Model Output Discussion - 28th November

[Paul]

Please continue the model related discussion in here, if you want to have a moan about 'downgrades' or whatever else please take a look at the winter moaning thread:

We also have a new thread up and running as an experiment - the model thoughts and summaries thread is for you to copy your more lengthy / summarised model thoughts to, so that there is also a slower moving model info type thread for those who struggle to keep up in here!

http://forum.netweather.tv/topic/75105-model-thoughts-summaries-27th-nov-onward/

[Ice BIast]

Remember, there is still lots of time for change. A model that shows this is the NAM, which for a second consecutive run has the deep low in a very different and better position than all the other models. It would result in more WAA being drawn north. And remember, its a high res model, so its something to keep an eye on IMO.

NAM:

GFS:

[EML Network]

Looking into the more reliable time frame ? (+ 96) ..although even + 96 isn't all that reliable ...here's the latest offerings from the FAX ..is that snow I see for parts of the west ??

[john mac]

I think we need to compare the 0z with yesterday's and then 12z with yesterday's 12z then you would get a better idea. Taking each run at face value just doesn't work!!!

[NorthernRab]

The Northern Hemisphere charts continue (i.e consistent pattern across many runs) to paint a positive picture synoptically, so lots of potential and a very pleasing starting point to winter!

[Jonan92]

Remember, there is still lots of time for change. A model that shows this is the NAM, which for a second consecutive run has the deep low in a very different and better position than all the other models. It would result in more WAA being drawn north. And remember, its a high res model, so its something to keep an eye on IMO.

Amazing! That little things can change everything

[bluearmy]

Looking into the more reliable time frame ? (+ 96) ..although even + 96 isn't all that reliable ...here's the latest offerings from the FAX ..is that snow I see for parts of the west ??

Maybe before the T84 superceded it !

[bradymk]

Can't understand some posts in the older thread this morning? For me, another good run from the ECM, with a low diving SE through 216 and the cold pool still to our NE, just. But overall, not a bad run.

[nick sussex]

I think the slider low is now likely to turn into a damp squib for most with the ridge to the ne giving in very quickly, after 144hrs i'd bin all the operational output because we now have these sub-tropical lows on the scene which are likely to throw a curveball into proceedings.

Its very difficult to say where these will track and where they will phase with northern stream energy coming out of the USA. The ECM reverts from its winter wonderland of yesterdays FI to show potential again but really we're going to have to wait and see.

I'd expect even more model volatility now, the NH pattern does have potential but I think most people would now like to see this translated into tangible effects on the ground.

[Severe Siberian icy blast]

Lets not get hung up on each model every day please guys, we no how frustrating it can be , but in reality it will look completely different in 24hrs again so what does that tell you , any run that shows a strong PV and the Atlantic express alive and kicking is not going to happen, remember this is a massive pattern change there struggling with and it's no good looking in detail in fi, also take no note of upper air, do you think the pro's spend hours looking at the air temp at 850hpa what's 150hrs away?? I doubt it very much . Rather they look at trends, where's the general air coming from ? Where are the blocks likely to be sitting? Does what's showing go together with the strat profile , and the main drivers behind the scenes ? No doubt that's what we look at , pay very little attention to upper air , just look at its origin for a guidance.

Remember also we actually don't need 850hpa to be -5 to get snow, I remember last year we had snow on one occasion when we had a low from the south and we had upper air of around -2,-3 and we got forecast 10cms of snow, it actually didn't happen due to the ppn dieing out over the top of us but it did snow before it petered out but we had a cm rather than 10 lol. But take the moral of the story out of it pls.

[bradymk]

I think the slider low is now likely to turn into a damp squib for most with the ridge to the ne giving in very quickly, after 144hrs i'd bin all the output because we now have these sub-tropical lows on the scene which are likely to throw a curveball into proceedings.

Its very difficult to say where these will track and where they will phase with northern stream energy coming out of the USA. The ECM reverts from its winter wonderland of yesterdays FI to show potential again but really we're going to have to wait and see.

I'd expect even more model volatility now, the NH pattern does have potential but I think most people would now like to see this translated into tangible effects on the ground.

I know the first low will be a bit cold and damp but the second one, because it is a lot more to the south, will it bring alot more snow potential? I know FI is at 144 but that low at 216 is south of the country and looks interesting from my point of view. Is that where we need to see the low at 144? Thanks

[Frosty.]

I just looked through the GEFS 00z mean and there is nothing mild at all, what it shows is a predominance of polar maritime, some arctic, even some continental arctic but no tropical maritime, the polar front jet remains well south, the azores high does not stick it's nose in, we are in rather cold/cold/very cold air for the next 2¼ weeks at least with plenty of opportunities for snow beyond this week, frosty and foggy at times and quite a few wintry showers to all areas at times but especially for N/E coasts. The jet become tilted nw/se, high pressure builds in mid atlantic, we have a cold complex trough over the uk and further east for long periods. And from the pattern shown, there is potential for a severe wintry spell to emerge.

[nick sussex]

I know the first low will be a bit cold and damp but the second one, because it is a lot more to the south, will it bring alot more snow potential? I know FI is at 144 but that low at 216 is south of the country and looks interesting from my point of view. Is that where we need to see the low at 144? Thanks

The first low is agreed on now in terms of approx track, that cant end up to the south towards Iberia.

The second low shown by the ECM that depends on how much cold is left to the east, if you have enough of that as the low heads se the flow turning more from the east as it clears will import lower dew points and could see some back edge snow, of more importance though is getting lower pressure in the Med.

Once that happens if the upstream pattern remains amplified then you get a ridge building to the north or ne of the UK.

I would stress though that I'd be very wary of anything shown outside of 144hrs, as you can see from looking at both the GFS and ECM they both handle that sub-tropical feature differently.

[Paul]

Can I make a request - if you feel the need to start a post with something along the lines of "Sorry, I know this is off topic" or "This will probably be deleted but..", please don't make the post. You clearly know it's off topic, know that there is a better place to make it so please go and make it there rather than in the model thread because you can't be bothered to click the mouse a few times!!

[weather eater]

I think the slider low is now likely to turn into a damp squib for most with the ridge to the ne giving in very quickly, after 144hrs i'd bin all the operational output because we now have these sub-tropical lows on the scene which are likely to throw a curveball into proceedings.

Its very difficult to say where these will track and where they will phase with northern stream energy coming out of the USA. The ECM reverts from its winter wonderland of yesterdays FI to show potential again but really we're going to have to wait and see.

I'd expect even more model volatility now, the NH pattern does have potential but I think most people would now like to see this translated into tangible effects on the ground.

Morning Nick, I think the low slipping further south was always a forlorn hope, plenty of posts over the last couple of days suggesting it may move further south but if you look at the recent modelling it never really appeared to shift, I think the models have had its track pretty much nailed for several days.

Looking ahead we have the usual expectation that the models are going to find an evolution out at 240hrs and just reel it in, that’s never going to happen, however there is plenty of potential within the longer term model guidance and we will have to see how the models deal with the blocking over the coming days, patience not petulance is required. Personally I would rather see average synoptics at 240hrs, then have them fall into place at 120hrs, only in 2010 did synoptics at 240hrs develop into the real deal, usually raging easterlies at 240hrs are a dead cert to fall apart once we hit high res.

[Rose]

Good morning everyone, I usually follow the regional forums & sometimes contribute but now I have discovered this one, I'm hooked! Not knowlwdgable enough yet but I'm learning, thank you for all your enthusiastic posts, the suspence is killing me!

[Guest]

The second low shown by the ECM that depends on how much cold is left to the east, if you have enough of that as the low heads se the flow turning more from the east as it clears will import lower dew points and could see some back edge snow, of more importance though is getting lower pressure in the Med.

How low does the pressure need to go in the med, ECM at +240 seems to take the LP there or is the positioning wrong?

[NL]

Looking ahead we have the usual expectation that the models are going to find an evolution out at 240hrs and just reel it in, that’s never going to happen,

Yes but this time it has support from the 500mb charts, so looking more likely than this weeks attempt.

[Gibby]

Good morning. Here is my morning review of the 00zs from GFS, UKMO,GEM and ECM for today Wednesday November 28th 2012.

All models show fairly good agreement out until the beginning of next week. A Northerly flow becomes slack over the UK in the coming days as small disturbances run South close to western Britain and Low pressure persists to the East. The weather between now and Monday will be typified by rather cold conditions with wintry showers in the East, heavy at times while all other areas see mostly dry conditions with frost at night. The far West may see some cloud cover for a while tomorrow as one such disturbance runs a little close to the West but this will clear again later. Over the weekend with a slacker flow freezing fog may well develop too for many with further wintry showers in the East and widespread overnight frosts.

GFS then leads us into next week with a cold front crossing the UK from the West bringing a spell of rain with sllet or snow on hills and in the North for a time. Brighter showery conditions will follow but with a cold NW breeze with wintry showers in the North and West as the Low pressure area responsible tracks SE down the North Sea and into Europe. Through FI this morning it looks likely that Low pressure on a more Southerly latitude tracks East to the South allowing winds to turn into the East with another spell of rather cold conditions with some rain at times in the South. Later a ridge collapses South from the North with quieter weather with frost before a return of milder weather under Westerly winds reach all areas by the end of the run.

The GFS Ensembles continue to show a rather cold prospect for the next few weeks without ever showing anything desperately cold. With some precipitation at times shown from the beginning of next week in the South it looks like the favoured option is still one of a spell of rather cold zonal type weather from the NW rather than from the East.

The Jet Stream continues to show a returning arm of the flow running South to the West of the UK. Into next week the flow becomes more disrupted for a while before it settles on a track at 50 degN over the Atlantic moving SE to the SW of Britain and on east over Southern Europe in a week or so time.

UKMO for midnight on Tuesday shows a rather cold NW flow following a trough that has crossed east over the UK a day earlier, all in association with a Low centre tracking ESE between Scotland and Iceland. There would be sunshine and showers everywhere with the showers heavy and wintry on all high ground and even maybe some low ground in the North.

GEM shows a similar pattern at that time with its cold NW flow giving way to a temporary ridge crosssing East ahead of a very deep depression which slips slowly South over the UK late in the run with heavy rain for many, falling as snow on the high ground of the North.

ECM shows a similar pattern as UKMO to complete the set with the NW flow quickly giving way to the approach of a very deep depression close slipping slowly SSE to the west of the UK, affecting the South and West with heavy rain followed by a raw east wind with wintry showers running into eastern Britain as it retreats down to Southern Europe at the end of the run.

In Summary the rather cold conditions that have now set in over the UK look like persisting in one form or another through the coming two weeks. It never looks like turning desperately cold with a spell of cold zonality looking a favoured option but nevertheless with unsettled conditions gradually returning from early next week snowfall will be in the mix of weather that affects the UK with the greatest risk as always on the high ground and in the North. Frost will occur on occasions too as ridges pass between depressions and winds fall temporarily lighter.

[beefy201]

Lets not get hung up on each model every day please guys, we no how frustrating it can be , but in reality it will look completely different in 24hrs again so what does that tell you , any run that shows a strong PV and the Atlantic express alive and kicking is not going to happen, remember this is a massive pattern change there struggling with and it's no good looking in detail in fi, also take no note of upper air, do you think the pro's spend hours looking at the air temp at 850hpa what's 150hrs away?? I doubt it very much . Rather they look at trends, where's the general air coming from ? Where are the blocks likely to be sitting? Does what's showing go together with the strat profile , and the main drivers behind the scenes ? No doubt that's what we look at , pay very little attention to upper air , just look at its origin for a guidance.

Remember also we actually don't need 850hpa to be -5 to get snow, I remember last year we had snow on one occasion when we had a low from the south and we had upper air of around -2,-3 and we got forecast 10cms of snow, it actually didn't happen due to the ppn dieing out over the top of us but it did snow before it petered out but we had a cm rather than 10 lol. But take the moral of the story out of it pls.

Well said Shaun i am very impressed i have been model watching for many years indeed Shaun i use to give you good forcasts for snow when you were a pupil in St Stephens ( MR MORGAN ) :-] . But back on topic the potential showing up this year is quite exceptional, i have not seen such cold pooling!! it wont take much for the flood gates from the east to open and we will be in the deep freeze.!!

Trust me i am Mr Morgan

[Radiating Dendrite]

I am sorry, this may be off topic as it is model related...........but the ECM is lovely out in FI.

We have a great looking easterly and some cold uppers which would certainly get the old North Sea snow machine started.

The ECM looks quite a clean run to my eyes, nothing too dramatic and all plausible.

The GFS on the other hand looks a dogs dinner, shortwaves all over the place including one making its way up from the tropics and rapidly deepening as it does so.

I know the current "cold spell" may have disappointed, but when I look at today's chart I see ridging into Greenland and a link up with the high by Svalbard. This is what was being shown this time last week near enough, so the models were not too far wrong.

[weather eater]

Yes but this time it has support from the 500mb charts, so looking more likely than this weeks attempt.

I think you are missing the point, most members are just looking at the day to day GFS, ECM, model runs and it’s these I’m talking about, however I also said that there is plenty of potential in the long term guidance (ie the 500mb charts), despite that potential there is still no guarantee that it will all fall into place for our tiny island.

[bradymk]

Been said a few times over the last few days but still a big difference between the GFS and higher resolution NAM at +84 regarding the low south of Greenland. http://www.weatheron...S=0&WMO== NAM http://www.weatheron...0&ZOOM=1= GFS

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html ECM Ensembles, not bad, look at the control run!

[Frosty.]

I am sorry, this may be off topic as it is model related...........but the ECM is lovely out in FI.

We have a great looking easterly and some cold uppers which would certainly get the old North Sea snow machine started.

The ECM looks quite a clean run to my eyes, nothing too dramatic and all plausible.

The GFS on the other hand looks a dogs dinner, shortwaves all over the place including one making its way up from the tropics and rapidly deepening as it does so.

I know the current "cold spell" may have disappointed, but when I look at today's chart I see ridging into Greenland and a link up with the high by Svalbard. This is what was being shown this time last week near enough, so the models were not too far wrong.

I fully agree, the gefs 00z mean is showing a cold unsettled outlook with a mix of rain/sleet/snow and widespread frosts plus freezing fog. Some people are just too hard to please. It's the type of pattern which something very potent could jump out and bite us. My glass is ¾ full today. I think northern britain in particular could have a fair bit of snow in the next few weeks and some even for the south at times.

[offerman]

john mac

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Posted Today, 08:08

I think we need to compare the 0z with yesterday's and then 12z with yesterday's 12z then you would get a better idea. Taking each run at face value just doesn't work!!!

Spot on statement bud and i am learning this. I am now just going to take a view with only 36 hrs ahead as all the other charts and gismos further ahead can be completley wrong and you just as well pluck a no.out of a hat to what we would get and further ahead than this. Its all guess work and there are no experts who can predict the weather so far ahead. these are all computer generated graphics and as well all know computers can be wrong but its mother natures way it will do what it wants to.

Saves any frustrations if best viewed that way.

Ill be posting much less now apart from very near term charts that show massive potential and on the day itself to any falling snow events.

A.T.B