Model Output Discussion

[phil nw.]

So far the 06Z is rather different to the 0Z. The LP system is much further E at +162 just off the W coast of Scandi. Whereas the 0Z had this sitting to the W of Iceland!!

Such changes within the reliable timeframe makes what happens after pretty pointless to be honest.

Yes this where luck often goes against us Dave.

See here at T120hrs.NH view,

http://91.121.94.83/...snh-0-120.png?6

The Vortex splits but the extra energy coming off the Canadian centre spins off towards us and indeed past the meridan.

Notice too at this stage the main heights at t`other side of the Pole.

Edited December 3, 2009 by phil n.warks.

[TEITS]

I feel very deflated by the outputs again this morning!

Yes its only the 3rd of Dec but we really are stuck in the most awful rut and i just cant see a way out

of it at the moment.Fingers crossed things improve after the first week of Dec,but thats just an aspiration

in my eyes.Cold charts remain firmly in FI,and even their number have decreased on gfs ens.

Could be alot worse.

If your only looking at the models for a cold spell then you will be disappointed. However if you look at the wider picture then you can see the potential.

When I say it could be alot worse I mean we could be looking at a strong PV being sat over Greenland. However this isn't the case and the models continue to suggest a splitting of the PV with HP being present to our N/NE. They also suggest a bitterly cold airmass moving S out of the Arctic.

What you have to consider is the models will never accurately predict an E,ly at +300 which will work its way down to +0. All im looking for at the moment is the models to continue to predict some kind of N blocking to develop. If this cold airmass does come our way then the models won't model this until the +169-+240 range. Don't forget if you get the right synoptic set up then its a certainity the cold airmass will arrive.

but this is going to run and run lots more options to come I think.

Indeed and thats what makes F.I so fasinating to me.

The GFS comes out with so many outcomes in F.I the trick of following the models is knowing which one is right. However despite so many different runs from the GFS the outcome in recent days has been rather similiar i.e blocking, cold airmass. This is why im fairly confident a bitter airmass will move S out of the arctic in mid Dec with a part of the PV being sat underneath the HP. However at this stage im unsure whether we will experience this cold airmass.

[kold weather]

The 0z ECM shows a very good -ve AO BUT a utterly useless Atlantic pattern, very much like 97-98 in that respect where we had plenty of Arctic support but El Nino made a total mockery of it.

For those who are saying we need the Atlantic break, I'd just say your looking for the wrong thing, your just not going to get it when you have a high end moderate El Nino, you have to work around it because if anything the models will underestimate the strength of lows past 144hrs rather then the other way round.

Also I think the 06z GFS is actually better for cold then the 0z, sure the 0z did have a brief easterly right at the end but the run before that is a pig, at least with the 06z we get a cold high far sooner. Thats what I would look too, the jet buckling enough to allow any Euro high to transfer northwards, there does seem to be some support for that idea.

[Polar Continental]

Although nothing really wintry in the reliable time frame, these are interesting times, as know one really knows what the models are going to produce, even in what would normally be deemed as reliable. The fact the Polar vortex forms in random spots for short intervals, only to be smashed in to fragments all over the northern hemisphere each time is making for unpredictable times. I don’t think anyone can say with confidence that this winter will turn out cold or mild. Back to the old days, before model watching.

Edited December 3, 2009 by Polar Continental

[Frosty.]

You never know what you are going to get with the gfs from one run to the next, a bit like pulling the lever on a slot machine, it's pot luck. The 6z is ok, a cold high would be very welcome with some decent frosts to kill off the bugs going around.

[kold weather]

By the way just to show us how cold the 06z actually is in the FI part of the run:

http://www.wetterzentrale.de/pics/Rtavn32417.png

Its very similar to many of the colder spells in December over the last few years and they often have left to a 10 day period with the CET close to 1.5C, indeed some of our coldest spells from this decade have actually came from these sorts of spells.

[Shunter]

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images/euT2mMonNorm.gif

CFS update doesn't bode well for Dec or Jan....a warming trend

Edited December 3, 2009 by Shunter

[Stu_London]

Another easterly solution on the 06z, albeit a much more benign outcome than some of the operational runs over the last couple of days, mainly due to a lessening of high and mid latitude heights.

A fairly good chance of some sort of battleground scenario now exists between a block to the east and the atlantic. The form horse would be that we are either on the mild side or the northern jet invorigates too much, however whilst the possibility of tapping into cold air exists, model viewing remains interesting.

It's nice not to see 16 days of zonal south westerlies on the GFS as we were treated to in November, even if ultimately we end up with little material difference.

[Methuselah]

Although nothing really wintry in the reliable time frame, these are interesting times, as know one really knows what the models are going to produce, even in what would normally be deemed as reliable. The fact the Polar vortex forms in random spots for short intervals, only to be smashed in to fragments all over the northern hemisphere each time is making for unpredictable times. I don’t think anyone can say with confidence that this winter will turn out cold or mild. Back to the old days, before model watching.

Good post, PC; that's exactly how I'm seeing (or, perhaps, not seeing them?) things just now. It's also why I'm not about the over-criticize the MetO's winter forecast; sometimes (IMO), uncertainty can be more revealing than, sometimes foolish, attempts at precision?

[chionomaniac]

Could be alot worse.

If your only looking at the models for a cold spell then you will be disappointed. However if you look at the wider picture then you can see the potential.

When I say it could be alot worse I mean we could be looking at a strong PV being sat over Greenland. However this isn't the case and the models continue to suggest a splitting of the PV with HP being present to our N/NE. They also suggest a bitterly cold airmass moving S out of the Arctic.

What you have to consider is the models will never accurately predict an E,ly at +300 which will work its way down to +0. All im looking for at the moment is the models to continue to predict some kind of N blocking to develop. If this cold airmass does come our way then the models won't model this until the +169-+240 range. Don't forget if you get the right synoptic set up then its a certainity the cold airmass will arrive.

Wise words Dave.

The last time that the vortex split into two was in February. The models forecast great amounts of northern blocking that never materialised. What does that tell us?

It tells us that the models struggle to forecast correctly what is likely to occur after the split has occurred and what we should be concentrating on now is that the split is going to occur, leaving two separate vortices. What happens to these vortices is important and we have already seen a number of different solutions being modeled. However we won't know exactly for at least a week what is likely, so any fretting in the meantime is pointless.

An interesting weeks model watching I feel.

c

[snohobo]

I agree with Eye, there is often a probable trend set up in late FI but often what happens is that it suddenly appears as a more solid possibility within 144 with little warning, that has happened quite often in the past and especially when a more unusual pattern develops, like an easterly

[Frosty.]

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images/euT2mMonNorm.gif

CFS update doesn't bode well for Dec or Jan....a warming trend

Is this the first winter is over post?

[Guest North Sea Snow Convection]

Could be alot worse.

If your only looking at the models for a cold spell then you will be disappointed. However if you look at the wider picture then you can see the potential.

When I say it could be alot worse I mean we could be looking at a strong PV being sat over Greenland. However this isn't the case and the models continue to suggest a splitting of the PV with HP being present to our N/NE. They also suggest a bitterly cold airmass moving S out of the Arctic.

What you have to consider is the models will never accurately predict an E,ly at +300 which will work its way down to +0. All im looking for at the moment is the models to continue to predict some kind of N blocking to develop. If this cold airmass does come our way then the models won't model this until the +169-+240 range. Don't forget if you get the right synoptic set up then its a certainity the cold airmass will arrive.

Wise words Dave.

The last time that the vortex split into two was in February. The models forecast great amounts of northern blocking that never materialised. What does that tell us?

It tells us that the models struggle to forecast correctly what is likely to occur after the split has occurred and what we should be concentrating on now is that the split is going to occur, leaving two separate vortices. What happens to these vortices is important and we have already seen a number of different solutions being modelled. However we won't know exactly for at least a week what is likely, so any fretting in the meantime is pointless.

An interesting weeks model watching I feel.

c

I agree. It could be that angular momentum will be more favourable by the time the vortex split occurs. It is quite possible that models will over cook atlantic energy/low pressure strength in line with the uncertainties over vortex split and changes in momentum levels or we may just see a reigning back process over the next few days as signals become closer and stronger.

Perhaps it is as well that the timing of the vortex split is when it is - there is a possible window of opportunity there for us.

I'm not convinced by the GFS 06z myself - I can't see things progressing that far east. Time as ever will tell though

[Michael Fishermans Friend]

Noticing though the cold or more interesting charts though are in FI - isn't that just resorting to typical GFS in general in mild winters? and you usually find the cold is put further and further back.

[karyo]

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images/euT2mMonNorm.gif

CFS update doesn't bode well for Dec or Jan....a warming trend

Yes, today's update is not very good!

However, I visit this link often and today is the first day it shows January above average so unless it may be a one off rather than a trend. We'll soon find out!

As for Kold Weather's comment, I would love to see a mid latitude high if we can't have the proper Artic blast. It would give some impressive inversions and save us from this Atlantic nightmare. Even Dec 2006 (el nino winter) had a cold anticyclonic spell.

Looking at the 6z ensembles : http://www.netweather.tv/index.cgi?action=ensviewer;sess=

the operational was a bit progressive in pushing the trough east but had some support. Importantly, the scatter in the ensembles is now beginning on the 12th December!

Karyo

[Polar Continental]

Good post, PC; that's exactly how I'm seeing (or, perhaps, not seeing them?) things just now. It's also why I'm not about the over-criticize the MetO's winter forecast; sometimes (IMO), uncertainty can be more revealing than, sometimes foolish, attempts at precision?

Exactly Pete, the wise will not state a mild nor cold for this winter.

Also, some of the more emotional and less experienced model watchers in here should take note, don’t take each run to heart. It can get very frustrating in any ‘normal’ winter, but this winter I think, they could suffer great anguish.

[karyo]

Noticing though the cold or more interesting charts though are in FI - isn't that just resorting to typical GFS in general in mild winters? and you usually find the cold is put further and further back.

During the first half of winter 06/07 (one of the worst I can remember)the models were showing zonal outputs from start to finish! I remember the depression and limited posts in the model discussion thread.

At least this year we're having some interesting possibilities...

Karyo

Edited December 3, 2009 by karyo

[Weather-history]

Yes, today's update is not very good!

However, I visit this link often and today is the first day it shows January above average so unless it may be a one off rather than a trend. We'll soon find out!

To be honest, I find those charts a waste of time.

[karyo]

To be honest, I find those charts a waste of time.

At the very least, the cfs charts are a bit of fun in a gloomy day!

Some trends can be identified though.

Karyo

[pyrotech]

Yes this is a continuation of a cold air mass arriving over Europe with GFS. Fi is really getting this trend going and it looks feasable even in Fi

The next week will hopefully continue this trend allowing the cold air to sweep accross Europe, yes it Fi but its consistancy and feasability make it fairly likely.

As for the COLD reaching UK, that will probably be on and off for a few runs but the potential is there. A very cold Europe will be a good start for the potential for the UK for prolonged cold. The last few runs with GFS have been consstantly cold in Fi but we all know that Fi can do a huge turnaround. Its the consistency that is interesting. Potential is huge, a deep low to south of the uk in two weeks time if that cold filtered towards us would have the forum on meltdown. The cold sweeping south looks pretty likely, a deep low forced south of UK would drag very cold air accross the Northern flank from Europe and give us amazing cold spell. Its all ifs and buts as its in Fi but its a huge start and much better outlook than two weeks ago. At least we now have some real feasable potential. Low, prolonged solar minimum has already effected many parts of USA, Hongkong and India with record low temperatures, Its causing all the models some headaches but they are now showing real what we should expect with the conflict of El Nino and solar min.

[phil nw.]

Chionomaniac has suggested 1987 with similar background signals and looking at the Archive you can see how a pressure rise from the South can start a change to cold.

We have the split vortex here with the trough across the North of the uk and a Swesterly flow.

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870105.gif

At that stage the pattern looked unexciting for cold it was all heading to Greece and the Balkans from Arctic Russia,here

http://www.wetterzentrale.de/archive/ra/1987/Rrea00219870105.gif

However 2 days later pressure ridged north linking with Heights to the NE ,

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870107.gif

2days further on and the main centre of the High transfer completed and centered over N.Scandi

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870111.gif

redirecting the bitter cold this way

http://www.wetterzentrale.de/archive/ra/1987/Rrea00219870111.gif

Obviously this time maybe different but it shows what could happen from a relatively mild setup where we have a split vortex and a centre towards Canada and cold air ready to our NE.

[Frosty.]

The meto update has dismissed the 6z output, staying unsettled until 17th December with temps up and down a bit, milder for the south for a while next week but then temps returning to near average with a risk of snow over the hills in central & northern britain, i'm a bit surprised, given their mention yesterday of more settled conditions later in the period which is what the gfs 00z-06z are showing today, they must favour the latest ecm 00z output which is unsettled throughout.

[Shiny_Bottom_1]

Indeed Frosty.

I did write quite a lengthy analysis (for me anyway) for the 06z.

Generally, I would say some good potential for the pressure to increase from week 1 to week 2.

850's are a little over the place in the same period, but 2m temps look like falling in line with the pressure rise (so would assume based mainly either average to below average 850's, or inversion with the high pressure even with above average 850's (I think inversion is the correct word - where high pressure creates below average 2m temps (December 2008?))

[mushymanrob]

They also suggest a bitterly cold airmass moving S out of the Arctic.

hi dave!

erm, if the arctic airmass moves, it HAS to move south!

charts look pretty usual to me, typical early winter with nothing much extreme on any horizon and with as much potential for a prolonged mild spell as a prolonged cold spell. tbh i wouldnt be surprised if we have the warmest crimbo on record, imho its only a matter of time.

but fear not, i for one dont think this current unsettled regime will last, it rarely does, im expecting a settling down at some point quite soon. this hunch is based purely on experience, ive no scientific data or any model hint to support this notion. the question is.... what type of settled weather will we get? mild or cold?

[Snowyowl9]

Todays chart is quite a strange one in how theres so much mild air about, but the -5c upper gets into the west/SW only.

http://91.121.93.17/pics/Rtavn062.png