Winter Model Discussion - Cold Hunting -12Z 30/12/12

[bobbydog]

yet again, greenland blocking appears in FI-

strat vortex torn apart-

[bluearmy]

maybe the day 10 ens mean is still just aout useful but as we go through into deep fi, the wide variation in the longwave pattern shown on the various clusters makes the ens mean pretty useless. Either the amplified set are right or the flatter mobile ones will be. I cant see how we get a half way house solution

[Bobby]

The latest CFS anomalies for January shows a big lump (my technical language) of low pressure to our West with above average temperatures and rainfall around average, above average in the South. I think the CFS is useful to check for trends but obviously not to taken at face value but here it is.

Temps

Edited December 31, 2012 by Bobby

[Frosty.]

The latest CFS anomalies for January shows a big lump (my technical language) of low pressure to our West with above average temperatures and rainfall around average, above average in the South. I think the CFS is useful to check for trends but obviously not to taken at face value but here it is.

Temps

Yes that's abysmal. hope it's wrong is all I can say about that, to remain snowless until february would be a bit disappointing but I do believe the SSW will have a major impact after mid month, hoping the metoffice continue to think so too, if not, we are sunk.

Edited December 31, 2012 by Frosty039

[Iceaxecrampon]

Aberdeen!

Daffs well and truly popping.....

Ian

Edited December 31, 2012 by Iceaxecrampon

[bobbydog]

The latest CFS anomalies for January shows a big lump (my technical language) of low pressure to our West with above average temperatures and rainfall around average, above average in the South. I think the CFS is useful to check for trends but obviously not to taken at face value but here it is.

Temps

drop that LP anomaly south and east a bit and we have ourselves a winter.....

[IDO]

CFS latest runs show the height anomalies well. Strong northern blocking later in Jan:

Jan: Heights building over the pole in Jan as the SSW works it's way through. The UK remains in a cyclonic westerly flow.

Feb:

In Feb heights are forecasted in Greenland and Eastern Europe. This gives us a relatively mild block to our east and with heights to our NW the cold flow is diverted from Siberia through the pole to the US. The remnants are then dissipated as they cross the Atlantic, though the feed remains cool, and the block to our east diverts the cold south:

They have been very consistent with this for a while now. On this outlook some topplers possible but not great for prolonged snow.

In March, heights remain to our east as the heights remain close to the pole; back between a zonal flow and the Continental high. What it does show is that once the cards fall and blocking sets in, you tend to be in a relatively locked pattern (according to CFS), so the initial setup appears to be important for the UK. Also the SSW has the potential for longer term blocking, which is good for those who are on the cold side of it.

[Frosty.]

Aberdeen!

Daffs well and truly popping.....

Ian

LOL yes the scottish ski industry will not be happy bunnies if that chart verifies, at least they have had some snow whereas most of the uk hasn't had a flake yet. We will need some luck in terms of where the high ultimately ends up.

[Panayiotis]

So the 06z at 189hrs has the low coming from the eastern see board taking a more northerly track compared to the 00z which had it more to the south. Combined with the stronger PV on this run, this doesnt allow warm air to advect into Greenland and therefore not allowing heights to build into Greenland like we saw on the 00z.

[Jason M]

Although it doesn't quite get there on this run GFS yet again tries to build heights over scandi at day ten. Hopefully the ensembles will continue to trend towards this solution. Broad trends is all that matters at present as the detail is irrelevant at that range.

Jason

[bluearmy]

The trend remains the same. The first hint of amplification off the eastern seaboard and 'up she goes'

[Duane S.]

06z , IMO, bang on the money. High pulled out west in FI and there is the Mid Atlantic ridge (may take a couple of bites to produce anything of note though).

Will be a slightly longer way to cold than the 00z as there will be more energy in the Northern arm here but much more in keeping with the background signals right now I'd say.

[snowking]

Well the FI trend of building high pressure across greenland continues with the 6z. Whilst in the previous two runs we had seen an almost perfect transition to this scenario via the HP building over the UK in the next few days, this run looks more in kilter with ECM/NAEFS ensemble means, and still arrives at a similar result. This is thanks to our secondary stratospheric warming around Greenland, still consistently showing:

We then have to negotiate the fragments of the PV moving south. One of these getting stuck in the wrong area could be problematic for us, but given the trend towards MJO phase 6 (mid atlantic height rises) then phase 7 (greenland height rises), the risk of this seems a little lower, as the logical place for LP to head after this is S and E of us (ideally in towards iberia).

SK

[Frosty.]

The Gfs 06z op run ends up being pretty good from a cold perspective, initially we will see pressure rising from the south which will cover the southern half of the uk with a more settled pattern with light winds but probably a lot of cloud being retained so sunshine looks limited, as does frost. The north and west of the uk remain more unsettled than further south and east but turning mild after a rather cold start. By next weekend and into early next week, the main high drifts further east or southeast but continues to hold it's dominance for southeast britain at least, at the same time a fresh anticyclone builds in from the southwest, the unsettled weather to the northwest is pushed away northwest with the jet being diverted well to the northwest and north of it's usual mid winter postition, meanwhile, the two anticyclones merge and create a large blocking high which brings a spell of faux cold for the uk with frost and fog becoming more widespread, the further outlook then shows cold and unsettled weather pushing in from the west with a cold cyclonic pattern later with temps barely above freezing and some snow around. So, a much different FI evolution than the gfs 00z but the result is rather good for coldies.

Edited December 31, 2012 by Frosty039

[IDO]

Another good FI run by the GFS 06z. The high that builds over the UK next week gets flattened after a week, as it fails to reach Scandinavia. The Atlantic ridges to our west and fails around the same time. Late in Fi the Atlantic ridges again towards Greenland and the Polar/Siberia high nearly joins the link.

Just need the PV piece to the west of Greenland to move north or west to give the ridging a better chance to build.

Edited December 31, 2012 by i'm dreaming of...

[Panayiotis]

No worries though because the 06z, gets the warm air to advect into Greenland afterwards,causing the Azores to ridge into Greenland, becoming a weak-ish block in the Atlantic. Because its Fi some might say it wont happen or <1% chance of verifying but Fi in the last 5 out of the last 6 runs has shown this type of pattern, which is something we don't normally see as Fi on every run is different.

Edited December 31, 2012 by Panayiotis

[Nick F]

All the 'right' changes still post t+240 on GFS runs, though good to see the continuing theme of northern blocking over recent operationals - which really kicked-off big style on last night's 18z.

We still need to wait until the 2nd half of Jan starts to come into range on ECM to see if it picks up signs of this potential change mid-month as well, as for now the deterministic and ens mean is still keen a strong PV over Greenland and NE Canada right up to day 10.

[bluearmy]

yet to find out if the gefs are the same but worth noting that the ecm ens do not go above 5hpa

The 51 EPS non-linear integrations are performed twice a day, with initial times 00 and 12 UTC, up to forecast day 15, with a (T639) resolution from day 0 to day 10, and with lower (T319) resolution from day 10 to day 15. In the vertical, all integrations have 62 levels, with the model top at 5 hPa.

that may explain why a top down warming scenario has not been picked up too well by the extended ens? of course the warming is now showing at 5hpa so will be included in the starting data but further wave energy from above this level will not be taken into account at T0.

[fergieweather]

So far as UKMO are concerned, the suggestion of a broadscale change of type & cooling trend around & after day 15 remains their MR view. They note the "very marked" EC signal for a SSW event / reversal of zonal flow and the effects of this likely becoming manifested on the ground around mid-month, albeit current model signals for this remain somewhat tenuous/elusive. This isn't surprising in the turnaround circumstances. However, with a number of ENS members hinting at the cooler type it's the preferred solution from Exeter presently albeit with many obvious current uncertainties.

[Bobby]

The GFS 06z ensemble mean is more in line with the other ensemble/NAEFS means with a weaker HP.

Day 10

[Panayiotis]

Interestingly the CFS 1 month and 9 month, has maybe picked up the signal that the GFS is getting with heights to our NW.

CFS 1 month:All at 360hrs

00z06z

12z 18z

CFS 9 month:All at 360hrs

00z 06z

12z 18z

As you can see the charts posted show some sort of heights rise in the NW (except for 3) but what I found interesting is the two 00z (which are the latest runs), show something similar to each other and to the GFS.

Edited December 31, 2012 by Panayiotis

[Froze were the Days]

Yeah the 'grumpy' model ECM not buying into any northern blocking for the moment and it does seem GFS only shows this in FI which doesn't seem to be getting any closer. One piece of good news is that the CFS v2 model 0z run that has been rock steady with zonal type conditions for yonks now shows a far more blocked synopsis in the medium and long term out beyond mid-January (well this morning anyway).

As per the post I have just seen above

Edited December 31, 2012 by Froze were the Days

[fergieweather]

Yeah the 'grumpy' model ECM not buying into any northern blocking for the moment and it does seem GFS only shows this in FI which doesn't seem to be getting any closer. One piece of good news is that the CFS v2 model 0z run that has been rock steady with zonal type conditions for yonks now shows a far more blocked synopsis in the medium and long term out beyond mid-January (well this morning anyway).

As per the post I have just seen above

? But there's a greater number of EC and NCEP EPS members showing blocking to NE into trend period... where was a notion EC wasn't in tune with this?

[stodge]

Morning all

My first post on NW - it's my birthday on the 15th and having done some research on the charts for that day over the years, it's remarkable how often we get an anticyclonic period around the middle of the month (about one in three over a 50-year timeframe). The output points to that anticyclonic period albeit still at the extreme edge of FI.

I don't know enough about the physics of SSW to comment on its possible impact but historical research and life experience tell me that the key period for "winter" is basically late January to early March. All we are seeing is the first outriders of what may or may not be "something". I also find it strange how quickly people have forgotten last winter's memorable European cold wave which fringed the UK and I well remember frantic study of output when it seemed as though the cold might reach us as well. Positioning and orientation of HP cells is or are the key and there's plety of time for that to be resolved.

[johnholmes]

is on the technical thread-my post is NOT technical, so most of you may wish to have a read, the usual guarantees about accuracy!!

shame its not April 1st

also welcome to stodge-I am sure you will enjoy this web site, lots on the forum and masses of data etc on other parts.