General Model Output Discussion

[MKN]

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Faxs

[West is Best]

the only model that has been consistent and also the first one to show the next low undercutting the block was the ECM, there is absolutely no argument on this, the gfs is still performing poorly!

Agree Nick, but GEM has been even more consistent on this.

Any reason why people don't use GEM more when it seems so consistently good at the moment?

[Duane S.]

Could the projected split Polar Vortex actually work against us here? My thinking is that as it drops into Scandi this could serve to hinder westward advection of the cold stuff.

[Archie_Lewis]

Alex deakin on breakfast this morning going for snow north of the M4!

With the snow line reaching north midlands

well that was interesting, Sky news going for snow across much of Wales midlands and home counties tomorrow, wet snow into central London too.

Heading into Wednesday they have the front across N England Southern Scotland with the midlands and south bone dry!

[Duane S.]

morning all i can see the whole of the UK coming to a halt by Friday if you if the gfs is right!!!

Nope, that chart won't affect me other than to make my back garden even more muddy than it already is

Edited December 28, 2009 by s4lancia

[TEITS]

That sounds about right before the low pulls away, in these situations with a fine balancing act between strengthening Greenland high and low coming in from the sw its incredibly difficult to accurately call where snow will fall. We often see resident blocks with attacks from the sw but this set up is even more complicated hence even at this stage there is likely to be further movement in the models.

I tell you what Nick at this rate the LP system will be upon us whilst the models still disagree. I feel this is going to be a case of tracking the LP via satellite.

This week is reminding me of what happened in the 1980's when I was at school enduring another boring french lesson. Whilst sat there being bored stiff the weather outside was dreadful, heavy persistant rain all morning. However late morning a friend of mine said "its snowing outsidw". To cut a long story short by the time I left school at 3.15pm there as at least 6inches of snow outside which was amazing considering there was huge puddles everywhere at 11am.

During the evening I watched the BBC forecast and Bill Giles was apologising for getting the forecast wrong. He said the LP system had tracked much further S thah they were expecting. Some will say forecasts are better these days due to models but to be honest I found the countryfile forecasts in the 80's to be as reliable as they are today.

What happened to me could very easily happen elsewhere this week.

[Snowaddict]

that ECM T48 op still has the low further north than it did yesterday. we were thinking that this occlusion would be difficult to place at 36/48 hours. looking impossible to place its direction of movement, never mind its likely place of situ!!

Morning BA,

The above is a bit out of place from what I can see, the overnight ECMWF.

The initial T+48 timeframe discussed above is virtually unchanged from yesterday, as seen from the two frames below:

T+60 (Yesterday)

T+48 (Today)

For 12 Noon Wednesday the 00Z ECMWF has the low and colder air even further south than the 12Z yesterday, comparing the relevant timeframes from the 12Z/00Z..

SA

[Rollo]

Yes indeed,I hark back to the old days of even the 60's when forecasting was apparently much more difficult(John Holmes may disagree) when surprise falls were probably more frequent than these days of super computors. All this imo will come down to virtual nowcasting and in a way that is reassuring to me in the days when we think we are so much more advanced.

[bluearmy]

well that was interesting, Sky news going for snow across much of Wales midlands and home counties tomorrow, wet snow into central London too.

Heading into Wednesday they have the front across N England Southern Scotland with the midlands and south bone dry!

the GEFS mean precip shows north of the M4 as snow tomorrow which then moves north over a period as far as cumbria whilst to the south of there it becomes rain. beyond that, the whole lots comes back south and shows snow for much of the country thursday into friday. so in answer Archie, yes, there could well be a period of snow on the leading edge tomorrow am before the warmer air pushes the whole lot further north. its how far that goes before returning south thats the issue i think. the overnight FAXES introduce far more pivoting than was previously the case. up till now we were more concerned with N/S. now we have to consider E/W aswell. so very complicated.

http://www.meteociel.fr/modeles/gefs_cartes.php?code=21&ech=6&runpara=&mode=2

and apologies SA re the ecm placing of the low centre. it does, as ever, look consistent although the precip does look further north than yesterday.

Edited December 28, 2009 by bluearmy

[johnholmes]

Yes indeed,I hark back to the old days of even the 60's when forecasting was apparently much more difficult(John Holmes may disagree) when surprise falls were probably more frequent than these days of super computors. All this imo will come down to virtual nowcasting and in a way that is reassuring to me in the days when we think we are so much more advanced.

don't agree at all very difficult then without any computers

today shows it can be just as difficult with computers in the same short time frame.

[Snowaddict]

and apologies SA re the ecm placing of the low centre. it does, as ever, look consistent although the precip does look further north than yesterday.

No need for apologies BA, I can easily get it wrong also looking at any chart! At this rate we have looked at so many they all become a blur..

Also, the overnight NAE is much better than the previous 18Z one, with quite significant snows possible over southern Ireland, Wales and the Midlands towards later Tuesday and into Wednesday:

[tinybill]

as blue army is saying the main worry wil be now jan 4 when we all go back to work we hope dont look good of any one going any were at the moment!!

[phil nw.]

the GEFS mean precip shows north of the M4 as snow tomorrow which then moves north over a period as far as cumbria whilst to the south of there it becomes rain. beyond that, the whole lots comes back south and shows snow for much of the country thursday into friday. so in answer Archie, yes, there could well be a period of snow on the leading edge tomorrow am before the warmer air pushes the whole lot further north. its how far that goes before returning south thats the issue i think. the overnight FAXES introduce far more pivoting than was previously the case. up till now we were more concerned with N/S. now we have to consider E/W aswell. so very complicated.

http://www.meteociel...runpara=&mode=2

Yes the fax`s show the front stalling around the S.Midlands and pivoting as you say.Very difficult for the forecasters to pin detail,even now.

http://www.meteociel.fr/ukmo/fax/fax60s.gif

It`s definately a situation to follow by radar and updates on TV and of course Net Weather.

[LomondSnowstorm]

Wow! Never thought the UKMO would move back towards the GFS output! Very Interesting for Scots, though, as this event now has the potential to deliver not just from convection showers, but potentially from frontal precipitation.

Interesting times ahead.

LS

[nick sussex]

Agree Nick, but GEM has been even more consistent on this.

Any reason why people don't use GEM more when it seems so consistently good at the moment?

Thats a good question, as a model it's really improved over the last year and verifies better than the gfs at 144 hrs, i actually find it sometimes picks a trend which is then followed by the others, a good example of this was the recent easterly, it suggested the euro high ridging north before any of the so called big 3.

Edited December 28, 2009 by nick sussex

[bluearmy]

Bluearmy,

a bit of wishful thinking I know, do you think it could stay all snow in the home counties and not change to rain? Basically if the front doesn't push that far north!

given the overnight output Archie, i would be shocked if we got snow to begin with that didnt turn to rain. the pivoting front is not in our favour in the se. the extent of the precip north on the ecm also indicates rain for us beyond any pre frontal snowfall. you just have to hope that one it all comes back, there is something of note left on it and that it doesnt come through too quickly on its return.

[Weather-history]

Wow! Never thought the UKMO would move back towards the GFS output! Very Interesting for Scots, though, as this event now has the potential to deliver not just from convection showers, but potentially from frontal precipitation.

Interesting times ahead.

LS

When it comes to UKMO, I think it is better off looking at the FAX charts and the FAX charts don't really support frontal preciptation as far north as Scotland.

[TEITS]

Wow! Never thought the UKMO would move back towards the GFS output! Very Interesting for Scots, though, as this event now has the potential to deliver not just from convection showers, but potentially from frontal precipitation.

Interesting times ahead.

LS

Thankfully the Met O have ignored their model as the front doesn't get anywhere near Scotland.

http://www.wetterzentrale.de/pics/brack2a.gif

I mean this in the nicest possible way but I really hope this is the case. I would be pleased to see members in Wales/W Midlands experience some heavy snow as these have missed out during our last cold spell. Also what follows afterwards would be beneficial for the whole of the UK.

[nick sussex]

This isn't related to the infamous low track directly but gives us an idea of what NOAA prefer upstream in the USA for this coming Friday to Monday. They go for a compromise between the ecm and gem 00hrs runs.

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

[Tucco]

Meto Invent rainfall model is less progress into the North of England than on previous run a few hours ago.

Pressure charts go further, till wed 00z. These have a small secondary low running across S Coast. Look at the pressure pattern one would expect the band of precipitation to move further North with milder air reaching the Midlands by that time.

I would expect front to rotate move SW/NE across N England this is perhaps shown with kink in the isobars at 00z wed.

Mark

Teesdale

Edited December 28, 2009 by Tucco

[TEITS]

Just as I thought, I'm only expecting wet snow here at best before the soaking rain sets in!

One thing to note though! BBC tv weather forecasts this morning have White PPN on graphics all day north of London!

You can see why when you look at the fax chart below.

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Im thinking come tomorrow places like Bristol, Cardiff could see some very large snowfall amounts. Infact anyone along the M4 or just N is at risk.

[Paul Sherman]

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Faxs

Nice to see those Faxes and some comments if they were right, not saying they are but if it goes that way.

Somewhere in the Midlands would be very happy with some elevation at first, the 528 Dam line always staying around the Yorkshire area, would expect the Hills of Wales to experience possibly some of their best Snowfall since the 90's at least.

It is going to be a hard slog for most of the populus South and East of Oxford on those Faxes as they show rain, rain, rain and possibly sleet before maybe some back edge Snow on New Years Eve/Day early doors.

We rarely do well out of these Set-Ups and you have to remember that when we have it usually has been bone crushingly cold for at least the week before with a Solid High in Scandi, the last couple of days has seen 10c in some parts of the Thames Valley and you have to now worry with the UKMO Shifting towards the GFS That ECM Does not show the same this evening for the Wed-Fri time period.

Paul S

[Frosty.]

Chance of a foot of snow plus drifting in the west midlands and parts of wales tomorrow, this area of disruptive snow then pushing further north before being dragged southeast as a weakening feature after midweek with the cold air to the north pushing south to all areas by thurs/fri. There should also be snow flurries into the northeast as NE'ly winds become stronger. Severe frosts in scotland continuing, perma frost.

[MAF]

as blue army is saying the main worry wil be now jan 4 when we all go back to work we hope dont look good of any one going any were at the moment!!

some of us have not been off work

i really think that with the utter confusion over the next 48-96 hours, that looking as far ahead as 4th Jan is perhaps a bit too optimistic :o i would put FI around T+72 right now

[TEITS]

As I have said on other threads, the GFS won't be wrong at this range, why Exeter haven't backed down just yet I don't know. But obviously a big disappointment for Wales and the Midlands will only more cold and dry weather to come later in the week.

Must be a good reason though IB.

Im sure the Met O don't look at the models like I do i.e fag in my hand with a cup of tea and briefly look at the UKMO/ECM/GFS. Obviously the vast amount of data they have access to is why the fax charts look like they do.