Model Output Discussion:

[Snowyowl9]

Really good 12Z runs from the UKMO and GFS, both showing a strong easterly flow, uppers are certainly cold that for sure! I don't think many on here would really care if we get uppers of -10 or -15 aslong it snows.

Now we just need the ECM to come on board with its easterly flow being stronger and longer lasting than it was on this mornings run, something similar to yesterdays 12Z run will do!

A similar wind flow to this very famous spell on this date anyway,UKMO is.

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870114.gif

Are we looking at a repeat of last feb`s Easterly for snowy amounts further west I wonder, that was a NE-ly and a snowy one.

As for GFS later on.

http://91.121.93.17/pics/Rtavn2641.png

[kold weather]

In the second link it looks as if there is a pocket of warmer air covering Eastern England from The Borders down to North Kent, I cant see what the 850's are for this area, anyone able to let me know?

Its a warm sector but its all realtive, you've got a very cold flow aloft and that won't be giving anything other then snow, probably even by the coast IMO.

Of course its true we are still close enough to need to preach caution but I'm seeing good general agreement now on the synoptic evolution.

[No Balls Like Snow Balls]

You have to hand it to the GFS, the Easterly was spotted by the GFS nearly 2 weeks ago, ok it's had it's wobbles and we have all had our doubt's, but it has got there in the end, so fair play to the GFS.

[karyo]

So can you give an estimate as to what day next week we can expect the return of the snow? To me it looks like Wednesday.

It's difficult to say at this early stage and I am not sure where you live. However, according to the UKMO and GFS current charts, I would say Tuesday. Of course, it's all subject to change.

Karyo

[Solar Cycles]

You have to hand it to the GFS, the Easterly was spotted by the GFS nearly 2 weeks ago, ok it's had it's wobbles and we have all had our doubt's, but it has got there in the end, so fair play to the GFS.

Agree, it gets it's fair share of stick, but it did predict the last cold spell well in advance also. We will soon find out if it's the leader of the pack!

Edited February 4, 2010 by Solar Cycles

[kold weather]

Control run looks exceptional for NE/East England, though the flow is VERY slack on that run as a LP develops in the north Sea...once again you'd have to think if that solution occured there'd likely be several disturbances coming down as well.

Oh...and did I mention sub 510 thickness as well....

[swilliam]

Looking through the ensembles at t192 there is only one (17) that does not go for the cold spell. This is due to what we have seen previously where the Atlantic LP and the SW over Norway link up and we get SW winds. However there is a lot of variation in what they do with the shortwave and cold pool. most go with the op but there are several other options which would affect the degree of cold and amount of snow.

[Thundery wintry showers]

The progged setup has a lot in common with the north-easterly outbreaks of 17/18 December 2009 and 5-8 January 2010, but would not bring the widespread preceding frontal snow event of the latter as it would have very cold air replacing moderately cold air, as opposed to a frontal zone between two very cold airmasses.

Most eastern areas get hit by frequent snow showers from that setup but in central and western areas it is usually hit and miss. On 6, 7 and 8 January 2010 showers often didn't get very far inland across the south if I remember rightly, but there were some surprisingly potent "snow streamers" which made landfall over NE England and penetrated right across to parts of NW England.

I don't agree with the praise of the GFS even if this progged NE'ly comes off. If so, it will be right in terms of eventual outcome but for the wrong reasons. However, since all of the models have been chopping and changing recently, we can at least say that the GFS hasn't been "cannon fodder territory" with the Euros being good!

Edited February 4, 2010 by Thundery wintry showers

[The PIT]

Well on the GFS it's just sinking into the reliable time frame UKMO same so it maybe actually on this time around. Only one model run to go now will that be a party pooper.

[No Balls Like Snow Balls]

The progged setup has a lot in common with the north-easterly outbreaks of 17/18 December 2009 and 5-8 January 2010, but would not bring the widespread preceding frontal snow event of the latter as it would have very cold air replacing moderately cold air, as opposed to a frontal zone between two very cold airmasses.

Most eastern areas get hit by frequent snow showers from that setup but in central and western areas it is usually hit and miss. On 6, 7 and 8 January 2010 showers often didn't get very far inland across the south if I remember rightly, but there were some surprisingly potent "snow streamers" which made landfall over NE England and penetrated right across to parts of NW England.

I don't agree with the praise of the GFS even if this progged NE'ly comes off. If so, it will be right in terms of eventual outcome but for the wrong reasons. However, since all of the models have been chopping and changing recently, we can at least say that the GFS hasn't been "cannon fodder territory" with the Euros being good!

When you say wrong reasons, do you mean because it had the wrong evolution to the E'ly?, if so there is no way in the world any model could spot the evolution that far out but a trend yes.

[Polar Continental]

A Very cold and some times snowy output for quite a large swathe of the country from the 12z GFS, and UKMO, especially the UKMO at T144. Though the GFS is nothing to be sniffed at ether, good agreement given the time period. The –10c 850 hpa shown on the GFS would be quite adequate to create the instability needed for heavy snow showers to form and push well inland.

Hopefully the 12z ECM shows a similar set-up as well.

[locneverstop]

All this one way to go stuff, weren't we all saying that when the Easterly first showed all that time ago? Now it's back, it's even better! Perfectly plausible that it could upgrade IMO.

I'm loving the way that giant LP just falls apart as it approaches!

[Thundery wintry showers]

When you say wrong reasons, do you mean because it had the wrong evolution to the E'ly?, if so there is no way in the world any model could spot the evolution that far out but a trend yes.

Yes- and also the GFS went for raging south-westerlies for a good 6-8 runs in between the current outputs and the previous "easterly" outputs- if the GFS shows everything under the sun it has to be right one way or another!

[swilliam]

Looking through the ensembles at t192 there is only one (17) that does not go for the cold spell. This is due to what we have seen previously where the Atlantic LP and the SW over Norway link up and we get SW winds. However there is a lot of variation in what they do with the shortwave and cold pool. most go with the op but there are several other options which would affect the degree of cold and amount of snow.

As now shown on the full ensemble set.

[The PIT]

Yes- and also the GFS went for raging south-westerlies for a good 6-8 runs in between the current outputs and the previous "easterly" outputs- if the GFS shows everything under the sun it has to be right one way or another!

I think that was the ukmo and ECM while GFS went for easterlies before flipping to the UKMO/ECM thinking.

[pinball wizard]

The broad evolution now looks IMO pretty nailed out to at least 96hrs, the very interesting period between 96-144hrs could yet change somewhat and moderate away from the very snowy set-up progged but this does look interesting.

Somewhat reminds me of the December cold spell between say the 16-23rd of December, and we got a decent event out of that one!

I dont have a clue where to find past charts but was wondering if anyone could post up a picture of the 850s at 18z for the 17th December 2009, I had a really good fall from that setup and wanted to see the charts, if anyone can help, i'd be very grateful.

[kold weather]

GFS ensembles still rather uncertain with regards to the period between 120-168hrs, whilst pretty much all agree on cold-very cold, the exacts vary depending on exactly where the LP ends up forming. The ideal solution for the most of the UK is for the LP to develop in the North-Sea then sink SW/SSW, that should help drag in easterlies in its wake.

Either way most ensemble members look very good right now, and quite a few would bring a very snowy flow I'm quite sure!

[Thundery wintry showers]

Can't find the 17th at 18Z, but the 18th at 00Z is available from our own Datacentre under the historic chart archive from Wetterzentrale.

http://www.wetterzentrale.de/archive/ra/2009/Rrea00120091218.gif

http://www.wetterzentrale.de/archive/ra/2009/Rrea00220091218.gif

[swilliam]

Yes- and also the GFS went for raging south-westerlies for a good 6-8 runs in between the current outputs and the previous "easterly" outputs- if the GFS shows everything under the sun it has to be right one way or another!

I don't believe an Easterly and SWesterly constitute everything under the sun do they - I think we have some other types. This was discussed earlier in the day an this is what I posted earlier

Posted Today, 14:04

LeighShrimper, on 04 February 2010 - 13:35 , said:

Was it not the GFS model that picked up on the cold signal first, nearly 14 days ago?

If I remember rightly it predicted a cold outbreak from the E/NE around the 8th Feb?

And that date still stands by the looks of it...

You have to give the model credit really. OK it's been like a rollercoaster since, but all of the models have.

If the pattern verifies (which is looking increasingly likely) then there has to be a big tip of the hat to the GFS in my opinion.

I agree with this - that is the whole point of looking at and discussing FI which some people moan about - identifying possibilities and discussing the likelihood of them coming off. It is easy for the UKMO GM to look good - it only goes out to +144. Yes the pattern has come and gone and come back again but the 8th Feb has always been the favoured date for the start. Let's see if it does actually happen now - If so I would definitely say we would need to give the model some credit - it just needs to be used in the right way - particularity not slavishly following each run.

Strider, on 04 February 2010 - 13:56 , said:

It did, but then by last weekend it went blowtorch again.

It a model keeps blowing hot and cold (sorry) then it is guaranteed to be correct at some point!

A more relevant question is which model consistently predicted the cold spell before the others? UKMO..?

errrr no - when it finally came into range -first it didn't show it - then it did - then it didn't and now finally it has come back to it again.

Just Below Zero, on 04 February 2010 - 13:57 , said:

14 days? Thats 56 model runs all totally different.

Well if there were enough monkeys........

No - it stuck with it (somewhat intermittently - especially wrt to the start) for several days which is why it was discussed - then 'came into line with Euros' by dropping it for the extended SW/NE LP with SW winds - then cam back to it (albeit after the ECM).

[pinball wizard]

Can't find the 17th at 18Z, but the 18th at 00Z is available from our own Datacentre under the historic chart archive from Wetterzentrale.

http://www.wetterzentrale.de/archive/ra/2009/Rrea00120091218.gif

http://www.wetterzentrale.de/archive/ra/2009/Rrea00220091218.gif

Thanks for that Always think a more northerly element to any easterly is better for my part of the world, will be very interesting to see how similar a setup develops.

[Tattooed Fox]

With the excitment growing with the model outputs looking more to a snowy spell again, can anyone confirm if the charts do come off what temps we are looking because with the GFS+144 posted by Paul B shows some very deep blues and as a beginner on here I'm not sure what temps we are looking, but i'm sure if it is very cold.

[Mark Bayley]

Good GFS ensembles, i like that little ensemble member all on its own (P17 i think)

Good agreement overall for a prolonged cold spell. Also looks quite snowy as well. The ECM which is also good is less snowy, but still cold. So widespread heavy snow showers on the UKMO and GFS is not guaranteed yet. Its going to turn colder. How cold and how snowy is yet to be decided

[Guest North Sea Snow Convection]

Note how much the shortwave energy from the atlantic has continued to be squeezed out of the modelling as the high pressure near Iceland and Norway has gained its easterly ascendancy over the BI. This process started in earnest yesterday and has continued right up to and including the 12z's so far. I think it very unlikely that the ECM is going to be any different.

Incredible turnaround from the atlantic bombardment suggested of barely 36 to 48 hours ago, although there were questions asked right up to this time, repeatedly, about what was then the t120 timeframe and the suspected overcooking of the strength, extent and orientation of the atlantic short waves spinning towards the west coast of Ireland and pushing south westerlies across the greater part of the UK

I think now it is just a question of how cold it gets in terms of the pull of cold air advected south westwards from Scandinavia over the north sea. That in turn will determine the ppn (snow distribution)

In the interests of protocol the overnight outputs will officially rubber stamp the cold spell, but I can't see anything now to stop the initial evolution which begins by Sunday.

Edited February 4, 2010 by North Sea Snow Convection

[TEITS]

As others have said a superb set of 12Zs so far. I said early this morning I was happy to go with the GEFS mean and the 12Z UKMO follows the GFS/GEFS very closely. Im still going to remain cautious with regards to the cold pool over Scandi backing SW until this appears within +48/+72.

I will add if the UKMO/GFS verify then the potential is far better than our previous cold spells. The cold spell in Jan started with a very slack NE,ly flow. By the time this veered E,ly the cold pool of -10Cs only lasted around 24/36hrs. This time round the convective potential could be much longer.

I remain very happy with the GEFS mean at +120 and will continue looking at this until the potential comes into the NAE/NMM range.

http://91.121.94.83/modeles/gens/run/gens-21-1-120.png?12

[johnholmes]

In terms of which model is doing best, perhaps the one to believe over another, then the NOAA stats show that UK Met and ECMWF are well in the lead over the past 3 days, on their 6 day checks.