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

[snowingman]

Oh dear

I sense the optimism is waning in the South

The shift north of the cold barrier and hence the snow is continuing, in addition over the past 72 hours the timeframe for coldness is also being pushed back.. first its was Tuesday, then Wednesday now next Friday until cold air swamps the country once more

YES - if yo live above 300m from North England northwards - or in the whole of Scotland to Sea level, perhaps N Ireland above 300m, otherwise lots and lots of cold Rain on its way next week,

Only glimmer really is that pressure remains highish right across North from Canada through to Siberia - producing a strong flow of easterlies - they are bound to encroach further south..

ah well

It was the Xmas day charts and the wine that got me going.. at least for 24 hours anyway

role on mid January

[john mac]

Well GEM shows blizzards down to the South coast while GFS has snow only for N. England/Scotland. Pretty big difference at just 3 days out I think.

The GEM IMO has been consistant with its outputs in this situation, it is giving itself good credibitlity as long as its outcome is correct.

[nick sussex]

Hi Nick.

Yep that's how I see it. A better GFS run up to the mid term than the 00z in terms of a prolonged long spell. Although I must say the spoiler could well be an advancing ridge from the south, a trend that has been rearing it's ugly head recently. We need to see that Northern blocking not get too far North.

There are alot of variables here, with so many teleconnections the models are likely to implode!part of the problem is what happens over the eastern USA in terms of the troughing, what we want is the PV and troughing near Canada to block the Greenland high from wanting to retrogress further west, this then allows the pulse north in the jet to come at exactly the wrong moment and wrong location, then you add in that feature near Norway heading southwest in some of the output, you need this to head se to allow ridging from the Siberian high to push west and help sink the jet further south, it's a difficult and complex set up which will lead to model meltdown!

Edited December 27, 2009 by nick sussex

[SMU]

Interesting today that the ECM has moved back to a more southerly solution- its rarely wrong @72 ......

All to play for along the 12z runs-

Steve

Edited December 27, 2009 by Steve Murr

[Barb]

GFS has the atlantic smashing in by 2nd of Jan. Personally I think it's lost the plot, especially considering the OP was big mild outlier in FI on the 00z. Or it's somehow picked up something none of other models have.

[swilliam]

ECMWF model to 240 hours

Rating meteorologist

Sunday, December 27, 2009 09.49 hours, valid from Monday, December 28 to Tuesday 05 januari

Synoptic development

The focus has to do with a southwesterly flow over. The layer responsible for the flow around Ireland attracts the north east coming days and will at the beginning of the week for a temporary westerly flow. A low pressure area over the ocean east and pull remains lie southwest of the United Kingdom. A core pulls east on Tuesday for the Benelux and provides an easterly flow. Simultaneously drops a new low height above the ocean south and ensures that the flow is again southwest. This low altitude over the next weekend Benelux attracts then further east. After passage over the northern flow.

Model Assessment and uncertainties

DThe uncertainty is particularly great because the focus is close to an air mass boundary where small differences yield a completely different weather. This process takes place in the coming period on two moments off. The first was Tuesday when our country is in a saddle area and a failure to pull the Benelux. The second time is next weekend, when a low pressure core of our country attracts. For both events is that small timing differences or position have significant impact on the weather. There is only 1 tube is present. This indicates that the diversity in the solutions is not as large scale is very large, but clearly (also seen in the plume, especially on Tuesday and next weekend so) that there are several possible solutions. Since even small differences in our surroundings has a major impact on the type of precipitation at temperatures around zero. The cluster plates allows the bulk of the members (90%) a more or see more westerly airflow over. Even here in the assessment should be included in the model that the snow is not good. In the initial situation in our country is still at least 20 cm, with also a relatively large area with 50-100 cm. The model is really not that snow melt away until Tuesday. This has very much influence on the temperature in the saddle area for at least Tuesday night!

Notes to adjustments in Table

Temperatures at the beginning incremented (both Tx and Tn).

Summary multiple day period

Many clouds and precipitation from time to time, starting Tuesday with a winter nature. Afternoon temperatures gradually lowered, the night's most progressive light frost.

Summary period EPS

Probably a transition to a more winter weather with temperatures slightly below normal values.

Sorry about the translation but this was done by Google not me. When you cut and paste the page you get both the Dutch and English. I have deleted the Dutch for you this time. To find this you need put KNMI in Google and ask it to translate for and the navigate to the ensemble page. If you go direct to the KNMI site and use their English translation the discussion pages do not seem to come up (unless I have missed something). Could be useful when we want a professional opinion about the models.

It seems they have a large area with >0,5m of snow and think this will have a major influence on the next weeks weather. They are also saying that there is a lot of uncertainty boty for next week and the following weekend.

2nd there is also a detailed 48 hr discussion

<br style=""> <br style="">

Weer Weather

Models generally 48 hours

Rating meteorologist

Sunday, December 27, 2009 08.41 pm, valid until Tuesday, December 29, 2009, 00 UTC.

<br style=""> <br style="">

Guidance weather for the Netherlands, the Dutch coastal waters and the North Sea based on the HIRLAM run from 00 UTC and the other models listed and directories associated with runtime.

Assessment Models

Synoptic SITUATION:

A low pressure area west of Scotland the next day to pull the North Sea and then to the south of Scandinavia. Associated cold front lies over the Frisian Islands. Golf Training over English Channel makes the front pulls slowly eastward. This afternoon in front pulls the declining activity over our country to Germany. In the night from Sunday to Monday passes the occlusion of previously known low and the flow turns to northwest. After we benefit from temporary high pressure influence.

MODEL ASSESSMENT:

The output is consistently large. The pressure and precipitation fields show great similarity between EC18, UKMO00 and GFS00. In the boundary layer, there are concerns.

Considerations

WIND: WIND:

Along the West Coast 6 to 7 Bft. Monday coast no longer signals.

CLOUDS:

Increasing clouds on the approach of cold fronts (including ST). Near the cold front with high CSF basis (potentially unstable). Sunday (especially in the afternoon) in the entire country several CSFs. Monday spells behind the occlusion with a single CB (peaks FL200). For HiRLAM fog late Monday night and ST arise. This seems unrealistic because HiRLAM too cold (see merged time series). There is probably a snow expected.

RAINFALL:

Scattered showers extending over the next day the country. Suggestion of sleet / freezing rain in NESO fields. We honor not because the models are too cold. When it is cloudy, the temperature drops are not as strong. Possible smoothness by opvriezing during spells.

: VISION:

Well.In moderate rainfall.

TEMPERATURE:

Hir DMO is too cold (see merged time series). Prog Temps have a stable thick cold layer. In the source region is less windy and colder than in the Netherlands. KTG provides a good indication. Tx Sunday around 5 degrees. Tmin monday 3 degrees, Tx Monday, 4.6 degrees.

I like the golf training over the English Channel<br style=""> <br style="">

[SilverWolf]

Well GEM shows blizzards down to the South coast while GFS has snow only for N. England/Scotland. Pretty big difference at just 3 days out I think.

Not so sure about this - I don't understand a lot of the models tbh, but these differences don't strike me as that unusual with 3 days to go. Perhaps we're all personalising the affect 200 miles can have! Trust me I've been guilty of that with regards to snow many times

[Guest North Sea Snow Convection]

Last post before I pop to bed.

Im going to stop being cautious and post what I think will happen.

What Tamara said earlier was spot on in my opinion. I think the models are over playing these SW and underestimating the blocking. I also believe the LP will eventually be further S. As I was saying yesterday the chances of an E,ly are now far greater than a N,ly via a Greenland HP. The link between the GH & SH is certainly appearing in the models and I reckon the blocking will eventually be further S. This might not appear straight away in the models but I think it will be the eventual outcome.

There are far more positives in the models than negatives and this is something members need to remember. We don't have a PV centred over Greenland. We have the AO which is off the scale and we have the NAO ensembles suggesting an index of -2. I have also witnessed one of the best cold spells in recent times and the lying snow I had on Xmas day was the first time in 28 yrs.

Picking up this post from last night and what we were saying about over playing of shortwaves etc. The GEM and ECM have gone on this morning to show the sort of very cold easterly that we were suggesting. Without the overcomplications and erratic inconsistencies of the GFS.

Obviously the GFS can't be ignored, but as of now it is so out of kilter at such an incredibly early stage - one has to wonder about these data issues, even if we are now officially in the post xmas period. The GEM especially, has been very consistent for at least a couple of days now in keeping the low further south and allowing the easterly in afterwards. ECM has blinked a little, but has not been far behind - and now indicates the sort of very cold easterly that we have been looking for. Furthermore, the ECM ensembles are very encouraging to underpin snow and cold.

There is not model agreement yet, but I think the pattern is being made to look far more messy and unconvincing purely through the antics of the UKMO of late with its erratic northward positioning of the low, and as stated the wayward GFS which has only served to stress certain NW members.

As Carinthian has said, I would expect full model agreement later in line with the ECM and GEM of this morning.

Edited December 27, 2009 by North Sea Snow Convection

[TEITS]

I'm not sure ECM and the GFS 06 are a million miles apart at T+72hrs and even UKMO shows a very similar set up at this time.

As far as the south is concerned it may well be NYE or even NYD before the proper cold air arrives and looking at the T+120hrs I wouldn't expect it

to hang around very long either, with nothing really developing over the UK to stop milder air moving back slowly NE'wards once again.

Relatively speaking there isn't that much difference. However the actual weather would differ hugely between the ECM/GFS at +72 especially for those in the Midlands/Wales.

http://91.121.94.83/modeles/gfs/run/gfs-1-72.png?6

Looking at the +72 to +144 charts and to be honest these couldn't differ from our normal weather patterns if they tried. We have an E,ly stretching from Siberia to Canada thanks to the link up between GH & SH. We also see 1050mb HP in the Polar region!!

The GFS is doing its usual thing and if you think back our previous cold spell should of finished on the 22nd Dec and yet it still continues in Scotland.

Personally im doubting all the models at the moment and this even includes the GEM/ECM. We cannot even begin to wonder what will happen at +144 if the pattern as +72 is uncertain.

[Cecil Hogmanay Melchett]

It's very easy and very convienient to dismiss charts that you don't like the look of, just as it's very easy and very convienient to shift FI around between 24-180hrs when the situation requires it, but IMO there is a strengthening signal that any cold weather in the south will be short lived across the New Year period.

This is not to say things can't and won't change across the next 6-8 runs and it's not saying other models like GEM that show a much deeper and more protracted spell of cold weather are wrong. However I think the MO will be less bullish re cold today, both with their Countryfile output and their 6-15 day outlook later today and therein will lie the biggest clue to diminishing confidence in the spell.

I think the meto will be very bullish,ecm has cold air flooding the country and its ensembles look very cold.

If meto go with ecm the update will be very good imo.

[Stu_London]

Disappointing but not entirely unexpected output this morning but it is only output and a number of scenarios remain in play.

It does look like there will be snow line somewhere with the front on Tuesday and a period of at least 48 hours where the whole of the UK is in a cold regime also looks likely thereafter.

However, the probable breakdown from the south west would be a bit of a let down given what is going on with blocking to the north.

It's very easy and very convienient to dismiss charts that you don't like the look of, just as it's very easy and very convienient to shift FI around between 24-180hrs when the situation requires it, but IMO there is a strengthening signal that any cold weather in the south will be short lived across the New Year period.

This is not to say things can't and won't change across the next 6-8 runs and it's not saying other models like GEM that show a much deeper and more protracted spell of cold weather are wrong. However I think the MO will be less bullish re cold today, both with their Countryfile output and their 6-15 day outlook later today and therein will lie the biggest clue to diminishing confidence in the spell.

I think that this is a sensible post, however it does probably open you up to personal attacks from people who dont like the content.

[grab my graupel]

Morning everyone

Once again, the Moderating team is having to remove too many posts from this thread.

Rather than have your post deleted, please think whether it might be better suited to the Model Moods thread first

Doing this will save your and the team's time.

Thank you

Brian

[scott_anthony_glasgow]

Going by the models look like Scotland could be in for some serious snow winters like this just arent ment to happen anymore!cheers

Scott

[Guest North Sea Snow Convection]

Relatively speaking there isn't that much difference. However the actual weather would differ hugely between the ECM/GFS at +72 especially for those in the Midlands/Wales.

http://91.121.94.83/.../gfs-1-72.png?6

http://www.meteociel...M0-72.GIF?27-12

Looking at the +72 to +144 charts and to be honest these couldn't differ from our normal weather patterns if they tried. We have an E,ly stretching from Siberia to Canada thanks to the link up between GH & SH. We also see 1050mb HP in the Polar region!!

The GFS is doing its usual thing and if you think back our previous cold spell should of finished on the 22nd Dec and yet it still continues in Scotland.

Personally im doubting all the models at the moment and this even includes the GEM/ECM. We cannot even begin to wonder what will happen at +144 if the pattern as +72 is uncertain.

As stated above, as as we had agreed at the time Dave - I still expect the GEM/ECM to be right. I am talking about from t72 here - which in turn makes everything else plausible as a solution.

What will be will be - but I will be very surprised indeed if that isn't the case.

Edited December 27, 2009 by North Sea Snow Convection

[Terminal Moraine]

It seems ironic and rather strange that the GFS 06z has the low moving further north into the Irish Sea than on the 00z but the mild air is acutally held further south for longer and there is a greater chance of snowfall across the north Midlands, and places north, on this run than on the last, even though on the face of it it's more progressive; the cold air also returns more quickly.

You can just tell that this one is going to go to the last 24 hours or so before it's resolved.

[TEITS]

It's very easy and very convienient to dismiss charts that you don't like the look of, just as it's very easy and very convienient to shift FI around between 24-180hrs when the situation requires it, but IMO there is a strengthening signal that any cold weather in the south will be short lived across the New Year period.

I have to say but aren't you doing exactly the same as what you describe above. When you say "there is a strenghening signal that the cold will be short lived" this means you are ignoring what the ECM/ensembles are saying. What makes you think the GFS is correct and the ECM is wrong.

Forgive me but didn't you recent post the GEM model because it was showing a downgrade. How come you aren't focussing on the GEM output this morning or the GME?

Im sorry but you seem to focus on any model that suggests mild. I bet if the GFS trends back to cold but the NOGAPS goes with a mild SW,ly you will be posting the NOGAPS model. This is very odd behaviour for someone who prefers cold weather.

A fair assesment of the models without bias is the future model output is very uncertain due to the large differences between the GFS/ECM. Nobody at the moment whether they prefer mild or cold can say what the outlook will be.

[Guest North Sea Snow Convection]

What is of note on ALL the models is the intensely cold air that is being shown now over North East europe and Scandinavia. As much as there is talk of this imploding for the UK, it won't take much either for us to be suddenly looking at a Feb 91 or Jan 87 type real freeze.

The chances of such an occurence are steadily increasing at this time. Should we get that model agreement for an initial easterly, then output from around t144 onwards could start to look quite different and ever more exciting.....

[Gavin P]

At T72 GFS is pretty much on its own in relation to how far north it pushes that low pressure;

http://www.wzkarten.de/pics/Rtavn721.png

Vs

http://www.wzkarten.de/pics/Recm721.gif

http://www.wzkarten.de/pics/Rukm721.gif

http://www.meteociel.fr/modeles/ukmo2.php?ech=72&carte=2000

http://www.wzkarten.de/pics/Rgem721.gif

http://www.wzkarten.de/pics/Rgme721.gif

http://www.wzkarten.de/pics/Rngp721.gif

Either GFS has got it right and all the other models are wrong or GFS has gone off on a tangent.

Edited December 27, 2009 by Gavin P

[Barb]

Has anyone looked at the Fax charts for 72/84 hours? They look pretty great to me for more southern areas, though I am not an expert. Looks nothing like the GFS. Expert opinion?

Here:

http://www.meteociel.fr/modeles/ukmo2.php?carte=2000&ech=0

[carinthian]

Right, we have now entered the all important 72 hour prediction period. The UKMO have all the best numerical forecasts at hand this morning including snowfall models in place. Its that forecast which is going to be best placed.Active fronts are often easy to position with-in this time span, but may diffuse or become slow moving. For the progess of the front as shown by the latest 06h GFS to be rejuvenated at that pace , a secondary depression has to be in existance. Its simple not there. Back the Exeter boys today folks !!!

C

Edited December 27, 2009 by carinthian

[West is Best]

The 6z looks like synoptic nonsense to me: bin it. GFS has got problems. Some of the developments are utterly implausible.

Suspect there'll be big scatter with the operational problem out on its own at times.

Stick to the euros for now which show: UKMO marginal but interesting. ECM excellent. GEM superb.

[stewfox]

Is a 200 mile difference 72 hours away really a huge disagreement?

Exactly my thoughts. There isnt a 'huge disagreement' we are talking at T72 100/150 miles variation.

Its huge if you live on the M4 but not of your looking at the wider trend

Too much now casting when T72 is almost F1

[Cecil Hogmanay Melchett]

Not to bothered about that to be honest Stu, it's more important IMO to bring a bit of balance to the discussion, especially for new members that read 99% of the posts and think another bitterly cold spell has already been rubber stamped.

For the record tho I still keeping a very open mind on the eventual outcome. I think few can genuinely deny that the current set up means all models are struggling for both consistancy and accuracy, but on the other hand I think a clear trend has emerged across the last 24-48hrs that suggests getting and then locking in another protracted cold spell across the south will be anything but easy/guaranteed.

er,who said a bitterly cold spell is rubber stamped.

Lets hope gfs is wrong but the truth is none of us know!

[Altostratus]

The model outputs are better than I was expecting this morning. The ECM and UKMO have both improved with the low further south. It is about time we see a run like this from the ECM, as this is a better reflection of the ensemble suite. The GFS looks wrong to me and I wouldn’t be surprised to discover it is an outlier. Regarding data issues, I think this is being blown out of proportion. I expect we are just seeing the inherent over-progressiveness of the GFS again. A good rule of thumb is to tone-down and moderate anything the GFS shows.

[Weather-history]

People across northern England, north Wales and north Midlands will be snowed in for the New year if the control run was to occur

http://91.121.94.83/modeles/gens/run/gens-0-2-114.png?6

http://91.121.94.83/modeles/gens/run/gens-0-1-114.png?6

http://91.121.94.83/modeles/gens/run/gens-0-0-114.png?6