swilliam

If you read his post it says that the mean flow direction will change to more NW'ly so an average colder. He also states that this gives the possibility of N'ly outbreaks and more significant cold. However it is too far away for something like this to show up on the models yet and is only a possibility. Hope this clarifies it for you.

At the least the GEM is showing what is possible if the PV clears away enough eastwards and the daughter vortex if far enough W as NS has been saying.

I think whilst the GEFS anomalies are still showing these kind of outputs in FI then there is always the chance for something interesting to develop although we could do with some lower heights in Europe. 264 348 Strong anomalies at this range and certainly no raging vortex.

Because it is freely available

No - those that have full access to other models (ECM, UKMO etc.) use these (i.e. met office, BBC). The reason why GFS is used by many other websites is that it is freely available.

Some very tasty FI ensembles tonight (where is Mucka when you need him) Nothing better than this though (just for fun but shows what is possible)# No prizes which one is P16. However overall everything is lower - something interesting is going to happen

Sorry keeps loading up old replies and I do not know how to get rid of them - plenty of bugs in the new system - wonder when these will be addressed. JMA shows the absolute best of what could be developed from this pattern Nirvana from there. In reply to Yarmy JH is absolutely right - going back to zonal is always a bad thing. If the overall pattern is in general amplified then anything can happen (as we are seeing). If it goes back to zonal then something special has to happen and this is often difficult requiring something like Fred or whatever the depression was called that instigated the large scale WAA at the end of Dec. Ever since then we have had interesting models to look at. I have never understood people saying a reset back to zonal is needed or would be good.

It s because the overnight feature on Sat/Sun is further E introducing moister air.

Yes - this is the only model showing this much - Euro4 last night showed something similar. As IF just said FI is T36

Err - yes - this is the accumulation after it has snowed.

Looked much better on the Aperge - gave 4/5 cms even down to the S coast

Because of the angle of the front the winds in ppn area would from the SE and coming from the cold pool on the continent. This would mean air with low DPs even the upper air temps are quite high - could even be an inversion. For the Aperge at this time the 850s are about -3 at the time the snow falls anyway. V small changes in the model output give big changes in the weather in this situation In fact a lot of the snow shown accumulating comes on Sunday Morning from the area of moisture to the NW which dives S Be nice if that came off.

Temps from GFS, More importantly Dewpoint below zero Lost of other factors as well so should be some snow about but a bit marginal in places - without going into discussion and off topic about predicted temps on BBC TV charts

Not sure I would agree the majority show this (and if it is only a small majority). There are 6 clusters (plenty of uncertainty) with cluster 1 including the det and 3 (the worst) showing Atlantic going through. The other ones all show some ridge in different places (2 is to the NW and zonal coming underneath, 4 with the ridge over the UK or to the N of it and zonal coming underneath, cluster 5 with it to the E but probably about to collapse and 6 with ridge over the UK but more to S maybe collapsing a bit later). So there are plenty of options and no clear majority. This evidenced by the spread with many prolonging the cold longer by a couple of days compared to the OP. Admittedly they all go mild after this.

I think that is pretty unlikely with the current set up. We may get a bit of snowfall from the disrupting trough. If it was significant would be quickly followed by rain and then SWesterlies. The more likely scenario is that we get a high somewhere near us which essentially makes it dry for most places. How cold depends on the exact - the further N the better.

Yes it was the first one to show the Atlantic SW problem and the thinner initial ridge with a more westward position leading to the loss of the big block over Greenie that was there recently. This was likely because it is always a bit fast (more zonal) than the others so when the models are moving to a less amplified outlook then it shows this first. However if the model outlook is tending to show a more amplified position then it picks this up last (in the range medium term range). As we know the EC is prone to a bit of over amplification at times at long range. It does seem that UKMO maybe be better at handling undercut scenarios at the 120/144 range (however remember this one has not happened so we still do not know if it going to correct). So this means we should look at all the models to see which way they are trending and make a judgement from there. Just to add as Mushy and JH pointed out earlier the 500 mb anomaly charts have been pretty stead fast in predicting the maintenance of the ridge and the prolonging of the cold till about the 21st.

V good support for the 06 op from the GEFS ensemble it has to be said. Mean at 144 ECM at the same time (-6) - bascially the ridge tilts to the NW rather than the NE and the euro trough is much deeper This arises because the depth of the trough in W Atlantic at t90 and the angle of it are very different and therefore amount of energy going SE - still plenty to be resolved GEFS t90 ECM T96

The progression of the rain is slower and more energy going SE - also note the curve over N France. Slow progression makes a longer snow event 06 00

Latest AO update from Cohen is available. Forecasting extended -AO and -NAO for 3-4 weeks +SSW + _ve temp anomaly so looks good for cold - depends how much faith you have in this stuff. http://www.aer.com/science-research/climate-weather/arctic-oscillation Looking at the ensembles even if we get a flat pattern later next week many of them re-amplify so I would expect something interesting to come in down the line Best is P12 even though it is one the least promising at 120hrs 120 276

Yes -pity that except of course we paid for it in the first place.

No way will it be singled out as trendsetter - quite the opposite in fact. Still not decided though but the ensembles are very encouraging. If we get cross model agreement for next weekend with a cold highnear or to the W of us I will begin to believe it - no doubt the UKMO will now show a sunken high next weekend though.

P5 shows what can happen if we do not phase the PV with the lows in the W Atlantic and these then merge and then we get trough disruption - builds the high much further N

The reason was that the PV chunk in Canada was held further W due to the initial lows (in the PV chunk) being at least 5mb deeper and taking a slightly more N route - the PV chunk did not then phase with the lows in the W Atlantic and the jet coming off the E seaboard was then a lot weaker and did not blast through or over the tenuous Atlantic ridge

Probably not worth looking at far FI as the GFS has set off one of its customary bombs in the W Atlantic (935 mb) (Edit:- unless it shows something good of course)

Yes quite - this thing is wholly undecided (as it was before this run) but at least we do not have to keeping reading that the GFS has been really consistent (in showing a progressive outlier IMO). If we could get some trough disruption of the trough in the W Atlantic then you could get some really interesting charts again.