Model Output Discussion 12z 30/11/2012

[EML Network]

is that another Tropical development heading up??

coming from EXACTLY the same place as the previous one too ...is someone doing some experiments down there ?? very odd to see one let alone 2 in December , very weird !

[bluearmy]

very interesting to read that mogreps-15 supports a transfer of heights into europe. given the extended ens modelling with a low anomoly in this area, one would expect this to tramsfer east quite quickly if it happens. of course its possible the models are clueless in which case anything is feasible.

[Cheshire Freeze]

very interesting to read that mogreps-15 supports a transfer of heights into europe. given the extended ens modelling with a low anomoly in this area, one would expect this to tramsfer east quite quickly if it happens. of course its possible the models are clueless in which case anything is feasible.

I don't think many of us would want to see heights pushed into Europe.Though that troublesome PV segment over Greenland is causing a headache....we need it to do one really!

[weather eater]

Where do we go from here? That high is trapped in no-mans land

It will shift north, a northerly will follow for us.

Edited November 30, 2012 by weather eater

[IDO]

Is that a crooked quasi omega block and the UK is in the heights? http://cdn.nwstatic.co.uk/gfsimages/gfs.20121130/12/192/h500slp.png

[Cheshire Freeze]

It will shift north, a northerly will follow for us.

It can't shift north because the jet is far too strong & flat as a result of that PV around Greenland.

Strong +NAO here...

Edited November 30, 2012 by CreweCold

[The Eagle]

GFS is the worst 12z run we have seen in a long time from a cold point of view post 144hrs. Trend seems to be to build in a mid latitude blocking high pressure.

[bradymk]

GFS is the worst 12z run we have seen in a long time from a cold point of view post 144hrs. Trend seems to be to build in a mid latitude blocking high pressure.

Depends what your defining as cold?

[Tom Jarvis]

what if these tropical lows dont actually form. where do we go from there

would like some help as im quite new to looking at moddeles

Edited November 30, 2012 by Tom Jarvis

[Tim Bland]

12z backs up Ian's statement on previous page re heights building into the uk next weekend. Where we go after that depends on the PV and whether we can get heights to our NW. If we don't the pattern will likely go flat and were back to square 1

[Jupiters Winter]

That low is huge influence on the GFS. Looking beyond that is really F1 at the moment until positioning of it is agreed upon.

[IDO]

All in FI but that has been several runs by GFS leading to very poor synoptics for the UK mid December. It appears that there are numerous permutations for the UK and about 50% involve an average/cool outcome (poor for snow), the other 50% are cool/cold.

This one has us under HP for over ten days with little chance of snow and very average temps in the last 5-6 days: http://cdn.nwstatic.co.uk/gfsimages/gfs.20121130/12/336/ukmaxtemp.png

At the end Atlantic takes charge: http://cdn.nwstatic.co.uk/gfsimages/gfs.20121130/12/360/h500slp.png and December is looking poor.

[Methuselah]

I've just realized: I've NEVER seen any individual model-run properly verify...

[weather eater]

It can't shift north because the jet is far too strong & flat as a result of that PV around Greenland.

Strong +NAO here...

I was a bit premature it did look like it might behave as previous runs but your right its stuck, doesn’t matter because there is no point worrying about post 120hr, this is the third idea the GFS has pulled up today.

[Great Plum]

I think weather eater is right - 3 gfs runs, 3 different ideas for post 120hrs... My knowledge of the strat and vortex etc is low but I cannot see a high +nao from the strat...

FI gfs to be an outlier?

[phil nw.]

Interesting how that little sub-tropical sourced low drags some cold air from further east as it nears the south west approaches.

possible snow for parts of N.France but it looks as if that`s as far north as it gets on this run.

This is T144hrs so pinch of salt and all that but it shows how a little development like this can crop up at relatively short notice.

[bradymk]

Another cold GFS run before t192 with more low single figure daytime maxes. It all depends on where the heights go after us and where the PV is displaced to which will determine whether it will be cold/snowy, cold/dry or mild/benign week after next, plenty more changes to come in the models though but before t168, a good run imo, brrrrr!

[Catacol]

Exeter's latest thoughts into the trend period. Nothing surprising in the broad scheme of things:

"Good model agreement now for a cold, cyclonic northerly spell at the beginning of this period, with

the low latitude depression looking less likely to affect the UK than was the case a few days ago.

Thereafter, an emerging signal now for a build of pressure within the cold airmass later next week,

which is rather different from that offered by the models recently, and is tentatively followed for

now. The longevity and evolution of this ridging is then subject to very large spread within and

between EPS suites. MOGREPS-15 favours this to transfer into Europe with a more southerly type

becoming established (albeit often with cold continental influence), which opposes EC EPS signal

for retrogression and a renenwed risk of a northerly outbreak. In either case, the probabilities

favour a colder-than-average theme which is consistent with EC monthly output."

Well - that's interesting. Southerly type? That goes against what I expected to hear and not necessarily good. Makes me laugh a bit though: they admit that MOGREPS and EC differ in their evolution, but are happy to say that, either way, it will be cold. Just because the overall temperature result might be the same it is hardly the basis for confidence in the forecast if the 2 major models have the air from a different quadrant overall!

Sounds to me like even the top models hardly have a clue on the detail. At least the overall pattern remains the same in terms of dominant blocking. Will keep hunting for that Feb 91 evolution... :-)

Edited November 30, 2012 by Catacol_Highlander

[NL]

Really great to see such a balanced view in the model discussion this evening, no tantrums just because it doesn't show continued cold or deep cold after 144hrs. Still all to play for as weather eater has already stated three different scenarios after 120hrs.

[MKN]

Interesting how that little sub-tropical sourced low drags some cold air from further east as it nears the south west approaches.

possible snow for parts of N.France but it looks as if that`s as far north as it gets on this run.

This is T144hrs so pinch of salt and all that but it shows how a little development like this can crop up at relatively short notice.

The track of this low will be difficult to predict until its on the satelite images approaching our shores I imagine. Channel lows always have a tendancy to go to far north or to far south at the last minute. If of course it comes our way at all

[ChartViewer]

Models have under estimated the -ve zonal wind signal over the far NE Atlantic and the net result is that we see the cold conditions sticking - beware using the operational GFS and keep sticking to those ensemble means and spreads.

That was from GP this morning so we can expect many different solutions from GFS at moment trying to get to grips with dynamic patterns happening aloft

[swebby]

Interesting how that little sub-tropical sourced low drags some cold air from further east as it nears the south west approaches.

possible snow for parts of N.France but it looks as if that`s as far north as it gets on this run.

This is T144hrs so pinch of salt and all that but it shows how a little development like this can crop up at relatively short notice.

Not liking that second image. Somone asked if those features tracking further north would be a good or bad thing. I assume that was in respect to snowfall but for anyone drying out from last weeks deluges then snowfall is the least of your considerations and i feel a more northerly track would be a very bad thing.

S

[SMU]

Bradley that meteociel chat is excellent- much better than the WZ one-

I think the GEM looks the best case scenario-

http://modeles.meteociel.fr/modeles/gem/runs/2012113012/gemnh-0-138.png?12

S

[Buzzit]

These atlantic lows showing on the GFS are FI material. The initial one has already lowered in intensity as opposed to yesterdays GFS and also todays 6z output, I do not see them happening in the form that the GFS is showing at all : FI still at +48 for me, especially as these lows have so much impact on the pattern to follow.

[Iceaxecrampon]

Thought this would get Southern forum members interested for Thursday..... Us Northerners not always IMBY

Just a bit further North but Exmoor should do well.

Ian IAC