Model Output General Discussion

[grab my graupel]

A new Model thread

Please remember that this thread is for General Model discussion, so try to stay on topic.

To help those who are unsure of where to post, I've reposted the list of threads and their descriptions:

Technical model discussion:

In depth and technical discussions about the models, teleconnections and related items. A slower paced and non chatty discussion area.

General model discussion:

This is effectively the same thread as the single model discussion that always runs and the same key rule still applies - posts need to be model related and constructive.

Model moods and chat:

This much more laid back and free discussion is again required to be related to the model outputs but can be much more chatty and emotive - talk of upgrades, downgrades, good and bad runs need to go in here.

Also, don't forget the various Regional threads

All the latest Model Output is available here on Netweather - Netweather's charts are at a higher resolution than those on Wetterzentrale, and they are in English too

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

Please continue

[Thundery wintry showers]

I think i over simplified it a bit. Of course rain and high dew points are the number one enemy, but as we are unlikely to see much of either then the attention turns to the sun as the number one snow melter, and this is a favourable time of year for the sun to do not much.

The snow you talk about in 2001 had that been through a freeze? Obviously that helps longevity.

Just recapping on this post, overnight 2nd/3rd March 2001 the temperature at Cleadon dropped to -10.2C (the only time since I began recording that it dropped below -10C, although 28/29 December 1995 came close). I certainly agree that a sharp frost helps to preserve a snow cover- without a frost there is always the chance of it thawing from underneath in marginal setups for example. That will also be a factor in the upcoming spell of weather because there are sure to be some sharp frosts. Many places that see lying snow on Friday or the weekend may well keep some snow on the ground right through until the breakdown, whenever it occurs.

I don't think Tyne & Wear/Durham are likely to see much rain or high dewpoints but from the Midlands southwards there would be a risk of that happening on the evidence of the GFS 06Z run. However, having surveyed the evidence I don't think people should worry too much about that run. It's an outlier in the truest sense of the word, and I find it hard to believe that any airflow could spawn that number of shortwaves.

[phil nw.]

<BR>Thnaks Phil,<BR>I must say im quite disappointed how quickly this huge Greenland high is progged to erode.<BR>ALL the models have it subsiding far to fast for my liking and once you start losing heights to the North <BR>things get verry messy and generally ends in a quick end to any cold snap or spell/<BR>

Yes i fear that we will lose this lovely pattern if those ht. projections come to pass.

I believe it`s what some call a West based -NAO,too far west and as you say we lose those Greenland highs.

I think even if we stay North of the front, without real hts. the cold surface air will eventually mix out,still it can change yet.

Edited December 15, 2009 by phil n.warks.

[paul tall]

Just recapping on this post, overnight 2nd/3rd March 2001 the temperature at Cleadon dropped to -10.2C (the only time since I began recording that it dropped below -10C, although 28/29 December 1995 came close). I certainly agree that a sharp frost helps to preserve a snow cover- without a frost there is always the chance of it thawing from underneath in marginal setups for example. That will also be a factor in the upcoming spell of weather because there are sure to be some sharp frosts. Many places that see lying snow on Friday or the weekend may well keep some snow on the ground right through until the breakdown, whenever it occurs.

I don't think Tyne & Wear/Durham are likely to see much rain or high dewpoints but from the Midlands southwards there would be a risk of that happening on the evidence of the GFS 06Z run. However, having surveyed the evidence I don't think people should worry too much about that run. It's an outlier in the truest sense of the word, and I find it hard to believe that any airflow could spawn that number of shortwaves.

Sorry mods for going off topic, but just out of interest TWS what did you record on the morning of 29th December? I only got as low as -6.7º, whereas other private stations in the north east widely reported -8's. Teesside Airport (IMO a bit of a frost hollow) recorded -11º.

[Thundery wintry showers]

Regarding the snow potential for Thursday into the weekend, I think showers will turn increasingly wintry in the east of Scotland and England on Thursday and will produce some accumulations inland during the evening. During Friday showers will slowly become confined to the east coast, as drier brighter weather sinks southwards, but the east coast will see accumulations of snow as the winds ease and the cold air intensifies. Snow depths are likely to be quite small, except for localised areas that pick up snow streamers.

I expect the weekend to pan out as per GFS 00Z, UKMO and ECMWF. A front or two will move south during the weekend with a pool of warmer air out to the west (there may even be a real "warm sector" tied in with this, if it ends up as a warm front followed by a cold front). Recent experience with this kind of setup suggests that most eastern parts will see snow from this, but that most western areas, particularly near the west coast, will only see sleet or even just rain.

Re. recording on 29 December, it was -9.6C on 29 December 1995 but I cannot vouch for the accuracy of the readings from my earlier instruments. I don't know if you're meaning 29 December 2005, which only got down to -5.4C (the North Sea modified things a little by the coast), but the 09-21Z maximum that day was just -1.2C- which, appropriately, was the lowest daytime max since 29 December 1995.

Edited December 15, 2009 by Thundery wintry showers

[Yeti]

Just recapping on this post, overnight 2nd/3rd March 2001 the temperature at Cleadon dropped to -10.2C (the only time since I began recording that it dropped below -10C, although 28/29 December 1995 came close). I certainly agree that a sharp frost helps to preserve a snow cover- without a frost there is always the chance of it thawing from underneath in marginal setups for example. That will also be a factor in the upcoming spell of weather because there are sure to be some sharp frosts. Many places that see lying snow on Friday or the weekend may well keep some snow on the ground right through until the breakdown, whenever it occurs.

I don't think Tyne & Wear/Durham are likely to see much rain or high dewpoints but from the Midlands southwards there would be a risk of that happening on the evidence of the GFS 06Z run. However, having surveyed the evidence I don't think people should worry too much about that run. It's an outlier in the truest sense of the word, and I find it hard to believe that any airflow could spawn that number of shortwaves.

It's funny you should mention melting from underneath - I'll never forget the disaster of March 10th 2006:

http://www.wetterzentrale.de/pics/archive/ra/2006/Rrea00120060310.gif

Heavy snow was forecast for the North for most of the day - however the reality was moderate snow falling all day, settling on the ground for a few minutes before the sludge beneath it engulfed the fresh whiteness. DPs remained just above 0 all day in Harrogate and humidity was high due to the Atlantic air sweeping in on top of the embedded cold. The day was an all-time disappointment and the memory of it has haunted me ever since.

Those sorts of setups can go either way...

Edited December 15, 2009 by Yeti

[paul tall]

Regarding the snow potential for Thursday into the weekend, I think showers will turn increasingly wintry in the east of Scotland and England on Thursday and will produce some accumulations inland during the evening. During Friday showers will slowly become confined to the east coast, as drier brighter weather sinks southwards, but the east coast will see accumulations of snow as the winds ease and the cold air intensifies. Snow depths are likely to be quite small, except for localised areas that pick up snow streamers.

I expect the weekend to pan out as per GFS 00Z, UKMO and ECMWF. A front or two will move south during the weekend with a pool of warmer air out to the west (there may even be a real "warm sector" tied in with this, if it ends up as a warm front followed by a cold front). Recent experience with this kind of setup suggests that most eastern parts will see snow from this, but that most western areas, particularly near the west coast, will only see sleet or even just rain.

Re. recording on 29 December, it was -9.6C on 29 December 1995 but I cannot vouch for the accuracy of the readings from my earlier instruments. I don't know if you're meaning 29 December 2005, which only got down to -5.4C (the North Sea modified things a little by the coast), but the 09-21Z maximum that day was just -1.2C- which, appropriately, was the lowest daytime max since 29 December 1995.

Ah sorry TWS, I thought you said 2005, and yes that is what I was referring to. Blonde moment! My daytime max that day was -3.4º although the 24 hour max 0000-0000 was -2º at 0000 under heavy snowfall.

[The Enforcer]

I don't think Tyne & Wear/Durham are likely to see much rain or high dewpoints but from the Midlands southwards there would be a risk of that happening on the evidence of the GFS 06Z run. However, having surveyed the evidence I don't think people should worry too much about that run. It's an outlier in the truest sense of the word, and I find it hard to believe that any airflow could spawn that number of shortwaves.

I looked at the ensembles first so I was prepared for a milder option. It's one of only four runs out of about 22 that start going significantly mild before Xmas Eve.

[john w]

I agree regarding ensembles and the 6z does appear to have a mild hint of an outlier about it.

I hope this post is in the correct place but i do have a question.

If the GFS is suc an outlier, then why post it and not rerun the model. Is it that it takes so long to run?? I dont understand why if its such an outlierm, you would post it as the operational??

Also...and a request, can the technical model discussion be pinned. Obviously not as many people post, but they are an aducating read, but with the slower pace of posts and indeed all the regional discussions, it does sink away and get forgotton about.

Thanks

John

[Paul Sherman]

http://www.weather.gov/os/notification/tin09-32aabgfs_changes.txt

Just wanted to remind everyone that as from the 12z (15.12.09) the GFS Will be solely using the Parallel Run from now on and forever

Paul S

[Neilsouth]

http://www.weather.gov/os/notification/tin09-32aabgfs_changes.txt

Just wanted to remind everyone that as from the 12z (15.12.09) the GFS Will be solely using the Parallel Run from now on and forever

Paul S

Great news! , thanks Paul

[Iceberg]

It will be interesting to see the parallel run ensembles as we have not had access to those before. !

[johnny1972]

It will be interesting to see the parallel run ensembles as we have not had access to those before. !

Iceberg

Is the parallel run the more accurate run in terms of what it is showing chart wise and the likely outcome?

I for one have sat back and looked in awe at the charts produced in the last week to ten days. However again getting to the nuts and bolts apart from late wed/thurs till monday they aren't any longer showing anything exceptional and the northerly is starting to have warm sectors progged as we get closer to the event. In terms of the longer trend the GFS picked up milder weather for the 22/23 Dec and beyond a few days back and that trend remains for not only the UK but also Europe on the recent runs. The 6z personally looks rubbish with blocking and deep cold still well to the north and blocking in eastern europe meaning there is nowhere for the low pressure systems to go but spiral around to the west/SW of the UK drawing in SW/S winds throuughout the UK and Europe for the forseeable future. This pattern concerns me not only for our winter but also the effects on the ski resorts in europe particularly the lower ones. I travel too Europe late January and with limited snow at present in austria these charts are not at all favourable.

Maybe one of the experts will shed some light on the longer range pattern and correct me if im wrong which i really do hope i am.

[dallas]

http://www.weather.gov/os/notification/tin09-32aabgfs_changes.txt

Just wanted to remind everyone that as from the 12z (15.12.09) the GFS Will be solely using the Parallel Run from now on and forever

Paul S

Cheers Paul, as for accessing the charts will it still be as is?

Thanks

[kippure]

http://www.nws.noaa.gov/os/notification/tin09-34gefs.txt

As of 15.30 we start a new 12z run, Lets see what happens.

[Iceberg]

I have to admit I've thought the parallel run has been poorer than the main operational, but that is only through a bit of looking and is very unscientific.

It has tended to be even quicker than GFS ops in bring down cold air.

purely just my opinion though.

[kold weather]

On the otherhand Iceberg I've never seen a model been so sure of a cold spell occuring, whilst details have changed, the general global synoptic pattern never wavered once on the Paralell run ever since 240hrs out, thats an amazing amount of conisistancy.

Anyway what I'm looking for is the low digging a big further south and being quite a bit stronger, we can only hope!

[Thundery wintry showers]

Yes, the parallel run was the most consistent of all (even more so than UKMO/ECM), but it showed a number of "fantasy" scenarios at long range, which slowly downgraded towards what we have now.

I'll be interested to see how the parallel performs in the coming months. I am expecting the parallel run, in particular, to be less obsessive about shortwaves than the GFS 06Z run which will probably go down as a failure for the "original" GFS's last-ever run.

[Hammer]

Will the chart in the data centre be the parellel run as of a 3.30pm today?

[chrisbell-nottheweatherman]

Will the chart in the data centre be the parellel run as of a 3.30pm today?

As I understand it, it should be - the 06z run was supposedly the last "old-style" GFS run, so I'd expect it to be the first in which the GFS parallel is THE main GFS run, with the only other GFS run being the ensembles.

Edited December 15, 2009 by chrisbell0033944

[peterf]

As I understand it, it should be - the 06z run was supposedly the last "old-style" GFS run, so I'd expect it to be the first in which the GFS parallel is THE main GFS run, with the only other GFS run being the ensembles.

will we notice any differences with it?

as in layout or presentation.

Edited December 15, 2009 by peterf

[Paul]

Will the chart in the data centre be the parellel run as of a 3.30pm today?

Yes, the GFS has been upgraded today to what was the parallel run - it's coming in now:

http://www.netweather.tv/index.cgi?action=nwdc;sess=

[chrisbell-nottheweatherman]

will we notice any differences with it?

My (very) limited understanding is that it should theoretically be more accurate; certainly those here who really know their stuff say that, this past week, it's been very consistent compared to the outgoing GFS.

[Paul]

will we notice any differences with it?

as in layout or presentation.

No, not to start with, although there are some additional data fields which we'll probably use in charts / forecasts going forward.

[peterf]

No, not to start with, although there are some additional data fields which we'll probably use in charts / forecasts going forward.

thanks Paul.