Model output discussion - heading into 2018

[blizzard81]

1 hour ago, Catacol said:

For those hoping for some cold and seasonal weather heading into January the signals have taken a significant turn for the worse. Negative anomalies in the tropical western pacific forecast to be removed altogether, allowing a big surge in trade winds and removal of AAM from extratropical regions

 

Vortex profile also now forecast to grow substantially, with the 10 day Berlin chart not making pretty reading - unless westerly influence at mid latitudes is what you are after... 

Loss of AAM at 10 days now sees ensemble data remove pretty much all high lat blocking, with high pressure instead forming a neat belt around most of the hemisphere in mid latitudes. As Cohen has reported recently, this is really a setup now pointing at a mild January with cold bottled up in the arctic. 

All of this is then reflected in the excellent GWO tool - for the first time in a good while the spiralling rise in GLAAM has zigged back towards 7.00 on the phase chart... and we are headed now for a period of phase 1-2-3 activity.... low on blocking and high on westerlies in a more "classic" Nina setup.

It has been a sudden and somewhat unexpected turnaround. There was no suggestion of a sudden removal of tropical pacific convection strength: indeed the NOAA report of only a week ago saw a slow and steady movement through 7/8.. and ongoing wave 1 activity via favourably positioned blocks had kept the vortex quiet. So what has changed? A very good question. I scan the web and twitter pretty frequently and have not spotted an explanation yet: only observed reality and a prognosis for the next 15 days brought in line with observed data. We know from IF that Glosea suddenly lost its SSW signature... and we can see that the massive surge of heights into the arctic from alaska is now forecast to moderate very quickly and be suppressed. What is driving this? Has Nina simply won the day? Is a warming world making composite data and analysis less accurate? Has extreme arctic sea ice loss got wider ramifications than we are currently aware of? 

We will see what comes out of this analysis as the days/weeks progress because I'm sure some of the big guns out on twitter will have their say in time... but for now it might be a good time to take a break from model watching. Current conditions will take a good 2 weeks to play out - maybe closer to 3 or 4. Winter is not over yet by a long chalk... but we we will need to see factors alter again if the drivers that create the NWP are to produce some better eye candy. For a while the best we can hope for is some mid lat blocking to take the sting out of the atlantic and give some calm, chilly maybe frosty days. MetO forecasts hint at exactly this I think. 

If people as knowledgeable as you are perplexed by this "yet again" sudden reversal in fortunes for cold weather then I would suggest that there are other forces at hand that most people in this world are not privy to. 

 

[nick sussex]

Good to see the GFS 18hrs run also developing that shortwave near Newfoundland like the ECM.

That manages to delay the purple doom which is approaching, we almost got the shortwave ahead of the main low to clear south east. It doesn't quite manage to detach from the mothership which would have helped to angle the jet more se.

There still looks too much energy upstream but we have seen tonight some changes upstream. Probably not enough time for a major salvation operation given the timeframes.

I'd like to wait for the morning runs to see if we can squeeze a bit more amplification upstream.

At least theres a few days with some wintry potential so its not all bad.

[January Snowstorm]

10 minutes ago, Catacol said:

Yes  - transient processes always possible in the dead of winter even from a westerly pattern.

Maybe so but I've seen enough winters to know that predicting beyond about 8/9 days is fraught with danger and the next 5 are cold.....how many times have all models said cold, all ensembles agreed and the met on board and still it backfired!!

Answer!? Too many which means the opposite also applies when all routes show mild

[MP-R]

4 minutes ago, January Snowstorm said:

Maybe so but I've seen enough winters to know that predicting beyond about 8/9 days is fraught with danger and the next 5 are cold.....how many times have all models said cold, all ensembles agreed and the met on board and still it backfired!!

Answer!? Too many which means the opposite also applies when all routes show mild

Indeed, a week ago it wasn't looking like a particularly interesting week next week, yet now we have at least 3 below-average days with a chance of snow. Best to take each week as it comes in my opinion, whether it be mild or cold one is after. 

[comet]

 

37 minutes ago, s4lancia said:

Top post again Catacol. Many thanks for going to the time, as indeed did (still does I sincerely hope) Tamara and GP.

At least going to the effort to explain why that in all likelihood we are going into a less blocked phase. As opposed to just basing everything on a static seasonal LRF, which in all likelihood was only (or at least primarily) based on the ENSO state. 

Now, that doesn't make that LRF ultimately any less accurate and, at the moment at least, it looks a pretty good call, as Nina seems to be returning to the forefront..

For me though, the real skill is in the ONGOING interpretation of the dynamics of the ever changing atmosphere and its drivers.

Phrases like Knife edge and tipping point certainly seem to reflect this winter and just because we end up going default doesn't mean (necessarily) that we didn't miss out going the other way by a whisker. It's a bit like a striker with an open goal in front of him and scoring off the underside of the crossbar. That is exactly the same result, a goal, as smacking it clean between the posts. But if the ball instead hit the crossbar half an inch higher, the end result would of course have been completely different, a miss. The goal being a standard mild winter. A miss being something of a colder nature. Not sure if what I am trying to get at makes sense, sort of does in my head anyway :-) 

Keep up the good work. Maybe we will get lucky for once, against the odds! 

Will it still be a top post if say in a couple of weeks it proves to be totally incorrect like the ones of GP and Tamara plus if things in the tropics can change as quick as that then they can do so again.  Its as  if  these teleconnects and AAM budgets, GWO etc are the holy grail of weather forecasting lol. I am sure they play a part but I have yet to see any reliable long range forecasts on here or anywhere else.  Sure on the face of it the outlook beyond some interest next week does not look great but that can soon change. Also there is never much mention of the strat forecasts in any these musings and yet when the strat and trop are coupled the strat plays a very important part on the tropospheric weather patterns regardless of the above teleconnets etc.

Edited December 23, 2017 by comet

[East_England_Stormchaser91]

2 hours ago, Catacol said:

For those hoping for some cold and seasonal weather heading into January the signals have taken a significant turn for the worse. Negative anomalies in the tropical western pacific forecast to be removed altogether, allowing a big surge in trade winds and removal of AAM from extratropical regions

 

Vortex profile also now forecast to grow substantially, with the 10 day Berlin chart not making pretty reading - unless westerly influence at mid latitudes is what you are after... 

Loss of AAM at 10 days now sees ensemble data remove pretty much all high lat blocking, with high pressure instead forming a neat belt around most of the hemisphere in mid latitudes. As Cohen has reported recently, this is really a setup now pointing at a mild January with cold bottled up in the arctic. 

All of this is then reflected in the excellent GWO tool - for the first time in a good while the spiralling rise in GLAAM has zigged back towards 7.00 on the phase chart... and we are headed now for a period of phase 1-2-3 activity.... low on blocking and high on westerlies in a more "classic" Nina setup.

It has been a sudden and somewhat unexpected turnaround. There was no suggestion of a sudden removal of tropical pacific convection strength: indeed the NOAA report of only a week ago saw a slow and steady movement through 7/8.. and ongoing wave 1 activity via favourably positioned blocks had kept the vortex quiet. So what has changed? A very good question. I scan the web and twitter pretty frequently and have not spotted an explanation yet: only observed reality and a prognosis for the next 15 days brought in line with observed data. We know from IF that Glosea suddenly lost its SSW signature... and we can see that the massive surge of heights into the arctic from alaska is now forecast to moderate very quickly and be suppressed. What is driving this? Has Nina simply won the day? Is a warming world making composite data and analysis less accurate? Has extreme arctic sea ice loss got wider ramifications than we are currently aware of? 

We will see what comes out of this analysis as the days/weeks progress because I'm sure some of the big guns out on twitter will have their say in time... but for now it might be a good time to take a break from model watching. Current conditions will take a good 2 weeks to play out - maybe closer to 3 or 4. Winter is not over yet by a long chalk... but we we will need to see factors alter again if the drivers that create the NWP are to produce some better eye candy. For a while the best we can hope for is some mid lat blocking to take the sting out of the atlantic and give some calm, chilly maybe frosty days. MetO forecasts hint at exactly this I think. 

A bit early to be writing on average, the most coldest month of winter right off!! 

We still have over a week of December yet to go through, with possible snow before its out, and a potential slider low scenario. 

Surely you know and have experienced that cold patterns can often be a flash appearance in the mid term, and most have actually arisen in that form. A bit too early for knee jerk reaction at a few charts that could change substantially in the next few days! 

Edited December 23, 2017 by East_England_Stormchaser91

[Daniel*]

22 minutes ago, feb1991blizzard said:

Its 21.6% chance of a situation I would love to be in right now, looking at it another way - if I was really going to put a positive spin on it (and I don't feel that way right now) then you could say that there's only a 43.1% chance of a synoptic which completely rules out any cold verifying.

Highest % yet I’ve seen for height rises to NE.  

Mm....anything but the main cluster cheers! 

[snowray]

Well at least if we get a few more snow events in the bag before the end of the month it will not be so bad if we end up having to endure an Atlantic dominated first half of January. December would at least go down as a half decent month for snowfall and many on here will have had at least one snow fix for now.

Edited December 23, 2017 by snowray

[Catacol]

16 minutes ago, s4lancia said:

For me though, the real skill is in the ONGOING interpretation of the dynamics of the ever changing atmosphere and its drivers.

Phrases like Knife edge and tipping point certainly seem to reflect this winter and just because we end up going default doesn't mean (necessarily) that we didn't miss out going the other way by a whisker. It's a bit like a striker with an open goal in front of him and scoring off the underside of the crossbar. That is exactly the same result, a goal, as smacking it clean between the posts. But if the ball instead hit the crossbar half an inch higher, the end result would of course have been completely different, a miss. The goal being a standard mild winter. A miss being something of a colder nature. Not sure if what I am trying to get at makes sense, sort of does in my head anyway :-) 

Absolutely. Interpretation of dynamics is what it is all about - and understanding what creates ensemble and operational output, not just taking that output at face value. If it were easy the Met Office would have cracked long term forecasting years ago.

The near miss analogy is interesting. I'm not sure if weather works this way - I'd like to think it does, and that within a system of structured chaos there are tipping points and near misses that can fall one way or another. But the more I learn of the GWO and the research behind this representative tool the less certain I am that it works like this. I am leaning towards a perspective of less chaos, and more structure, to global patterns... always accepting that tiny fluctuations in a global pattern can have immense repercussions for a single postcode in the UK sat between atlantic gulf stream, and continental land mass. Perhaps on a microcosmic scale the near miss works - but on a hemispheric level less so.

Which makes the developments of the last week or so all the more interesting and frustrating in equal measure. Let's be clear about one thing: the MetOffice 6 - 30 day reports were favourable for cold and blocked only a short time ago. Met Office insider blogs pointed to high lat blocking.... and CreweCold has correctly stated that we have had this kind of reversal before. Last year was somewhat different in terms of background drivers, not least in terms of the ENSO state, but there was a spell of colder weather on the horizon that just melted away (no pun intended...)

I wonder how things would have been back in the 1980s had we had the internet and all these tools at our disposal? Would there have been so many "near misses" as feels the case the last few years? Maybe there would... and we are just looking at the past through rose tinted specs - coloured by a handful of crunch moments like Jan 87. Or maybe we would have found predictive driver tools more reliable back then. I think we have to be realistic - the arctic is experiencing massive change in a very short space of time, and I refuse to believe we have a full handle on the implications. Climate change, whether man made or not, is an ongoing process - and higher temperatures appear to be coinciding with higher pressure anomalies, and we seem to be experiencing a series of winters with cold stratospheres, helping whip up zonal wind just at the wrong time of the year for snow lovers in the UK. And what of global sea temperatures? If the anomaly charts are to be believed the oceans are all warmer than they were - and I'm not convinced the implications of this are fully understood yet either.

Anyway - this is a MOD thread and I recently had half a post cut for not keeping to MOD output.. so in an effort to bring it back to something concrete: the ongoing dynamic pattern for at least a fortnight and probably longer will see more of this:

as the atmosphere slips into a state of low momentum and therefore flat patterns. 

 

[Frosty.]

Plenty to like about the Gfs 18z next week with a wintry spell bringing snow in places and sharp frosts..a happy ending too!???

[Catacol]

5 minutes ago, comet said:

 

Will it still be a top post if say in a couple of weeks it proves to be totally incorrect like the ones of GP and Tamara plus if things in the tropics can change as quick as that then they can do so again.  Its as  if  these teleconnects and AAM budgets, GWO etc are the holy grail of weather forecasting lol. I am sure they play a part but I have yet to see any reliable long range forecasts on here or anywhere else.  Sure on the face of it the outlook beyond some interest next week does not look great but that can soon change. Also there is never much mention of the strat forecasts in any these musings and yet when the strat and trop are coupled the strat plays a very important part on the tropospheric weather patterns regardless of the above teleconnets etc.

Then stick to your tea leaves. Either try and understand what drives the weather... or decide it's impossible and see it all as luck. And if that's your approach then following each and every op run and accompanying ensembles is likely to drive you mad. Good luck with that.

Strat conditions are regularly mentioned - you are in error there.

Agreed - it could all flip again later in January - but if it does you can be assured some of us will try and explain why. We cant control the weather so there is no point getting annoyed by its fluctuations - but can we not try and understand it a bit better?

[Catacol]

9 minutes ago, East_England_Stormchaser91 said:

A bit early to be writing on average, the most coldest month of winter right off!! 

We still have over a week of December yet to go through, with possible snow before its out, and a potential slider low scenario. 

Second half of January still up for grabs. I think I said the next 2 weeks... which takes us to Jan 7. Beyond that - all could change. However we will need something substantive to spike AAM once again and create the amplification needed for a high lat block in a Nina year. That's not to say it couldnt happen... but at the moment it looks less likely than was the case a week ago!!

A SSW event would also change things. Very hard to predict, and beyond my skill to try and do so.

[blizzard81]

Anyway, fax charts look good

[karlos1983]

Tis the season to be jolly, tra la la la la, la la la laaaa!

Play nicely people blimey!

some look set to see snow mid week, i as usual can’t wait for the cold rain ?‍♂️

 

 

 

Edited December 24, 2017 by karlos1983

[Frosty.]

I wish Tamara and glacier point could post more often, love their expert input!..anyway, the Gfs 18z shows some wintry weather on the way, especially next midweek when there could be significant accumulations in places..good luck to all!

[A Frayed Knot]

Yes stick with the Fax ' Moosh the computer models ' very bullish all the time . they look good but never ever give what they show '

No wonder this is called the MAD thread ' all Hunting snow , like i said a week ago ' its a coming within a week .

1 hour ago, blizzard81 said:

 

[geordiekev]

A very Merry Christmas ? Eve all. We're all here to share our thoughts, feelings and grumblings, to the most fickle of weather regions in the world, but let's play nice please. We are all a bit stressed in what should be a serene time, due to travels and last minute rushing so just take a minute and think how your post might affect a fellow member of our unique club.

Enjoy the season to the fullest,  there's a wide range of options in the models so just try and enjoy the ride.

Personally I'm peeved, as again it looks like I'll be glued to a radar instead of enjoying the festivities,  for my white Christmas Newcastle bet. (at least for the last few hours). One of these years the models will predict a truly green Christmas, without giving my area possibilities of flakes an hour before midnight or an hour into boxing day. Believe me this has occurred about 3 out of last 5 years and so annoying,  so thanks GFS for ruining the peace again. 

Enjoy it gang and raise a glass to fellow members ? ? 

[SLEETY]

4 hours ago, January Snowstorm said:

Interesting that many of the experts are predicting a mild fest ahead whilst the models continue to upgrade the short term. Many parts could see at least falling snow over next 5 days yet I struggle to remember anyone predicting it.....

Actually Darren bet on the week ahead forecast a week ago said it could turn colder after Xmas day.i remember it because a lot of people here said that they couldn’t see how he could be forecasting that,as at that time none of the models  that we can see were showing that scenario,so well done to him.

Just shows you how quickly things can change,I wouldn’t be writing off Jan just yet.

 

[knocker]

Today persistent rain over western Scotland will move south to cover N. Ireland and north west England whilst elsewhere a moist, freshening WSW airflow will persist with perhaps patchy drizzle in the west and temps a little above normal,  Tomorrow the rain in the north will track east, possible some snow in eastern Scotland, whilst a front and rain will approach from the west and make inroads across Wales and the western half of England

The front duly clears the south east early Tuesday morning but the two high pressure cells, one in mid Atlantic and the other eastern Europe are beginning to amplify resulting in the upper trough in the vicinity of the UK being forced south and the wave depression forming out in mid Atlantic being forced south east by the strong low level jet running around the Atlantic ridge. The low duly arrives over Pembroke 984mb by 1800 Tuesday and six hours later is over Salisbury en route to the eastern Channel. This could well produce snow along it's N/NW flank across Wales and the southern midlands. As always to be sorted nearer the time.

The low quickly moves away east initiating a cold northerly regime over the UK on Wednesday and Thursday with perhaps some snow in the south east initially on Wednesday Meanwhile the Atlantic and frontal systems are trying to gate crash the party from the west but the upper trough to our east is not going anywhere fast as it continues to be blocked by the HP to the east and is actually in the process of deconstructing. Ergo any fronts are struggling to make any  headway east and tend to dissipate before reaching our shores leaving the UK pretty much in a col by Friday 00. Quite chilly during this period with frosts.

But by Saturday the Atlantic does get the upper hand with a deep low south of Iceland and subsidiary lows tracking across Scotland and fronts and rain tracking east across the rest of the UK in a strong SW/W airstream with temps now way above average reaching 13C in places.

 

Edited December 24, 2017 by knocker

[Duane S.]

6 hours ago, Catacol said:

Absolutely. Interpretation of dynamics is what it is all about - and understanding what creates ensemble and operational output, not just taking that output at face value. If it were easy the Met Office would have cracked long term forecasting years ago.

The near miss analogy is interesting. I'm not sure if weather works this way - I'd like to think it does, and that within a system of structured chaos there are tipping points and near misses that can fall one way or another. But the more I learn of the GWO and the research behind this representative tool the less certain I am that it works like this. I am leaning towards a perspective of less chaos, and more structure, to global patterns... always accepting that tiny fluctuations in a global pattern can have immense repercussions for a single postcode in the UK sat between atlantic gulf stream, and continental land mass. Perhaps on a microcosmic scale the near miss works - but on a hemispheric level less so.

 

Yep, I should've made that clearer. My analogy was in reference specifically to the weather we end up getting here in the UK as opposed to global patterns.

[West is Best]

6 hours ago, Catacol said:

Absolutely. Interpretation of dynamics is what it is all about - and understanding what creates ensemble and operational output, not just taking that output at face value.

Is it?

A few years ago chaos theory was all the range. The infamous and unfortunate butterfly flapping its wings on Vanuatu was the cause of a hurricane thousands of miles away.

Until it was pointed out that lots of butterflies flap their wings and hurricanes don't result.

I agree with you that hard science must explain our weather. But the cynic in me reckons a lot of teleconnection forecasting is little better than reading tea leaves. Humans look for patterns in order to explain the world: it's how and why brain tricks work. A bend in the jet over Hawaii does not definitely produce a 10 centigrade rain shower five days later in Haverfordwest. The variables are so huge from the Pacific to the UK shores that we might do better to stay focused a little closer to home.

So to those preparing to don their best mourning black, the models might look a touch Atlantic orientated a week hence, but perhaps we should stay focused on the exciting prospects of another cold northerly followed by boundary snow. I've lost count of the number of times we are told that our weather pattern is now set in stone, only to find it all changes a few outputs later.

Happy Christmas everybody  

x

 

[knocker]

The ecm continues to want to form a little wave on Monday's front to the south west and tracks it across northern France Monday night/Tuesday morning whilst the front itself brings a fair bit of rain to England and Wales, It then proceeds to track the wave depression further south than the gfs and has it 984mb over Cornwall at 1800 on Tuesday. Isle of Wight by 00 and Kent by 06 Perhaps snow on the moors and the M4 corridor. Very knife edgy and the precise track of the low still up for grabs

Edited December 24, 2017 by knocker

[Tim Bland]

00z ECM has Wednesday’s slider going through the Chanel. M4 corridor up to south Mids area prime spot for wet snow, Downs and Chilterns best bet for a decent covering. 

 

[KTtom]

33 minutes ago, West is Best said:

Is it?

A few years ago chaos theory was all the range. The infamous and unfortunate butterfly flapping its wings on Vanuatu was the cause of a hurricane thousands of miles away.

Until it was pointed out that lots of butterflies flap their wings and hurricanes don't result.

I agree with you that hard science must explain our weather. But the cynic in me reckons a lot of teleconnection forecasting is little better than reading tea leaves. Humans look for patterns in order to explain the world: it's how and why brain tricks work. A bend in the jet over Hawaii does not definitely produce a 10 centigrade rain shower five days later in Haverfordwest. The variables are so huge from the Pacific to the UK shores that we might do better to stay focused a little closer to home.

So to those preparing to don their best mourning black, the models might look a touch Atlantic orientated a week hence, but perhaps we should stay focused on the exciting prospects of another cold northerly followed by boundary snow. I've lost count of the number of times we are told that our weather pattern is now set in stone, only to find it all changes a few outputs later.

Happy Christmas everybody  

x

 

Totally agree, if the teleconnections which strongly favoured a cold blocking January can 'suddenly' flip, then they are not more accurate than the model outputs and are liable to flip at anytime?

 

Anyway...interesting fax charts for the 26th and 27th....certainly some snow around post Christmas.

 

[booferking]

Teleconnections flip just like the model runs start of Jan all to play for no matter what some in here would like you to believe we still can't give an accurate 5 day forecast this week is a prefect example of that.