Model Output Discussion:

[mackerel sky]

I have been a member here for a couple of years and i learn by reading all the opinions from the many experienced members on this forum. As has been correctly said there is a learners area within the forum and taking issue with well respected posters on the forum is not going to earn you any friends or teach you anything

On topic where do people feel the FI point is with the current models at the moment??

I am by no means the best person to comment. But if you reverse to say Monday/Tuesday the ensemble scatter was huge. So really FI then was perhaps +60hrs, now I would say +120 (+120 is always a good one as we have the visual aspect of the FAX charts) but perhaps with the ensemble mean we could push it further now? Cold uppers are one thing, that's set. But precipitation is another. The positioning of, or building of a high whether on our doorstep or hopefully further northwest towards Iceland is going to dictate somewhat. Whether its a weak easterly or northeasterly flow or something more substantial. That is my take and probably completely wrong.

[mackerel sky]

If this is not a place to learn then I will leave.

I wouldn't be so hasty. Accept that the model discussion thread would be full of well thought out and considered posts with backing and thoughts behind them. Filter out the nonsense and look for the respected posters. There are lots of resources on here which people have put together for the love of it in their own time. Please remember that and also contribute.

[cheeky_monkey]

more of the same from the GFS 00hrs..cold and fairly benign from what i can see right out until next friday/saturday before things become more interesting. From there on in its anyones guess as to where it goes..but again cold throughout the whole run.

[Iceberg]

Some very good runs this morning again, I am hardly ever around to witness the 18Z, but tbh I am glad as it tends to bring out the worst in people.

How about people on here just allow a bit a leeway, just because somebody doesn't jump on a band wagon and agree that a particular run is a peach, or the best they've ever seen, or that it won't lead to sub -10s and 100cms of snow etc doesn't mean that they are negative or unrealistic, equally if your going to say it won't come out as the models are shown they try and explain why. Hopefully there will be a bit more realism in todays posts.

Anyways back to the 00Zs.

Very good agreement from Mon-Wed of a NE wind bringing some cold air -5 to -8 850's with snow showers for the east, possible streamers in the favourite locations which will bring the showers inland(but generally in the streamers).

From Wed - Fri the winds might back more easterly, bringing in some colder air -8 to -12C, when winds back more eastward and on the boundary of the cold to very cold air a more organised front is quite possible bring more organised snow, particularly to more central or eastern areas. But still showers to the east during this time

From Sat-Mon the winds become much more easterly and quite a bit stronger, feeling very cold even though 850's are between -4 and -7, some pockets of warmer -4 air look likely to be mixed in, so feeling less cold further north. Across southern and SE counties there does look to be some instability pepping up the showers.

Going very long term, the high does retrogress back to GH (again, must be approx 5 runs in a row now), allowing colder air and return to a NE wind. Worth saying that ECM EPS and GFS really keep the cold going out to the 20th and possibly beyond

The above might change a bit, but I really do feel the basics are pretty certain now, or at least as certain as they can be at this range.

I think it's worth saying that the showers are unlikely to be really heavy in the east and could be quite scattered, however anybody under a tyne/wash/thames streamer might get very lucky.

[bluearmy]

again, the ecm continues to be more supressed with the ridge early in the week. each run,the flow becomes weaker in the se. i mention the se as this is the only part of the country expected to see a strength in the flow according to this model (no imbyism). can we rely on the med shortwave deepening in the right way to facilitate a flow of any sort or will the verification simply be the high gently sinking over us before retrogression via a sandi ridge allows a flow to become established? slowly but surely the other models have come round to ecms way of thinking on this evolution. i read posts that talk about gfs 18z from thursday introducing this. not the case, ecm since thurs 00z has gradually supressed the strength of the flow, run by run. i suspect this is about as far as it will go and there may be a slight correction northwards.

i imagine we will begin to look for the white stuff now? no sign of anything frontal until retrogression (although i note a small disturbance shown on the T84 FAX to the north, complete with warm sector - this could run around the high as it repositions itself E-W). the troughs will prove elusive, FAX to FAX and there is no way of knowing how potent they might be until NAE picks them up < T48.

the GEM is still behind the curve and shows an almost carbon copy repeat of decembers cold spell.

[Great Plum]

Morning all,

I'd echo Iceberg's comments - from Monday until pretty much the end of the run the vast majority 0f the country is under -5 air and from Tuesday onwards, a lot of the country is uner -10 air which should create some instability. One caveat to this is thatwe do have high pressure over us for most of the week so my belief is that it will be drier the further north you are.

Have a look at the GFS ensembles:

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

quite an agreement for a cold spell. However, the operational is towards the lower end of the spectrum.

The 96 hour fax is looking good...

http://www.netweather.tv/index.cgi?action=charts;type=ukmomod;sess=

[Iceberg]

This post is intended to nip in the bud any complaints come the middle of next week of "Wheres the cold spell ?"

I would also add that people might be expecting a repeat of a big freeze reading the 18 pages of this thread, however in the west, out of the wind, it won't feel to bad at all, paricularly wed when temps might get to 4C or 5C, it will obviously be colder the further east you are and with some cold nights the mornings will be very chilly indeed, but it won't be a repeat of sub 0 days for the vast majority in the reliable timeframe.

Alot of the more experienced members will know this, but we are in the middle of feb and -10 850's tend not to produce 0C 2M temps now.

[MAF]

having read the discusion over the past few days, i am tending to think a few of the more knowledgable people have indicated a sense of caution for the coming week. mainly in the amounts of PPN that may be about. yes, agreed, its getting cold. but the PPN doesn't appear to be that great. showers are more the order. and we all know how hit and miss showers can be

[winterof79]

Morning all,

I'd echo Iceberg's comments - from Monday until pretty much the end of the run the vast majority 0f the country is under -5 air and from Tuesday onwards, a lot of the country is uner -10 air which should create some instability. One caveat to this is thatwe do have high pressure over us for most of the week so my belief is that it will be drier the further north you are.

Have a look at the GFS ensembles:

http://www.netweathe...;type=ens;sess=

quite an agreement for a cold spell. However, the operational is towards the lower end of the spectrum.

The 96 hour fax is looking good...

http://www.netweathe...e=ukmomod;sess=

Yes that 96 hour chart ties in well with the METO 3-5 day outlook of snow showers moving in tues/wed.Having only briefly looked at the output,it seems that overall the cold air is moved in quicker than was previously forecast,i.e. sunday pm.As always lets let the cold uppers in then worry about precipitation.One things for sure,there is no atlantic influence for quite a while.If we become part of the block,for want of a more technical phrase,the breakdown to average will be special,in my opinion,enjoy people.

[bluearmy]

Alot of the more experienced members will know this, but we are in the middle of feb and -10 850's tend not to produce 0C 2M temps now.

agreed - still seeing this fresh ese progged for a day or so by ecm next weekend. if it vefrifies, i fancy that might produce a sub zero day in the se, irrespective of the uppers.

again, ecm leads the way now the general pattern is set - first to pick the scandi ridge supporting our 'lost meandering surface high' later this week. expect the models to continue to pick up on its general evolution of sausage shaped high retrogressing to greenland followed by northerly reload and trough incursion from the south towards day 10.

[Cecil Hogmanay Melchett]

This post is intended to nip in the bud any complaints come the middle of next week of "Wheres the cold spell ?"

I would also add that people might be expecting a repeat of a big freeze reading the 18 pages of this thread, however in the west, out of the wind, it won't feel to bad at all, paricularly wed when temps might get to 4C or 5C, it will obviously be colder the further east you are and with some cold nights the mornings will be very chilly indeed, but it won't be a repeat of sub 0 days for the vast majority in the reliable timeframe.

Alot of the more experienced members will know this, but we are in the middle of feb and -10 850's tend not to produce 0C 2M temps now.

Rob Mc said temps struggling to get much above zero as go through next week which conflicts with your post it would seem.However,to counter your analysis the ssts are lower than early Jan so there will be less modification.

Swings and roundabouts.

[bluearmy]

by the way, the T96 FAX is now the current T84 one and is a bit less 'sexy' as the norwegian shortwave is progressively downgraded in potency. as it happens, this is not disimilar to decembers cold spell onset and then, the scandi shortwave became more of a player closer to verification after being downgraded by all the models between T48/T96.

[Great Plum]

Just seen the 120 fax - that looks like a trough is going to cover nearly the length of the country!!

[bluearmy]

Just seen the 120 fax - that looks like a trough is going to cover nearly the length of the country!!

out of date now, looking at the T84 / T96 comparison. however, ecm precip does show something sliding down the eastern side of england on wednesday so i suspect it will still play a part.

http://en.vedur.is/weather/forecasts/atlantic/#type=prec

[Iceberg]

Rob Mc said temps struggling to get much above zero as go through next week which conflicts with your post it would seem.However,to counter your analysis the ssts are lower than early Jan so there will be less modification.

Swings and roundabouts.

You could be right HD, but IMO it's not really about SST modification and more about the strength of the sun and how much it warms the lower atmosphere near the ground. This obviously doesn't effect DP's or 950 temps much so has little effect on how much snow we get.

[SLEETY]

Excellent output again.So it seems the snow threat increases as we head in to the middle part of next week,judging by the latest met forecast.What an amazing winter it has been compared to the last 20,bar the odd one or two.

[Cecil Hogmanay Melchett]

You could be right HD, but IMO it's not really about SST modification and more about the strength of the sun and how much it warms the lower atmosphere near the ground. This obviously doesn't effect DP's or 950 temps much so has little effect on how much snow we get.

The sun will probably play a part as we reach the last third of Feb but its the 6th and it wont even be mid Feb until next sunday.The days are still short so personally i think its a superb time of year to get a cold spell.

Check out Feb 1986 which was a sub zero month (i think),similar set up to what we are looking at right now.

[Weather-history]

Just thinking back to the beginning of the week, when the models were showing a shift to Atlantic dominating, SWly flow for this weekend, talk of high winter maxima, premature congratulation of UKMO, it turned out UKMO was way off base. One GFS op run even had a severe gale for the south today. The models have made a mug of a lot of people this past week.

[Iceberg]

Completely agree it will be cold for many, but the really deep cold doesn't really come into play until the end of next week.

Both METO and GFS are forecasting 3-5C for Tues/Wed in the midlands(taken purely because its central) as a top temp, temps at this range arn't very accurate and anything can happen.

IT will certaintly feel very cold for the east and particularly the south, later on in the week.

Cheers

[johnholmes]

I may be wrong Kevin but you seem to have developed a bit of an anti Met bias? Regardless of their own model they have stayed, for well over a week, in their outlook for next week, with the cold idea, so that is fairly solid unchanging I would have thought. All the models now show that this was probably a very good call-at least 7 if not 10 days ago, although you or someone else may search back through the thread Stew keeps with most of their daily updates on the 6-15 day outlooks.

As to the models this morning then cold is the theme-and quite prolonged looking at ECMWF and GFS outputs. This again has been an increasing theme from them both over the past week, after one or two attempts to return the Atlantic several days ago in their FI outlooks.

Looking at the temps predicted for my area, and adding the usual 2C to the max predicts, and I end up with about 14 days at around 1.8C mean temp-the same as my stats show for the whole of January, so a fairly cold spell seems very probable; 7-10 days perhaps 14 days or so.

As to snow then mid week currently seems the most probable for the eastern half but detail is not going to be apparent or trustworthy much more than 24 hours ahead. Surprises can and do occur as many discovered in January.

ps

looking at the Doncaster skew-t for the 00z output and its less convective than the 12z from yesterday with tops only to about 8-9000ft for a spell of 24 hours or so.

Edited February 6, 2010 by johnholmes

[Nick L]

I may be wrong Kevin but you seem to have developed a bit of an anti Met bias? Regardless of their own model they have stayed, for well over a week, in their outlook for next week, with the cold idea, so that is fairly solid unchanging I would have thought. All the models now show that this was probably a very good call-at least 7 if not 10 days ago, although you or someone else may search back through the thread Stew keeps with most of their daily updates on the 6-15 day outlooks.

I'm sure Mr D will answer this himself, but I read his post as if he were referring to the UKMO model, not the Met Office? In which case he does have a very valid point! I agree with you though John - the Met Office have stuck with their guns throughout and look like being proved right.

[johnholmes]

I'm sure Mr D will answer this himself, but I read his post as if he were referring to the UKMO model, not the Met Office? In which case he does have a very valid point! I agree with you though John - the Met Office have stuck with their guns throughout and look like being proved right.

I believe you may be right about it being the UK model Nick-will await the response from Kevin.

[Weather-history]

You could be right HD, but IMO it's not really about SST modification and more about the strength of the sun and how much it warms the lower atmosphere near the ground. This obviously doesn't effect DP's or 950 temps much so has little effect on how much snow we get.

Wouldn't ground temps be modified in the same way as sea surfaces? I would have thought that with a marginal snow event, you are more likely to get accumulation if the ground has been subjected to a long cold period than after a mild period? Also with ground frosts, you are more likely to get a ground frost in the same way.

[TEITS]

The models have made a mug of a lot of people this past week.

Most certainly have although I did send a PM to a member last Sunday and said to keep this PM as I expected the models to change. Thankfully they did and for the reasons I said.

If we look at the chart below we can see why the trend changed in the models.

http://www.wetterzentrale.de/pics/Rtavn061.png

The LP you see became detached from the Atlantic trough and tracked SE not NE as some of the model projected. This allows the block to the NE to become established and what we then see is the Atlantic LP become weaker and back W not E. So the LP we see tracking SE this morning creates a domino effect. This is why I posted my drawings to explain why the LP has to track SE.

I don't know why but the models seem to have some bias in taking the energy NE in the +144 range and it isn't until this moves closer that this sometimes changes. Until this model bias is resolved then E,lys will continue to be a nightmare for models to get correct.

Back to the models and the excellent trend continues. A simple way of summing up next week is snow showers in the E with these becoming more widespread towards midweek onwards. Thge medium range looks excellent again with good agreement of the block eventually moving to Greenland.

Here is the GEFS mean at +240.

http://91.121.94.83/modeles/gens/run/gens-21-1-240.png?0

Edited February 6, 2010 by THE EYE IN THE SKY

[Weather-history]

I may be wrong Kevin but you seem to have developed a bit of an anti Met bias? Regardless of their own model they have stayed, for well over a week, in their outlook for next week, with the cold idea, so that is fairly solid unchanging I would have thought.

I am criticising those who prematurely congratulated particularly models saying this got it right before even has happened, that model is suspect until this particularly model comes aboard etc. All 3 main models have got it wrong at some stage this winter and because of that, for me, I can't see how anyone, 144hr before the event, can say "well done this model you were right."

Edited February 6, 2010 by Mr_Data