Model Output Discussion 26/11/2012 18Z onwards

[cyclonic happiness]

Hats off to one or two posters on here who had doubts regarding this cold snap, just shows how the weather can make a fool of us all.

Still time for it to make a fool of us again though, but in our favour.

We won't know until after the cold snap/spell has been and gone.

And do we really want a cold spell this late in the Autumn?

[UV-RAY]

One question I'd like to ask is this. If the blocking didn't 'work' this time what is in place to have confidence that it will happen come mid month? Models now showing the breakdown happening as quickly as it set up, so a short term cold period. GEM or GFS with the easterly solution at 240? Do we trust it?

BFTP

Indeed Fred, teleconnections say yeah but they did for this weekends cold blip. We've still got a lot to learn really.

[Mucka]

One question I'd like to ask is this. If the blocking didn't 'work' this time what is in place to have confidence that it will happen come mid month? Models now showing the breakdown happening as quickly as it set up, so a short term cold period. GEM or GFS with the easterly solution at 240? Do we trust it?

BFTP

This is religion. We don't do confidence, we do faith!

I have faith in the blessed BOM and the sacred perturbation 1 of the GFS ensembles, Amen.

[Gibby]

Good morning. Here is the report on the 00z output from GFS, UKMO, GEM and ECM for today Tuesday November 27th 2012.

All models show a rather cold spell to come with a Northerly flow progged to persist for the rest of the week from all models as Low pressure migrates to the East while High pressure lies to the West and NW. The current damp conditions over Southern Britain will give way to clearer weather later today and the rest of the week sees similar weather day by day over the week and probably through the weekend too. There will be sunny spells by day with some wintry showers at times in the East. The South and West will be largely dry and bright throughout. All areas will develop frost at night with some icy stretches developing with the addidtional hazard of freezing fog patches developing later in the week and through the weekend, slow to clear in places by day.

GFS then shows a weak ridge move across from the West on Sunday followed by a front bringing rain preceded by snow on hills in the North. Winds will strengthen from the west bringing milder air across briefly. Next week is then shown to become rather chilly with a WNW flow bringing rain and showers widely again, wintry on hills in the North. As we move into FI Low pressure migrates across the UK and a way to the SE with very cold air flooding SE over all areas with a wintry mix of precipitation clearing SE to a spell of cold NE winds and wintry showers, heaviest in the East. High pressure then slips SE over the UK with fine and cold conditions developing with widespread frost and freezing fog though Northern and Eastern areas may see more cloud come around the top of the high meaning less frost and fog here to end the run.

The GFS Ensembles show a rather cold spell on the way, likly to persist to some degree through the run as uppers stay below the long term mean throughout. The operational is a cold outlier in the cold and wintry phase towards the end. It also becomes more unsettled again after this week as Low pressure from the NW comes into the mix. It looks like most members cold zonality a a more likely outcome with no deep cold shown by any member North and South bar the aforementioned operational.

The Jet Stream shows a continuation of the ridging through the Atlantic before it returns South over the UK. Later the flow disrupts briefly before resetting to run East over the Atlantic to France into the middle of next week.

UKMO for midnight on Monday shows Low pressure South of Iceland and Greenland with a 'col' area over the South of the UK giving way to an Atlantic trough bringing rain preceded by snow across Britain early next week.

GEM also shows an Atlantic trough bringing wind and rain in from the west early next week with a brief snowfall for the hills of the North before a rather chilly and windy cold zonal period of weather develops with wind and rain mixed with wintry showers. At the end of its run it becomes deeply unsettled again with a deep Low crossing England with heavy rain and gales once more.

ECM too shows a similar scenario with wind and rain moving East early next week as Low pressure breaks across the Atlantic and the British Isles with rain and strong winds returning to all areas at times with rather cold interludes with wintry showers in the North.

In Summary this morning's output has come together in their prognosis for next week. The rest of this week will be rather cold but benign away from Northern and Eastern coastal counties where some wintry showers could occur. The South and west will be dry with frost and freezing fog for a while over the weekend. It now looks like an attack from the Atlantic is guaranteed next week as the cold feed is cut off with a spell of rain, preceded by snow on hills moving across from the west early next week. Thereafter it looks like the best hope for coldies is cold zonality and brief Northerlies on the back of passing depressions. It's also not godd news for those wanting drier conditions in recently flooded areas as it looks like the return of some pretty wet weather for all again next week.

[weather eater]

Exactly. Looking at archive charts for some classic snowy spells, in 1979, 1981, 1984 etc shows some shockers for early December, yet we had some great snowfalls in Jan/Feb, so plenty of time yet.

I'd be happy for a breakdown every week if we ended up with a Feb 1991 type scenario.

That’s always been true Paul, traditionally we do not get much in the way of cold and snow until after Christmas, that’s one reason why white Christmases are so rare, lest wise that’s certainly been true of my 50 years.

As Steve has said, there is still time for adjustments and at least mild south westerlies are not on the table for the foreseeable future. In fact, had it not been for the drama of projected snowy prospects this last week, I would class what the models are currently projecting as a good start to the winter season and some should think on that.

Edited November 27, 2012 by weather eater

[kold weather]

One question I'd like to ask is this. If the blocking didn't 'work' this time what is in place to have confidence that it will happen come mid month? Models now showing the breakdown happening as quickly as it set up, so a short term cold period. GEM or GFS with the easterly solution at 240? Do we trust it?

BFTP

I think its a cumulative effect on the PV, we are just real unlucky that a PV lobe decides to move our way JUST when the block is the weakest and shunts it out of the way. The good news is obviously its only ever a diving LP away from a cold spell being reintroduced but who knows.

Still, the conditions aloft are still decent enough so I don't think northern blocking is going to go away totally.

[swfc]

One question I'd like to ask is this. If the blocking didn't 'work' this time what is in place to have confidence that it will happen come mid month? Models now showing the breakdown happening as quickly as it set up, so a short term cold period. GEM or GFS with the easterly solution at 240? Do we trust it?

BFTP

In a word no!Were at a stage now where an area of low pressure as totally altered the outlook and it has not even formed yet?I was shot down on a few occ for mentioning the blocking didnt look robust on certain runs.Stick with the 500mb and the "trend"i was told?.People are now discussing "sliders"for gods sake after what they have just seen in the output at 96hrs!!!!!!.Obv as the met prove in the media forecasts these situations are so fluid that 24-48 hours synoptics wise let alone conditions are very difficult.You can have all the teleconnections ete in place but the time frames to me are just to long imo

[johnholmes]

One question I'd like to ask is this. If the blocking didn't 'work' this time what is in place to have confidence that it will happen come mid month? Models now showing the breakdown happening as quickly as it set up, so a short term cold period. GEM or GFS with the easterly solution at 240? Do we trust it?

BFTP

an interesting learning curve for me at least. It is the first time in 11 months checking the 500mb anomaly charts that I have seen any synoptic model get the T+240 weather more correct than the anomalies. That is unless they did show something and I did not spot it. I will be taking a good look in hindsight at them all to see if and when something showed. Whatever the result I will drop a pdf in the model thread when I have had time to check things out.

Currently they keep blocking well north of the UK with a strongish W'ly flow over the 6-15 day time scale they give guidance on. This W'ly is also apparent over much of north America. There is little to suggest it is going to be mild at all, after this short cold spell into and over the weekend. Around/below normal and possibly near rather cold at times and fairly unsettled. So it may well turn out to be quite good for the Scottish ski centres.

[No Balls Like Snow Balls]

UKMO has seriously gone down in my estimation and do have the meto for believing it ie faxs and longer outlook. I doubt 90% of the uk will see any snow in the next week

It's not even dec yet tho so plenty of drams left this winter. We are still in a good position for blocking to reform as per GFS fi.

Here we go with the METO bashing LOL, when will people learn that weather forecasting is not an exact science and never will be, so why expect models and humans to be 100% correct 100% of the time. One thing that is 100% is that the METO have more knowledge than most of us mere mortals on here can ever dream of.

But are they actually wrong though!!, any update they have given has always stated with great uncertainty

Edited November 27, 2012 by No balls like Snow Balls

[Paul]

Winter forecast issued

http://forum.netweat...inter-forecast/

(please don't discuss it in this topic)

[swfc]

Here we go with the METO bashing LOL, when will people learn that weather forecasting is not an exact science and never will be, so why expect models and humans to be 100% correct 100% of the time. One thing that is 100% is that the METO have more knowledge than most of us mere mortals on here can ever dream of.

But are they actually wrong though!!, any update they have given has always stated with great uncertainty

For what its worth i think both ecmw and the ukmo have called this one pretty good.the ecmw picked this out and ran with it and it looks to me just a continuation post ukmo at 144 hrs

[johnholmes]

Rather than complaining at whoever is your favourite for bashing , UK Met is the usual one, but then many on here really do not read CAREFULLY what is printed by them. Like I have already posted I would rather learn something from this-the first time in 11 months of closely following the anomaly charts that they have been wrong compared at the same time scale to the models, so I will spend some time looking carefully and hopefully understanding the issues a bit better for next time?

[Eskimo]

I understand people are a little fed up, we have been watching this evolve and deflate for the last 3 weeks and it almost feels like it was all a waste of time. However we need to begin to understand that there is a hell of a lot of winter ahead of us, 2010 was the only winter I can remember that started very early and ended very early, other than that...winters normally started in January in the UK or never at all.

The models may only see nothing but a short lived, mediocre style cold blip but the longer term still looks positive for cold and incredibly better than last winter and the winters before 2009.

Edited November 27, 2012 by PerfectStorm

[Glacier Point]

If the blocking didn't 'work' this time what is in place to have confidence that it will happen come mid month?

I must be completely imagining the split vortex and the cold spell that is about to ensue.

Just because we are not seeing a glowing orange beacon over Greenland does not imply no blocking.

The GEFS mean height and temperature anomalies continue to advertise a well defined trough signature across Europe throughout the 15 day period with temperatures well below average. Whether this is the '2010 factor' at work I don't know but we must consider that this is late November and early December and we are looking down the barrel of a sustained cold spell, unusually so for the time of year.

Looking at short to medium term those small scale adjustments in the track of the low driving down from the NW continue almost on every run so by the time we get to 2-3 days out, could wel be interesting, especially with the trough engrained over Europe.

Looking further ahead, we have the strong teleconnector in the North Pacific and downstream ridge over the North Atlantic south of Greenland. That essentially keeps us locked in a cold puddle of air for the duration. The AO looks on the negative side too which is a bonus for December as far as I'm concerned given other factors.

[swfc]

I understand people are a little fed up, we have been watching this evolve and deflate for the last 3 weeks and it almost feels like it was all a waste of time. However we need to begin to understand that there is a hell of a lot of winter ahead of us, 2010 was the only winter I can remember that started very early and ended very early, other than that...winters normally started in January in the UK or never at all.

The models may only see nothing but a short lived, mediocre style cold blip but the longer term still looks positive for cold and incredibly better than last winter and the winters before 2009.

Hi.Would you elaborate why you think it looks positive for cold ?GP forecast gives his direction in which way he thinks it will go im just curious on your thoughts.thanks in advance

[bobbydog]

Rather than complaining at whoever is your favourite for bashing , UK Met is the usual one, but then many on here really do not read CAREFULLY what is printed by them. Like I have already posted I would rather learn something from this-the first time in 11 months of closely following the anomaly charts that they have been wrong compared at the same time scale to the models, so I will spend some time looking carefully and hopefully understanding the issues a bit better for next time?

are the anomaly charts wrong though john? a few days ago, when the block looked like breaking down but then rebuilding repeatedly, i had in mind these charts you have been most insistent on. my (novice) thoughts were, if at this time of year, blocking is unusual, then repeated blocking, even if not sustained, would show an anomaly, therefore the charts are not necessarily wrong. also with such wild swings in the models, even if i am mis-interpreting how these anomaly charts work, there is still plenty of opportunity for you to be proven right yet.

[Methuselah]

Mystified by the childish UKMO bashing. This is science, not football. They're fairly happy with how the GM sits now:

" 3. Modifications: The GM’s ideas of a slack and cold northerly over the UK during the weekend is supported by other models. The next Atlantic system pushes in during Monday and this will have a snow risk ahead of it. The GM was accepted without modification"

Well, I'm certainly with you on that one, Ian. Every year, each and every time Snowmageddon fails to materialize, it's the UKMO that takes the flak. Why not aim it that those who continually ramp everything out of all proportion, as well?

Or better still - just calm down and think about it?

Edited November 27, 2012 by Rybris Ponce

[Snowman31]

Does anyone have an update from the ecm 32 day model?

[Eskimo]

Hi.Would you elaborate why you think it looks positive for cold ?GP forecast gives his direction in which way he thinks it will go im just curious on your thoughts.thanks in advance

I won't be able to provide any analysis as technical as GP's, although blocking still looks favourable across northern latitudes and the PV doesn't want to merge back together into FI. The stratosphere is beginning to warm (albeit slowly) the downstream pattern will change in Mid January due to the lag effect the strat has on the mid to lower levels, however in the medium to longer timeframe blocking will reform, whether or not it is favourable to the UK is another game. The broader pattern is indicative of a colder than average winter, just hope this comes to fruition.

[snowking]

ECM32 updated overnight

Again just as a reminder I only get to see the control run (hopefully someone else may be able to give us an insight into the full 51 member EPS suite...)

Initially (as you'd expect) very similar to what the models are suggesting now, temporary NEly flow, followed by the LP heading in from the west across the UK up until around +168. As this clears through, we are left in a northern feed until around +240 when the next LP heads in....however, the key detail here is that the next LP slides SE. The reason? Blocking, in situ to our N/NW throughout the run, has finally managed to make friends with our atlantic ridge, this gets pulled up into Greenland, and cuts off the LP system as it slides SE towards the UK.

We then see a further shortwave drop down from Iceland, and this sets up a NNEly feed behind it, as a mean trough sets up just to our east.

The HP then sets up to the N/NW of the UK, giving a relatively fine and dry but cold spell to the UK, but the block continues to be pushed eastwards under pressure from the atlantic. It does, however, hold firm just to the N of the UK, and the atlantic has no choice but to go underneath it, giving an ESEly feed from the near continent

The block then gets pushed away finally by another atlantic LP around the 20th, but with heights rebuilding up to its NW around Greenland/Iceland again, so a temporary milder spell (with a likely snowy breakdown), followed by, towards xmas eve, the HP to the NW pushing the LP SEwards, and another easterly flow follows.

And rinse, and repeat.

Remember GP talking about the blocking waxing and and waning, well the ECM control is a perfect example of that.

In terms of more specific details 850's across the UK are below -5c for around 60% of this run. Temperatures at the surface below 40F for around 80% of the run.

The accum. snowfall animation is a joy to watch too, with all but the far SW covered by xmas.

However, take all of those specific details with a (snow) shovel of salt.

The overall pattern through december from this run is this in summary - Below Average, largely unsettled, and a tendancy for HP to our north and undercutting LP to the south

SK

[AWD]

Does anyone have an update from the ecm 32 day model?

From Matt Hugo;

ECM 32day update remains very interesting with pressure constantly higher to the NW of the UK up to Xmas with temps slightly below avg.

[Matty M]

Comparing 6z GFS to 0z at T84hrs.

The trough just west of Norway is decent bit further south ~ 100 miles.. if we see a trend for this over coming runs we could get some real cold embedded before any Atlantic attack.

[nick sussex]

The shortwave to the north is further south, this is a good trend.

The quicker this clears se the better chance of the ridge putting more forcing on the incoming low.

Edited November 27, 2012 by nick sussex

[SLEETY]

People arent bashing the met office itself. its more the computer model they use and the fact for several days in a row it was showing the very cold air reaching the uk by the weekend which doesnt look like happening now. even last nights fax chart was agreeing with the ukmo model and I understand the fax charts are drawn by a human and not a computer! and I presume more than one human has input into what the final fax chart will look like So that tells us that the chief forecaster agreed that the ukmo model was correct last night,which sadly doesnt appear to be the case.

[UV-RAY]

Well, I'm certainly with you on that one, Ian. Every year, each and every time Snowmageddon fails to materialize, it's the UKMO that takes the flak. Why not aim it that those who continually ramp everything out of all proportion, as well?

I can't understand why people blame the models as if they control the weather. What I will add is just how difficult it is to make an accurate long range forecast for a tiny island in the middle of the ocean, not one person, model or mystic meg, can accurately make a forecast for anything over 14 days away.