Model Output - General Discussion

[johnholmes]

Hi John,

any chance you could do a quick update on the models as its all getting a bit mad on here.

Your input would be welcomed by the users who like Teits, Jackone, steve, nick and the others who post regular informative posts and the pople like myself who respect them.

I've don a blog and I'm watching Sports P but I'll give a quick view shortly

[Thundersquall]

On a more positive note regarding this approaching colder spell, scanning the computer model charts and snow-risk charts, there's a good chance of something happening Tuesday night into Wednesday.

With not much wind any precipitation could hang around for a while!

Edited December 13, 2009 by Thundersquall

[johnholmes]

A quick update for the Model thread as requested on it and in a couple of pm’s

The quickest way of checking what is going on is take a quick look at the UK Met Fax charts-currently there are THREE all for the same day. Note how the first one you scroll down to is somewhat different from the two earlier issues!

Its complex and its no use expecting things not to change as we count down to nearer T+00 on that 12z Wednesday chart.

Beyond that is probably a touch easier – IF the models are correct in their GENERAL idea of what is going to happen. Continuing to get colder and with the attention turning more to the north. First signs of it on the, current, UK Met Fax for T+120 off Norway.

Supported, admittedly in different degrees, by the 3 model outputs.

Patience it will get colder and, I think in an earlier blog I suggested, 60% if not more of the country will see lying snow for at least 2 days or more over the coming cold spell.

How long will it last-10 days at least probably longer.

Now what on earth do I say on the video tomorrow?

[bluearmy]

http://www.ecmwf.int/samples/d/banner/page.html

definite spread at the end of the run and much more precip on offer with the less cold options. note the op only scraping above freezing on day 10 despite that apparent s flow. plenty of chances of ice days over the preceding 7 days.

thank goodnes sm was around to calm some of you down earlier.

i await the NAEFS 12z's to see what they make of the greenland blocking T240. seems rather a swift exit of heights on the ecm 12z. also, the shortwave coming out of the gulf of mexico that becomes the fi atlantic low on recent gfs offerings and 12z ecm is not at all certain according to todays NOAA mutterings.

[Snowyowl9]

Lets have a look at a few charts after this easterly,how long or snowy is still a hard forecast from this easterly let alone what comes next.

Not quite upto the standard of december 1981 as there was much more deep cold,which came further west.

http://www.wetterzentrale.de/archive/ra/1981/Rrea00119811209.gif

http://91.121.93.17/pics/Recm1681.gif

http://91.121.93.17/pics/Rukm1441.gif

http://91.121.93.17/pics/Rtavn1381.png

http://91.121.93.17/pics/Rgem1201.gif

[Lewis]

Nothing wrong with the ECM at all.

Mods excuse me for posting this, but if you feel it should be deleted, then please go ahead;

Earlier on today i had regular showers pushing in off the N sea, at the moment we are stuck under high pressure.

Now... A lot of people on here don't have a clue! and keep under-estimating the precipitation level/potential, the North Sea is warmer than average, your going to get convection kicking up.

I recorded just over 5.1mm today from a couple of heavy showers, the radars showed them as light, but they was far from it. I also had a drop in temp of 2.3c in one shower, and the dew dropped from 5.8c to 3.6c.

What I'm trying to say is that precipitation will be there, that's a fact. We cannot rule out troughs/organized bands of precipitation 24-48 hours out never mind 72.

So everyone saying oh no this is a downgrade etc, please think before posting, it saves people like me from having to spend 5 mins typing a post.

Whether you have a "Slack" flow or "Tight/strong" flow, if it's a LP you'll get convection, and if it's coming from the N sea, it's a 110% certainty, a slacker flow just means the showers are less likely to penetrate further inland.

Hope this helps peeps

Lewis

[Cecil Hogmanay Melchett]

http://www.ecmwf.int/samples/d/banner/page.html

definite spread at the end of the run and much more precip on offer with the less cold options. note the op only scraping above freezing on day 10 despite that apparent s flow. plenty of chances of ice days over the preceding 7 days.

thank goodnes sm was around to calm some of you down earlier.

i await the NAEFS 12z's to see what they make of the greenland blocking T240. seems rather a swift exit of heights on the ecm 12z. also, the shortwave coming out of the gulf of mexico that becomes the fi atlantic low on recent gfs offerings and 12z ecm is not at all certain according to todays NOAA mutterings.

STUNNING ensembles for Reading.

Looks cold right out to the 22nd and even then there is a big spread at the end.

[Thundery wintry showers]

Looking at the ECMWF more closely, it appears that part of the reason for the slacker easterly flow is a trough over the northeast of the country. That in itself could be a source of precipitation. But I don't think the positioning of any troughs will be decided until T+48!

[MAF]

A quick update for the Model thread as requested on it and in a couple of pm's

The quickest way of checking what is going on is take a quick look at the UK Met Fax charts-currently there are THREE all for the same day. Note how the first one you scroll down to is somewhat different from the two earlier issues!

Its complex and its no use expecting things not to change as we count down to nearer T+00 on that 12z Wednesday chart.

Beyond that is probably a touch easier – IF the models are correct in their GENERAL idea of what is going to happen. Continuing to get colder and with the attention turning more to the north. First signs of it on the, current, UK Met Fax for T+120 off Norway.

Supported, admittedly in different degrees, by the 3 model outputs.

Patience it will get colder and, I think in an earlier blog I suggested, 60% if not more of the country will see lying snow for at least 2 days or more over the coming cold spell.

How long will it last-10 days at least probably longer.

Now what on earth do I say on the video tomorrow?

thank you very much John. Hopefully your views will stop a lot of the "when will it....?" questions.

as for the video tomorrow, you could recite your Christmas present wish list now that you have used your script up in the post you made

[winter watcher]

A quick update for the Model thread as requested on it and in a couple of pm’s

The quickest way of checking what is going on is take a quick look at the UK Met Fax charts-currently there are THREE all for the same day. Note how the first one you scroll down to is somewhat different from the two earlier issues!

Its complex and its no use expecting things not to change as we count down to nearer T+00 on that 12z Wednesday chart.

Beyond that is probably a touch easier – IF the models are correct in their GENERAL idea of what is going to happen. Continuing to get colder and with the attention turning more to the north. First signs of it on the, current, UK Met Fax for T+120 off Norway.

Supported, admittedly in different degrees, by the 3 model outputs.

Patience it will get colder and, I think in an earlier blog I suggested, 60% if not more of the country will see lying snow for at least 2 days or more over the coming cold spell.

How long will it last-10 days at least probably longer.

Now what on earth do I say on the video tomorrow?

John can i say on behalf off us newbies on here and probably those who was just about too prepare a looped rope over their necks THANKYOU SIR. I be honest i am sitting here stunned by your latest update and jumping for joy AT LEAST A TEN DAY BITTER COLD SPELL now how often in December have we been told that with a very good chance off it coming off? I think i am going to have a celebratory beer and book late next week off from work. Cheers John

[Thundersquall]

The 12Z ECMWF chart for T+240, now shows a monster LP in the Atlantic with central pressure of less than 944mb. The 00Z chart didn't show this at all!

Just goes to show we can't tell what's going to happen yet in 10 days time.

00Z:

12Z:

[Thundery wintry showers]

Model accuracy is usually low at T+240 at the best of times, let alone in a blocking setup that the models traditionally don't handle very well.

Regarding John's assessment I'll be interested to see how long this cold spell lasts as I'm personally doubtful whether it will go on for >10 days, but of course as the models are usually too hasty to break down such cold spells, it's entirely plausible (and would result in a widespread white Christmas). I'm confident that it will go on for at least a week though. I agree that >60% of the country is looking, potentially, at a prolonged snow-covered spell. After the easterly on Thursday, which is likely to deliver snow for some (the distribution of snow cover depending on the specifics which are yet to be pinned down), temperatures look unlikely to rise enough in the following week or so to initiate any significant thawing- and possibly longer.

Edit: thus I think the "white Christmas" assessment is on something of a knife edge! Which is far more than we can usually say at this stage of the month, of course.

Edited December 13, 2009 by Thundery wintry showers

[PB22]

ECm extended ensembles show a definite milder theme for Christmas week, so both GFS and ECM seem consistent on this already. Will be interesting to see how it actually pans out:

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

[chrisbell-nottheweatherman]

The 12Z ECMWF chart for T+240, now shows a monster LP in the Atlantic with central pressure of less than 944mb. The 00Z chart didn't show this at all!

Just goes to show we can't tell what's going to happen yet in 10 days time.

00Z:

12Z:

I can't recall if it was in this thread or another, but someone earlier suggested that that low looked almost hurricane-like! Of course, before someone thinks I'm actually suggesting it is, well, of course not. The point is that the lack of consistency on this issue proves yet again what has been stated over and over by the likes of John Holmes here that models that far out do produce unpredictable results.

Edited December 13, 2009 by chrisbell0033944

[winter watcher]

The 12Z ECMWF chart for T+240, now shows a monster LP in the Atlantic with central pressure of less than 944mb. The 00Z chart didn't show this at all!

Just goes to show we can't tell what's going to happen yet in 10 days time.

00Z:

12Z:

Hi TS hope your well.

I think a poster mentioned this earlier on re the deep low out to the south west and said that this is just the ECM way flipping about with different scenarios which i agreed with. I think we have to look at the more detailed picture i,e trends within the realms off the reliable time frame and the trend is biting cold and by the looks off things could easily stick with us to Christmas and beyond which atm i would say is 50-50 but with more major factors in our favour. The odds for a bitter cold spell for me is nailed on for at least 10-12 days great great stuff and long may it continue

Edit damm Chisspell beat me too it. Just to add i also had another conversation about a hour and a half ago with inside info and he says nothings changed its going to be a severe one guys.

Edited December 13, 2009 by winter watcher

[keithlucky]

Dont look good for swales easterlies no good for us.The best we could hope for is transient snow, if the Lp over portugal heads north over xmas.

[kold weather]

The ECM certainly isn't as good as the 0z run but the only reason for that is the huge Atlantic LP that has periodically also be shown as strong by the GFS, the actual jet pattern still looks pretty solid and there is still relative heights over Greenland which aren't bad.

If the LP was closer to the GFS 12z op run's strength then I suspect the 12z ECM would have looked quite a bit more interesting, however with such a big low there can be no doubt a breakdown would probably occur shortly after that chart...just in time for xmas.

As Steve said though I think the models still maybe somewhat progressive, its looking increasingly likely milder air will creep into the south but the north shows a lot more uncertainty with quite a few runs still cold at xmas day and this shows how close the pattern could turn out to be, I would not yet rule out a big xmas day snow event for at least the north...

[Richie V]

18Z rolling

Please accept my apologies for my eariler outburst, YES I'm thoroughly ashamed at that.

Edited December 13, 2009 by Chassisbot

[Harsh Climate]

Hmm maybe somethings been overlooked, the gfs 18z is now predicting mod/heavy precipitation in northern england tommorow with temps of 1 degrees??

http://www.wetterzentrale.de/pics/Rtavn1817.png

http://www.wetterzentrale.de/pics/Rtavn184.png

could be interesting especially on high ground.

Edited December 13, 2009 by Jed Bickerdike

[Upgrade]

I have a feeling the dartboard low in the ECM is being overdone and will move further to the south of the uk and not be as strong, and we will remain in the cold zone.

[johnholmes]

have to say it

some of you lot-and some should know better gobsmack me

we have the daddy of cold spells about to start-frost-snow for many and we are already looking to T+300+ for the breakdown-come on kids give everyone a break-talk about the next 24-120 hours perhaps out to 168 hours-salivate-enjoy-watch each b- run if you want but for heavens sake stop wishing your lives away on manyana land.

enjoy this week if you are a cold fan-get real

end of another jh rant

tara

[Paul]

This is a request to everyone involved in this thread - please, please keep it on topic and civil, the team are working flat out here and cannot continue to patrol this thread continuously.

Have a read of this and please try to post into the relevant thread:

http://forum.netweather.tv/topic/58023-winter-topics-please-read/

This is a community and as such we all need to work together to make it a enjoyable and interesting place for everyone to be involved in, so please help us help you by a. keeping things on topic and b. reporting any posts you think are an issue.

Thank you!

Paul

[TEITS]

Tomorrow night/Tues morning does need to be watched closely.

http://www.wetterzentrale.de/pics/Rmgfs362.gif

http://www.wetterzentrale.de/pics/Rmgfs364.gif

Possible to see snow on the E flank of the precip with E Midlands most at risk.

[Weather-history]

The 12Z ECMWF chart for T+240, now shows a monster LP in the Atlantic with central pressure of less than 944mb. The

12Z:

That looks unrealistic to me, a low of that intensity south of 50N? Me thinks not....

[Snow Queen one]

That low wouldn't be out of place in Oct 87 lol wow. I don't see that coming off