Model Output Discussion - 26Th Dec 21:25-->

[The PIT]

Just seen the BBC weather for the week ahead and you know what it looked nothing like the GFS would have you believe. Well Well

Snow in Wales and the midlands in the run up to new year then south of the M4 for new years eve and new years day.

You clearly missed the bit where he said we're not sure how North or how South the front will lie which ties in with the uncertainites of the models. The only place where it's sure to be cold is North yorkshire Northwards. More modeling watching required.

[chionomaniac]

You have to bear in mind that the presence of high pressure over Greenland will have the effect (it already is) of drawing the Siberian High further west. This is also being allowed to happen in respect of the flat west based -NAO pattern that GP mentions. I actually think that eyes could too easily go off the ball in respect of the intense cold pooling to the NE - as that is clearly, and almost insidiously, coming more and more into play.

As this happens it is going to get harder for mild air to advance very far north eastwards - and any attempted downstream ridging over europe (as an often consequence of a west based -NAO) is nullified on the basis that the flat southerly jet allows lows to invade europe, which is crucial for keeping cold air advection flooding back southwards and westwards as well as sustaining higher pressure above it to the north east

As much as the cold pooling reservoir looks to me like being underplayed - on the other hand the strength of low pressure to the south west is in danger of being overestimated and over progressed by the models.

We are seeing the first signs of an extensive NH high latitude block extending from Russia to Canada, and this does look like too-ing and fro-ing for some time yet. That is going to be extremely hard to break down.

After just having looked into the strat profiles and reported in the strat thread I do agree that things are looking quite rosy indeed.

[snowlover2009]

apart from the snow potential being discussed, no one has mentioned the wind speed. the stronger it is the more large drifting we will get and more severe the weather would be eh? what wind speeds should we pssibly expect, at least 30 miles an hour wind?

You clearly missed the bit where he said we're not sure how North or how South the front will lie which ties in with the uncertainites of the models. The only place where it's sure to be cold is North yorkshire Northwards. More modeling watching required.

yes indeed.

the ppn on bbc forecast showed midlands, wales and southern north of england under a lot of snow for two days.

[john mac]

Latest update from the met office.

UK Outlook for Friday 1 Jan 2010 to Sunday 10 Jan 2010:

On Friday, and over next weekend it is expected to be generally cold with overnight frosts across most areas and occasional wintry showers affecting northern and eastern areas. There is also a risk of some rain or sleet, which may be persistent at times, affecting parts of the south over the weekend. Drier across central and western areas with overnight freezing fog which may persist locally. The following week looks likely to remain cold or even very cold in places, although perhaps closer to normal in the far south at times. Wintry showers look set to continue to affect northern and eastern areas for the rest of the period. There will be a further risk of bands of rain or sleet affecting southern parts at times.

Updated: 1203 on Sun 27 Dec 2009

LOL covering themselves for every possible outcome, but this was to be expected.

[Duane S.]

Just had a bath and whilst lying there the general pattern is becoming clearer especially after reading the Met O forecast/GPs post. The details however remain very uncertain as you will see.

Basically the trend into January is for the AO to remain strongly negative and blocking to be the dominant player. However when GP says W based NAO and this sometimes moving east to west and west to east. What this basically means is the boundary between milder air to the S and colder air to the N will move up and down like a yoyo. If you have a W based NAO then this leaves you open to an attack from the SW and the boundary between the two airmasses moves further N. If the blocking then moves west to east and is centred over Greenland then the boundary moves further S and would include all of the UK. So if you live in Scotland and the far N of England chances are you will remain cold. However further S and you could see a spell of snow turning to rain or a spell of rain turning to snow.

However it isn't as clear cut as this suggests. Only 2 days ago the models didn't have this blocking transferring W with the blocking being centred over Greenland. However the past 48hrs have seen this blocking move further W hence why the risk of attack from the SW. So how do we know the models are correct this time and will this blocking see a W based NAO. The other thing to take into consideration is will the models trend towards bringing a bitterly cold airmass from the NE. If this happens the cold pool of air over the UK could deflect these LP systems.

So in summary the next 2 weeks could see Scotland/N of England remaining cold with further snow at times. Further S the risk of heavy snow but also possibly turning less cold with rain which could be shortlived as the cold air returns.

I shall be curious to see what snowfall amounts members like OON see next month. This also applies to members in live around the Pennines. If I had the money/time I would book myself into a B&B in Buxton next week!

I too have just returned from a bath and it is remarkable how much more clear things are during and after a good deep soak!

As is being repeatedly poined out, those in the North have less to be concerned about than us down South, certainly me sat here in the plughole of the UK! I think I may have to get used to cold rain a fair bit (not that I haven't had to already mind you) before getting in the action. As you say TEIS, we need the blocking to remain over Greenland and not amble off too far towards Canada as this would allow us open for attack and we want to be embedded in cold air countrywide for a true battleground scenario can take place. I also agree with Tamara about keeping an eye to our NE, the cold is building and could quite easily and relatively suddenly be dropped down towards us aka Jan 1987.

I really do expect the 12z and 18z to start sorting itself out and fall in line with the Euro, the GFS is out on a limb at the moment and the 06z just looks plain wrong, even in the very early stages.

All to play for and incredible model watching days ahead.

The 6z ensembles are all over the place: ridiculous scatter from the word go.

Ignore the run - bin.

Anyone know if GFS related discussions are referring to data problems? The synoptics on runs the past 24 hours are absolutely absurd with lows appearing out of nowhere, high pressures shifting 1000 miles in 2 days, and no relation to other model outputs.

Totally agree WIB, nothing to do with how poor it is for cold propsects, pressure systems just don't behave like that.

[Frosty.]

The 6z ensembles are all over the place: ridiculous scatter from the word go.

Ignore the run - bin.

Anyone know if GFS related discussions are referring to data problems? The synoptics on runs the past 24 hours are absolutely absurd with lows appearing out of nowhere, high pressures shifting 1000 miles in 2 days, and no relation to other model outputs.

Hi Richard,

A bit of artistic licence there with the hp shift of 1000 miles in 2 days but there are relatively large differences between the new gfs and the other models. The gfs parallel run was much praised recently but it may be suffering a malfunction or it may be right...the 12z runs will hopefully clear this mess up for better or worse.

Edited December 27, 2009 by Frosty039

[Methuselah]

Just a quick reminder to our younger members, who may be being a bit bamboozled by 'old codgers' (like me ) reminiscences of late '60s winters...

Contrary to impressions, those winters did not see the Thames frozen-over from November till March on a regular basis, or on any basis at all. In fact (unless I am mistaken) they were very similar to what this winter 'looks like' being (from models as well as teleconnections): cold snaps/spells alternating with mild spells...

And, also bear-in-mind that this is an El-Nino year - February and March have a better chance of providing colder/snowier conditions...Have patience!

[Rich_Clements]

Just a quick reminder to our younger members, who may be being a bit bamboozled by 'old codgers' (like me ) reminiscences of late '60s winters...

Contrary to impressions, those winters did not see the Thames frozen-over from November till March on a regular basis, or on any basis at all. In fact (unless I am mistaken) they were very similar to what this winter 'looks like' being (from models as well as teleconnections): cold snaps/spells alternating with mild spells...

And, also bear-in-mind that this is an El-Nino year - February and March have a better chance of providing colder/snowier conditions...Have patience!

The only reason the Thames didn't freeze in the 60's was because the old multi span bridges were removed to keep the flow moving.

[snowlover2009]

Just a quick reminder to our younger members, who may be being a bit bamboozled by 'old codgers' (like me ) reminiscences of late '60s winters...

Contrary to impressions, those winters did not see the Thames frozen-over from November till March on a regular basis, or on any basis at all. In fact (unless I am mistaken) they were very similar to what this winter 'looks like' being (from models as well as teleconnections): cold snaps/spells alternating with mild spells...

And, also bear-in-mind that this is an El-Nino year - February and March have a better chance of providing colder/snowier conditions...Have patience!

hi i know this is an el nino year, but if el nino sticks for summer, is there a chance of this coming summer next year being better. i know you could not possibly make detail but, i would just want to know with an el nino does it give better prospects for our summer. although sometimes i have heard if a la nina develops after an el nino, that this is not good for summer, which has resulted our previous summers to be very poor

[The PIT]

Thames always used to be frozen oh... no it didn't.

I was under the impression thta this winter was doing fairly well. Must have been dreaming about the white stuff and it's been mild and rainy.

The 06oz GFs has the mild air pushing well North. Time will tell. By the GFS had an upgrade on the 15/12/10. Or downgrade depending on how it performs in the next few weeks.

[john w]

Re Data issues.

I iterate that the christmas spoof of missing data is indeed that.

Long haul schedules on x-mas day are the same (virtually) as most other days. Im sure someone will now find a timetable to proove me wrong but the terrorist event on Delta flight from schipol to Detroit was a x-mas day trans atlantic flight!

Short haul schedules are less as aircraft may be at their hubs and so ground fees are less. Long haul he plane will make less of a loss flying 1/4 full! Also please remember that mid east - Schipol/Heathrow etc - North America flights still occur. Thus lack of data is not the issue. More likely is that perhaps the NOAA and others do not have the same manpower accepting data and inputting them in to models.

Of some interest, and I reiterate this. Over the North Atlantic Planes fly what are know as NAT tracks. They start when the UK airway system ends and they end where Canadian, Icelandic or North American Airways commence. The NAT tracks are set by shanwick and Gander. Generally East based NAT tracks follow the jet west based tracks generally will be North of the jet. If the jet is pronounced North they will be South.

Now as the jet has been so far south arc routes have also been further South. Therefore the number of aircraft (not the number of flights) flying over Greenland and Iceland is likely to have reduced because the NAT tracks are further south. These probably exist on the web somewhere.

This is the only relative example I think that data may be a problem for. If the jet was northerly, the routes would be more North. Found this http://www.turbulenceforecast.com/atlantic_eastbound_tracks.php detailing Eastbound tracks and http://www.turbulenceforecast.com/atlantic_westbound_tracks.php showing westbound. West tracks are definately further South and aircraft taking the most Northerly track are likely to be Canada/West USA ----> Germany East and beyond.

Not really related to models, but interesting regarding data perspective. No NAT tracks take craft at the moment over any of Greenlands Landmass.

[rmc1987]

I see the Met Office have a weather warning out level 'be aware' for Wales and West Midlands for heavy snow accumulations between 5-20cm with a strengthening easterly wind causing drifting. So it seems there is some degree of confidence that the snow will fall around that area - that's as far South as it's getting. In a few days this forum will be bedlam building the excitement!

IS this the general picture the models are painting? I have come to the conclusions that Midlands Northwards will be the snowy areas. South of the South Midlands rain/sleet with a risk of flooding and ice. Nothing in the way of snow, unless the models change a bit?

Now that's what I'm getting from reading this forum. I can't really read the models to make an informed decision but by other posts the above is what I've come to. I do not expect any snow here, from this event here or any further South sadly. Maybe Oxfordshire will get a bit though turning increasingly to sleet as one heads South?

[Sawel]

I think some people need to relax and not take every single GFS run as the gospel. Let's get the facts straight...

Some people are too hung up on what the GFS shows because it runs out 4 times a day and we can access the entire run out to +384 hours including precipitation charts and temperature charts and pretty much everything associated with it as it's free to the public.

The GFS verifies 4th out of all the models. It is behind the ECM, UKMO and the GEM. We only have limited access to the UKMO and the GEM so some people ignore what the say despite the fact that they verify better than the GFS. Someone posted earlier about the "big two" when referring to the ECM and GFS, how wrong that is...

These verification stats tell the story. The ECM has been the best model this past 10 days at 120 hrs, very consistent to say the least.

http://www.emc.ncep.noaa.gov/gmb/STATS/html/acz5.html

Come on people, stop wrist-slitting after every single GFS run.

Edited December 27, 2009 by Sawel

[snowlover2009]

I see the Met Office have a weather warning out level 'be aware' for Wales and West Midlands for heavy snow accumulations between 5-20cm with a strengthening easterly wind causing drifting. So it seems there is some degree of confidence that the snow will fall around that area - that's as far South as it's getting. In a few days this forum will be bedlam building the excitement!

IS this the general picture the models are painting? I have come to the conclusions that Midlands Northwards will be the snowy areas. South of the South Midlands rain/sleet with a risk of flooding and ice. Nothing in the way of snow, unless the models change a bit?

Now that's what I'm getting from reading this forum. I can't really read the models to make an informed decision but by other posts the above is what I've come to. I do not expect any snow here, from this event here or any further South sadly. Maybe Oxfordshire will get a bit though turning increasingly to sleet as one heads South?

i agree, but the pressure system pushes south so snow will coem for the far south anyway.

[NorthNorfolkWeather]

Just had a bath and whilst lying there the general pattern is becoming clearer especially after reading the Met O forecast/GPs post. The details however remain very uncertain as you will see.

TOO much information, just in the first sentence

Seriously, you make some very good points, especially about the cold to the NE of us. To me, it looks as though there is quite a pool of -18 (or colder) 850hp air already over Finland/Northern Sweden, temperatures for southern Finland, currently are between -8 to -16, but as low as -30 in the north of the country, this is certainly colder than the norm for the last few years. The Baltic is now beginning to freeze as well, usually a good sign if we want good cold air from our northeast.

And I keep reminding people that it is still December, the worst of the cold usually happens January or February.

[rmc1987]

i agree, but the pressure system pushes south so snow will coem for the far south anyway.

Far South, do you mean South West? So basically this snowy mass will head over Bristol/Bath Southwards and peter out I guess?

[Hammer]

I think as some have previously said this is very much a knife edge situation, with a return to widespread mild in no way completely out of the question in the early part of the New Year. However, with such profound short and medium term disagreement it's almost impossible to have any confidence at all in the longer term pattern, but for my money a return to rather more average conditions for most will probably emerge as the likely favourite by mid week.

So in summary. With the short term proving difficult to call and medium to long term forecasts almost impossible to call even for pro mets. Your calling for average. I suspect that might be the safest assumption. But for me the models disagreements even at shorter time frames is a reason for people to not look to far ahead. Later today and during tommorrow is certainly a time I expect to see some very interesting developments towards both clearer picture of the mid week, but also of an interesting new years eve and day period.

[J10]

TOO much information, just in the first sentence

Seriously, you make some very good points, especially about the cold to the NE of us. To me, it looks as though there is quite a pool of -18 (or colder) 850hp air already over Finland/Northern Sweden, temperatures for southern Finland, currently are between -8 to -16, but as low as -30 in the north of the country, this is certainly colder than the norm for the last few years. The Baltic is now beginning to freeze as well, usually a good sign if we want good cold air from our northeast.

And I keep reminding people that it is still December, the worst of the cold usually happens January or February.

Slightly off topic but it would be nice to have a cold snowy January for once (in terms of the past decade). The building blocks seem o be coming together, but will everything come together.

[yamkin]

Very interesting WNC - Moscow 00Z 84h charts

[NorthNorfolkWeather]

Hi Richard,

A bit of artistic licence there with the hp shift of 1000 miles in 2 days but there are relatively large differences between the new gfs and the other models. The gfs parallel run was much praised recently but it may be suffering a malfunction or it may be right...the 12z runs will hopefully clear this mess up for better or worse.

I couldn't agree more. When the GFS Parallel was going, the model seemed consistent and believable, with the possible exception of it being too progressive. Now, it's all over the shop, really strange, switched from Parallel to Main run, consistency seems to have gone out of the window.

Excellent post, by john w, about the Tracks that the planes are flying being further south due to the jet being further south, I wonder if that does affect the data collected?

Edited December 27, 2009 by NorthNorfolkWeather

[snowlover2009]

Very interesting WNC - Moscow 00Z 84h charts

how accurate are moscows runs?

[yamkin]

how accurate are moscows runs?

Not sure how accurate WMC is, but Moscow are used to winter model runs for their neck of the woods, so their model runs for the UK can not be ruled out.

[snowmadchrisuk]

Not sure how accurate WMC is, but Moscow are used to winter model runs for their neck of the woods, so their model runs for the UK can not be ruled out.

Over the last few days they have had -40 850's over me .. there run can be discounted on 850's full stop. It shows extremes all the time.

[Barb]

Latest NOGAPS looks fine:

Basically no model remotely agrees with GFS. Even the small ones.

Edited December 27, 2009 by Barb

[bluearmy]

the GFS output at the moment taken in context with decent GEFS fi consistency is strange indeed and shows how complex a situation we are approaching. i wouldnt rule anything out beyond the approach of the occlusion mid week.