General Model Output Discussion Thursday December 24Th:

[bluearmy]

One of the great mysteries to me is how the UKMO apparently has such a good verification record at T120 and more especially T144 - IMO it is is very poor at this range compared to the GFS (0z and 12z runs) and the ECM.

i wonder if it has to do with the fact that the meto model is never very keen to 'over deepen' features. that way, where its wrong, its never as wrong as the other models re pressure variations from verification. its output at T144 is often more reflective of an ens mean chart rather than an operational.

[Barb]

Met Office warning - that doesn't look very far North - all of Wales and much of the Midlands. Met Office trending a bit more towards GFS than their own output?

Of course a lot of uncertainty. I think that area is about right though...

[Fozfoster]

couple of points:

joe B showed an anomoly chart for dec/jan mid november that had a large positive anomoly iceland/greenland ridging towards scandi and an eastern euro trough. therefore the flow was ne across the uk and the coldest air went into eastern europe. the ridge came away from due north jan/feb which introduced the colder flow over the uk. i note that he blogged last night about the cold first fortnight of the new year in europe and he asked for 'brownie points' re getting the spirit of the forecast right, if not the detail. my take on this would be that the cold has backed further nw than he had forecast which is obviously better for us though not for e europe (bulgaria/romania/n greece.

the lastest T84 FAX shows the approach of the occlusion to be less exciting for the south than yesterdays T96. obviously we wont know exeters take on where the push of energy from the trough heads until we see T96/T120 tonight but it could be a classic chart this evening (many of you will see several at the same time!!). in the old days, the energy always got pushed back if it approached on a sw-ne axis with a resulting devonian blizzard. i think there are several factors to consider. the most important is to get a stronger kick from the trough to our ne to get cold air undercutting the warmer uppers spreading north. not too much though or the front will fail to get north of the coast. it will also help that the continent looks to get a cold couple of days ahead of the fronts. a se draw will be just fine for the south though you want to avoid to0 long a sea track as the north sea is still warm enough to modify the lower layers.

enough divergence in the solutions in the mid term to keep us 'on our toes'. splendid model watching times.

Good post, think i got a good handle on what could or could not happen , cheers

[yamkin]

Met Office warning - that doesn't look very far North - all of Wales and much of the Midlands. Met Office trending a bit more towards GFS than their own output?

Of course a lot of uncertainty. I think that area is about right though...

Don't forget that the MetO have their own private model the public will/do not see.

[BristolBlizzard]

I've just seen the early warning and I'm very suprised given that the PPN will not even be affecting the mentioned areas by Tuesday ! Expect the warning by Sunday to have changed to take NW England, N Wales, Staffs & Shrops out of the warning zone with places like Warks, Northants, , Beds, Hereford & Worcs, Mid and South Wales, and maybe Cambs, Notts and the West Midlands county in the 'red' zone.

Where does the South West stand at the moment in this potential cold period? Will it be a rain followed by snow scenario 'If' it were to come off.

[MR EXTREMES]

well all i cant say is,

the met office futher outlook beyond the warning has filled me with confidence,

even if i do live on the crappy south coast.

i hope this winter continues this trend the models have been superb.

i just wanna see country wide event from north to south with lying snow for weeks lol.

and to think this started around the first week of december when we got jan and feb to go whoop whoop i gotta ramp for now anyway.

[yamkin]

Where does the South West stand at the moment in this potential cold period? Will it be a rain followed by snow scenario 'If' it were to come off.

Will hand from uk.sci.weather: http://groups.google.com/group/uk.sci.weather/browse_thread/thread/e6b6f29e9182bd87?pli=1

Possibly serious disruption again and this time SW'ern areas will be hit too

by heavy snow and strong winds with drifting, especially above 100m asl.

Snow levels falling on Tuesday and then on Wednesday the snow moves

east probably moving away slowly by new year. This has the potential for a

very severe episode in my opinion. My confidence is moderate and anyone

travelling, especially in the south, needs to be aware. ECM seems to model

this quite well, the charts may look innocuous, but don't be fooled! I have

already warned some of my family who are considering leaving Haytor earlier

now.

[kold weather]

Yep the UKMO is further north with the system on Tuesday, though the warning suggests the data they have are probably pointing to something more in line with the GFS.

Still the general basics of that map is where I'd put the greatest risk, of course that will be extended as confidence increases over the next few days and I suspect much of southern England wil eventually be included for Wednesday's chart as the cold air undercuts the low pressure system, of course the SE probably is at the least risk but even here I'd have thought the 06z GFS would give something.

[snowmadchrisuk]

well all i cant say is,

the met office futher outlook beyond the warning has filled me with confidence,

even if i do live on the crappy south coast.

i hope this winter continues this trend the models have been superb.

i just wanna see country wide event from north to south with lying snow for weeks lol.

and to think this started around the first week of december when we got jan and feb to go whoop whoop i gotta ramp for now anyway.

And to top it off , It is well known in El Nino Winter's , Late winter is usually very cold and Snowy . This could be a 3 month long and cold Winter. I agree with Joe B regarding the met office winter forecast predicting that this will be in the top 5 warmest winters. The Winter CET must have already taken a dent .

[BristolBlizzard]

Will hand from uk.sci.weather: http://groups.google.com/group/uk.sci.weather/browse_thread/thread/e6b6f29e9182bd87?pli=1

Possibly serious disruption again and this time SW'ern areas will be hit too

by heavy snow and strong winds with drifting, especially above 100m asl.

Snow levels falling on Tuesday and then on Wednesday the snow moves

east probably moving away slowly by new year. This has the potential for a

very severe episode in my opinion. My confidence is moderate and anyone

travelling, especially in the south, needs to be aware. ECM seems to model

this quite well, the charts may look innocuous, but don't be fooled! I have

already warned some of my family who are considering leaving Haytor earlier

now.

Wow, thanks..

[yamkin]

Wow, thanks..

Off topic, but Will Hand got the latest cold period correct in the beginning of December.

Edited December 25, 2009 by yamkin

[Craigers]

is the north of the band the best for full snow fall? im in southyorkshire and that could be such a sweet event! what a xmas present

[Wales123098]

is the north of the band the best for full snow fall? im in southyorkshire and that could be such a sweet event! what a xmas present

No mid/south Wales is likely to be best, i.e. South Wales Valleys.

[BristolBlizzard]

Off topic, but Will Hand got the latest cold period correct in the beginning of December.

Fair play to him It would be awesome if it were to come off of course, but i'd still be happy with a few inches.

Good times ahead.

[Wales123098]

is the north of the band the best for full snow fall? im in southyorkshire and that could be such a sweet event! what a xmas present

No mid/south Wales is likely to be best, i.e. South Wales Valleys, it will be snow up there but not as heavy I wouldnt of thought.

Edited December 25, 2009 by Wales123098

[kold weather]

is the north of the band the best for full snow fall? im in southyorkshire and that could be such a sweet event! what a xmas present

Yep the northern section of the front will be purely snow, the situation is a little more complicated then most as quite a fewq models bring in a second front. At the same time the colder air is digging south-westwards so slowly but surely more and more of the precip mass will turn.

[cooling climate]

A MERRY, MERRY CHRISTMAS EVERYONE.

Christmas morning and the models have not disappointed.

Its so easy to get blase about these stunning synoptics and apparent weather we have had

and are about to get but as so many have said already these are dream charts and weather

patterns that many of us only dream-pt about. Yet here they are again virtually on our door

step.

One thing I will say is IF the winter carries on in this vain then as to where it will sit in the

record books is anyones guess.

I was rather dismissive the other day as regards to the snow threat the middle of next week

consentrating more on developing pattern into the new year but that now looks to be almost

a lock. Whether it be n/easterly or northerly it looks to be turning very cold and wintry.

This snow threat for the middle of next week does look as though it will for many many areas

be a major event with severe disruption likely as a result and this is only the starter as the UK

and Europe head into the freezer again.

Have a great day everyone.

[Optimus Prime]

Cooling Climate - Is that meant to be a poem or a forecast? Looks like something Greg Lake would have written.

[Mark Bayley]

Is there anyway we can see precipitation charts for the ECM? I have a link to the site below however you can't view precipitation.

http://www.meteogroup.co.uk/uk/home/weather/latest_model_forecasts/ecmwf/archiv/WEurope/thgt850/2009122500/nothumb/ch/c50645b399.html

[Troubleatmill]

Fair play to him It would be awesome if it were to come off of course, but i'd still be happy with a few inches.

Good times ahead.

You poor lad!!

[Wilxy]

Merry Xmas everyone by the way I was wondering about bristols chances of snow next week it looks amaszing at the moment hope someone knows if Bristol will be seeing anymore White stuff

[Snowaddict]

Is there anyway we can see precipitation charts for the ECM? I have a link to the site below however you can't view precipitation.

http://www.meteogrou...c50645b399.html

Indeed, the following is the T+120 frame from the overnight ECMWF 00Z evolution:

Southern and eastern Ireland looks like potentially doing very well out of this also:

Merry Christmas To Everyone,

SA

[bennytes]

Noticed just now that there is a half moon in the sky, which means that come next week, the moon will be just about full, which is an abiding memory i have of the two blizzards in 78 and 82. In the aftermath, the big bright full moon shining down, through freezing cold night skies.

below is a newspaper report of the 78 blizzard showing the full moon.

http://img.photobucket.com/albums/v645/zloty/Feb1978b.jpg

waxing gibbous at the moment, which means come this event happening, we'll be just about at the full moon!

http://www.calculatorcat.com/moon_phases/phasenow.php

actually, it's full on new year's eve..

http://www.woodlands-junior.kent.sch.uk/time/moon/

Edited December 25, 2009 by bennytes

[Frosty.]

One of the great mysteries to me is how the UKMO apparently has such a good verification record at T120 and more especially T144 - IMO it is is very poor at this range compared to the GFS (0z and 12z runs) and the ECM.

I think the trend will be to take the PPN slightly further South and East,so if we draw a line from the Humber to Mid Wales, thats where the heavy snow will be, extending South from that line but rain for South of the M4 probably turning to snow later.

That sounds realistic Ian, although at this range there is still a margin for error around 50-100 miles north or south. There is very good agreement that the uk will become covered in an Arctic flow of some considerable magnitude from the second half of next week with snow for everyone in one form or another and a return of sharp frosts...it doesn't get much better than this

[Mark Bayley]

Indeed, the following is the T+120 frame from the overnight ECMWF 00Z evolution:

Southern and eastern Ireland looks like potentially doing very well out of this also:

Merry Christmas To Everyone,

SA

Thanks, do you have a link please so i can add to my bookmarks ?