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General Model Output Discussion


Methuselah

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Posted
  • Location: Peterborough N.Cambridgeshire
  • Location: Peterborough N.Cambridgeshire

My view on the models is very simple.

Based on the 12ZGFS it isn't until +288 that I finally see mild temps. So for this reason and because there is so much to look forward to over the next few days, I couldn't careless what the models are showing in F.I as it will most likely change. :air_kiss:

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Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl

Mind you, it's nice to see cold getting shunted west for a change instead of that "oh so annoying" northerly toppler, that gets shoved eastwards into the north sea.

Synoptics are so unusual for the internet model watching era, that they may be badly wrong (or they may be right), but one thing is for sure...we won't end up with EXACTLY the ending shown smile.gif

My point though is we may well lose the cold pattern through the back door as i explained.

We really need those lows further east next week to hold off the mild flow from the south,but still as you suggest changes will probably show soon enough.

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VERY unconvincing breakdown on the models tonight, nogaps is very promising with a bitterly cold airmass just to our northeast a pressure rise over scandinavia is not out of the question, JMA not exactly warm either at T+192 hrs keeping us on the cold side of the jet, the runs tonight have BIG potential for snowy breakdowns with cold air returning quickly afterwards.

http://www.wetterzentrale.de/pics/Rngp1442.gif

http://www.wetterzentrale.de/pics/Rjma1921.gif

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Posted
  • Location: Wales, Valleys - 700ft ASL
  • Location: Wales, Valleys - 700ft ASL

Just need the low pressure to keep south. If it does so we could see a major frontal snow event for the South and then a renewed freezing easterly following on behind. A few hundred miles North or South will make all the difference and at this range all is up for grabs, the trend tonight however is not certainly not in the right direction.

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

The euros are both now going in the same direction only the ukmo is going there faster, less cold by xmas day or boxing day at the very latest with the gfs currently a day or so later, 27th-28th for scotland, the cold air being mixed out with atlantic flow, there seems little doubt we wont be looking at the entrenched freeze up the models were indicating previously.

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Posted
  • Location: Bedworth, North Warwickshire 404ft above sea level
  • Location: Bedworth, North Warwickshire 404ft above sea level

My point though is we may well lose the cold pattern through the back door as i explained.

We really need those lows further east next week to hold off the mild flow from the south,but still as you suggest changes will probably show soon enough.

Is there a danger if they are further east of letting the warmer air in via the front door? :air_kiss:

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Posted
  • Location: Stoke Gifford, nr Bristol, SGlos
  • Location: Stoke Gifford, nr Bristol, SGlos

VERY unconvincing breakdown on the models tonight, nogaps is very promising with a bitterly cold airmass just to our northeast a pressure rise over scandinavia is not out of the question, JMA not exactly warm either at T+192 hrs keeping us on the cold side of the jet, the runs tonight have BIG potential for snowy breakdowns with cold air returning quickly afterwards.

http://www.wetterzen...cs/Rngp1442.gif

http://www.wetterzen...cs/Rjma1921.gif

Interesting reading posts that keep mentioning the word "breakdown". Here in BTL and the West there is no cold, snowy weather to be 'broken down'!laugh.gif

In terms of detail the models seem to be flipping around alot; i suppose that's typical of this kind of winter setup.

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Posted
  • Location: Perth (Huntingtowerfield, 3 miles West) asl 0m
  • Weather Preferences: A foggy and frosty morning with newly fallen pristine snow - Paradise!
  • Location: Perth (Huntingtowerfield, 3 miles West) asl 0m

The scenario through to Monday for Scotland appears to have descended into total downgrade and confusion. Sunday night Minimums this morning were projected to be minus double digits Centigrade, the latest seems just below freezing. This is ominous for us all I feel.

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Posted
  • Location: Kippax (Leeds) 63m
  • Location: Kippax (Leeds) 63m

The scenario through to Monday for Scotland appears to have descended into total downgrade and confusion. Sunday night Minimums this morning were projected to be minus double digits Centigrade, the latest seems just below freezing. This is ominous for us all I feel.

Thats ridiculus. Once a northerly wind sets in parts of scotland will allways get most of the snow. Obviously the highlands and the west or east depending on it being NW/NE. Probably not much snow for southern scotland though.

Edited by Jed Bickerdike
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Posted
  • Location: LEVEN, Fife
  • Weather Preferences: snow, thunderstorms and extremes
  • Location: LEVEN, Fife

Thats ridiculus. Once a northerly wind sets in parts of scotland will allways get most of the snow. Obviously the highlands and the west or east depending on it being NW/NE. Probably not much snow for southern scotland though.

I agree with that. I hope the low moves south and develops a cyclonic easterly by Mon/Tue (GFS 18z yesterday showed some great charts) and that will bring heavy snow showers to the east of Scotland.

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Posted
  • Location: Dorset
  • Location: Dorset

Winds on the ECM t+240 chart are off the Atlantic and the charts available to the public only show the geopotential height not 1000-500mb thickness, you can have a 500mb height of 528 decameters (5280m) but it can still be mild at the surface at lower levels if winds are sourced from a mild direction. Lapse rates would be steep towards the NW though on the t+240 chart - so the low heights would give snow over high ground of the N and W.

Agree Nick the Thickness was calculated and about the snow further north, given things a little cooler though and snow would still be widespread for many.

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

Since around 2002/03, for whatever reason the BBC forecasts have consistently tended to overstate maximum temperatures in northerly regimes, sometimes by a few degrees- oddly they rarely do this when the winds are easterly. I will be extremely surprised if maxima of 4C occur widely across Scotland on either day of the weekend.

Perhaps they are erring on the side of caution when past frontal events of this kind gave rise to snow in the east and rain in the west, when the BBC predicted snow for nearly all parts, e.g. 27/28 January 2004, 22/23 March 2008.

Like many I am quite disheartened by this trend on the models for the lows and the -NAO to be progged further west as we get close to the big day, resulting in a gradual change to a mild southerly regime for Christmas. However, this is not fully supported by the ensembles- in fact the ensemble support for much of the British Isles hanging onto the cold air until well after Christmas is similar to what it was yesterday. It should also be noted that this morning's runs and ensembles strongly supported a delay of any breakdown until after Christmas. As long as low pressure moves from west to east instead of stalling out west as per UKMO/ECM, we should end up on the cold side of the block for a while.

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Posted
  • Location: hertfordshire
  • Location: hertfordshire

Much stronger area of convection crossing the date line now

The mjo also heading back towards phase 7-8

http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/phase.Last40days.gif

I may be wrong here but this may slow the retrograde of the Greenland block which would shunt everything further

east.

Edited by cooling climate
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Posted
  • Location: Morecambe
  • Location: Morecambe

If i have to be honest, i will guess the breakdown will occur between the 23rd December-26th December which is just a guess because i really don't know but most model output suggest the breakdown will occur at this stage BUT that is all FI so it could be much later or much earlier(hopefully not).

So that is a pretty lengthy cold spell if i have to be honest albeit for some, it might not be all that particularly snowy. So i don't really get all the disappointing posts unless you have actually took them literally.

For me personally i am going to try and take it a 100 hours at a time. What i mean is that after 100 hours, it's FI and subject to change whilst below that timeframe, it's less likely to change but as we know even then we can still see changes in the output which of course would affect the long term.

And to reply to Highland Snow post, maybe because the models are showing a nice low pressure over you with alot of snow hence the higher temps. I assume before that, those cold temps were down 2 clear skies and snow cover.

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Posted
  • Location: ipswich <east near the a14> east weather watch
  • Location: ipswich <east near the a14> east weather watch

well all i say next week there some mouth watering gfs maps next week for sure its there going to be a break down my money on DEC 26 with a battle l over us

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Posted
  • Location: Kippax (Leeds) 63m
  • Location: Kippax (Leeds) 63m

Interesting despite a possibile breakdown the gfs is still predicting a negative NAO all the way into january? Hopefully this bodes well for further height rises to the north after any breakdown.

http://www.cpc.noaa.gov/products/precip/CWlink/pna/nao.mrf.gif

And like wise for the AO forecast

http://www.cpc.noaa.gov/products/precip/CWlink/daily_ao_index/ao.mrf.gif

Quite good signs for the rest of winter :lol:

Edited by Jed Bickerdike
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Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl

No point in looking at what the models are showing for middle of next week onwards, even in the reliable timframe i.e. Sunday into Monday there isn't a clear picture of what track the low pressure from the north is going to take, so really I would just leave looking at prospects for christmas until Sunday and just sit back and enjoy and concentrate on the here and now, as others have said the picture come christmas day is very unlikely to be exactly what is being shown in the models today.

Just like the colder air progged for this week has taken longer to set in than expected last week, so too I feel the same will happen with any loss of the cold air, it will be a much slower affair than is being shown by the models, prospects for the north look very good for cold air remaining in situ into christmas - longer term very condicive synoptics for real cold as we head toward new year, a short term southerly may not be a bad thing - one thing that is looking very unlikely is a SW airstream the teleconnections don't support it - negative NAO greenland high..

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Posted
  • Location: Worcestershire/Warwickshire/North Oxfordshire
  • Location: Worcestershire/Warwickshire/North Oxfordshire

Despite a warmer air source,temps on Christmas Day are set to be cool, and Meteociel version of GFS going for snow event for southern areas.

Last night everyone was looking at the charts and saying it was going to be -15°C next week, and yet some sites (accuW) are quoting 10°C daytime temps for my location on Christmas day..

Was everyone wrong or are the professionals correct?

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

12z op for De Bilt appears on the milder side of the ensembles after Tuesday next week:

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

... so possibility that the 12z op is too keen to bring in milder air from the Atlantic as it tries to align the mean trough SW-NE (positively-tilted) across the E Atlantic.

Before next week's uncertainty though, although the next few days' focus is on the east and SE for snow potential - Saturday could be the best day for widespread snow as a set of fronts moves down from the north, 510dam air reaching far N of Scotland on the latest fax for 12z saturday - which suggests some rather cold air following the fronts (another Jan 28th 2004 event?):

post-1052-12609985343306_thumb.png

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Posted
  • Location: Peterborough, Cambridgeshire
  • Weather Preferences: Thunderstorms and snow
  • Location: Peterborough, Cambridgeshire

I have a question about the GFS ppt. modelling.

Does the GFS factor in the strong winds when predicting the extent of the precipitation?

I would have thought that with this strong NE flow:

http://charts.netweather.tv/gfsimages/gfs.20091216/18/30/h850t850eu.png

snow showers would penetrate further inland than is being shown on the chart here:

http://charts.netweather.tv/gfsimages/gfs.20091216/18/30/ukprec.png

Is this the case? Therefore how accurate a representation are the GFS precipitation charts of what will actually occur?

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

Nice Fax chart with 510 dam line appoaching northern scotland by noon saturday, should be a wintry weekend in scotland with strong Northerly winds and snow showers, it looks as though the balance of power in this cold spell will transfer north of the border.

post-1052-12609985343306_thumb.png

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

Good news for cold/snow lovers- the GFS 18Z has the Arctic low slipping south right across the country again rather than to the west, so towards Xmas we can expect the slack, cold low pressure scenario seen on this morning's runs rather than the slow warm-up from the south. I know the 18Z isn't traditionally a reliable run but I'm not sure if the new GFS might re-write the rulebook on that- the 18Z yesterday certainly set the trend that this morning's model runs picked up on.

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