Model Output Discussion

[Cheese Rice]

Interesting GFS output, nice to see -10 air coming in on Monday, but after that the chances of snow in the south decreases quite alot.

For anyone in the south the GFS could end up been a pretty poor run, the air may not be cold enough for snow, while anywhere north of Birmingham could experience some of the heaviest snowfall in a long time. I'm not too sure as to what i would prefer, the latest GFS run of the low pressure battle ground scenario or a north easterly flow, if I was been selfish I would prefer the battle ground scenario as i would more than likely receive plenty of snow. But this would be a more northern event only so I would have to go for the North easterly, so at least we all get some snow.

Edited December 10, 2009 by 10123

[bluearmy]

no need for any particular concern - the increase in the southerly arm shouldnt come as too much of a surprise, although it may not run as far north as is advertised on the 00z ouput. as sm indicates, it does give us a better chance of a snow event although it increases the risks that the less cold air will make it through. all variations on the general theme. the deep low in the southern north sea next w/end looks less likely now although it may come back again on tomorrows output. the chance of the shortwave drifting sw into the atlantic trough looks to me to be an ensemble favourite. hopefully the higher resolution of the ops will be more reliable on this. i think tonights FAX T120 is an important pointer. yesterdays didint really help re the likely path of the first shortwave and we should get to see if there is any appetite for the stronger e/se flow early next week.

also, for us southerners, once the continent is cold and we have had a few days of cold, the uppers are not that important in geting snow if the flow remains anything east of south. even a southerly flow is acceptable as the lower level wind will be se. (assuming uppers are below 0c of course)

Edited December 10, 2009 by bluearmy

[Nick F]

The milder runs are because the low pressure to our SW absorbs the shortwave at just the wrong time which means the flow over the UK switches to a southerly briefly and raises those 850hpa temps ahead of the low.

Given the nature of shortwaves and that jazz, its far too early to make any half decent call in that respect.

I find that the models, especially GFS, can be too progressive in bringing in milder air in from the SW and breaking down a cold block. 06z looks too progressive to me in introducing milder air from the SW ... a habit of GFS at times.

[chrisbell-nottheweatherman]

I find that the models, especially GFS, can be too progressive in bringing in milder air in from the SW and breaking down a cold block. 06z looks too progressive to me in introducing milder air from the SW ... a habit of GFS at times.

Sorry mods, not strictly on-topic, but could that have been the cause that swayed Mr Bett to predict mild weather next week?

EDIT: no more posts here - promise, so thanks in advance for any replies!

Edited December 10, 2009 by chrisbell0033944

[snowmadchrisuk]

I find that the models, especially GFS, can be too progressive in bringing in milder air in from the SW and breaking down a cold block. 06z looks too progressive to me in introducing milder air from the SW ... a habit of GFS at times.

You also have to remember that the low would bump into some very cold air already here , temps around -1 so Some heavy snow would be likely . Last year we seen a lot of snow from SW winds. I think though , that won't even happen as I think the low will be to far south and west by the time it comes to even effect us.

Edited December 10, 2009 by snowmadchrisuk

[WhiteFox]

http://www.wetterzentrale.de/archive/ra/1991/Rrea00119910207.gif

Neil- Feb 1991 had winds just south of East-

I cant believe why people are some down on todays outputs- im very happy- I guess the expectation of that huge ball of cold air arriving had something to do with it-

THe watered down version can be just as good....

S

Thanks Steve. I was looking for that chart and couldn't find it. There's no reason why winds south of east cannot deliver snow; if the air in place is cold enough then it is fine. It's different if the source of the wind is further south, i.e. Southern France, but in that chart it is still ultimately sourced from further east and more than cold enough. Basically the same reason why a North wind does not always deliver snow despite the old maxim 'When the north wind blows, we shall have snow"...

[Michael Fishermans Friend]

To me GFS and ECM are a slight downgrade but lets face it from yesterday evenings outputs there was only one way to go. No bone bitingly cold easterlies and something less cold from the NNE after about 168+ and maybe marginal, still alot of runs for things to change. Also what happened to that shortwave moving south after about 144 or so?

[Frosty.]

Really folks! Some of the doom-and-gloom is really quite surprising...

With the ECM 00z it's fully justified but all the other models are awesome, the standard gfs & the turbo charged parallel version continue to promise a big freeze with mega snowfalls and this includes the GEM etc. If we can't get a decent wintry spell out of all this then we never will! Excellent meto update promises much snow and frost for the north and east

[SMU]

http://www.meteociel.fr/modeles/nogapse_cartes.php

In terms of what I think will happen evolution wise - all things considered- where we have seen the change in emphasis of the southern arm of the jet I think the NOGAPS is spot on with the balance of energy-

Thats the trend of the day-

Steve

[Thundery wintry showers]

I find that the models, especially GFS, can be too progressive in bringing in milder air in from the SW and breaking down a cold block. 06z looks too progressive to me in introducing milder air from the SW ... a habit of GFS at times.

Yes, I think you're right- it was certainly the case during late February/early March 2005 and early March 2006, and indeed at times to a lesser extent last winter. I remember many GFS runs around 26-27 February 2006 going for Atlantic lows pushing up from the SW around 1/2 March 2006 and some runs even had mild south-westerlies taking over altogether.

[Glacier Point]

Composites for Global Wind Oscillation phase 4 continue to best describe the overall state of the atmosphere which is predisposed to the evolution and persistence of a strong blocking signal over Greenland likely to transfer towards the Canadian Arctic over time.

Note the southerly displaced jestream extending across Europe and trough solution over Scandinavia which is chiming really well with the GFS, GEM and UKMO outputs.

GFS and CMC ensemble mean upper height anomalies for days 11-15:

http://raleighwx.eas...htAnomalyNH.gif

http://raleighwx.eas...htAnomalyNH.gif

Like September and October, the global weather pattern has become stuck in phase 4 of the GWO - its just the changing wavelengths and seasonal implications of an El Nino and a huge -AO that have made the difference. Speaking of the AO,

http://www.cpc.ncep....ndex_ensm.shtml

... of the scale, I reckon anything up to -5 or -6 SD.

Remember how persistent the pattern earlier on in September was ? That should infer that we shouldn't expect the cold pattern to go anywhere fast. Any significant change here is going to be related to a transfer of tropical convection into the Indian Ocean from where it is in the central Pacific. By my reckoning, that's at least two to three weeks off, as it is by the MJO forecasts which only go as far as the 23rd December with the MJO still in phase 8 (remember that phase 1 is located over east Africa / Sea of Arabia)

http://www.cpc.ncep....O/foregfs.shtml

As stated previously, maybe not the deep cold, but oozing snow potential to take us up to and perhaps well beyond Christmas.

Phase 4 GWO composite:

Edited December 10, 2009 by Glacier Point

[smich]

Excellent update GP - thanks.

I still can't get over those -AO Ensembles. -5 or -6 SD might be a rather conservative estimate I reckon!

smich

[Harsh Climate]

Gem is the best of the lot, certainly my favourite!

http://www.wetterzentrale.de/pics/Rgem1561.gif

http://www.wetterzentrale.de/pics/Rgem1921.gif

http://www.wetterzentrale.de/pics/Rgem2041.gif

[johnholmes]

its not often we have seen the AO go off the bottom scale-even the NAO is trying to get in on the act-whilst the PNA is determined to join in the fun at the +ve end-even the 30mb temperature is listening and has decided to climb again.

The 500mb hemisphere charts from all 3 sources NOAA, GFS, ECMWF all like the sound of the Christmas Carol the longer tele' links are singing so have joined in.

All it wants now is for it all to --ts up and we could have an awful lot of people being extremely grumpy in the lead up to Xmas-new toys wanted for empty cots etc!

My own view is buy your sledge before the shops run out!

Edited December 10, 2009 by johnholmes

[Neilsouth]

My own view is buy your sledge before the shops run out!

Hopefully , it's just strange that the ecm keeps looking like a flabby high with no real interest apart from dry. It's generally done the same bar one blip yesterday , it's also on its own regarding all the other models.

[Reading FC]

Hopefully , it's just strange that the ecm keeps looking like a flabby high with no real interest apart from dry. It's generally done the same bar one blip yesterday , it's also on its own regarding all the other models.

I've kind of got everything crossed that the ECM is correct this time. As much as I'd love some snow for purely selfish reasons I've organised our annual Christmas golf do on the 17th next week and there's 40 of us playing (hopefully!) so could od with that model being the correct one at the moment!

[Neilsouth]

I've kind of got everything crossed that the ECM is correct this time. As much as I'd love some snow for purely selfish reasons I've organised our annual Christmas golf do on the 17th next week and there's 40 of us playing (hopefully!) so could od with that model being the correct one at the moment!

So what if it snows on the 18th or 19th , yes that is very selfish lol. This COULD be a once in a lifetime event are you willing to put that aside for a boring game of golf lol

[Harsh Climate]

ECMWF:

http://www.wetterzentrale.de/pics/Recm1921.gif

http://www.wetterzentrale.de/pics/Recm2161.gif

http://www.wetterzentrale.de/pics/Recm2401.gif

To be fair this has been the order of the day in recent years.. All so close but yet so far.

I think the ecmwf certainly shouldnt be ignored. Lets hope it comes on board later.

[smhouston]

My own view is buy your sledge before the shops run out!

John! You should know better being a pro than to go ramping! You'll cause meltdown on here, lol

It certainly is looking good though. It's concerning that the ECM keeps being undecided,but I guess it's such a hard pattern to handle. I'm still siding with the ECM (to try cushion the blow if it does go pear shaped), but I must admit it's starting to get harder each run not to get excited bearing in mind we're already pretty much about to start the whole show in a day or so! Truely amazing synoptics whatever happens. I'm just hoping the new GFS parallel model is correct...if not then I've got a feeling it's going to be causing quite a lot of heartbreaks in the future when it replaces the old GFS with the sort of things it's been showing, lol

We just need Steves model tracker to come back now *hint hint hint*

[Neilsouth]

Jed thats the old run and the worst one , we've been discussing it all day so far... Apart from last nights amazing ecm it's been very poor lately and has NOT been consistant

[stewfox]

its not often we have seen the AO go off the bottom scale-even the NAO

I have read the oscillation has tended to stay in the positive phase in the last 30 years, hence causing lower than normal arctic air pressure and higher than normal temperatures in much of the United States and northern Eurasia

Given this what's you take on why the big change?

Edited December 10, 2009 by stewfox

[Thundery wintry showers]

Or maybe we could get some kind of easterly setup with snow showers in the east but not getting as far west as Reading? That could also work, but it might displease some snow lovers in the Berkshire area... (Or the suggestion of it holding off till the 18th or 19th- a lull on the 17th with snow showers fore and aft might actually be in my favour as I'm getting a train up north that day). "Boring game of golf" is a little harsh though.

Today's 12Z runs will be very interesting. Will the ECMWF back down from its cold dry 00Z scenario for the third day in a row? Will the UKMO keep up its high-potential outlook? Will the GFS go for a repeat of yesterday's 12Z run? All will be revealed shortly.

[Harsh Climate]

Jed thats the old run and the worst one , we've been discussing it all day so far... Apart from last nights amazing ecm it's been very poor lately and has NOT been consistant

I know, what im saying is thats a very poor run, but it does have similarities to recent years and the crap outcomes normally produced.. thats why I hope it changes later as that would be a worrying trend for it to start picking up. But yes I agree the emwf has been all over the place recently. Id look mostly into the gfs and ukmo at the moment

[Frosty.]

NOGAPS 12z says YES....even a chance of a borderline sleet-wet snow combo on mon/tues in the southeast but the real fun and games will occur once the scandi trough floods increasingly cold air in from the NE by midweek with high pressure heading NW, we are now nudging the outer rim of the reliable timeframe of 5 days away, subsequently the nogaps would go on to mirror the latest gfs runs with a prolonged very cold & wintry spell. I'm praying the ecm moves back towards the 12z stunner yesterday and no repeat of the damp squib it gave us this morning with flabby highs and weak N'ly skimming the east coast.

Edited December 10, 2009 by Frosty039

[Neilsouth]

Have you seen how strong the winds are possibly going to get , going by gme?

http://www.wzkarten.de/pics/Rgme1324.gif

hah