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Model Output Discussion 29th December - Into mid-Winter.


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11 hours ago, ghoneym said:

Been meaning to ask this for a while, why are the previous runs on the GFS not available at +237 & +240 ?

Cheers

Couldn't see this answered but I think it's because when the previous run came out 6 hours before those time-slots would have been +243 and +246, which don't exist (the chart viewer 'shifts' things forward 6 hours so we're comparing at the same forecast hour).

I guess it's the same reason that the T+384 chart doesn't change from T+372 for previous runs on the Netweather viewer

Edited by Evening thunder
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Evening All For those of us who have been here for a long while there is times when you know you have to throw in the towel on chasing cold & times ( very rare ) when you 'just know' that the

Boom goodnight vienna

People being a bit harsh on Steve Murr, at least he has the balls to try and read and predict what may happen from his viewpoint rather than just posting what charts show.

Posted Images

A bit of an improvement on the 06Z GFS compared to the 0Z. Some cold air producing show showers does begin to move in but it will be transient unless we get some height rises behind it.

gfs-0-186.png?6gfs-2-192.png?6gfs-1-198.png?6

Edited by radiohead
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npsh500.png h850t850eu.png

Well, GFS has made some notable progress, but the US trough takes around a day longer to get its act together which leaves more time for disturbances to get into the Atlantic flow prior to the amplifying tendency.

The run almost produced the hang-back secondary low near S. Greenland that I warned about... stress.com :crazy:

 

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54 minutes ago, fromey said:

i ve seen this posted 

"Models are indicating a stratospheric ridge to build in over Europe during the late 11-15d period."

what does this mean and how would this effect us here on our small little island.

also the zonal winds are indicated to drop, i assume this is taken into account in the models

Be gentle, trying to learn

 

fromey

The only thing I would say to that (presume you were looking at Michael Ventrice's tweet), is that the chart posted is way out at T+360. So far too far away to be taken seriously IMHO.

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This run ends up very cold, but it looks transitory, with the energy coming out the eastern seaboard and troughing around Greenland we won't get anything sustained (IMO)

 

Close to a potential scandi high at day 9/10, as usual! Not this time though.

Edited by Weathizard
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2 minutes ago, Paul_1978 said:

The only thing I would say to that (presume you were looking at Michael Ventrice's tweet), is that the chart posted is way out at T+360. So far too far away to be taken seriously IMHO.

The broad idea carries some merit though, as it ties in with developments in the 6-10 day range in terms of what the impacts should be on the stratosphere.

@fromey, the stratospheric ridge could connect down to the troposphere (surface layer of the atmosphere) and discourage much influence from Atlantic storms in our region, but this is far from assured. What's more reliable is the fact that it would interfere with the stratospheric polar vortex, and perhaps, thanks to another ridge on the Pacific side, perform a 'pincer movement' that splits the vortex in two, allowing high latitude blocking to gain a foothold quite widely and with good positioning to benefit us thanks to the location of the stratospheric ridges - but I must add the caveat that I'm taking a very optimistic, 'no complications' view for the sake of simplification and recent times have seen no shortage of complications interfering with developments.

Really, what with the westerly QBO established at the moment but few other strong signals, the remainder of this winter is largely about seeing whether forcing from multiple relatively weak* sources might happen to align in the right way to overcome the odds and bring us either a short wintry spell of weather or two (if no stratospheric support) or something more prolonged (if the stratospheric vortex splits - main impacts likely in Feb-Mar if that happens).

*Assuming the MJO doesn't go beyond all model expectations. I've seen it do that in winters past so you never know!

 

I realise this post doesn't offer much in the way of clear guidance as to what to expect going forward, but that's pretty much the state of all long range forecasting with respect to this particular winter. Next winter may be more manageable. Hopefully.

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3 minutes ago, northwestsnow said:

Rtavn23417.gif

Bitterly cold weekend next esp places with snowcover from the those juicy snowshowers..

Have not posted for a while   but however short lived it may be  there is the potential for some heavy wintry showers, At least on this run, some may see a covering.  North west in prime location  and maybe a chesire gap streamer for those further inland.  Ill take this for what so far has been a winter of let downs

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Leaving aside the GFS 00Z to a very small extent, nice to see consistency from the models. The GFS 06Z is fairly in line with other main models.

GFS 06Z - most of UK under -6C upper air by T192

gfs-1-192.png?6

Still under -6Cs 48 hours later

gfs-1-240.png?6

Though of course NW areas will be wettest (snowiest?), not exactly dry anywhere except the far SE maybe

gfs-2-204.png?6

though over a 48 hour period with low pressure close by, a trough could well form crossing the whole country.

Is it cold enough for lowland snow? Absolutely. It's January - 2/3rds nighttime, little heat from the sun during the day. And the sea-track is from nearer Greenland than Newfoundland over this little period. -6s will do for most right now.

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What's notable on the ECM 00z is the way it lifts the PV out of Canada by day 10.

if we can get those low anomiles down into Europe, and the lows coming in are trending NW/SE as opposed to the normal SW/NE, which is good, then we could end up creeping into a much colder pattern beginning with that cold north west flow.

ECM 24,PV entrenched over Canada

IMG_1726.PNG

ECM 240, PV lifting out of Canada and moving east with that lobe dropping down into Europe.

IMG_1725.PNG

Not a bad place to be in mid Jan TBH.

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Well the gfs backtrack continues on the 06z although more transitionary than a sustained cold spell. But who at present wouldn't take a northerly with potential snow showers than hunt for the phantom easterly. I would bank the 06z.

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What's been showing for next week is a good building block to something better. Heck, even us in North Somerset would get a dusting - haven't seen any snow for four years! 

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Well the  control  may be short lived  but it certainly follows the cold theme  Edit   easterly garden path again?   no nor me.

gensnh-0-0-240.png

gensnh-1-1-288.png

Edited by weirpig
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Keep watching his forum with interest but just how long do we have to wait for anything to verify with regard to Snow , Many of you seem to trust these models with little success, not sure I would buy a product that produced the correct result very rarely ,

Anyway looks like we might finally be onto something or is there a chance that once again we will be disappointed by daily downgrades to cold rain !

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I find the difference between the GFS 06 and 00 quite interesting. It all appears to depend on the little feature that is spawned from out old friend the upper low to the south. You can see it clearly on this chart at the boundary of the cold/warm enclosed by the 1020 isobar.

gfs_t2maf_slp_eur3_26.png

It tracks NE and suddenly deepens in the next 18 hours after engaging the strong jet to be here

gfs_t2maf_slp_eur3_29.png

And 24 hours later is 963mb off the coast of Norway and the UK is in a strong NW and very wintry weather which would portend heavy snow showers up north, certainly on the high ground. A very good example of cyclogenisis but will it be repeated on the next run?

gfs_6hr_precip_eur3_33.png

Edited by knocker
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I think 06Z is closest to the mark yet, with it showing pretty much what the met office text forecasts suggests, in regard to 'mild, cold, mild, cold'. Winds from NW quadrant seem most likely for this. 

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30 minutes ago, Backtrack said:

I think 06Z is closest to the mark yet, with it showing pretty much what the met office text forecasts suggests, in regard to 'mild, cold, mild, cold'. Winds from NW quadrant seem most likely for this. 

I myself going to stick with the uk model and ECM for the med term as they have shown pretty much the same theme last couple of days not much difference between them,  as for the longer term ECM is the model for me most consistent over the last few days GFS has swap and changed not very consistent performer for me chart below are ECM yesterdays 00z run v  ECM todays 00z for the same day mirco differences.

ECM also shows a milder interlude day 10 but has a 3 day cold spell before hand and looks to turn colder again days 11-12.

Hopefully not to be laid up the garden path again fingers crossed.

ECM1-168 (5).gif

ECM1-192 (3).gif

Edited by booferking
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11 minutes ago, radiohead said:

Clear as mud. But at least the average stays hovering around the -5 mark.

graphe_ens3_bsu2.gif

What location is the set of ensembles for please ,altitude  353 metres ??  

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