Model Output Discussion: 12Z (02/12/12) And On...

[nick sussex]

Hi guys, im not a regular poster on here and certainly not in the models thread so here goes with a quick question which im sure most of you can answer. Alot of you mention convection over the sea/rivers caused buy the cold uppers, will the saturation of the land be taken into consideration from the models from a PPN point of view? There alot of swollen rivers and flooded land at the moment surely this will enhance convection amounts as the cold uppers pass over our island. Do the models look for this?

Theres really not the expanse of water available in the UK to develop that kind of convection.

If a ne/e flow develops though you do have the North Sea to provide the energy needed, in terms of the models they're pretty useless in convective type scenarios, in more frontal precip situations though they are a lot better.

[Frosty.]

Latest meto update keeps the wintry theme going which ties in with the latest gefs and ecm mean perfectly, the devil in the detail being the unknowns regarding amounts of snow but much easier to say there will be widespread sharp frosts and freezing fog at times. There could also be some problems this week with thurs/fri bringing more unsettled weather from the northwest with rain, sleet and snow, snow threat could upgrade depending on the angle of attack of that low as areas to the east and north may remain in sub 528 dam air.

Also, watch out for widespread snow showers to the far north and down the eastern side of the uk on tues night and through wednesday, northerly winds digging in for a time with heavy frequent snow showers, especially for northern isles and northern scotland, ne and e scotland, ne and e england bordering the north sea (probably not much inland penetration), icy.

Edited December 3, 2012 by Frosty039

[pyrotech]

Hi All

Just like to point out the slightly different treatment of events on the 5th December according to todays GFS and NAE

6z

What i find of most signifigance is before that on the NAE

Tue 04.12 18 GMT timescale, look at last 3 runs and you get three upgrades for snow over West Wales and North Devon, now this matters for all parts of the UK as it shows that cooler air is being upgraded on each run by the NAE. So on what i believe is one of the most reliable short term models we are getting constant upgrades with more and more rain being forecast as snow. The next run is vitally important as the 6z that you show above has widespread snow, we need to see a further upgrade in that and its game on.

With actual percipitation in the models beyond 36 hrs for snow i give very little notice on the models, all i look for really beyond that is the cold as the slight changes on the run up changes and has huge differences in regards to who actually gets anything.

[Frosty.]

Haha that's class, well done !! And as for us collides , lots of sleepless nights , nagging wives , square eyes , lots of drink , and a trip to B&Q for a wooden sledge !!

you forgot lamp post watching

I think the snow shower potential midweek is upgrading (for the usual areas most exposed to a Nly), as is the risk of snow for thurs/fri but that would be a marginal event away from hills but can't be dismissed.

Edited December 3, 2012 by Frosty039

[Frosty.]

should excite these already negative tendencies

my negative tendancies have become extremely positive in recent times which is reflected by the latest models and upcoming synoptics.

We are now witnessing some wonderful cold potential in the model output, the best since dec 2010, fingers crossed the potential will be converted into reality with a prolonged cold spell rather than the current cool/cold chopping and changing.

[Polar Maritime]

my negative tendancies have become extremely positive in recent times which is reflected by the latest models and upcoming synoptics.

We are now witnessing some wonderful cold potential in the model output, the best since dec 2010, fingers crossed the potential will be converted into reality with a prolonged cold spell rather than the current cool/cold chopping and changing.

Yes Frosty, It's been one of the best build up's to winter here on NetW this year. everything seems to be pointing in the right direction for some severe prolonged cold weather building over the next few weeks. Very exiting times ahead and for model watching, just booked my week in Scotland at start of Jan, and hopefully conditions will be excellent for winter climbing

[Jaffusmaximus]

Does any kind gentleman on here have a link to where I can view up to date NAO -/+ charts

[Wadey]

Hi All

Just like to point out the slightly different treatment of events on the 5th December according to todays GFS and NAE

6z

I take it the pink is snow ? As I'm from the west midlands

[Just Before Dawn]

Hi guys, im not a regular poster on here and certainly not in the models thread so here goes with a quick question which im sure most of you can answer. Alot of you mention convection over the sea/rivers caused buy the cold uppers, will the saturation of the land be taken into consideration from the models from a PPN point of view? There alot of swollen rivers and flooded land at the moment surely this will enhance convection amounts as the cold uppers pass over our island. Do the models look for this?

It probably won't make any difference Pipsta - it's not water that drives convection per se, it's the relative differences in temperature between two air masses. In the UK, that's usually associated with water, but not everywhere. In this scenario, the North Sea is warm enough to heat the air mass close to the surface as the relative difference in temperature between the sea and the air mass travelling over it might be 10-15c, as the air mass close to the surface warms, it rises and the water in it condenses, creating showers. This is probably superficial explanation (someone please put me right)!

In the case of flooded land, the water just isn't deep enough to create the disparity of temperature sufficient to heat the lower levels of air to encourage convection to take place. Nor are the areas flooded sufficiently large to start convection generation. Besides which, hopefully, the water levels will have subsided a bit in the next few days.

[weather eater]

But (and this is not an entirely rhetorical question), if you recall about a week ago the UKMO was rock solid in its consistency in giving very cold and unsettled weather this weekend just gone, and of course in the end, as many predicted on here, it bowed to the GFS and ECM. So does it not follow that consistency is not necessarily a good trait?

Perhaps the appropriate reply is that in the current scenario, all the models are singing from the same hymn sheet - it is not a case of one defying the others with its consistency. However, this is all a very long way off, and if you remember, at longer range the GFS and ECM were (at times - not consitently) agreeing with the UKMO, hence all the excitement on here.

I still consider it a little too far off to be too excited, although it's better to see what we are seeing than a promise of zonal dross, which seems nowhere near the cards.

There is no certainty in weather modelling, so being consistent is certainly no guarantee, anyone who remembers the consistently modelled easterly of a few years ago that then imploded when in touching distance can vouch for that. To say it scared model watching for a long time would not be an understatement. I would go as far as to say that many of the nervy posts from long term members that we see every winter can be traced back to that incident. However if you are not a real weather pattern expert then I would still look for consistency over models that are jumping around all over the place its as good a bet as any, and the GFS has been extremely consistent, not just in the short range either. Not long until the 12z and I would be more than happy to put a few quid on it being similar to its earlier runs.

[SnowBallz]

Be a good call that i think.im struggling to see past 96-120 hrs!!!

I see it as a bit macro ~ micro.

I'm not so much bothered about the variance in short-range, because - to me anyway - it's so predictable that it doesn't really hold much interest for me. What holds greater sway and interest for me, are background signals and teleconnections because it is those which set conditions to be conducive or not; cause and effect.

As we enter January, it would appear that we're looking to be in an excellent position, teleconnectively. That's where we want to be. Of course nothing is certain, but - to coin an analogy - if you want to build a house, then you first need to lay some foundations, and then have your tradesman on-hand. My understanding of Stewart's posting, is that the teleconnections are proposing strong foundations locking into place.

We all know that that doesn't guarantee anything. But it does work in our favour. Winter is 3mths, and we've only just entered the beginning of it, so there's plenty of excitement to come I'm sure. I'm extremely excited about this consistent signal which is appearing for the strong build of the Scandi high, and also the Siberian one. Shortwaves, as we know, can cause endless frustration, but re-amplification of background conditions look set to be 'the norm'.

Very interesting to see where we are in 10 days time; whether this Easterly will develop as we all so wish, or whether we'll have to wait a little bit further. The SR/MR models have been broadly consistent across 72hrs, in showing that this is a strong signal and the LR models are also resonating a similar, if not always identical, theme. So, we have some agreement here.

Remember, it isn't always about chasing the runs, one after the other; however exciting that can be - if that's your thing - I don't think it'll tell you a great deal about 'confidence', specifically whether throwing a party or shredding your nerves are justified. I just think we learn more through assessing the wider picture, over a number of days and a multitude of runs.

I think we can all agree though that - for once - we're starting a winter right on the front foot in terms of potential, and that's got to raise the excitement levels all around. Let's hope we maintain this momentum though the season, and - with any luck - we'll have some amazing stories and pictures to share at the end of it

[SnowBallz]

Does any kind gentleman on here have a link to where I can view up to date NAO -/+ charts

Can a gentlewoman help?

Here ya go (NAO):

http://www.cpc.ncep....index_ensm.html

Edit:

And the (AO) is there:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml

Edited December 3, 2012 by SnowBallz

[Jaffusmaximus]

Can a gentlewoman help?

Here ya go (NAO):

http://www.cpc.ncep....index_ensm.html

Edit:

And the (AO) is there:

http://www.cpc.ncep....ndex_ensm.shtml

Even better! many thx

[Dampdorset82]

I see it as a bit macro ~ micro.

I'm not so much bothered about the variance in short-range, because - to me anyway - it's so predictable that it doesn't really hold much interest for me. What holds greater sway and interest for me, are background signals and teleconnections because it is those which set conditions to be conducive or not; cause and effect.

As we enter January, it would appear that we're looking to be in an excellent position, teleconnectively. That's where we want to be. Of course nothing is certain, but - to coin an analogy - if you want to build a house, then you first need to lay some foundations, and then have your tradesman on-hand. My understanding of Stewart's posting, is that the teleconnections are proposing strong foundations locking into place.

We all know that that doesn't guarantee anything. But it does work in our favour. Winter is 3mths, and we've only just entered the beginning of it, so there's plenty of excitement to come I'm sure. I'm extremely excited about this consistent signal which is appearing for the strong build of the Scandi high, and also the Siberian one. Shortwaves, as we know, can cause endless frustration, but re-amplification of background conditions look set to be 'the norm'.

Very interesting to see where we are in 10 days time; whether this Easterly will develop as we all so wish, or whether we'll have to wait a little bit further. The SR/MR models have been broadly consistent across 72hrs, in showing that this is a strong signal and the LR models are also resonating a similar, if not always identical, theme. So, we have some agreement here.

Remember, it isn't always about chasing the runs, one after the other; however exciting that can be - if that's your thing - I don't think it'll tell you a great deal about 'confidence', specifically whether throwing a party or shredding your nerves are justified. I just think we learn more through assessing the wider picture, over a number of days and a multitude of runs.

I think we can all agree though that - for once - we're starting a winter right on the front foot in terms of potential, and that's got to raise the excitement levels all around. Let's hope we maintain this momentum though the season, and - with any luck - we'll have some amazing stories and pictures to share at the end of it

Agreed, The bigger picture is what we need to focus on. I watch the models and they really would confuse even the most experienced forecaster even within 7 days recently 1 run will tell you your going to be snowed in and the next run shows just cool conditions. However over the past couple of days there has been more consistancy between models and well worth focusing on later this week and high chance of a block forming early next week. Important to keep a close eye on the NAO and AO data that posts stronger signals. I dont usually ramp but im getting excited regarding January more especially because I live in Dorset where it snows in every other county but this one!

[AWD]

The 500mb anomaly charts show extensive northern blocking in week 2;

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/test8.gif

The GFS a tad more bullish in terms of the depth of heights to our north & trough to our SE.

[lewis028]

Looking at the 12z NAE +48, look at all the ppn in the North Sea that is falling as snow, could that low possibly move sw and cause a widespread snow event..

Good to see never the less!

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2012/12/03/basis12/ukuk/prty/12120512_0312.gif

Edited December 3, 2012 by lewis028

[Eskimo]

Looking at the 12z NAE +48, look at all the ppn in the North Sea that is falling as snow, could that low possibly move sw and cause a widespread snow event..

Good to see never the less!

http://expert-images...120512_0312.gif

It's possible but to me it's mostly just shower activity, you can see that the precipitation is heavier just along the coast...probably enhanced by offshore winds perhaps.

[Methuselah]

I see it as a bit macro ~ micro.

I'm not so much bothered about the variance in short-range, because - to me anyway - it's so predictable that it doesn't really hold much interest for me. What holds greater sway and interest for me, are background signals and teleconnections because it is those which set conditions to be conducive or not; cause and effect.

As we enter January, it would appear that we're looking to be in an excellent position, teleconnectively. That's where we want to be. Of course nothing is certain, but - to coin an analogy - if you want to build a house, then you first need to lay some foundations, and then have your tradesman on-hand. My understanding of Stewart's posting, is that the teleconnections are proposing strong foundations locking into place.

We all know that that doesn't guarantee anything. But it does work in our favour. Winter is 3mths, and we've only just entered the beginning of it, so there's plenty of excitement to come I'm sure. I'm extremely excited about this consistent signal which is appearing for the strong build of the Scandi high, and also the Siberian one. Shortwaves, as we know, can cause endless frustration, but re-amplification of background conditions look set to be 'the norm'.

Very interesting to see where we are in 10 days time; whether this Easterly will develop as we all so wish, or whether we'll have to wait a little bit further. The SR/MR models have been broadly consistent across 72hrs, in showing that this is a strong signal and the LR models are also resonating a similar, if not always identical, theme. So, we have some agreement here.

Remember, it isn't always about chasing the runs, one after the other; however exciting that can be - if that's your thing - I don't think it'll tell you a great deal about 'confidence', specifically whether throwing a party or shredding your nerves are justified. I just think we learn more through assessing the wider picture, over a number of days and a multitude of runs.

I think we can all agree though that - for once - we're starting a winter right on the front foot in terms of potential, and that's got to raise the excitement levels all around. Let's hope we maintain this momentum though the season, and - with any luck - we'll have some amazing stories and pictures to share at the end of it

Spot on, Snowballz!

[tonbridgemole]

Those minus 16 uppers look to be moving closer to the uk

[ITSY]

Beijing Climate Centre going for extensive northern blocking this winter. I can't seem to post an image with the type of file extension, but for those after it it is one Joe laminate floori's twitter feed

[snow drift]

Looking at the 12z NAE +48, look at all the ppn in the North Sea that is falling as snow, could that low possibly move sw and cause a widespread snow event..

Good to see never the less!

http://expert-images...120512_0312.gif

To soon to be looking for this kind of detail really but you never know. East side in better position.

[Timmytour]

Early days but tropical low a little less intense and low over Germany filling quicker.....this run could be more willing to push in something from the east...

[Interitus]

There is no certainty in weather modelling, so being consistent is certainly no guarantee, anyone who remembers the consistently modelled easterly of a few years ago that then imploded when in touching distance can vouch for that. To say it scared model watching for a long time would not be an understatement. I would go as far as to say that many of the nervy posts from long term members that we see every winter can be traced back to that incident. However if you are not a real weather pattern expert then I would still look for consistency over models that are jumping around all over the place its as good a bet as any, and the GFS has been extremely consistent, not just in the short range either. Not long until the 12z and I would be more than happy to put a few quid on it being similar to its earlier runs.

This is a misconception and not really the case as the ECMWF explain with regards jumpiness - http://www.ecmwf.int...cast_skill.html

"It is intuitively appealing to assume that a forecast is more reliable, if it has not changed substantially from the previous run. Objective verifications, however, show a very small correlation between forecast “jumpiness†and the quality of the latest forecast (see Figure 21). The “jumpiness†relates rather to the skill of the average of the forecasts"

On a related point, flip-flopping - this is not necessarily a bad thing as sucessive consistent forecasts can be because of correlations, a forecast which flips one way and another to give the same result showing agreement between less correlated forecasts can carry more weight.

http://www.ecmwf.int..._forecasts.html

"The order in which the “jumpiness†occurs can provide additional insights. According to Table 1 the likelihood that precipitation occurs seems to be about equal for the last two forecasts being consistent (R R -) or the last three “flip-flopping†(R - R). This might be because, although the last two forecasts are more skilful than the earliest forecast, they are also, on average, more correlated. What the earliest forecast might lack in forecast skill, it compensates for by being less correlated with the most recent forecast. The agreement between two on average less correlated forecasts carries more weight than two on average more correlated."

[Tom Jarvis]

i hope the south east will get some snow this week tha would be a nice star to winter. hope to have a whgit chismas as well>

just had a look at the track that the tropical low will take. it shows it doing a long loop towards morroco.

Edited December 3, 2012 by Tom Jarvis

[Summer Sun]

Beijing Climate Centre going for extensive northern blocking this winter. I can't seem to post an image with the type of file extension, but for those after it it is one Joe laminate floori's twitter feed

Is this what you were trying to post?