Model Output Discussion

[kold weather]

Yep I quite agree Iceberg in these set-ups you really do need to look at the higher resolution models simply because looking at the ensembles most also have only one center, where as the further south models do seem to have multiple centers.

Still a very tough call though it has to be said!

[LomondSnowstorm]

Yep I quite agree Iceberg in these set-ups you really do need to look at the higher resolution models simply because looking at the ensembles most also have only one center, where as the further south models do seem to have multiple centers.

Still a very tough call though it has to be said!

How many times has this been said in the past three months - the ECM 12Z is going to be crucial in determining what will occur. And how many times has this actually been true? Fewer than most people might expect, I think.

[TEITS]

Ahhh these models are driving me nuts.

The NAE is now suggesting snow for Sunday rather than Saturday.

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/19/basis12/ukuk/prty/10022112_1912.gif

After viewing this I looked at the UKMO and then finally the GFS 12Z and you could imagine my reaction to the 12Z!

I think I can safely say the model output is volatile and even the NAE isn't exactly consistent.

[kold weather]

Yep TEITS I'd like to just for once we total model agreement but this evolution is involving a set of complex lows, with various other depressions trying to form, it really is a forecasters nightmare because one tiny difference means the difference between a very wet day and a very white day for a mammoth part of the country!

The 12z NAE is a little further north with Sundays set-up whilst the GFS is a little more to the SE so we are coming closer to an agreement but even then still so much uncertainty to be had it has to be said!

[Interitus]

Yep TEITS I'd like to just for once we total model agreement

Of course model agreement is no guarantee of the outcome, wasn't there strong agreement ahead of last week's easterly which never really materialised? The models essentially perform the same calculations with a more or less similar dataset, hence any large enough discrepancy will manifest itself in all the model outputs.

Personally I think agreement is good for trends, but a bit of divergence is a handy pointer to the possible range of outcomes, much like using the ensembles.

[TEITS]

Latest fax is a carbon copy of the NAE which isn't surprising.

http://www.meteociel.fr/ukmo/fax/fax48s.gif

[bluearmy]

Of course model agreement is no guarantee of the outcome, wasn't there strong agreement ahead of last week's easterly which never really materialised? The models essentially perform the same calculations with a more or less similar dataset, hence any large enough discrepancy will manifest itself in all the model outputs.

Personally I think agreement is good for trends, but a bit of divergence is a handy pointer to the possible range of outcomes, much like using the ensembles.

But we're talking about model agreement within T72 !!! i guess the general pattern does have x model agreement. its just the shortwave tracks and troughs which are always going to be liable to change, certainly within T24 on troughs and T48 on 'shortwave runners'.

LATEST t60/t72 fax brings snow into the south of england sunday night which turns to rain as the occlusion passes through. seems to set the persistant falls up for the same areas as yesterday.

Edited February 19, 2010 by bluearmy

[BLAST FROM THE PAST]

Now back to the models, 12z has a tasty couple of LPs for the next week. I tend to agree as the jet won't move that far north so quickly as the 06z in the short term. Although likely to be rain IMBY I have to say that I do enjoy LPs tracking across the channel as it brings quite impressive weather to the south.

BFTP

Edited February 19, 2010 by grab my graupel

[TEITS]

Well so far the +72 fax chart goes with the ECM rather than the UKMO.

The key here is the centre of the LP is further E and if anything the fax chart has the LP slightly further SE. Now if you want to see snow and this continue without changing to rain then you need to be on the NW side of the LP. This is why the LP being further E is better for all of us.

I still think there is room for improvement. I wouldn't be surprised if the eventual outcome is the LP being further E than currently progged before tracking NE. This has been a general trend in the model output recently.

[kev238]

The ECM is much more alike the GFS than UKMO. The GEM model is also thinking along similar lines. The Fax charts seem to concur with this- therefore surely there must be a greater likelihood of that solution occuring than the UKMO. There doesnt seem to be that much support for the low pressure to the West of Scotland scenario shown on the UKMO.

There is so much unpredictability I am unsure as to what is going to happen on Sunday (maybe even tomorrow!)!

[kold weather]

12z ECM is very close to the 12z GFS in terms of the actual outcome, snow line probably close to what it was yesterday, its certainly not clear cut though at least the GFS and the ECM give the Midlands northwards a real good shot at some pretty impressive snowfalls...

TEITS, yeah thats key, the further east it gets the better for everyone, firstly it'll help the chances of the snow holding on throughout on the western side, whilst at the same time allowing some cold air back down again.

[LomondSnowstorm]

12z ECM is very close to the 12z GFS in terms of the actual outcome, snow line probably close to what it was yesterday, its certainly not clear cut though at least the GFS and the ECM give the Midlands northwards a real good shot at some pretty impressive snowfalls...

TEITS, yeah thats key, the further east it gets the better for everyone, firstly it'll help the chances of the snow holding on throughout on the western side, whilst at the same time allowing some cold air back down again.

Not sure about this - too far east and very few places in northern Britain are likely to see much precipitation.

[Paul T]

With regard to Mon/Tue:

I think the GFS ensambles illustrate what we are seeing with these charts - total uncertainty only 2-3days out.

See the circled area for potential 2m temps for Wilts (choosen as its central southern UK; an area that highlights how marginal things are).

You will very rarley see so much disagreement with only 2-3days to go.

Another example:

Last 4 runs for Wiltshire for Monday day and Tue Night:

18Z

Heavy Rain Mon

Light Rain Tue

00z

Heavy Sleet Mon

Heavy Snow Tue

06z

Light rain Mon

Heavy Sleet Tue

12z

Heavy Sleet Mon

Heavy Snow Tue

The North/East/South/West positioning differential of the Monday and Tuesday lows are as follows:

circa t96 = +/- 250miles

circa t72 = +/- 200miles

circa t48 = +/- 125miles

circa t24 = +/- 50miles

Im a betting man, and i wouldnt put a bet on either rain or snow at this stage!

Edited February 19, 2010 by Paul T

[TEITS]

12z ECM is very close to the 12z GFS in terms of the actual outcome, snow line probably close to what it was yesterday, its certainly not clear cut though at least the GFS and the ECM give the Midlands northwards a real good shot at some pretty impressive snowfalls...

TEITS, yeah thats key, the further east it gets the better for everyone, firstly it'll help the chances of the snow holding on throughout on the western side, whilst at the same time allowing some cold air back down again.

Yes the 12Z ECM would be very good for N Wales, N Midlands/N England. For locations such as S England/E Anglia/E Midlands we would need the LP to be further E as you say. However once this clears we all experience upper temps ranging from -9 to -5C in the extreme S as it becomes colder from the N.

Alot is going to depend on members locations whether the track is ideal for them. Like I say further E would suit me but then members in N England would miss out on the precip. Based on the behaviour of the models in recent days I feel the LP will be further E than currently suggested. The ideal locations IMO are Wales, Midlands S parts of N England.

[kold weather]

Well thats a risk for you guys further north thats true LS, but saying that I bet even if this one was too far SE for you guys the one that comes up behind it will give you guys what you want, whilst in the Midlands if this one doesn't come off then it may well be hard to get enough of a cold shot down again to set-up for another set-up that has nearly as much risk.

Overall the 12z GFS/ECM/GEM are all good runs bar maybe the south but really in this set-up the south will no be favoured unless we get a quick secondary depression zipping like on the 12z GEM.

120hrs ECM also gives another snow set-up for the Midlands.

[Higher Ground]

ECM 192h to 216h wins my award for most unexpected evolution of the week (SW-NE tracking low evaporates, only for the next one to intensify towards the ESE towards the Pyrenees )

[tinybill]

Its snowing here and the outlook is for more snow!

Buxton snow capital of England

evening all just had a look at the gfs for the week end just put it mildly looking very interesting to say the least!!

[Higher Ground]

ECM 192h to 216h wins my award for most unexpected evolution of the week (SW-NE tracking low evaporates, only for the next one to intensify towards the ESE towards the Pyrenees )

Though 216h to 240h is pretty bizarre too. Been a while since we saw a deep(ish) low between southern tip of Greenland and Iceland (I think?). Another scenario for next pattern change hinted at?

[kold weather]

Very interesting charts between 192-240hrs, for once we see that very rare thing, a upper low over Greenland helping us out. If you look at the way the upper pattern evolves over Greenland you'd see an upper low heading ESE, which in turn also shunts the low to our west ESE as well, which buys us more time in a cold pattern, though the pattern would be quite close to evolving into something much different then we've seen recently...but thats a rather interesting run!

Buxton Codge, get ready for a bit of a hammering this next 5-7 days I suspect!

Edited February 19, 2010 by kold weather

[cooling climate]

Well thats a risk for you guys further north thats true LS, but saying that I bet even if this one was too far SE for you guys the one that comes up behind it will give you guys what you want, whilst in the Midlands if this one doesn't come off then it may well be hard to get enough of a cold shot down again to set-up for another set-up that has nearly as much risk.

Overall the 12z GFS/ECM/GEM are all good runs bar maybe the south but really in this set-up the south will no be favoured unless we get a quick secondary depression zipping like on the 12z GEM.

120hrs ECM also gives another snow set-up for the Midlands.

The way the models are performing the low could be 300miles or more out in all directions from

what is being shown at present so no one is excluded I think.

A much more encouraging run from the ECM tonight and IF the lows are slightly more

suppressed then this would be a very wintery run for many.

Tentative signs of some good blocking to the northeast in the FI part of the run.

[LochGarman]

Interesting to see that the UK met office have just issued new weather warnings for Friday and Saturday! They are equally confused by the models!!

The Irish weather service has just issued a weather warning for up to 10cm of snow for the southern half of the Country for tomorrow afternoon and night.

The low will then makes its way across to northern wales and northern england.

Edited February 19, 2010 by LochGarman

[BLAST FROM THE PAST]

Models are showing that we must look SW for future developments, looking NE is so so far from what will happen. Great way to see out winter and enter Spring...which looks like starting pretty cool. March in like a lion...out like a lamb???

BFTP

[Paul T]

Sorry for posting quick here logged in quick, but can you tell me why 3 inches of snow fell in a few minutes here and still coming down fast?

I am a bit worried as I went to the doctors and he wants me to go straight to the hospital with palpitations and blacking out I have been having but this snow may stop me. Anyone know will it clear up?

please move the post if needed.

I can see its snowing in Stoke on the radar..it will stop within minutes!

Palpitations and blacking out - if you were suffering those you wouldnt be able to type rationally, but not sure about that prognosis.

Paul

[snowmadchrisuk]

Interesting to see that the UK met office have just issued new weather warnings for Friday and Saturday! They are equally confused by the models!!

The Irish weather service has just issued a weather warning for up to 10cm of snow for the southern half of the Country for tomorrow afternoon and night.

The low will then makes its way across to northern wales and northern england.

They are warnings for the Ice risk tonight .

The only warning the MetOffice have other than that is an advisory for Heavy Snow in the Midlands on Monday which the Ensembles say will be rain .

[Tim Bland]

They are warnings for the Ice risk tonight .

The only warning the MetOffice have other than that is an advisory for Heavy Snow in the Midlands on Monday which the Ensembles say will be rain .

The advisory for snow on monday covers more than just the midlands. The fax would suggest a repeat of yesterday with Norh West Mids favoured for snow with rain on the SE side of the low. As this pulls away in a SE direction more areas will see snow including East mids and East Anglia. It looks very marginal for anyone from Midlands south and I wouldn't be optimistic of snow after sunday if I lived south of the M4.