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


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ECM is not looking too shabby in the middle range at 168hours with -5 in 850hpa so on the slightly colder side, i won't look or think of the GFS for months beacuse of the disappointment last week. NAO value is trending positive for the coming 10 days and AO suprisingly negative

NAO value.gif

AO value.png

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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.

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6 minutes ago, weirpig said:

It all depends on ones expectations.   For me im happy with the outcome if not ecstatic    snow still a possibility for some  and still chances of upgrades in the future( we can hope)  I really dont know what spam fritters are  but if you havnt eaten in a while i suspect they are lovely.

You're obviously much younger than me! lol spam fritters are utterly vile ! Unfortunately given the models today I wouldn't be holding my breath re that PM flow and the depth of cold shown. Any brief interest still has to break through the UK's cold and snow forcefield which is a lot happier today than it was yesterday. Overall the outputs are going in the wrong direction and the GEFS bar a few solutions are pants. We need more amplification tonight to stop the rot but this flattening trend doesn't normally reverse once started. Anyway we'll see tonight if the spam fritters can be taken off the menu.

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1 hour ago, frosty ground said:

Everything has backed west a little and the snow threat moves south.

Something I've noticed over the last week is the 0z and 6z runs have been poor for cold following a decent previous run, only for the 12z's to be a lot more encouraging. As a result the threads have been downbeat in the mornings and more encouraging in the afternoons. What evolutions will win out is still anyone's guess for the next few runs but it's part of the chase I guess. 

 

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6 minutes ago, Faronstream said:

ECM is not looking too shabby in the middle range at 168hours with -5 in 850hpa so on the slightly colder side, i won't look or think of the GFS for months beacuse of the disappointment last week. NAO value is trending positive for the coming 10 days and AO suprisingly negative

NAO value.gif

AO value.png

You say that you won't look at gfs output and then post NOAA NAO /AO data ??

fwiw, the drift towards the predicted neg AO looking a pretty weak affair  continues (ref all ens output) and the same applies to the NAO which seems to be headed broadly neutral. 

Forcing from the polar profile which looked promising to help sustain some amplification drifting away for the time being. 

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There is a bi-modal distribution of opinion on the model forum this morning with a split between those pleased by a potential North Westerly flow and wintry precipitation and those of the opinion that once again winter is over.

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The big problem today is we've lost the forcing to hold the Euro troughing in place, the Russian ridge is less evident and less favourably orientated.

Then if you add the loss of amplification upstream it all goes downhill. The issue with PM flows is that the coldest air never gets a chance to get sufficiently south as the next wave of Atlantic energy moves east and at longer range shortwaves near Iceland aren't modelled well.

If you're viewing the 850's in a PM flow its best to wait to within T120hrs max or even better T96hrs because all models but more particularly the GFS has a bias to show colder 850's at longer range.

If more amplification shows up tonight then that would help but really we've started the day on a very disappointing note. Lets hope for better this evening.

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2 minutes ago, Seasonality said:

There is a bi-modal distribution of opinion on the model forum this morning with a split between those pleased by a potential North Westerly flow and wintry precipitation and those of the opinion that once again winter is over.

Completely with you on this comment. Winter is far from over especially for us here in the North West going by current output. Comparing overnight runs with this mornings run can show how little tweaks in the output can change the outlook from run to run and still plenty of changes to come.

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As I said yesterday, the pattern of the jet stream at present is not conducive to HLB. Look at it like waves rotating around the globe, and we need one to break, there just isn't enough slack in the Jet Stream to allow this to happen at present, so we get these peaks and troughs.

I am going for first 2 weeks of February to get a breaker, and then the fun begins, because the pattern has been right all winter, just the breaks have been in the Pac and not the Atlantic so far. (Maybe because of continuing wQBO).

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17 minutes ago, nick sussex said:

You're obviously much younger than me! lol spam fritters are utterly vile ! Unfortunately given the models today I wouldn't be holding my breath re that PM flow and the depth of cold shown. Any brief interest still has to break through the UK's cold and snow forcefield which is a lot happier today than it was yesterday. Overall the outputs are going in the wrong direction and the GEFS bar a few solutions are pants. We need more amplification tonight to stop the rot but this flattening trend doesn't normally reverse once started. Anyway we'll see tonight if the spam fritters can be taken off the menu.

Absolutely agree spam fritters are nasty lol.

Theres clearly a trend for Northern areas to have wintry blast.

But north easterly and easterly are certainly all becoming a distant memory compared to the last few days. 

Be warned the Stella charts they will turn up again!.

but until there in place with in 94hrs I'd be extremely sceptical.

But cold nw will feature in forecast but even this and northerly could be pushed east of us even with in the reliable time frame.

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GEFS 6z FI shows a few interesting scenarios. IF we can finally get that low anomaly into Europe we don't necessarily need the big obvious high to deliver the goods. 

Small wedges can be enough and p12 shows this. With the pattern backed west enough. 

IMG_1730.PNG

This would also explain how we can get colder air in with the low anomaly signal to the south but with no clear signal to the north east.

All in the spirit of cold hunting of course, and no firm conclusions to be made. Just shows what is possible.

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47 minutes ago, mountsbaysnow said:

aaaarrrrgghh we are bang on the 528

 

To be honest mate that chart will chop and change and there are lots of other factors required for snow bar thickness.  Dew points, Air temp, 850s etc 

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Not often we look at the near term in MOD, as we are normally chasing snow potential out in the medium range, but risk of freezing rain just over the Channel tonight/early Saturday morning, as a warm front with rain and 850s over 0C rides over surface temperatures below freezing across northern France and Benelux

rain_03z.pngT850_06z.pngtemp_06z.png

Edited by Nick F
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GFS ensembles for south of the midlands are pretty shocking comparably to a few days ago, even longer term there is little sign of anything interesting, high pressure is just too close by no matter what!

Looking like a transient shot for the north with some snow around, it's been the winter of MLB and we still can't shift it. As I said yesterday as well I suggest being careful regarding the 850's from any PM air as they are often exaggerated cold wise

Edited by Weathizard
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Well I've seen plenty of poor charts / weather this winter so far but at last the current models indicate the first snow since November across parts of the uk during the second half of next week, initially across northern uk and then digging further south..beggars can't be choosers when it comes to snow. Longer term, it appears we are looking at short-lived milder interludes but generally temps are expected to be below average and occasionally cold with frosts, wintry showers and freezing fog at times..could be worse!:)

Edited by Frosty.
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1 hour ago, mountain shadow said:

You've lost me Nick, surely a 2/3 day North Westerly was all that was on offer, not much change that I can see.

Incidentally, I loved spam fritters but then I'm from the land of the deep fried Mars bars.

Much has changed in the output this morning.

For the reasons Nick and myself mentioned we are seeing the cold spell for next week being shorter in duration and potentially less cold. Based on todays output the potential for snowfall for low lying areas is only around 36hrs. Furthermore with the way it is going the NW,ly at +168 could be downgraded further. We need to see the models backtrack towards last nights ECM so the cold N,ly flow becomes sustained and not temporary.

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Looking at how mobile the pattern is expected to be next week with little sign of any ridging in the Atlantic as the n.Jet picks up then a 2 day polar incursion would be good going considering the expected NH pattern.

EDH1-144.GIF?06-12

The ens graphs still backing the colder spell from the end of next week.

graphe3_1000_267_96___.gifgraphe_ens3.png

so around -5c uppers for C.England briefly before the upturn towards average.Probably a degree ot 2 colder up north where snowfall for 2/3 days is quite possible especially higher up but of course as ever details on that to be ascertained much closer to the day.

The problem with these polar n;westerlies within a fairly flat pattern there is more likely to be secondary wave developments along the polar front as it comes south which can delay or modify the coldest air,especially the further south we go.We can see this on the 06z gfs charts

viewimage (1).pngviewimage (2).png

It get's there in the end but these sort of features can be missed until nearer modeling shows them and let's hope something more significant doesn't show up to modify the coldest air even further as we get closer.This is why it's much better with a more amplified Atlantic high where you tend to get a more direct and quicker transport south of Arctic air from a more northerly direction.

Still for what it's worth we do seem to be looking at a 2/3 day cold spell of sorts,let's hope for a bit more ridging upstream to make the most if it whilst we have this window. 

Edited by phil nw.
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31 minutes ago, fromey said:

Would this make any difference in what we are seeing at the moment 

IMG_2232.PNG

Nope - that's the ec op 00z and we know from nick's excellent analysis that it's the extra wave in the flow that's the culprit here re the flatter pattern. 

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