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Model output discussion - 5th December 2016 - Into Winter we go

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Up soars the pressure in Iceland

prmslReyjavic.png

Down drop the air temps to our N/E

t850Copenhagen.png

Luvin it

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I know it's Christmas and all.. But let's try and keep the thread clean and educational especially during these busy times. Theres always the moan/ramping thread for chit-chat.

Thanks please continue.

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gens-21-1-168.png

This is quite enough for the moment. 1035mb high in the mid-Atlantic, stretching up to Iceland. At this time of year, it should be enough to turn precipitation white after a day or two. 

I think the one possible fly in the ointment is the low heights over Europe - or rather, the certainty of them happening. A flatter evolution still possible but quickly running out of time.

Great performance by the new ECM so far - if its forecast holds

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Freezer door open, freezer door closed springs to mind, cold clusters appearing and one that is still on the sherry. We are trending downward into the New Year.

pluim_06260_15D.png

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GFS - Jet stream

gfs-5-162.png?6

ECM - Same time frame

ECH1-168.GIF?26-12

Pretty good model agreement there!

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34 minutes ago, East_England_Stormchaser91 said:

Well well well, hope you all had a merry Christmas and are having a jolly Boxing Day :santa-emoji:

beginning to see some agreement within the far end of the mid timeframe scale with the big two as from this morning, which is the main thing.

just to note also, the sun has been blank with no sunspots at all for 3 days in a row and even before that, only one or two tiny ones over the past week. Just wondering if this is playing into our hands and if the models take these kind of things into account. 

Anyway enjoy those turkey sandwiches and Boxing Day buffets :D! I'm sure many will be keeping a close eye on these runs from now on in!! 

 

No turkey left but plenty of eye candy in the charts. lets hope the 12z is as good

 

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The GFS 6z ens are insane! Mean of below -5 850's from third till the end of the run, pretty incredible really. *

Not all are snowy but very noteworthy ENS suite, Santa has definitely been for snow lovers! 

 

*theres still enough scatter to urge big caution though, as well as it being nearly a week away.

Edited by Weathizard
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4 hours ago, Steve Murr said:

Hi Mate

a nice reply-

I think the reality & argument for me is that  there was some delay in propergation to the lower levels however the 'actual' observed trop pattern ( especially AO ) was near identical to the strat- so whilst the lower levels didnt signal immediate response in terms of overall zonal wind speeds, the pattern & shape it took most certainly didnt portray a disconnect - especially post the 15th when we ramped up to +4.5 AO.

So I dont really see how anyone can argue a trop 'pattern' disconnect as the facts from the AO timings indicate the total opposite-

 

Hi Steve - good to see some better short term model runs eh?

Yes - I totally get what you mean here. There was a definite pattern match between TPV and SPV through mid December... and again we now see a break up of the trop vortex just as TPV wind speeds fade. I agree that smells like a very big coincidence and smacks of a link. I guess my uncertainty with this is that I would have expected a wind speed response as well as a pattern response had the two been connected. I'm no physicist... but if the SPV pattern was able to imprint itself on the TPV then it implies a friction response - and would that not also increase the zonal wind speed in the trop?

Anyway - there is no way I'm going to claim to be an expert in this. The Strat Thread is rather poor this year without the input of Chio in particular, and I wont labour the point. I'm happy to be sceptical that there has/is an ongoing connect but an very happy to be better educated!

Also agree that signals point to a flattening of the ridge scenario we are seeing the NWP output at the moment... but with the Met now swinging suddenly (and it certainly feels a very sudden swing...) from a westerly to a blocked forecast for January I'm busy scanning all my links to try and get to the bottom of this change. 

Edited by Catacol
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1 minute ago, Catacol said:

Also agree that signals point to a flattening of the ridge scenario we are seeing the NWP output at the moment... but with the Met now swinging suddenly (and it certainly feels a very sudden swing...) from a westerly to a blocked forecast for January I'm busy scanning all my links to try and get to the bottom of this change. 

It's quite clear RE the Metoffice...as Fergie has said, there are a lack of clear cut background signals this year...they're all fairly neutral. Hence they have been relying solely on model output- model output which has either been swinging around or just plain wrong at times. I think that is why they appear to be changing direction a little more than they normally do.

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12 minutes ago, CreweCold said:

It's quite clear RE the Metoffice...as Fergie has said, there are a lack of clear cut background signals this year...they're all fairly neutral. Hence they have been relying solely on model output- model output which has either been swinging around or just plain wrong at times. I think that is why they appear to be changing direction a little more than they normally do.

Yes - and hence perhaps the system is prone to a swift response from a modest change. Stewart alluded to this in his last post. But can it really be as simple as a modest convection wave in the Pacific pushing up a North Pacific ridge and in turn alteration of wavelengths to promote ridging to our NW? That feels like an awfully basic chain creating an almost instant response - and would imply that weather forecasting is a doddle! 

But perhaps this is exactly what's happening, and beautifully timed to coincide with the TPV relocating mostly to the Russian side. I'm still scanning the charts... but if this is indeed what is happening then the good fortune of this progression certainly matches the bad luck of the last 3 weeks.

Truly a wildcard winter so far and a great descriptor.

Edited by Catacol
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This run shows a good cold spell, but spoiled by a party-pooping mild(er) sector coming in from the north-west:

image.png

= cold rain if you don't have the benefit of altitude.

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2 minutes ago, Nick L said:

I'll worry about such details at Day 3, not Day 10!

Indeed, minuscule details at this range is pointless and the overall pattern is what's more important, and that is very good!

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I hope everyone has had a good Christmas and the current models certainly look more seasonal.

We now have a quieter few days to come under high pressure with some frosty nights to come before a change from the north west brings colder upper air behind frontal systems at the start of the new year. 

The mean charts for NY day show the results of the Atlantic ridge as it brings in a cold northerly.

viewimage.pngecmt850.168.png

The Warks temperatures looking quite cold throughout.

viewimage (1).png

No exciting snowy charts yet as generally the ens are quite dry with the Atlantic high situating quite close to the west in the medium term 

Still with a Scandinavian trough and a ridging Atlantic bringing the jet south of the UK it will certainly feel more like Winter.

Edited by phil nw.
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25 minutes ago, Nick L said:

I'll worry about such details at Day 3, not Day 10!

Yes worry being the operative word though for you, being a forecaster, it could end up being one of those forecasting nightmares where you cant win and could end up on the front page of the Daily Express!!!

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Very encouraging output this morning but we are not there yet and I say that as someone who outlined this as a potential early Jan pattern a week ago.

We have been this close a few times to cutting off the Atlantic but obviously never quite made it.

At least the Atlantic ridge is sneaking into the more reliable time-frames of the models and the ensembles have largely come on board but I would like to see the ridge consistently modeled and for WAA into the heart of Greenland as with ECM, that way any energy off of Greenland will only move South down the Eastern flank of the ridge and deepen pushing the pattern West and drawing in cold polar air rather than deepening S of Greenland and pushing the pattern W/SW (At least temporarily) cutting off any potential polar flow. (toppler)

If the ridge is not as secure it will allow for energy to move East over the top in the usual area that is the bane of any prospective cold spell brought about by Atlantic blocking (SW tip Greenland) in this scenario we would need another bite at the cherry which could well happen but there are so many more things that can go wrong from there including the high being too far SE to bring any chance of widespread snow though it would remain mostly dry and cold,esp further S and E. 

Those two scenarios are pretty much painted by this mornings ECM 00z and GFS 06z.

ECM/GFS comparisons 144/192

ECH1-144.GIF?26-12gfsnh-0-138.png

ECH1-192.GIF?26-12gfsnh-0-186.png

 

The further N and W into Greenland we can get the initial Atlantic ridge the better so let's hope the clean no fuss, ECM 00z is the way forward.

 

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1 minute ago, radiohead said:

Latest GFS P is out. This might interest some.

gfs-0-264_srg9.png

Looks like we could get some blizzards out of that:yahoo:

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1 hour ago, Nick L said:

I'll worry about such details at Day 3, not Day 10!

Day 9 actually. The pattern of a low moving down from the north-west over the top of the high is the issue rather than the detail. This is because my experience is that in that pattern, the detail is always a variation on the theme of an intrusive and unwelcome mild sector. Hoping that this low will have disappeared from the 12z.

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