Model Output Discussion 4th Dec.2013-12z onwards.

[mountain shadow]

November was written off too as a mild month, the models at very best can only forecast 7 days in advance accurately, so what happens after that is anyones guess. Far to much importance is placed on the PV, it would be easy to forecast the weather if all you did was look at the pv...

 

Well Barry, if we could model the PV more accurately then forecasting would be simpler, that's for sure. I don't believe its simply coincidence that we are now staring down the barrel of a Euro high rather than a Scandi High because of the vortex strength.

 

The models have been underestimating the PV strength which is why they have been so poor of late. By default, the GFS then looked to be performing better by offering a flatter pattern, which is what it always does.

 

Will GEM be correct?, can't see it, and would expect it to back down on the 12z later.

 

If we have a Euro High in place in ten days time then it's a long way back to a colder pattern, 10-15 days at least which would take us towards month end, so yes, it is possible to write of widespread snow this month, even on the 5th.

Edited December 5, 2013 by mountain shadow

[Weather Boy]

Well Barry, if we could model the PV more accurately then forecasting would be simpler, that's for sure. I don't believe its simply coincidence that we are now staring down the barrel of a Euro high rather than a Scandi High because of the vortex strength.

 

The models have been underestimating the PV strength which is why they have been so poor of late. By default, the GFS then looked to be performing better by offering a flatter pattern, which is what it always does.

 

Will GEM be correct?, can't see it, and would expect it to back down on the 12z later.

 

If we have a Euro High in place in ten days time then it's a long way back to a colder pattern, 10-15 days at least which would take us towards month end, so yes, it is possible to write of widespread snow this month, even on the 5th.

 

But, assuming you're right (as you may well be) that is not a case to write off December.  The most far sighted forecast would take you to about 15th i.e. mid-month.  Nobody can state with any confidence at all what will happen after that, so that's (at least) half the month not 'written off'.

 

......and that assumes that you are right....!

[Don]

Looking at the latest GFS and longer term CFS charts today, I'm starting to get really worried that we maybe looking at a late 1990's style winter.  High pressure staying over France and South/South Westerly winds constantly over the UK.

 

Well that could always be the case but there's nowt we can do about it and it's early days still.  If this Winter turns out to be a stinker then so be it!

[Gavin Hannah]

Sheeesh, so much negativity in here today.  I know the charts aren't pretty for us coldies to look at, but keep the faith (as Bon Jovi said), good things come to those who wait.  The GEM could be the only model heading in the right direction so before we get hung up on the next two weeks trends, lets wait a few more runs to see which model gives way.

[Ian Brown]

Sheeesh, so much negativity in here today.  I know the charts aren't pretty for us coldies to look at, but keep the faith (as Bon Jovi said), good things come to those who wait.  The GEM could be the only model heading in the right direction so before we get hung up on the next two weeks trends, lets wait a few more runs to see which model gives way.

There  is nothing to suggest HLB can be achieved with a poor Strat profile, strengthening PV and MJO only likely to support the status quo. The GEM won't be verifying.

[bluearmy]

apart from a scenario where the GEM is right and we pluck an outlier as the way forward (very unlikely), the most likely route to deep cold (and possible snow) is a more eliptical shaped block somewhere to our north/northeast and the 'strong vortex' dropping low heights to its east to be advected west. its not so far fetched if we can somehow get heights over s europe to drop. thats the main reason why i was intrigued by ukmo at day 6. at the moment, the northern arm is taking nearly all the split traffic on the extended ens and ops. (we know ncep is prone to doing this but ecm suite is also showing a similar solution). if the jet energy is incorrectly modelled going forward then an outcome similar to the GEM is not so ridiculous. the p/v is modelled to slowly lift itself further nw in the canadian sector and tranfer some energy across to siberia. that isnt such an issue for us as its far enough to the north not to interfere too much with our blocking. it also adds to the chances of some low heights dropping in behind any scandi/sceuro block.whilst the outlook seems far far from anything really wintry, it really isnt so set in stone. keep an open mind but recognise the way the dice are currently loaded.

[ARNOTT ad]

I know pretty much most things meteorological but I'm trying to find out why there are such strong signals etc of this high CONSTANTLY stuck in or around us! What is causing this!? Any info would be useful....

On another note I would so much rather have raging zonality. It at least gives us an increased chance of colder interludes albeit brief.

[shedhead]

Absolutely.  Is it ever possible to "write off" (or indeed the opposite, expect hoped-for weather) a month on its fifth day?  Even in the shortest month, February, that's making an assumption as to the weather pattern over the next 3 weeks and 2 days, way beyond our current capabilities (apart from guessing at the broadest of trends, which guesses could be completely wrong).

 

So, I say the answer is no, one should never make an assumption as to the entire month's weather until the middle of that month at the very earliest.  Any post suggesting that a month is a 'write off' at such an early stage is just silly, I'm afraid.

 

That's particularly so when based on a couple of uninspiring runs.  Two days ago, the ECM wanted an easterly.  GEM hangs on to that.  Who's to say that the ECM (or, stranger things have happened, the GFS!) won't want one tomorrow or the next day?

Excellent points WB...however I suspect if it were now bitterly cold/snowy and Ian F had suggested the MO/ECM 32 dayer was keeping the bitter cold and snow in place until month end, very few would be offering up the same excellent points that you have above.

Edited December 5, 2013 by shedhead

[syed2878]

your rite the gem was the first model to pick up the october storm then drop it before the others picked it up. 

Clutching at straws i know but wasnt GEM first one to spot st jude storm earlier this autumn

 

[Mucka]

apart from a scenario where the GEM is right and we pluck an outlier as the way forward (very unlikely), the most likely route to deep cold (and possible snow) is a more eliptical shaped block somewhere to our north/northeast and the 'strong vortex' dropping low heights to its east to be advected west. its not so far fetched if we can somehow get heights over s europe to drop. thats the main reason why i was intrigued by ukmo at day 6. at the moment, the northern arm is taking nearly all the split traffic on the extended ens and ops. (we know ncep is prone to doing this but ecm suite is also showing a similar solution). if the jet energy is incorrectly modelled going forward then an outcome similar to the GEM is not so ridiculous. the p/v is modelled to slowly lift itself further nw in the canadian sector and tranfer some energy across to siberia. that isnt such an issue for us as its far enough to the north not to interfere too much with our blocking. it also adds to the chances of some low heights dropping in behind any scandi/sceuro block. whilst the outlook seems far far from anything really wintry, it really isnt so set in stone. keep an open mind but recognise the way the dice are currently loaded.

 

 

Spot on. If that energy is being modelled incorrectly the output will flip, whether that be GEM from cold to mild or the entire GFS ensemble suit from av/mild to cold.

If you had to make a forecast at present you would have to go along with the majority of NWP and it would look much like the MetO's forecast for the rest of December but we have the luxury of not having to make a forecast - unless our egos get the better of us.

 

For beginners.

 

There are a few who have been banging on about how the trough to our East shapes up being crucial and how this is defined by the energy flow over our ridge.and down its Eastern flank, In simple terms the steeper and closer to the UK the Eastern flank of the ridge is the better. I think Nick posted something similar this morning.

 

If you're not sure what to look for in those terms then you can also look for a link up between ridges a little later which, as mentioned, will be dependant on how the Eastern European trough is handled  (probably between 120 and 144 if things are going well). This is crucial for our chances because once the low is cut off from moving North it has to come back West which amplifies the pattern further because the ridge can't sink SE and the energy on its Western flank can not simply ride NE over the top through Iceland and Scandinavia but get pushed up to Greenland, over and back down through Eastern Europe with WAA through Scandinavia. In a perfect world this pattern would return back West (retrogress) and we start getting WAA  toward Greenland.

 

Here are some charts showing the link up and closed low with good amplification (GEM) a near link up with not so good amplification (UKMO) and no link up with poor amplification GFS.

 

 

 

Don't be fooled by a link up a little later at a lower lat because our ridge is already too flat by then with the writing pretty much on the wall, here GFS 00z missing the first and catching the second.

 

Missing (low pressure moving North

 

Connection made later at much lower latitude )with the ridge we wanted to link up with out of reach to the North.

 

 

It's a case of catch the first bus because the second is not going to take us where we want to go.

 

today's NAVGEM 06z (don't put too much faith in this model)

 

Edited December 5, 2013 by Mucka

[phil nw.]

Just for info.a new Model moans/ramps thread has been opened for Winter 2013/14 so please post more general chat in there- stuff that would stray off topic in this thread.

This is the link

http://forum.netweather.tv/topic/78680-model-banter-moans-and-ramps-winter-201314/

 

Btw a couple of recent posts have been moved into there.

 

Let's keep on topic in here please all.

Thanks.

[Frosty.]

The GEFS 06z mean shows a northwest / southeast split forming as time goes on, clearly shown at T+240 hours, beyond then the lower heights to the northwest make inroads further south and east eroding the fine anticyclonic weather which dominates the majority of the next 10-12 days across the southeastern half of the uk, becoming unsettled, relatively milder and windier further northwest.

[Gavin Hannah]

The GEFS 06z mean shows a northwest / southeast split forming as time goes on, clearly shown at T+240 hours, beyond then the lower heights to the northwest make inroads further south and east eroding the fine anticyclonic weather which dominates the majority of the next 10-12 days across the southeastern half of the uk, becoming unsettled, relatively milder and windier further northwest.

 

That kind of setup (2nd image) would introduce cold yet more mobile weather in the north. Not the jewel in the crown but far from mild for those in Scotland at least.  Plenty of wet snow potential.

Edited December 5, 2013 by IBTHToThoseShortwaves

[UV-RAY]

Well at this current time the outlook is pretty dross for us coldies, I suppose the best we can hope for is the EC32 painting a mild and zonal outlook.

[summer blizzard]

A great consecutive model run from the GEM0z today prompting a cold scenario but equally a poor showing from the ECWMF0z operational and its ensembles, also poor from the GFS6z ensembles.

 

As for my opinion on the GEM, i do actually rate it. I've followed it and done checks at day 10 and its held its own against the Euro and GFS, closer i do acknowledge the lead that those and the UKMO have within 144 hours but as a trend spotter its as good as the GFS.

 

My personal opinion despite the doom and gloom from some people is that the -GLAAM drop and continued wave breaking will present an opportunity between the 15th and 25th for blocking to occur to our north so i can see where the GEM is coming from although it's almost certainly too optimistic. Equally however i think both the Euro and GFS ensembles (and the Euro operational) are being far too progressive and as such i would put the GFS6z operational as the most likely outcome with pressure remaining pretty high over the UK through day 10.

 

 

My own percentages would be something like..

 

GFS6z Operational: 45%

GFS and Euro ensemble mean (plus Euro operational): 30%

GEM: 20%

Other: 5% 

[UV-RAY]

A great consecutive model run from the GEM0z today prompting a cold scenario but equally a poor showing from the ECWMF0z operational and its ensembles, also poor from the GFS6z ensembles.

 

As for my opinion on the GEM, i do actually rate it. I've followed it and done checks at day 10 and its held its own against the Euro and GFS, closer i do acknowledge the lead that those and the UKMO have within 144 hours but as a trend spotter its as good as the GFS.

 

My personal opinion despite the doom and gloom from some people is that the -GLAAM drop and continued wave breaking will present an opportunity between the 15th and 25th for blocking to occur to our north so i can see where the GEM is coming from although it's almost certainly too optimistic. Equally however i think both the Euro and GFS ensembles (and the Euro operational) are being far too progressive and as such i would put the GFS6z operational as the most likely outcome with pressure remaining pretty high over the UK through day 10.

 

 

My own percentages would be something like..

 

GFS6z Operational: 45%

GFS and Euro ensemble mean (plus Euro operational): 30%

GEM: 20%

Other: 5% 

I agree with your timing on a change to a more blocked and cold spell, though I just can't see how we will get HLB at this moment in time?

[summer blizzard]

I agree with your timing on a change to a more blocked and cold spell, though I just can't see how we will get HLB at this moment in time?

 

I don't necessarily think we'll get a split PV but something between NW and SE is probable around that time in my opinion. 

[tight isobar]

Far to much concern on current model out, and deff,overwellm. Regards mid/ long term..as it stands there's much to be gained as lost for evolutionary..

[Gavin Hannah]

A quick GEM comparisson of yesterdays 12z  (left) and this mornings 00z. (right)

 

 

 

 

 

 

 

 

 

 

 

http://meteocentre.com/home_e.html

Edited December 5, 2013 by IBTHToThoseShortwaves

[syed2878]

i do find u.k climate most boring and unreliable. Part from the gem none of the others r inspiring. 

Yes frustrating but not really sod's law, milder solutions are always more likely to verify than colder ones and that's part and parcel if you live in the UK. It's for this reason that the most model variability we see is generally with colder patterns because these go against the prevailing weather patterns for the UK during winter. As we've seen in recent winters we can still get decent cold spells but these are still the exception rather than the rule, I think it's part of the fun in terms of this thread anyway because if it was a simple countdown to cold it would be rather boring and also would this thread have many visitors if it was Canadian based. It's the rarity of those wintry spells that makes them all the more enjoyable when they come.

 

[shedhead]

Far to much concern on current model out, and deff,overwellm. Regards mid/ long term..as it stands there's much to be gained as lost for evolutionary..

Not quite sure what you are getting at here tight isobar...can you elaborate?

[johnholmes]

Not quite sure what you are getting at here tight isobar...can you elaborate?

 

Yes it would be nice if he wrote in English. I apologise sincerely if you have a problem that causes this.

the link below sums up what the 500mb charts are suggesting what the flow could be at 18000ft in 6-12 days time. They are all (the 3 I use) fairly solid in this idea. Detail at the surface of course is going to be with the synoptic models as we close down on the time.

[shedhead]

Yes frustrating but not really sod's law, milder solutions are always more likely to verify than colder ones and that's part and parcel if you live in the UK. It's for this reason that the most model variability we see is generally with colder patterns because these go against the prevailing weather patterns for the UK during winter.

 

As we've seen in recent winters we can still get decent cold spells but these are still the exception rather than the rule, I think it's part of the fun in terms of this thread anyway because if it was a simple countdown to cold it would be rather boring and also would this thread have many visitors if it was Canadian based.

 

It's the rarity of those wintry spells that makes them all the more enjoyable when they come.

 

I know you've been watching the models for a while Nick, so can I ask what you make of the GEM overall?  In this instance it seems to take the Svalbard low away much quicker in the T+144-168hr range, which in turn allows heights to build close to the White Sea and then regress into Scandi.  Looks a bit odd to me, but it would not be the first time it's picked up on what looks like a small change that ultimately has large implications.

Yes it would be nice if he wrote in English. I apologise sincerely if you have a problem that causes this.

the link below sums up what the 500mb charts are suggesting what the flow could be at 18000ft in 6-12 days time. They are all (the 3 I use) fairly solid in this idea. Detail at the surface of course is going to be with the synoptic models as we close down on the time.

No link posted John...

Edited December 5, 2013 by Paul

[Panayiotis]

Look at the similarities between the 12z CFS 12month and the 00z CFS 1 month for 174hrs!

Edited December 5, 2013 by Panayiotis

[johnholmes]

I know you've been watching the models for a while Nick, so can I ask what you make of the GEM overall?  In this instance it seems to take the Svalbard low away much quicker in the T+144-168hr range, which in turn allows heights to build close to the White Sea and then regress into Scandi.  Looks a bit odd to me, but it would not be the first time it's picked up on what looks like a small change that ultimately has large implications.

No link posted John...

 

 

you are quite right, trying to do 3 things at once, here it is - my apologies

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html