General Model Output Discussion:

[Guest North Sea Snow Convection]

Another possible cold reloading pattern does certainly look possible for the new month.

A bit of caution in terms of happiness about predictions being right - it hasn't happened yet, and the evolution whilst taking good shape, could still change and nothing is certain yet.

[TEITS]

If we can get too Sunday/Monday with the same model outputs outlining the block. I will certainly be singing my way through this thread. Mouth watering prospects again from the models, long may it continue.

Yep we need to see consistent runs showing this blocking. If we cast our minds back to early Dec many will remember how consistently the GFS progged some kind of N,ly blocking for mid Dec.

Personally I couldn't care if we see a Greenland HP or a Siberian HP bringing E,lys. However if we have both like the GFS has been suggesting then this place will become bedlum!

[The Weather Dragon]

Hi All - Models seem to be favouring some type of Northern Blocking scenario in the medium term. In the short term I think that this Weekends N/NW'erly will deliver for the favoured few. Can anybody verify whether the usual teleconnections are favourable regarding the Northern blocking (I know that the AO & NAO are predicted to Enter a - phase)

[TEITS]

Hi All - Models seem to be favouring some type of Northern Blocking scenario in the medium term. In the short term I think that this Weekends N/NW'erly will deliver for the favoured few. Can anybody verify whether the usual teleconnections are favourable regarding the Northern blocking (I know that the AO & NAO are predicted to Enter a - phase)

Well based on yesterdays AO/NAO ensembles this were predicted to be around Neutral with some AO ensembles being around -2. However once these are updated today I feel these will show a drop in both the AO/NAO.

Speaking of teleconnections I was reading a weather book last night by a senior forecaster who said that teleconnections were insignifcant to our weather! This book was written in 1996 so maybe back then they didn't fully understand them. Also worth mentioning that in the book the idea of weather models was first thought up back in 1922!!

Last ramp from me until later.

GEFS control run.

http://91.121.94.83/modeles/gens/run/gens-0-1-240.png?6

Blocking then transfers to Greenland.

http://91.121.94.83/modeles/gens/run/gens-0-1-300.png?6

Edited January 26, 2010 by THE EYE IN THE SKY

[snowmadchrisuk]

Well based on yesterdays AO/NAO ensembles this were predicted to be around Neutral with some AO ensembles being around -2. However once these are updated today I feel these will show a drop in both the AO/NAO.

Speaking of teleconnections I was reading a weather book last night by a senior forecaster who said that teleconnections were insignifcant to our weather! This book was written in 1996 so maybe back then they didn't fully understand them. Also worth mentioning that in the book the idea of weather models was first thought up back in 1922!!

Last ramp from me until later.

GEFS control run.

http://91.121.94.83/modeles/gens/run/gens-0-1-240.png?6

Blocking then transfers to Greenland.

http://91.121.94.83/modeles/gens/run/gens-0-1-300.png?6

Wouldn't that suggest what teleconnections are saying though , the opportunity for a brief Easterly Yes , but within 2 days the whole block has transfered to Greenland, either way looks good though .

[TEITS]

Wouldn't that suggest what teleconnections are saying though , the opportunity for a brief Easterly Yes , but within 2 days the whole block has transfered to Greenland, either way looks good though .

I've only looked at some of the ensembles but yes what some are indicating is intially an E,ly and this veers into a NE,ly as pressure rises over Greenland.

I would like to add that I don't want members assuming this is going to happen. However we can only comment on what the models are showing and for me the E,ly has always looked possible. However whether we see the monster block from Siberia to Greenland bringing alternating N/E,lys is a different matter. However synoptically this is plausible as the archives prove.

[Bobby]

GFS is incredible in FI, one of the best charts I've ever seen this:

Huge Northern blocking and buckets of snow.

Won't happen of course.

[Nick F]

A bit of caution in terms of happiness about predictions being right - it hasn't happened yet, and the evolution whilst taking good shape, could still change and nothing is certain yet.

Yes, certainly the reload isn't nailed yet, and it may not come from the east as GP's posts about upstream signals have been hinting at.

The mean trough is to the east until the end of the relaible timeframe, and it's only into the low res past t+180 that the trough sinks across eastern Europe to allow the Atlantic ridge link up with ridging to the NE and bring a draw from the E or NE. We probably need to see upper flow energy weaken to our N to allow this link up with the Atlantic and Siberian/Arctic ridges and the sinking of the trough to our E.

[Glacier Point]

Mean trough still there also at t300 based on 06z GFS esnemble mean:

http://www.meteociel.fr/modeles/gefs_cartes.php?code=21&ech=300&mode=0&runpara=0

The only mechanism by which we could feasibly get that sort of retrogression is for the stratospheric warming to propgate into the troposphere (angular momentum is inching upwards but not at the rate likely to deliver a high amplitude GWO phase 6-7 orbit necessary for that kind of output). This looks a little progressive as an operational.

[PB22]

The London ECM 00z ensembles:

http://www.meteogroup.co.uk/uk/home/weather/services/ensemble_forecast.html

Generally the majority keep conditions on the cold side throughout.

[Guest North Sea Snow Convection]

Yes, certainly the reload isn't nailed yet, and it may not come from the east as GP's posts about upstream signals have been hinting at.

The mean trough is to the east until the end of the relaible timeframe, and it's only into the low res past t+180 that the trough sinks across eastern Europe to allow the Atlantic ridge link up with ridging to the NE and bring a draw from the E or NE. We probably need to see upper flow energy weaken to our N to allow this link up with the Atlantic and Siberian/Arctic ridges and the sinking of the trough to our E.

Yes Nick, whilst I have myself have expressed 'eastern thoughts' as an eventual possible outcome, I think that there is a good chance also that HP might be closer to the UK for at least a time after the northerly.

The positive zonal winds are suggested to be slowing steadily in association with the MMW, and this will assist blocking development, but the models may be being a little progressive at the speed with which this happens. That is where the caution comes in for the timebeing I think

Edited January 26, 2010 by North Sea Snow Convection

[kold weather]

Mean trough still there also at t300 based on 06z GFS esnemble mean:

http://www.meteociel...ode=0&runpara=0

The only mechanism by which we could feasibly get that sort of retrogression is for the stratospheric warming to propgate into the troposphere (angular momentum is inching upwards but not at the rate likely to deliver a high amplitude GWO phase 6-7 orbit necessary for that kind of output). This looks a little progressive as an operational.

I agree, I suspect the 06z has seen a possible trend and taken it through to its extreme conclusion, make no doubt if the 06z came off we'd have a cold spell that could match early Jan which would be quite insane!

However a slower evolution could be even *better* because its looking increasingly possible that the mean high zone will be close enough to the UK to allow inversions/surface cold to develop and get dragged in from Europe which will help to keep temps in the CET zone down. I personally think the GFS is both too fast and a good deal too extreme however this pattern that the models prog will have lots of cold air to tap into thanks to the upper cold pool that is being dragged towards Europe over the next week.

[cooling climate]

Yes, certainly the reload isn't nailed yet, and it may not come from the east as GP's posts about upstream signals have been hinting at.

The mean trough is to the east until the end of the relaible timeframe, and it's only into the low res past t+180 that the trough sinks across eastern Europe to allow the Atlantic ridge link up with ridging to the NE and bring a draw from the E or NE. We probably need to see upper flow energy weaken to our N to allow this link up with the Atlantic and Siberian/Arctic ridges and the sinking of the trough to our E.

When you consider that I was talking of a prolonged cold spell a week ago when others could see

nothing of interest in the models and I kept telling people to look at the northern hemisphere charts

and the other signals such as convection in the Pacific, MJO, MMW etc.

I even joked three or four days back that we could see another 47 and now we are seeing charts

like this from all the models.

Just like the December and January cold spells this is as good as nailed, if it upsets posters for being

so confident then so be it.

I also said the worst of the winter was still to come and I still stand by this.

[bluearmy]

true ennough KW. even the extended ens underestimated the length of time the current block would hang around to our east before either retrogressing or sinking. it seems as though the ops are too progressive to get to the next step. its then not a straightforward delay to the evolution shown as by the time the block begins to move, other factors may not be conducive to evolve to what we currently see in fi. so whilst a scandi high/greeny high/ mid atlantic high/ uk high looks to be likely, the area where the block will end up is a fairly large spread. as a result, we could just as easily end up with a repeat of the past fortnight in nomans land as a frigid easterly.

When you consider that I was talking of a prolonged cold spell a week ago when others could see

nothing of interest in the models and I kept telling people to look at the northern hemisphere charts

and the other signals such as convection in the Pacific, MJO, MMW etc.

I even joked three or four days back that we could see another 47 and now we are seeing charts

like this from all the models.

Just like the December and January cold spells this is as good as nailed, if it upsets posters for being

so confident then so be it.

I also said the worst of the winter was still to come and I still stand by this.

CC, you're new to this i guess !! 'pride comes before a fall' and most of us on here have seen upcoming potential come to nothing on many many occasions over the past half dozen years model watching. maybe thats why there is rather more caution than you might expect. however, up until feb this year, cold spells never materialised and were almost always downgraded. dont forget the easterly in feb 2009 after the snow with complete ens agreement that disappeared at T96 !!

having said all that, i have been 'ramping' to a lesser degree for a fair old while re the end of the month so i'm not innocent on this either.

Edited January 26, 2010 by bluearmy

[BLAST FROM THE PAST]

When you consider that I was talking of a prolonged cold spell a week ago when others could see

nothing of interest in the models and I kept telling people to look at the northern hemisphere charts

and the other signals such as convection in the Pacific, MJO, MMW etc.

Just like the December and January cold spells this is as good as nailed, if it upsets posters for being

so confident then so be it.

I also said the worst of the winter was still to come and I still stand by this.

Hi CC

Nothing wrong with confidence [but a week isn't that long!!! Lol] but IMO you are right the cold pattern is very much on.

Interesting re December, the mild slot at beginning I mentioned with RJS was cooler/much less mild than anticipated and so the Dec cold was stronger. The same happened after Christmas into New Year and the cold was severe in Jan. Now we have the same thing, this current spell is although milder is still cold [overall] to average at best. This suggests to me that a cold pattern in Feb will be in very cold category [although like I say I think depest cold has been ie -22c].

Where confidence must be wary is that I believe the HP from Russia / Scandi is being shown way too soon.

Solar activity determining that northrn arm of the jet is pretty redundant and will drive the AO negative and the NAO too. Teles will IMO respond to the solar effect.

BFTP

Edited January 26, 2010 by BLAST FROM THE PAST

[TEITS]

Only just seen the rest of the ensembles and they are showing an excellent trend.

Again if we go back to early Dec some will remember how using the Iceland SLP mean proved a very reliable tool.

As we can see the mean rises to 1028mb in F.I.

http://charts.netweather.tv/ensimages/ens.20100126/06/prmslReyjavic.png

The rise in pressure can be seen from the Oslo SLP mean also.

http://charts.netweather.tv/ensimages/ens.20100126/06/prmslOslo.png

When your looking for a trend in the medium term you don't really want to be looking at the operationals. Using the mean of the GEFS/GEM ensembles is the way to go.

I disagree with some of the posts this morning. If we are to see blocking develop over Greenland then this will come intially from the block to the NE bringing an E,ly. You can clearly see this from the SLP ensembles because the rise in pressure over Iceland is later than it is in Oslo. Im actually surprised some can't see this because the synoptics the models runs are now showing were always possible a few days ago even though they didn't show it. Going to be an interesting few days as we see instinct vs teleconnections. I will add im not bothered whose correct aslong as the outlook remains cold.

[Nick B]

The below quotation is from the ECMWF Ensemble page as posted by GP (I hope they don't mind). I suppose the questions below are directed in particular to anyone who has professional or in-depth experience of how models work.

'In the European Centre for Medium-term Weather Prediction, the operational model is re-run at a lower resolution (the control run) and this is then repeated 50 times, each with slightly different starting conditions. These ensemble runs are shown in the graph above as the grey lines; the average is shown in yellow.'

(my emphasis)

1/ What is different about the starting conditions? Is it the choice of exact data used, or is the data very slightly manipulated by the modelling tool to represent tiny changes in real life which would naturally be happening?

2/ Are the ensemble runs done at a lower resolution purely for speed (i.e. if data is very slightly manipulated anyway, to create the range of possible outcomes, there is no point in having fine tuning)? Is it because of the ways the data is supposed to be interpreted (i.e. saying, "Oo, I wish we could have seen how number 32 got down to -20 deg C for next week" is pointless since it was never designed to be seen - but rather to show the likely spread of possibilities, with the yellow average being the mid-point of greatest likelihood)?

3/ When a model is upgraded (like the recent Parallel GFS becoming the new GFS), what is changed? Actual measured data? Programming within the modelling tool itself?

Thanks for any answers

Nick

Edited January 26, 2010 by Nick B

[sandstorm2]

Afternoon all, just had a look at the models after a couple of days break and I nearly fell off my seat! must admit though there has always been a suggestion of much colder weather round the corner but this looks just a tad over the top, do have a hunch though that this weekends northerly could last a bit longer than the average toppler.

If and its a big if, if these charts came off or even something like them, this country would come to a standstill.

SS2

[SP1986]

There is no trend in the ensembles, it's a complete mess.

I'd actually like to point out the fact that the GFS predicted -3 to -4C widespread last night, and yet the temperature in many places did not go below 0C, I'm certainly not convinced this GFS update that was brought out in September can handle programmed temperatures, also I'm not convinced it will be able to handle a warm up whenever that occurs.

[Cheshire Freeze]

Although initially sceptical of the idea of a cold February, it's certainly nice to see some interesting cold synoptics on offer. I feel we have had a long enough break from the cold and snow now, let's get some nice cold snowy weather for February before we can start thinking of spring in March/April

Aaron

[Methuselah]

The models may well be a 'mess' Ste, but there's a vast amount of cold air languishing over Europe...Riga was -21C at noon yesterday!!!

[SP1986]

The models may well be a 'mess' Ste, but there's a vast amount of cold air languishing over Europe...Riga was -21C at noon yesterday!!!

That may in part be due to the cold airmass being bottled up in Europe - you're right though, some impressive temperatures across the mainland, probably not record breaking but interestint nevertheless. I must check out the minimums for Netherlands, there were some very low temperature over NW Holland last night

[sandstorm2]

is it not unusual to see such agreement in the models at the +240 range, ie ECMWF, GFS and GEM and in fact they all show a similar way of getting there, must admit I am finding it difficult to keep my feet on the ground and I know +240 is FI land and it won't happen.

SS2

[cooling climate]

is it not unusual to see such agreement in the models at the +240 range, ie ECMWF, GFS and GEM and in fact they all show a similar way of getting there, must admit I am finding it difficult to keep my feet on the ground and I know +240 is FI land and it won't happen.

SS2

It is yes but when the signal is strong enough all the models pick up on it I guess.

[Methuselah]

That may in part be due to the cold airmass being bottled up in Europe - you're right though, some impressive temperatures across the mainland, probably not record breaking but interestint nevertheless. I must check out the minimums for Netherlands, there were some very low temperature over NW Holland last night

My son (also Ste! ) lives in Berlin; and he's sick-and-tired of snow and ice...He says it's been hanging-around for weeks. The interesting thing is, I think, that most of our (severe) cold spells follow low temps in Europe?? I remember seeing -20C in Helsinki back in the '60s! :unsure: