General Model Output Discussion

[Guest North Sea Snow Convection]

Evening Tamara well theres very little support in the GEFS ensembles for the UKMO raw output and i'm very surprised they didn't modify the fax charts towards the ecm operational run, the ukmo raw output isn't bad at all it just looks rather messy and the upstream pattern would still likely edge this south and east with time. Personally i think its wrong from as early as 96hrs and in a straight fight between it and the ecm at that timeframe IMO theres only one winner. I really wouldn't worry about it, i've gone with an easterly a few days back and one operational run from the ukmo is not going to change my mind about this.

Hi nick - I agree, I was also very surprised.

Tbh I had high confidence that the fax would reflect the ECM. They must have other data that suggests the UKMO is more likely. In situations like this they don't usually hesitate to ditch their own model unless there is good reason to.

Edited January 1, 2010 by North Sea Snow Convection

[kold weather]

Well I can't say about the 850hpas however but thickness is sub 520 so I'd imagine it wouldn't be that marginal, but its hard to say without the full data to hand, I'd imagine though you'd be unlucky not to get snow from the UKMO set-up...

Anyway the 18z ensembles are really superb, though we get some rather odd evolutions towards the back end of FI on some of these runs, with those super lows the GFS loves so much developing on many runs and toppling everything with ease...no doubt those ensembles will change back again at some point soon, just like they did before!

[Michael Fishermans Friend]

My God just come back from a NYD party and looked at the various models and there isn't one that's bad, UKMO looks slightly different in the evolution of cold and GEM is a bit reluctent to bring in the Scandy HP but the ECM, NOGAPS and GFS look fantastic especailly the ECM which looks unbelievable and slightly scary (if that's possible). looks like the first part of the evolution is almost nailed whilst the transfer to the Scandy High feed is still in the balance but with the majority of the models in agreement with heights just to our north by +120hrs.

Im trying not to get excited just in case we have the mother of all climb downs by the models but what evolution do the 'big guns' i.e. TWS,KW,TEITS,SM,Nick Sussex etc. believe will now take place on refelction of the 12z/18z models.

many thanks and a Happy New Year to all Tim.

Edited January 1, 2010 by Timmy H

[nick sussex]

Hi nick - I agree, I was also very surprised.

Tbh I had high confidence that the fax would reflect the ECM. They must have other data that suggests the UKMO is more likely. In situations like this they don't usually hesitate to ditch their own model unless there is good reason to.

I think you're worrying here too much Tamara, no model backs it's output and if it was such a clear signal upstream to hold the high that far north i'm sure even the gfs 18hrs run would have gone that way or at least trended towards it.

My advice have a brandy and a mince pie and don't lose any sleep over it, if i'm wrong you're free to have a go at me tomorrow!

[Guest North Sea Snow Convection]

I think you're worrying here too much Tamara, no model backs it's output and if it was such a clear signal upstream to hold the high that far north i'm sure even the gfs 18hrs run would have gone that way or at least trended towards it.

My advice have a brandy and a mince pie and don't lose any sleep over it, if i'm wrong you're free to have a go at me tomorrow!

Hi nick - it's only the weather, so I'm not going to lose sleep over it! And I don't drink brandy either But a mince pie (soaked in brandy) is nice!

Just expressing model related surprise

I'll be quiet now

[swilliam]

Another great run from the 18z including the ensembles.

This is showing nearly 2 weeks of cold weather. This was backed up by Chris Fawkes on the last BBC N24 weather forecast where he boldly stated that the cold 'snap' may last for as much as perhaps the next 2 weeks. This is almost unheard for the BBC/Meto to stick their necks out like this. They obviously believe the ensembles unlike some posters on here. I would like to know what they think a cold spell is if this is a cold snap though.

Edited January 2, 2010 by swilliam

[cooling climate]

This from the CPC prognostic discussion tonight.

6-10 DAY OUTLOOK FOR JAN 07 - 11 2010

RECENT ENSEMBLE MEAN FORECASTS ARE IN VERY GOOD AGREEMENT ON THE EXPECTED

500-HPA HEIGHT PATTERN FOR THE 6-10 DAY PERIOD OVER NORTH AMERICA. THE EXPECTED

PATTERN FEATURES UPPER-LEVEL TROUGHING ACROSS THE EASTERN PACIFIC AND

UPPER-LEVEL RIDGING EXTENDING NORTHWARD ALONG U.S. AND CANADIAN ROCKIES. A

DEEP TROUGH INDICATED OVER THE EASTERN PORTIONS OF THE CONTIGUOUS U.S. IS

EXPECTED TO BE HELD IN PLACE BY A BLOCKING RIDGE ACROSS GREENLAND. THE

BELOW-NORMAL 500-HPA HEIGHT ANOMALIES WITH THE EASTERN TROUGH EXTEND WELL

ACROSS THE GULF OF MEXICO.

The charts don't look to shabby either.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

The CPC seem quite adamant that a -AO and NAO will still be in place at day 14.

[kold weather]

Yep those anomaly charts are pretty stunning, they look rather close to the 18z it has to be said...

The 18z ensembles generally rather progressive past 264hrs but it seems odds on they are way too quick with trying to get rid of the -ve NAO signal, as we've time and time again thus far in FI...

[nick sussex]

Hi nick - it's only the weather, so I'm not going to lose sleep over it! And I don't drink brandy either But a mince pie (soaked in brandy) is nice!

Just expressing model related surprise

I'll be quiet now

I only ever use the nogaps in emergencies and that hasn't trended towards it either on it's 18hrs run! But i agree i was very surprised the ukmo didn't modify their raw output, lets say for arguments sake quite a few ecm ensemble members backed the ukmo raw output they don't go on to show anything but a very cold outlook anyway and so its still likely they sink the trough far enough south.

[Thundery wintry showers]

My best guess (will be updating the monthly forecasts early tomorrow with this sort of idea built in) is that after a couple of days of cold E and NE winds (the 7th/8th January) the high may settle over northern Britain for most of the remainder of the second week, keeping it mainly cold and dry but with an easterly flow over England & Wales bringing snow showers into eastern parts from time to time.

So in essence, a slightly watered down version of what GFS/ECMWF are showing, and maintaining cold and, in places, snowy weather through to midmonth.

[cj114]

My best guess (will be updating the monthly forecasts early tomorrow with this sort of idea built in) is that after a couple of days of cold E and NE winds (the 7th/8th January) the high may settle over northern Britain for most of the remainder of the second week, keeping it mainly cold and dry but with an easterly flow over England & Wales bringing snow showers into eastern parts from time to time.

So in essence, a slightly watered down version of what GFS/ECMWF are showing, and maintaining cold and, in places, snowy weather through to midmonth.

Thank you. This means that my Gas Bill will be around £500 for the next week or so!

Perhaps more with a little Snow thrown in.

Oh for the days when I was young and didn't have central heating and could put up with just a gas fire and cooking dinner in my Coat! lol

Let's remember the old folks who would rather freeze and save money. I personally will nag my neighbours, i.e sit in their homes and ask for the heating to be put on.

Also, don't forget to feed the wildlife either guy's.

Off topic I know but this set up reminds me of the 80's when we did look after the elderly who lived near us.

Also, get some decent Wellies for the ice days, can't beat them, but do wear two pairs of socks or you will get Chilblains.

[geordiekev]

I very rarely get involved in these model output discussions but i do appreciate the posts of all of those experienced members and over the years have been pleasantly surpised at the accurate interpretations of the models. This year to boot has been one of the most exciting with the GFS picking up on the current and still ongoing cold spell.

However, even though the GFS had a blip recently am I not wrong in stating that it was the unmodified GFS, pre 15/12/09, that forecasted this spell at long/medium range and since the modified GFS came into fruition itis now struggling with short/medium range.

Something I have been puzzled by this year is all of the IMBY posts, SE ANGLIA cold discussion has 21 discussion threads whilst NE has only 6, yet the NE have had treachourous snow events over a 2 week period with no thawing, and much like the BBC who fails to inform us of impending 15cm falls, (3 hours out) it seems that this forum is tending very much towards the IMBY (we need the low to sink south, it is only the north or east). What happened to impartial forecasting, do we further north only have the radar to rely on these days? Thanks TEITS and co who remember that members in the north also rely on forum members to anlyse model synoptics and provide reasoned forecats.

[danm]

I very rarely get involved in these model output discussions but i do appreciate the posts of all of those experienced members and over the years have been pleasantly surpised at the accurate interpretations of the models. This year to boot has been one of the most exciting with the GFS picking up on the current and still ongoing cold spell.

However, even though the GFS had a blip recently am I not wrong in stating that it was the unmodified GFS, pre 15/12/09, that forecasted this spell at long/medium range and since the modified GFS came into fruition itis now struggling with short/medium range.

Something I have been puzzled by this year is all of the IMBY posts, SE ANGLIA cold discussion has 21 discussion threads whilst NE has only 6, yet the NE have had treachourous snow events over a 2 week period with no thawing, and much like the BBC who fails to inform us of impending 15cm falls, (3 hours out) it seems that this forum is tending very much towards the IMBY (we need the low to sink south, it is only the north or east). What happened to impartial forecasting, do we further north only have the radar to rely on these days? Thanks TEITS and co who remember that members in the north also rely on forum members to anlyse model synoptics and provide reasoned forecats.

Mate, there are obviously more people on this board from the SE than the north, hence why there are 21 threads for the East Anglia & SE discussion and only 6 for the NE. There are posts from people giving information about prospects up north, but if you find people talking more about the south then that is because of a combination of this being a fairly rare event for the south, plus there being more ppl on the board from the south (It is the most populous area of the country after all. More people live in London than the whole of Scotland). A the end of the day, many people from the north have made this complaint on this and the TWO board. All i would say is that if 70% of people (or any other significant %) on this board were from the north, then i doubt they'd all be sacrificing making IMBY posts and making lots of posts about the south rather than the north.

If you are finding that you are not getting the information you require about your own area, then simply participate in the discussion and ask questions about prospects up north. I am sure you will get dedicated and well informed replies from the more senior members on the board about snow prospects for where you live.

[fear sneachta]

I'm just wondering...how accurate the GFS 'risque de neige' is generally regarded as being? It's showing a fair bit of snow for many parts of the UK & Ireland over the next week. I'm particularly looking at next Tuesday's chart with some reasonable snow forecast for Dublin. I'm wondering how big a pinch of salt I need to take with regard to these GFS charts!!

Edited January 2, 2010 by fear sneachta

[Mikel Nimbus]

00z looking like an upgrade so far. Out to +126 and the Atlantic high is further north and the Scandi block is a lot more prominent. Not to mention the much better thicknesses.

Regarding GFS ppn forecasts, I'm really not a fan unless it is within +36. To believe anything past that is pointless.

[Optimus Prime]

Wow hang on, the feature I've circled...that's interesting!!

[Mikel Nimbus]

Wow hang on, the feature I've circled...that's interesting!!

Yep that Scandi high is looking very healthy on this run. Hopefully GFS is doing what it does best and is picking up a trend in FI before the other models.

[Optimus Prime]

Morning Mikel...it's that feature that could give us bitter easterly. it's the sort of evolution that's classic of severe spells of old...we shall see!

[Gerry]

At short range all the model precip charts are fairly consistent i.e 24hrs but beyond that they are pretty much next to useless witrh regard to volume beyond this timeframe they are merely indicative of probable location of rain/snow fall. Using Dublin as an example with the current and progged set up at 24hrs both ecm and gfs are broadly the same

24hrs

by 72hrs again the distribution is simillar however greater variance is evident in intensity with the GFs widely recognised as overplating convection and the ecm always underplaying

By 144 we have reached a different synoptic set up so both distribution volume are not comparable.

The best model for short range precip is probably the WNM or Meto. I will say that if last nights 1wz ecm verifies Dublin will do well from convective showers

[Optimus Prime]

January 1947 here we come!

Cold short term

Very cold Medium term

Very blocked cold longer term

[Gerry]

Yep that Scandi high is looking very healthy on this run. Hopefully GFS is doing what it does best and is picking up a trend in FI before the other models.

Its broadly the same evolution as last evenings ecm although this variance would see the cold pool mixed out very quickly due to the source of the easterly not having a deep pool of cold air, would be nice if this is a trend only time will tell

[Optimus Prime]

Its broadly the same evolution as last evenings ecm although this variance would see the cold pool mixed out very quickly due to the source of the easterly not having a deep pool of cold air, would be nice if this is a trend only time will tell

it's a better setup for longer term cold. Large NH blocking with a conveyor belt of channel lows giving the threat of heavy snow to the south. Once the Greenland high sinks southwards we need this evolution to go ahead otherwise we could end up something much more milder in the longer term while eastern Europe starts to freeze up.

[Gerry]

it's a better setup for longer term cold. Large NH blocking with a conveyor belt of channel lows giving the threat of heavy snow to the south. Once the Greenland high sinks southwards we need this evolution to go ahead otherwise we could end up something much more milder in the longer term while eastern Europe starts to freeze up.

Agree, the amount of blocking in the later stages is quite remarkable and would return a CT well below zero ties in with stewarts thoughts for the latter stages of Jan, we d have a very stickly moment/hurdle to get over through later in the week with the high sinking, given the back ground drivers it would be just our luck to either get the high bang over us or to end up on the wrong side of the block. Still plenty of old school weather between now and then, will be very interesting to see how the infrastructure holds up. My parents were at the Oracle the night Reading and Basingstoke ground to a halt they even closed the M20 here in Ashford for 1.5 inches of lying snow yesterday.

Dont know if anyone has caught the BBC news 24 forecast talking of cold snap lasting 2 weeks read into that what you will but I can never recall the BBC ever stating such a thing.

[Gerry]

UKMO following GFS at 144 growing consensus for a scandi high and long fetch easterly?

[Iceberg]

I think the easterly at 144-168 is pretty much nailed now, lots of inter run consistance, the increasing trend to see a continental cold core LP to move across the south is nice to see as this could give considerable, slow moving snow without warm sectors to alot of southern, midland and even some more northern areas.

ECM this morning is very very nice. Beyond this to say 240+ its very difficult to judge what might happen, be it HP over the UK, lows coming in from the SW or even the high migrating NW allowing another northerly shot and a complete repeat.

Also as mentioned some very nice fax charts which show up the unsettled nature of the weather as we move into next week.