The PV chunk dropping south seems to be an issue in terms of how sharp the troughing associated with that will be, the angle of Atlantic attack still open for revision which will effect any snow chances before the deluge arrives.

Given my utter detestation of the Euro high at least that has shot its bolt finally!

 

It is good for that so long as you run through the ensembles manually and filter out the suspected noise and amplify what you believe is the correct signal.

I often mention signals within deep FI of GFS ensembles and many times they have proven correct. For example it picked up on the Height rises to our E/NE long before they were manifested in any anomaly charts or consistently modeled by any operational output. I could probably point to half a dozen times last year where I picked pressure anomalies out of GFS ensembles at 14 days+ that proved correct and about 2 or 3 that didn't come to fruition. I think they can be quite a valuable tool so long as we don't pretend to know what will happen and just report on strength of signal and what it is pointing toward. I don't have the skill to to make that sort of forecast so I simply report the signal in terms of strength.

If any of that was just a fluke we will soon find out this year. 

Edited January 1, 2016 by Mucka

[Singularity]

Ouch - GFS is producing some nasty scenarios for the far south (and southern North Sea) with that shortwave feature as it engages with a near 200 mph jet stream while under excellent upper level ventilation from the trough. Whether it will really end up so well positioned relative to the jet is another matter of course. 

 

Looking well ahead again and there's more of an Arctic High theme to the 18z compared to the Canada/Greenland block of the 12z.

Still issues with bowling ball lows and the jet not getting far enough south - but these have in past winters been some of the most reliable areas of bias in the GFS model based on what I've seen; it overlooks the imperfections that often cause lows to become less than rounded, and tends to overcook the jet a bit too with a corresponding northward bias.

- but whether these traits are still in place since the late Jan upgrade of 2015, I cannot say for sure.

 

I find ECM's broad, uneven trough digging slowly further south to be a more believable outcome, though the pace of developments can't be taken too seriously of course. The maintenance of the blocking highs on both the Canadian and Siberian sides seems very credible given the MJO signal, as does the refusal of the cross-polar ridging to give up even in the face of shortwave lows pressuring from both the Atlantic and Pacific sides.

I expect that mid-Atlantic LP development will do its best to be a major player due to the El Nino background and that mid-Atlantic Cold Pool. This may push mild air up from the southwest and throw aside initial attempts at getting the cold to our shores after only a brief, teasing visit. But maybe not - the trough may develop far enough south to in fact lend support to blocking across Greenland. At that point, it becomes a case of clearing away residual disturbances from the Greenland area - a task that clearly needs doing on today's ECM 12z det. +240 chart. The trough moving into the mid-Atlantic looks to be far enough south, but the ridge could be restrained to the mid-Atlantic on the first attempt.

If and when a block is achieved to our NW, any trough to it's south is likely to attempt to move northeast - at which point, if it has elongation SW-NE or even W-E under the best scenario, it could work wonders when engaging with a plunge of Arctic air from the north. It's that manner of reasoning that leads me to consider the possibility of a significant snowstorm to be unusually high in late Jan/early to mid-Feb this year. No guarantees but worth saying to encourage happy dreams for the snow seekers 

Anyway, there's a good chance that we'd need several bites of the apple to get the right results. Typically such a pattern sees a gradual progression south with time, hitting the north first, the south having to be more patient.

 

The 18z GFS det. sure is blowing up those troughs! Yet even in the face of that, progress is slowly but steadily achieved as the HLB becomes ever more prevalent. In typical fashion, it's only at the very end that we see a more favourabe mid-Atlantic trough capable of throwing a ridge up ahead of it which could then draw cold air in from the NE. 

Honestly though, I suspect GFS might be being a bit of a d!!k 

[Midlands Ice Age]

Hi guys,

Just been watching Louise Lear on News 24  for the week ahead forecast.

Very interesting   -  She is now going for strengthening heights over Scandy and the north Atlantic - by the end of the week(!), with low pressure systems gradually filling and moving south from Southern England.

The mention was of snow showers over Scotland by the end of the week and much colder air from Scandy.. 

Now where has that come from.?

Presumably one of the models seen and used  internally has flipped this evening.

Where is Steve M? He hasn't been seen today so could he have been somewhere in the Met Office?

Tonights runs may become more interesting, but I will leave them for the night shift as I need to catch up some sleep from last night!

Is this the Steve Murr switch?

 

Edited January 1, 2016 by Midlands Ice Age

[Robbie Garrett]

Interesting set-up probably going to develop late-mid month. 240hrs out the ECMWF and GFS are similar but not carbon copies.   FI looks to move a cold pool of Scandinavia post 240hrs,  first signs of a change to the norm?  That Jet Stream is really strong throughout January, no surprise for a rinse repeat of Oct-Dec 2015 throughout the majority of January.   Where's that Pesky Azores High?

 

[blizzard81]

We seem to have a pincer movement on the pv into next week. One from the alaskan side and one from what's left of our much talked about Kara high. This imo will cause quite a lot of confusion with the models over the next few days mainly in relation to how far south they push the jet stream in the atlantic. I feel there will be some nice eye candy showing for coldies in the next few days.

[nick sussex]

1 minute ago, Mucka said:

It is good for that so long as you run through the ensembles manually and filter out the suspected noise and amplify what you believe is the correct signal.

I often mention signals within deep FI of GFS ensembles and many times they have proven correct. For example it picked up on the Height rises to our E/NE long before they were manifested in any anomaly charts or consistently modeled by any operational output. I could probably point to half a dozen times last year where I picked pressure anomalies out of GFS ensembles at 14 days+ that proved correct and about 2 or 3 that didn't come to fruition. I think they can be quite a valuable tool so long as don't pretend to know what will happen and just report on strength of signal and what is pointing toward. I don't have the skill to to make that sort of forecast so I simply report the signal in terms of strength.

If any of that was just a fluke we will soon find out this year. 

Of course the ensembles can be helpful when they're not plucking a solution that looks totally against the background signals and theres a decent clustering around an outcome but still they're prone to some wild swings. Personally I'd shred all GFS operational runs past T240hrs and use them as cat litter! With 4 runs a day it gets lauded sometimes for picking up on the right solution when in fact all its done is throw 4 different solutions out and the odds eventually favour that it will be right eventually!

Anyway this counts now as two GFS moans from me so I'd better move on!lol

[Gary R Betreen]

Being on a steep learning curve here.  Does the 7th look very windy and stormy again with disruptive storm force winds?

 

[blizzard81]

4 minutes ago, Midlands Ice Age said:

Hi guys,

Just been watching Louise Lear on BBC2 for the week ahead forecast.

Very interesting   -  She is now going for strengthening heights over Scandy and the north Atlantic - by the end of the week(!), with low pressure systems gradually filling and moving south from Southern England.

The mention was of showers over Scotland by the end of the week and much colder air from Scandy.. 

Now where has that come from.?

Presumably one of the models seen and used  internally has flipped this evening.

Where is Steve M? He hasn't been seen today so could he have been somewhere in the Met Office?

Tonights runs may become more interesting, but I will leave them for the night shift as I need to catch up some sleep from last night!

Is this the Steve Murr switch?

 

That sounds like very poor wording from Louise.