General Model Output Discussion

[grab my graupel]

A new Model thread

All the latest Model output is available on Netweather

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

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[AtlanticFlamethrower]

This run is more supportive of a 'technical' white Christmas.

Colder 850hpa, 528 thickness way south and PPN. Still much evolution to come beginning much before T132 I suspect.

Edited December 19, 2009 by AtlanticFlamethrower

[kold weather]

The models coming into agreement with a milder set-up at least getting int othe South however the models keep the jet surpressed and the Arctic high in place...make no mistake about the 12z ECM we are probably 48-72hrs away from being in another cold flow on that run...

However the ECM is amazingly progressive with the breakdown, no doubt too fast given the other models...

Utterly messy synoptics, very much anything could happen if the models have not latched onto the strength or placement of certain placements correct.

[Tom D]

This run doesn't so much keep the cold over the Uk any more than it keeps the milder air away from us. This run keeps it cold up until next Friday, with a beautiful Christmas Day if it stays this way.

After that it keeps the huge low pressure forcing its way in. That system looks impressive at +168 and barges the breif high pressure away with ease.

[January Snowstorm]

A very obvious trend of a warm up just after the big day.

Definite risk of a white Christmas for some still though!

[kold weather]

This run doesn't so much keep the cold over the Uk any more than it keeps the milder air away from us. This run keeps it cold up until next Friday, with a beautiful Christmas Day if it stays this way.

After that it keeps the huge low pressure forcing its way in. That system looks impressive at +168 and barges the breif high pressure away with ease.

Yep there is quite good model support for that evolution but I'm still not convinced by it totally yet, esp with regards to how deep the GFS makes the low, no doubt its doing its usual over the top strenghening...

By the way, the GFS has got a HUGE difference in the arctic, lets say the global evolution really doesn't support the GFS at all, no doubt its being its overly progressive self!

Edited December 19, 2009 by kold weather

[SnowBallz]

cant see white christmas at all on that one :unsure:

[The PIT]

Pub run well is drunk and ecm 12 oz is considerintg the pub and is sayingt good bye cold very rapidly. I think we need a few more runs.

Edited December 19, 2009 by The PIT

[swfc]

poor gfs at the 100hr mark.the cold spell seems to be on a dodgy wicket now

[JamieUK]

Well this run has upgraded my chances of seeing snowfall on Christmas Day! from 00:00 to 09:00 xmas morning theres a 70% risk. Wont keep my hopes up obviously, but is nice to see!

[TEITS]

A very obvious trend of a warm up just after the big day.

Definite risk of a white Christmas for some still though!

How can you call this a trend!!

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

http://www.wetterzentrale.de/pics/Rtavn2401.png

I've never seen such uncertainity. The models are that confusing at the moment I can't be bothered to go beyond +72.

[Backtrack]

Yep. An easterly on Christmas eve looks probable!

What ever happened to Ian Brown's forecast of a record breakingly mild December?

[kold weather]

Ensembles do broadly agree on the idea that a deepening low develops and forces up a high from Europe to introduce somew armer air, however even that idea could go wrong if the model is overdoing the lows strength, then that will mean the low makes less astward progression and the risk is there for a high to build up right over us, just like it did at the start of this spell...beyond that and the ensembles have just about every single type of synoptic you can imagine, ther ereally is huge spread!

[azores92]

Ensembles do broadly agree on the idea that a deepening low develops and forces up a high from Europe to introduce somew armer air, however even that idea could go wrong if the model is overdoing the lows strength, then that will mean the low makes less astward progression and the risk is there for a high to build up right over us, just like it did at the start of this spell...beyond that and the ensembles have just about every single type of synoptic you can imagine, ther ereally is huge spread!

given that these progged synoptics are about a week away, i dont think its worth paying too much attention to them atm. if this low is shown in 2 or 3 days time, pushing the block away with such ease, then maybe its more worth considering.

[keithlucky]

How can you call this a trend!!

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

http://www.wetterzentrale.de/pics/Rtavn2401.png

I've never seen such uncertainity. The models are that confusing at the moment I can't be bothered to go beyond +72.

Yes wild disagrement the met said no sign of cold spell ending all here writing the cold spell as over.

[Yozzer]

Pub run well is drunk and ecm 12 oz is considerintg the pub and is sayingt good bye cold very rapidly. I think we need a few more runs.

Think you've joined them, hic...

Anyway, we can't knock the GFS for spotting a mild end to the month while congratulating it for spotting the current cold blast from about 2 weeks away. Caveat to that is that I broadly agree it is being too progressive given what I've read from GP's posts on the tech discussion. Some surprises likely over next few days methinks.

[karyo]

We still have sevral days of cold and wintry weather to come. Unlikely to warm up before Christmas and the ensembles keep it chilly up to Boxing day! That's a week from now! Just enjoy the wintry weather and don't worry about FI.

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

Karyo

[igloo]

it looks very likely a breakdown will happen over christmas with most models now agreeing. i would expect a few weeks of zonal type weather till mid january before more blocking gets going again after all when was the last cold spell lasting 10 days or so

[Thundery wintry showers]

On the GFS 18Z, staying cold and wintry from the Midlands northwards until Christmas Day then milder from 26/27 December. I would happily settle for that scenario.

Massive uncertainty still from around 24 December, strong agreement on it staying cold & snowy up until 23 December especially in the north. The chances of a white Christmas hang in the balance for most, but look increasingly odds-on for northern Scotland.

[mountain shadow]

Nigh on impossible to make predictions based on model output for the medium term.

Any "breakdown" is continually postponed and I have no doubt the 0z's will offer yet more confusion.

The problem is that the upper low projected to be sitting over us can pretty much go anywhere with nothing steering it and where that goes will determine what we get.

[Matt12]

Is it me, or do the latest ensembles offer more hope for a white Christmas for the South? The latest outputs seem to delay the arrival of any milder air for the South until the 26th/27th.

Matt.

[skifreak]

From a IMBY perspective / Snowsports perspective the 18z GFS breakdown is very interesting. Strengthening southerly to SW winds coming in ahead of the milder air is the interesting factor, because it will blow potentially large quantities of snow of the Cairngorm Plateau and Southern aspects over the mountain into the Lee aspects to the North ie, into the Ski Area!

As it starts to get milder this will continue, but snow will start to get wet as it drifts down and the FL on the 27th would stay below or just about the summits, thus this process would continue at the top of the mountain, coupled with driving heavy wet snow which would also blow down the mountain filling gullies that form the main ski runs with a layer of wetter snow that would bind the dry drifted snow from earlier. Possibly sleet or rain for a time at all but the highest levels, before colder air digs in again and hey presto a fantastic base!!

Obviously too far out for such detail, but such an event with a period of very marginal very wet heavy snow on howling SW gales is what happened on the evening of Hogmanay 2000 and set up what was to turn out to be the Classic 2001 season. Obviously one storm can't make a whole season, but getting the base down into the streams and gullies is more than half the battle. There's already a promising base in the most difficult to fill places and such an outcome would really set things up nicely to build from during Jan.

I know the days after Christmas will if they were to remain the same as the 18z get much gnashing of teeth, wailing and slitting of wrists, but I think I'd welcome it!

[wellington boot]

We still have sevral days of cold and wintry weather to come. Unlikely to warm up before Christmas and the ensembles keep it chilly up to Boxing day! That's a week from now! Just enjoy the wintry weather and don't worry about FI.

http://www.netweathe...ensviewer;sess=

Karyo

I want to worry about FI, when it looks like it does on the 00z. It's not quite there - I thought it would turn out even better but in fact it falters at t228 or t240 - but if we started seeing charts like that closer to reliable timeframe, that would be exciting.

[KTtom]

Nigh on impossible to make predictions based on model output for the medium term.

Any "breakdown" is continually postponed and I have no doubt the 0z's will offer yet more confusion.

The problem is that the upper low projected to be sitting over us can pretty much go anywhere with nothing steering it and where that goes will determine what we get.

Confusion is the word. At just T120 (xmas day) we have the UKMO with an easterly and ECM with a westerly, GFS somewhere inbetween. Interesting GFS has pressure re-building to the NE and any breakdown now pushed out to new year.

[Terminal Moraine]

The GFS 00z has the cold weather lasting until well after christmas, with a significant snow event thrown in for good measure between christmas and new year. A quick look at the ensembles reveals that the operational is one of the coldest members after the 26th, though not without support, and the sudden amount and degree of scatter after the 25th indicates that anything could happen.

We'll see if the next ECM gives GFS any support, somehow I doubt it will.