Model Output Discussions 12z 30/11/16

[Summer Sun]

9 minutes ago, Geordiesnow said:

I'm not sure how much sunshine there will be to be honest, looks like it could be a fairly cloudy week coming up, especially once the SW'ly sets in as tropical maritime air tends to have a lot of cloud associated with it. Rainfall amounts will be most great on Western hills although with the dry period we are having and the fact the models are not hinting at any fronts stalling then whilst some areas could recieve quite a bit of rainfall(because the air is so moist) I think flooding is unlikely so no real signs of any repeats of last December.

 

Cloud amounts for next week

Quite a cloudy but increasingly mild week

[Geordiesnow]

1 minute ago, northwestsnow said:

Gfs 12z is utterly hideous for coldies, raging jet, tick, strong westerlies,tick, very mild, tick,strong euro slug high,tick, zero blocking to the north, tick.

I disagree with this to be honest in some parts.

Raging jet - If the jet was raging then we would see the Atlantic steam rolling in but its not until Saturday next week when it does, Atlantic is blocked by the Euro high but not strong enough to stop some weather fronts coming in but all the lows are well to the West.

Strong South westerlies - Yep your right there but that is down to the orientations of the Euro high/Low pressure systems creating that SW'ly flow. And of course with a SW'ly flow it will be very mild for the time of year.

Euro high - It is becoming a feature that this could stick around for a bit longer than first thought however as slightly hinted on the GFS 12Z run, it could help to block the Atlantic thanks to help from any height rises further North.

Blocking - Blocking is very limited but there is some signs on the GFS 12z run that the Atlantic is for a little bit being blocked, As i say 144-168 hours seems a key area of note as we see slight heights from the Arctic heading southwards, sometimes on paper these look feable but they can actually play a role further down the line. The GFS runs has been fairly consistent on perhaps dropping heights from the pole but I would not put too much faith on this being right to be fair.

[Summer Sun]

11 minutes ago, northwestsnow said:

Gfs 12z is utterly hideous for coldies, raging jet, tick, strong westerlies,tick, very mild, tick,strong euro slug high,tick, zero blocking to the north, tick. And to cap it all, potential for flooding...

Hmm based on this run is doesn't look too bad yes NW Scotland is very wet but elsewhere the totals are lower

When we rewind back to last year...

[northwestsnow]

3 minutes ago, Grimers said:

Hmm, I think flooding is pushing it, yes there may be for parts of NW England and Scotland, but due to low ground water levels, there won't be on a national scale like we saw last Winter.

 

Hi Grimers, going off the last couple of gfs ops i suspect there is the potential for flooding, esp the north, north west, hope im wrong...:)

[Ravelin]

6 minutes ago, warrenb said:

Yep, GFS is carnage from start to finish.

But I think it is wrong

Even when split the PV (which is does), it seems to rotate them around themselves as if it were one entity, thuse keeping the zonal flow going.

There's also the fact that the GFS is changing significantly between runs even at moderate range, and as I pointed out earlier, it differs significantly from the UKMO across the USA at day 6. Not saying it'll necessarily get much better, but the end result won't be what we're looking at currently.

[Singularity]

For what it's worth, here's the moment GEM almost opened the door to disrupting the Atlantic trough during the mid-stages of its 12z run:

Of course, a massive westerly surge from the U.S. causes this to fail almost immediately.

However, given known modelling bias toward overcooking an addition of westerly momentum (shared with GFS), I'd be surprised if this westerly surge wasn't toned down nearer the time. Again I find myself thinking of getting height rises in our vicinity back up to the mid-latitudes.

GFS and GEM both lack any real eastward tropical propagation signal so little surprise to see GFS trying to do the opposite on some runs of late and shift the ridge out of Europe and into the Atlantic (but with this hampered by the strength of the westerlies!); this is the sort of thing that goes on under a La Nina-like base state. Trouble is, a La Nina-like base state is not actually expected to establish - instead something near neutral thanks to the decoupled atmosphere-ocean setup... although I wonder how much room the delay in tropical propagation opens up for a weak move below neutral? Meteorology is a never ending series of answers leading to questions, but that's because it's science, and science just works like that .

At least we have the split lower vortex on this run to potentially save the day - but what we really need is both that and the right tropical forcing to align the pieces nicely for us.

[northwestsnow]

1 minute ago, Summer Sun said:

Hmm based on this run is doesn't look too bad yes NW Scotland is very wet but elsewhere the totals are lower

When we rewind back to last year...

Hmmm  133mm of rain for NW Scotland, not good...

[jvenge]

Hmm...

GFS sending the AO and NAO to positive territory, strongly. Ensembles more interesting in sending it positive mildly and then returning to near neutral though. 

 

 

Edited December 2, 2016 by jvenge

[bradymk]

No consistency at all in the longer ranges of the models which is making it quite a challenge as to what happens after the warm up next week. Still a lot of uncertainty in the Pacific and there are changes of the intensity of the aleutian high every run from GFS. This afternoon run shows a much more intense ridge than 00z run. It's not going to change the outcome next week I know but a stronger poleward ridge may help us further down the line and affects the positioning and intensity of any arctic high 

 

Big differences between UKMO and GFS in America too at Day 6 and 7. Coldies like us on the east coast won't want the UKMO to verify over GFS here that's for sure. 

Pretty grim viewing for U.K next week though, but probably just had the coldest week here since Nov 2010 for the time of year. Now let's hope the EC and GFS ens start to pick up on a more blocked trend in the extended period. I probably sound a bit optimistic but there's a lot more to be optimistic about than the last few years...

 

Edited December 2, 2016 by bradythemole

[Frosty.]

15 minutes ago, northwestsnow said:

Gfs 12z is utterly hideous for coldies, raging jet, tick, strong westerlies,tick, very mild, tick,strong euro slug high,tick, zero blocking to the north, tick.And to cap it all, potential for flooding...

When the operational is hideous, best check the mean for signs of hope..plus, I'm sure some on here will like this run.

[Singularity]

3 minutes ago, Summer Sun said:

Hmm based on this run is doesn't look too bad yes NW Scotland is very wet but elsewhere the totals are lower

 

I'm amazed to see only 1 mm where I live, given that several bands of rain cross my location during the 10 day period. Sure, they look light, but that light? 

If that figure verified it would be by total for nearly half of Dec. Not seen that since the strangely abrupt dry spell in Dec 2013 (but nobody should expect the same follow-up!)

[Grimers]

4 minutes ago, northwestsnow said:

Hmmm  133mm of rain for NW Scotland, not good...

Yes, rethinking this I reckon surface water and flash flooding could be an issue but more widespread and river flooding is unlikely.

[Nouska]

16 minutes ago, Geordiesnow said:

I think the frustration is growing because going back in Mid November there was a lot of hype for the end of Nov to the start of December for blocking and that has not really happened  (...)

I have to take issue with this: at no time was it specified precisely where the blocking would be. The end of November/first days of December are very blocked and very cold at the surface.

The problem lies in how people interpreted this information and the inability to see the hoar frost covered landscape as a scene of winter cold.

No snow = no cold = winter over!

Impossible to forecast for that degree of pessimism.

[Summer Sun]

GEM continues with the milder theme

Eastern Europe looks to be the place for cold air

[northwestsnow]

2 minutes ago, Frosty. said:

When the operational is hideous, best check the mean for signs of hope..plus, I'm sure some on here will like this run.

Agreed karl, its all a kick where it hurts for those of us detest wind and rain on the run up to christmas, whichever way we look at it its back to the familiar tale of looking into deep FI for crumbs of comfort.

[bobbydog]

15 minutes ago, northwestsnow said:

Gfs 12z is utterly hideous for coldies, raging jet, tick, strong westerlies,tick, very mild, tick,strong euro slug high,tick, zero blocking to the north, tick.And to cap it all, potential for flooding...

 

10 minutes ago, warrenb said:

Yep, GFS is carnage from start to finish.

But I think it is wrong

Even when split the PV (which is does), it seems to rotate them around themselves as if it were one entity, thuse keeping the zonal flow going.

I have to disagree with both of these posts. Of course, the evolution we see is unlikely, only for the fact it is a 384hr run. However, if it by chance verified, at the end, the "raging jet" is shooting straight through iberia and into north Africa

Of all the options, that very southerly tracking jet is likely the key route into winter weather.  Lows barrelling  into the Med is what we want to see. If ridging builds behind that trough in the Atlantic, we are back in business

[jvenge]

2 minutes ago, Summer Sun said:

GEM continues with the milder theme

Eastern Europe looks to be the place for cold air

I'm happy to share ;-)

Things can change quickly, though. The EPS output was a little surprise, considering where the last run was. Bastardi from Weatherbell is not buying into the EPS output, for what that's worth.

I wouldn't be at all surprised to see it bring back the good times next week :-)

[Frosty.]

1 minute ago, northwestsnow said:

 whichever way we look at it its back to the familiar tale of looking into deep FI for crumbs of comfort.

Well we coldies have had plenty of practise doing that haven't we

I'm still clinging to the seasonal models colder anticyclonic second half of dec.

[chris55]

This cut off low developing in the mid Atlantic holds some speculative interest. If we could get it to stall or undercut then all sorts of colder options are a possibility. With the bias towards the return of climatology post 120 generally in the models i would not write anything off TBH. 

 

 

 

Edited December 2, 2016 by chris55

[Man With Beard]

GEFS ensembles ... signals for amplification mid-month continue to wax and wane - still there but not so strongly on the 12Z compared with earlier in the day. Quite a few now push heights north-east now leading to a few interesting results:

[heath]

Remarkable inter model and inter run consistency. This is unusual. The first sign of a change after the milder spell looks like a trough heading south over the UK per lo-res GFS. In the meantime enjoying the dry weather and the remaining snow on the hills.

[Summer Sun]

The 850's go just below 0 on the Inverness ens for a time

On the London ens they get down to around 0 by mid month

So a cool down is still on offer around mid-month still well out of the reliable timeframe for now

[bluearmy]

The GEFS are certainly not 'flat'.  those wedges being thrown up are leading to more scandi ridge members than ive seen for a while. the run ends with a high anomaly up there and crucially only a weak anomoly over n Europe. will be interesting to see if the eps later continue the drain away of anomolys end week 2 

[nick sussex]

Regarding the differences upstream between the GFS and UKMO/ECM.

The NCEP extended discussion mentions this but this won't include tonights outputs but there are still those differences even this evening. What we really need to see is more amplitude as that trough moves east to sharpen up the low to the west of the UK:

...MODEL EVALUATION/PREFERENCES...

MODELS HAVE COME INTO AGREEMENT THAT OF A SLOWER PROGRESSION OF
THE UPPER LOW EJECTING OUT OF NORTHERN MEXICO ON DAY 3 MONDAY
FOLLOWED BY MODEST SURFACE CYCLOGENESIS FROM THE TEXAS COAST UP
INTO THE OHIO VALLEY ON DAY 4 TUESDAY.  THEREAFTER...MODEL
SOLUTIONS BEGIN TO DIVERGE AS A LONGWAVE UPPER TROUGH IN THE
WESTERN U.S. MOVES OUT INTO THE PLAINS AND INTERACTS WITH THE
WEAKENING EASTERN U.S. LOW PRESSURE SYSTEM.  THIS DISCREPANCY HAS
LED TO LARGE DIFFERENCES IN SPEED OF PROGRESSION OF THE FIRST
SIGNIFICANT ARCTIC AIR INTRUSION ACROSS THE U.S. THROUGH NEXT
FRIDAY...WITH THE SLOWEST 00Z ECMWF REACHING ONLY THE EAST COAST
BY NEXT FRIDAY WHILE THE 06Z GFS TAKES IT WELL OUT TO SEA

[Connor Bailey Degnan]

18 hours ago, Catacol said:

No - not harsh. Spot on. Anyone prepared to slam Gav in that way - clearly demonstrating a failure to actually watch any of his explanatory videos that do a lot more than simply read model projections - deserved a flaying.

Hope I'm wrong, but i have that '13/14' feeling. 

Let's hope this changes soon.