Model Output Discussion - 1st - 7th January

[nick sussex]

This should go in the strat thread in relation to some research regarding previous SSW's but certainly shows why deciding what happens after a SSW is very difficult.

This is a quote from the abstract:

Finally, it is shown that the forecasts of the ECMWF ensemble prediction system for the onset of the major SSW were very skilful and the ensemble spread was very small. However, the ensemble spread increased dramatically after the major SSW, displaying the strong non-linearity and internal variability involved in the SSW event.

If you read the research the ensembles spread increases by as much as 500%!

We don't know yet whether we will actually see a SSW but if one does occur then don't expect the UKMO or any other agency to have a good handle on its effects in terms of the modelling.

[Frosty.]

You say we have plenty of time on our side but the days are starting to get longer, and seeing as (at present) there is absolutely nothing of wintry interest on the horizon you have to wonder whether we will run out of winter before the SSW takes effect on our weather. That's if it has any bearing on our weather at all. So far we have had only minor interest at the 240 stage, which stays at 240 when it actually appears at all. So being realistic it's not improbable that this winter delivers nothing more than we've already had in terms of wintriness and only continues to deliver what has already gone before (cold zonality favouring hills and mountains).

Even if we could discount the rest of this month for a cold spell ( which we can't yet), we will still have another 6 weeks for a few cold spells to evolve, last winter was basically over after new year but of course, if we had known that then, it would have been even worse! the latest models show a gradual change to more benign weather through next week as high pressure moves across the south with the unsettled weather becoming restricted to northern scotland but then probably more unsettled again nationwide from mid month.

[kold weather]

:huh:

Are'nt the stratosphere warmings already calculated in the number crunching that make up the different models we view? Therefore handling them exactly as they and us read them at present?

Yes they are, but its also a case of looking at the sginals and seeing whether the models are coming out with the right conclusion. I've seen it happen many times before, the stratosphere suggests one thing and the models something totally different. It happened last December, the models went for a rewended zonal burst from the jet for the 5-10th December with the PV powering up. However GP posted on here that this was effectivly rubbish and the model wasn't really picking up on the state of the stratosphere very well...and as GP said, the models eventually clocked and developed another powerful -ve AO.

The 06z GFS very briefly takes the AO negative around 264hrs thanks to a strong upper ridge over the E.Pacific, but it is very fast to pull that PV back together again and that ends that...

Another big warming event develops towards the end of the run so whewther that would be the one that finaly does it, who knows...but I'm pretty confident the 06z GFS is too positive on the AO and in truth the AO will be quite abit more negative, much like a large majority of the GFS ensembles. PV will stubbornly remain for the time being though.

I think GP's idea about a mild next 7 days followed by an increasingly Atlantic driven pattern with the chance of toppler northerlies and cool zonality sounds about right to me.

[SnowBallz]

Having read quite a few inputs, it's clear to me that there's two types of model-watcher:

i) those who feverishly hang on every single output of the GFS, ECM, UKMO etc, and chop and change their 'forecast' like - no pun intended - the weather.

ii) those who tend to avoid the 'chop and change' method, and place their reliance more on recurring or consistent long-range trends which imply signals.

If you like drama in your life, then - at the moment - chose option number 1; because there's plenty there to keep you occupied. Those of us who are firmly in the number 2 camp are happier with outputs, as there is an encouraging level of consistency.

I also think its worth bearing in mind that mathematical models are not that fantastic at applying credence to signals which go against their pre-determined bias. At the moment, the implied background is so far upstream, that - actually - the models are kinda doing the right thing, by discounting any major pattern change. After all, if mathematical models were that reactive, then they'd be all over the shop, all of the time.

Computers are wonderful things, but they can't do everything. In the short term, certainly they can be used as tools - but, in the longer time frame, I think it wise to revert back to old fashioned human intervention; old skool forecasting, if you will.

It IS all interesting of course, but I think those in the number 1 camp should realise that, I they chose to follow every whim on the models, then are likely to often be very disappointed. Personally, I don't and wouldnt really encourage it.

[mcweather]

For those getting worried about the relatively small amount of cold scenarios in the ensembles and panicking that we'll get to February before anything decent shows. Here's a pointer and a story.

Firstly GP's winter forecast suggested that mid January would be the first window of opportunity for cold and certainly the way the strat and AO are forecast to go that still holds true. Secondly I believe that in his forecast video he said it may take a couple of attempts before the really cold air got to us.

Seeing as we are still ten days away from the middle of January a little patience should be shown before deciding to write of both January in terms of cold and by inference GP'S winter forecast.

and now the story:

Back in late December 1977 and early January 1978 I was enduring the umpteenth mildish and snowless winter of the mid seventies here in southern Dorset

in mildish conditions. Around mid Januray the flow became a somewhat more north westerly based zonal flow (as some of the ensmbles are showing at present.) Late in January the PV became disrupted and on the 28th a cold low swung in from the west bring the great highland blizzard which marooned many highland villages. The essentially cold nw flow continued into early february but northern blocking started to build (much as suggested in GP'S winter forecast)

By the 8th February high pressure had built up over scandi and greenland pushing the jet further south and introducing a very cold east to northeasterly flow

which brough heavy snow to many eastern and north eastern parts then during the week of 12th -19th 3 seperate heavy falls of snow affected the south west of England thefirst two on the 15th and 16th giving about 6 inches each. The final of these falls was the great Blizzard of 78 which left much of the rural southwest marooned for at least a week with drifts between 10 and 20 feet common place from an overall fall of about 18 inches. I personally witnessed drifts as deep as telegraph poles and on Exmoor the undrifted depth was one metre!!

My point to all this is that on 5th January 1978we had a windy mild sw zonal flow with a high to our south and no indication of what was to come and dare I suggest it if this forum had existed then there would have been posts about how the models were crap and the winter was done for.

You cannot write of winter or even January for that matter on the 5th January and those that do so at their peril.

Edited January 5, 2012 by mcweather

[Midlands Ice Age]

snow ballz,

After working in software IT for 30 odd years..... I must say your post is sthe most sensible post I have seen on here.

Models are only as good as the understanding at the time they are written. The NeTX science is still progressing. Small anomalies can create chaos in computing models.

MIA

[phil nw.]

Keep to current Model Discussion please people.

As interesting as some posts are they are not really for this thread.

We don`t wish to see this thread cluttered up so regretably any further posts ,more suitable for General threads ,may be deleted.

Thankyou.

[Cecil Hogmanay Melchett]

GFS continues with the NAO+ signal on its 12z operational.

The first half of Jan is obviously going to produce little or no winter weather.Now we have to look towards the second half of the month.

There is seemingly no end to the convoy of lows departing the eastern seaboard its thorougly depressing watching them one after another flattening the pattern in their horrible wake!!

Edited January 5, 2012 by happy days

[johnholmes]

:huh:

Are'nt the stratosphere warmings already calculated in the number crunching that make up the different models we view? Therefore handling them exactly as they and us read them at present?

nope

[stratty]

Yes they are, but its also a case of looking at the sginals and seeing whether the models are coming out with the right conclusion. I've seen it happen many times before, the stratosphere suggests one thing and the models something totally different. It happened last December, the models went for a rewended zonal burst from the jet for the 5-10th December with the PV powering up. However GP posted on here that this was effectivly rubbish and the model wasn't really picking up on the state of the stratosphere very well...and as GP said, the models eventually clocked and developed another powerful -ve AO.

The 06z GFS very briefly takes the AO negative around 264hrs thanks to a strong upper ridge over the E.Pacific, but it is very fast to pull that PV back together again and that ends that...

Another big warming event develops towards the end of the run so whewther that would be the one that finaly does it, who knows...but I'm pretty confident the 06z GFS is too positive on the AO and in truth the AO will be quite abit more negative, much like a large majority of the GFS ensembles. PV will stubbornly remain for the time being though.

I think GP's idea about a mild next 7 days followed by an increasingly Atlantic driven pattern with the chance of toppler northerlies and cool zonality sounds about right to me.

nope

lol , so who's right! .................

........start of an interesting looking arctic HP - where will it go?

[mountain shadow]

GFS continues with the NAO+ signal on its 12z operational.

The first half of Jan is obviously going to produce little or no winter weather.Now we have to look towards the second half of the month.

There is seemingly no end to the convoy of lows departing the eastern seaboard its thorougly depressing watching them one after another flattening the pattern in their horrible wake!!

That's not quite true, the GFS 12z probably brings in a neutral NAO towards the end. But your right their is still zero sign of any long cold spell in the GFS ops runs.

[Radiating Dendrite]

Well the end of the 12z looks interesting.

Not cold for us, but some bitter cold piling into scandi and heights developing around Svalbard.

Is it finally picking up on what the ECM is seeing?

The 18z will be interesting, see if it follows this up.

[Climate Man]

OK 12z now we are talking. Signs of a split in the Vortex with a large section moving over Scandinavia and thus allowing heights to build to our North - as I suggested may happen last Tuesday evening. Still in FI and loads can change but all to play for and first signs of the Strat waming kicking in.

[kold weather]

GFS is far more believable, I could see a run like the 12z coming off as the AO does go negastive and we do get decent high pressure aloft over the Arctic but the vortex keeps enough about itself to keep the Atlantic going. We see an attempt to bring heights into the Arctic but it ends up getting rebuffed. Still thats a run I would put more faith in...

Still nothing interesting for us here, but at least this run has finally picked up on the -ve AO again...

[Cecil Hogmanay Melchett]

OK 12z now we are talking. Signs of a split in the Vortex with a large section moving over Scandinavia and thus allowing heights to build to our North - as I suggested may happen last Tuesday evening. Still in FI and loads can change but all to play for and first signs of the Strat waming kicking in.

TBH the 12z brings some intense cold into mainland europe in deep FI, but until we lose the AZzores high its going to be a long road advecting the cold to these shores.

[mcweather]

An interesting 12z operational which if viewed through the 850's shows that the trend is to bring the truly deep cold air closer and closer to the uk and pushing the jet on to a more NE/SW line which I believe was one of the precursors to cold mentioned in GP'S winter forecast.

[Summer Sun]

what is interesting is what happens after the storm at 240hrs passes through, the door so to speak opens for colder air to move in

Winter is not over yet by any means

Edited January 5, 2012 by Gavin D

[Matty M]

My advice campers is to go spend the next 7 days away from the models, come back and we may be looking forward to something.

The next 7 days are a write off though, so unless you enjoy painstakingly watching prospects 240hrs+ then stay away, because it is painful and torturous! Just speaking from experience to the newbies. We could have 5 days of excellant charts in FI, even hitting the T168hrs in 3-4 days and woooop it will be gone.

[winter watcher]

Brilliant looking chart that oozes potential may be the GFS is now beginning to play catch up with the ECM!

[Backtrack]

what is interesting is what happens after the storm at 240hrs passes through, the door so to speak opens for colder air to move in

Winter is not over yet by any means

Such a shame we then pick up a polar westerly. Was hoping for something a little more 'spicy' but there's potential in the charts this evening to bring a deep cold spell.

Edited January 5, 2012 by Backtrack

[Climate Man]

Such a shame we then pick up a polar westerly. Was hoping for something a little more 'spicy' but there's potential in the charts this evening to bring a deep cold spell.

Too early to worry about "Polar Westerlys" You use the key word - potential - lots will change but at last we have potential

[Summer Sun]

Such a shame we then pick up a polar westerly. Was hoping for something a little more 'spicy' but there's potential in the charts this evening to bring a deep cold spell.

The main thing is its a start now we need ECM on board then its a case of hoping the models keep this outlook untill it comes into a reliable timeframe.

[john mac]

My advice campers is to go spend the next 7 days away from the models, come back and we may be looking forward to something.

The next 7 days are a write off though, so unless you enjoy painstakingly watching prospects 240hrs+ then stay away, because it is painful and torturous! Just speaking from experience to the newbies. We could have 5 days of excellant charts in FI, even hitting the T168hrs in 3-4 days and woooop it will be gone.

Thats why we love watching the models mate, it keeps us on oue toes and makes us go grey a lot quicker lol. i will be watching them all the way to learn more about picking up on trends etc.

[Backtrack]

The main thing is its a start now we need ECM on board then its a case of hoping the models keep this outlook untill it comes into a reliable timeframe.

ECM has been a bit of a tease I think, it's been showing a gradual cool down for a couple of days, but probably brings in changes too quickly in FI. Would be good to see the ECM in agreement with the GFS, that cold pooling over Europe doesn't look too shabby either. Could give any easterlies a real 'kick'

Didn't have you down as a coldie, good to have you on board Gavin.

[sn0wman]

Love the 850hpa temps to the North-East of us in the latest GFS. It's nice to see that kind of cold there, instead of it only being over Canada, which is what the GFS has been showing for ages! :smilz38: