Model Output Discussion

[chionomaniac]

Perhaps the models are picking up on the stratospheric influence. Look at the GFS and ECM split PV at 10 days. Where would I put pressure rises looking at these? Hmmm.

c

[Cloud 10]

Some monumental northern blocking showing on this evenings ecm,which ties in with the AO/NAO forecasts,glorious to look at but not very likely to happen......or is it?

[nick sussex]

Oh dear the ecm looks like its trying to out do the gfs with outrageous FI scenarios! In terms of the pattern all the models generally agree with the slow moving trough over or to the west of the UK with lows cutting more east/se however the ecm for me is a step too far into fantasy.

The ecm during the last few winters seems to always overplay blocking in FI and because of this just too much needs to go right for tonights run to have any hope of verifying.

In terms of the limpet trough i can't see this going anywhere fast and if anything the trend has been for the models to pull this further west with time.

[shuggee]

Yes a very interesting evening of models out past T+144. Of course, illustrating that at T+80-odd the GFS has huge swings between runs upstream adds very nicely to the uncertainty but ECM is the current form horse at 5 days out so for me, this is encouraging that we won't be seeing any outrageously mild weather in early December

[Glacier Point]

not completey different Phil (how different can they be with the major features at t120???)

- but which one looks more likely? that was my point. the output is sniffing around the post xmas evolution hinted at by GP earlier. it was doing the same a week ago. how many times do we have to watch the rollercoaster go around before we can get on it ??? GP may be a week or so long but the models are defo short.

Probably a little too progressive although the basic evolution is correct I think.

Here's the theory:

There is overwhelming NWP and coupled ocean-atmosphere analysis for the longwave trough to become stationary over or just to the west of the UK t144.

Energy from this trough is ejected south-east across Europe because the trough elongation is not able to capture the cyclonic motion, aided by a negatively tilted jetstream.

Surface depressions forming along the jetstream will run into the base of the trough. The poleward side of the upper trough is pulled back west whilst the equatorward side is extended south-east along with the majority of the energy flow. Further south-east ejection of energy takes place, successively forcing height rises to the far NE. The process is likely to be repeated several times before we get a block strong enough to back a pulse of Arctic air underneath the warmer wedge of North Atlantic air as the jet is forced progressively south.

The evolution of GWO phases 5-6-7 supports this type of pattern which is classic cold pattern setting up in the longer term.

Latest GWO plot identifies relative angular momentum edging upwards. We are some way off the type of phase 5-6-7 evolution just yet so ECM 12z, maybe evolution correct, timing too early. The ensemble means will likely continue to best reflect the longer term prospects.

Edited November 30, 2009 by Glacier Point

[DAVID SNOW]

Forget the GFS run, the model is really struggling. I would expect the ECM to show a progressive pattern from T144 onwards.

Or perhaps not.With the start of december only hours away are you going to revise your CET prediction for the month?

In your LRF ( hats off to those who try ) you have said this december will return the highest CET value since 1988.

Stick or Bust...?

[chionomaniac]

Probably a little too progressive although the basic evolution is correct I think.

Great explanation GP, thanks. Patience needed at this point. Worth a punt on a white Christmas?

[TEITS]

Where`s Steve Murr and TEITS?

Certainly nice to look at but for now it`s in dreamland.

I've been following the wild model runs of late although when there is so much uncertainity I tend to avoid posting.

Im still convinced that something special is brewing for Dec and im sticking with the E,ly followed by a N,ly scenario.

The 12Zs have certainly put the cat amongst the pigeons. Whoever said the ECM isn't plausible obviously reads the models differently to me because it seems perfectly plausible. Im not surprised the models are struggling because what we're are seeing is unusual for early Dec.

Currently we have the PFJ wanting to track further S than usual. We are seeing a very weak PV and the AO/NAO want to tank into early Dec. The result of all of this is model uncertainity. The GFS in particular will struggle at the moment and I would say F.I begins around +96.

[Backtrack]

Some monumental northern blocking showing on this evenings ecm,which ties in with the AO/NAO forecasts,glorious to look at but not very likely to happen......or is it?

Well the charts are normally accurate one day out... That looks probable.

[tinybill]

if f1 comes off on the gfs i know it wont its mouth watering!!!

[TEITS]

, but we have seen in the past that the christmas pudding is capable of producing some phenomenal daily returns when the right set-up kicks in, as I believe it will.

Please Ian do you have to keep mentioning that phrase. Every time you do I have an urge to kick my cat up the backside. For the sake of my cat give it a rest.

[mcweather]

Probably a little too progressive although the basic evolution is correct I think.

Here's the theory:

There is overwhelming NWP and coupled ocean-atmosphere analysis for the longwave trough to become stationary over or just to the west of the UK t144.

Energy from this trough is ejected south-east across Europe because the trough elongation is not able to capture the cyclonic motion, aided by a negatively tilted jetstream.

Surface depressions forming along the jetstream will run into the base of the trough. The poleward side of the upper trough is pulled back west whilst the equatorward side is extended south-east along with the majority of the energy flow. Further south-east ejection of energy takes place, successively forcing height rises to the far NE. The process is likely to be repeated several times before we get a block strong enough to back a pulse of Arctic air underneath the warmer wedge of North Atlantic air as the jet is forced progressively south.

The evolution of GWO phases 5-6-7 supports this type of pattern which is classic cold pattern setting up in the longer term.

Latest GWO plot identifies relative angular momentum edging upwards. We are some way off the type of phase 5-6-7 evolution just yet so ECM 12z, maybe evolution correct, timing too early. The ensemble means will likely continue to best reflect the longer term prospects.

I can see where this is going GP. Because I saw this happen a number of time in the late 70's and early 80's. As has been mentioned this could be something of a reload situation where with each slider low ejecting its energy southeastwards

into central Europe the core of cold moves further southwest out of Scandi eventually making it all the way south across the UK.

I remember back in 78/79 I think it was where first the northern half of the uk was affected and gradually

with each low passing further south into europe the whole of the country gradually succumbed to the wintry weather.

Edited November 30, 2009 by mcweather

[Cecil Hogmanay Melchett]

OMG i almost fell of my chair when i loooked at that ecm run.Its too far out to be taken seriously but i guess

it does show that things can 'flip' unexpectedly if nothing else.

My current thinking is back to unsettled for the rest of the week and probably the weekend and then it will be

crunch time for the 1st half of Dec,we'll either see a euro high and the jet pull North or something along the lines

of ecm.At this range its an impossible call,but it wont half give the model anoraks something to chew on over the

next 3 or 4 days.the form horse is the +NAO and everything that goes with it,i'd love that not to be the evolution

but after so many years of false dawns that ecm FI would have to be at +96h for me to start believing,and even

at that range id be sceptical!

In some ways id prefer it if the models only went to 144hrs,lets face it guys,if they did there would be cobwebs

on this thread.And therein lies my sceptisism,the champagne synoptics are a million miles away in model terms.Ive been sucked in far too many times down the years and i wont be sucked in again.

Does anyone else find the evoluton from 168 to 192 a tad,erm suspicious?

Anyway,if we see this evolution gather momentum over the next 3 or 4 days i'll get interested,as it stands,i'd

expect this run to vanish into cyberspace come the morning.

[DAVID SNOW]

Please Ian do you have to keep mentioning that phrase. Every time you do I have an urge to kick my cat up the backside. For the sake of my cat give it a rest. :lol:

Easy tiger... Or tibbles.

Dave, just go with the flow, the phrase matters not.

Thank you for your reply IB, will be interesting come months end.

But i doubt we will reach your prediction of 6.5 to 7.0

[Frosty.]

I'm not goint to revise my prediction, obviously the CET for the first week will be below what my overall number is, but we have seen in the past that the christmas pudding is capable of producing some phenomenal daily returns when the right set-up kicks in, as I believe it will.

Have you ever been wrong before? just curious

I like the look of the latest ECM run, albeit in FI, this is becoming more interesting as the models try to get to grips with a rather unusual pattern. It's taking much longer than usual to develop any sustained cold weather across the uk, certainly compared to a year ago when we had already had 3 cold snaps by this time but the delay might be worthwhile if things remain on track.

[swfc]

After a couple of points posted by Steve Murr yesterday his take on the evolution of the current output is taking place be it way out time wise.Intersting reading Gp and Sm posts and there does seem to be a change of some kind on the way.Hopefully.????

[Snowyowl9]

One of the others models show some interest an undercutter low.

Nothing like as impressive as GFS or ECM but still showing lows taking a much more S-ly track.

http://91.121.93.17/pics/Rjma1921.gif

[Solar Cycles]

I'm a little surprised at the ECM, there is no plausible reason for the evolution from T168 to T192. One thing is for sure, deep troughing in the mid-Atlantic and I would expect that to be given the boost needed to transfer this energy further East and see a pressure rise over Europe.

Hmmm, I wonder if you would say the same if they showed blowtorch SW Ian?

[weather eater]

ian - the models continue to want to drive the trough into europe and raise pressure to the northeast. its a repeating trend and it may take a while before it comes closer than T144. why should your experience and intuitiveness be right and the nwp wrong ??? (by the way, the 'blocking from the north or northeast' may be just as powerful a presence as the energy from the west = undercutting). also, i note the trend for the temp gradient in the states next week to be less severe which may well take the jet back a few notches on what was expected.

It might well be a repeating trend, but so are several other evolutions, As I said the other day take several days FI charts from the GFS and the ECM lay them out on a table and you could in all likelihood pick out 4 or 5 trends, it means squat.

[phil nw.]

Here is a copy of the discussions by the Americans

MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

115 PM EST MON NOV 30 2009

VALID NOV 30/1200 UTC THRU DEC 04/0000 UTC

...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR

INGEST...

12Z/30 FINAL MODEL PREFERENCES...INCLUDING THE ECMWF

ANY INITIALIZATION ERRORS WITH THE NAM AND GFS DO NOT APPEAR TO

SIGNIFICANTLY IMPACT THEIR SOLUTIONS.

...CYCLOGENESIS OVER THE WESTERN GULF OF MEXICO DAY 2...

THE GFS...ECMWF...AND 00Z/30 EC ENSEMBLE MEAN ALL RESOLVE AN

INTENSE IMPULSE THAT RUSHES TO THE MISSISSIPPI DELTA BY 00Z/02

WEDNESDAY. THIS IMPULSE SKEWS THEIR TRACK OF THE PRIMARY SURFACE

LOW TOWARD THE APPALACHIANS THEREAFTER...WITH THE CENTER REACHING

NEW YORK STATE BY DAY 3. THE GFS DOES NOT DILUTE THE INITIAL

CIRCULATION WHATSOEVER...CONTINUALLY DEEPENING IT UNTIL IT REACHES

EASTERN LAKE ONTARIO BY 12Z/03 THURSDAY. THE NAM AND UKMET DO NOT

CARRY THE INITIAL IMPULSE LATE DAY 1...RESULTING IN A PRIMARY LOW

TRACK ULTIMATELY INTO THE LOWER PENINSULA OF MICHIGAN. THE GEM

GLOBAL COULD BE CONSIDERED A MIDDLE OF THE ROAD SOLUTION. WITH

THE GOOD RUN TO RUN CONTINUITY SHOWN BY THE ECMWF...AND THE

SUPPORT OF ITS MOST RECENT ENSEMBLE MEAN...WILL RELY ON ITS

SOLUTION.

...WAVE SKIMMING THE NORTHERN PLAINS DAYS 1 AND 2...

THE NAM AND UKMET ARE SLOWER AND MORE AMPLIFIED THAN THE ECMWF

WITH THIS SYSTEM...WITH THE GFS AND GEM GLOBAL BETWEEN THESE TWO

EXTREMES. AS WITH THE DOWNSTREAM SYSTEM...WILL RECOMMEND THE

ECWMF SOLUTION.

...MODEL TREND GRAPHICS AT

WWW.HPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML...

...500MB FORECASTS AT WWW.HPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML...

CISCO

It appears that ECM is favoured.

[Yeti]

Well here we are again before December has even begun, and already the ramping is well underway! The ECM has certainly reduced people's inhibitions in that respect.

However, aside from the eye candy it's weeks away from today... just remember it was only last night and everyone was moaning

As the ensembles show us, the GFS op was on the cold side and at times an outlier:

http://charts.netweather.tv/ensimages/ens.20091130/12/t850Cambridgeshire.png

[NorthantsSnow]

As the ensembles show us, the GFS op was on the cold side and at times an outlier:

http://charts.netweather.tv/ensimages/ens.20091130/12/t850Cambridgeshire.png

Not what I would call an outlier. It's just about the coldest member for about 24 hours at one point in the run, but never an outlier. Other members are too close to it for it to be classed as such.

Anyway, the ensembles are liable to change dramatically when it suits them, as I found out on many occasion last winter.

[phil nw.]

The 2 lesser used models also showing the undercutting SE into Europe at t120hrs.

http://www.wetterzentrale.de/pics/Rgem1201.gif

http://www.wetterzentrale.de/pics/Rjma1201.gif

The evolution from there forward still to be decided but a consistent trend with trough digging SE.

Maybe a little while before we get sufficient heights to the North though.

[LomondSnowstorm]

...

It appears that ECM is favoured.

Interesting times ahead, even a total amateur like myself could tell that the ECM 12Z looked rather impressive.

[DAVID SNOW]

The 2 lesser used models also showing the undercutting SE into Europe at t120hrs.

http://www.wetterzentrale.de/pics/Rgem1201.gif

http://www.wetterzentrale.de/pics/Rjma1201.gif

The evolution from there forward still to be decided but a consistent trend with trough digging SE.

Maybe a little while before we get sufficient heights to the North though.

Interesting times ahead.

10 to 15 days perhaps?