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Model output discussion - 16th Nov onwards

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It has, will be interesting to see the ensembles :)

Looking at the ensemble charts on Meteociel they offer very limited support to the GFS OP evolution, so low confidence in the GFS OP outcome at the current time. 

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Yet another run with a progression towards more seasonal conditions around midmonth - in fact slightly before on the last two runs. Without letting my coldie preferences get the better of me, I don't think this can be ignored now and in the current pattern I think it's a lot more likely a cold spell is going to come from the north rather than the east.

We have seen this already with heights towards Scandi. The ECM did not even play with the idea. The GFS is showing this at +288!! Hardly something that 'can't be ignored'. If this is still showing at 240 then we can await the ECM.

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We have seen this already with heights towards Scandi. The ECM did not even play with the idea. The GFS is showing this at +288!! Hardly something that 'can't be ignored'. If this is still showing at 240 then we can await the ECM.

In my ten years of model watching, i would say the GFS excels in one area, and that is picking out Northerlies in deepest FI. Now, that is not to say any Northerly will be as potent as currently showing as their will likely be short waves near Southern Greenland which can scupper the flow.

 

Another couple of days before the ECM comes in range, but well worth watching.

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In my ten years of model watching, i would say the GFS excels in one area, and that is picking out Northerlies in deepest FI. Now, that is not to say any Northerly will be as potent as currently showing as their will likely be short waves near Southern Greenland which can scupper the flow.

 

Another couple of days before the ECM comes in range, but well worth watching.

Yes fair enough.....also he GFS did pick up the initial northerly blast in 2009 before the others.

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Another beautiful GFS run with a stonking northerly as pressure rises across the north Atlantic.

This is a trend not to be ignored now , the model is for sure seeing a pattern change. :)

 

I'll start believing it when it comes into the reliable so I will need to see such charts pop up within the D5 to D7 timeframe. So at that rate, it's going to be a long wait yet and therefore will taking those charts with a truck-load of salt instead of the usual pinch for now. I'm not saying yay or neigh here by the way, just wanting to keep my cards close to my chest for now. What I'd like to witness firstly is my foreseen settled prediction and with that, the removal of next weekend's low from the various model suites. Time will tell, but give things another few days yet and we might well see those charts of wintry potential coming into much more reliable timeframes and the second half of December becoming one to remember for us coldies. Not to say, things aren't wintry right now up the North with a heck of a lot of snow about for some folk and then the eventual thawing come midweek. Nothing boring about this weather set up currently and perhaps this cold air/mild air battle will abate after a few days too as NH changes filter through into the mid to long-range outputs.  :hi:

Edited by gottolovethisweather

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Hi Fergie, I'm liking those words of yours, having been going on about a SSW in Jan with impacts around the middle of the month. While that may be some two weeks or so ahead of that suggested by the outlook for contingency planners, the general theme is there. 

 

I think it might also please a couple of Netweather members whose forecast was in part based around these suggestions too.  :D

 

Some useful analysis in your post as ever Singularity, Thanks.  :good:

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Aberdeenshire 850's show the GFS OP was one of the warmest around the 10th, then quite a large drop to become one of the coldest by the 14th. You'll notice a colder cluster around the 12th before the 850's recover, the OP keeps falling and has some but limited support. 

 

post-9615-0-78455800-1448886069_thumb.pn

 

 

 

 

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GEFS 06z probability

Chart weatherbell

In my opinion a mean chart is of little use in some circumstances . However in other circumstances it can be very useful. If you have a Situation where two potential outcomes are very different you end up with a mean which shows neither. An analogy, if you are flicking a coin and heads is one outcome and tails is the other the mean would be it's landing on its side which clearly isn't an outcome. Hope that makes sense.

Regards

That Ecm

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In my opinion a mean chart is of little use in some circumstances . However in other circumstances it can be very useful. If you have a Situation where two potential outcomes are very different you end up with a mean which shows neither. An analogy, if you are flicking a coin and heads is one outcome and tails is the other the mean would be it's landing on its side which clearly isn't an outcome. Hope that makes sense.

Regards

That Ecm

 

Agreed completely. The mean can be helpful in the shorter term but once you get to the 1-2 week mark the mean just becomes watered down and doesn't really help you at all, I'm not sure why some people swear by it so much.

 

You're much better off looking at the individual postage stamps to get an idea of what the ensembles are saying when you get to that kind of range.

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Aberdeenshire 850's show the GFS OP was one of the warmest around the 10th, then quite a large drop to become one of the coldest by the 14th. You'll notice a colder cluster around the 12th before the 850's recover, the OP keeps falling and has some but limited support. 

 

attachicon.gifens1.png

Yes i think expecting GFS op to be anywhere near at that range is pushing it,although nice to look at for cold lovers.

A look at the 00z ens graph and naefs show that the current pattern of low heights to the north and high to the south continue.

post-2026-0-49407500-1448889432_thumb.gipost-2026-0-58482400-1448889439_thumb.pn

 

the Op a cold run against the pack at the end there.

No doubt we can and have currently bursts of north westerly colder air ,especially further north, during the next couple of weeks but there is no sign of a movement away from this mobile westerly pattern yet.

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Agreed completely. The mean can be helpful in the shorter term but once you get to the 1-2 week mark the mean just becomes watered down and doesn't really help you at all, I'm not sure why some people swear by it so much.

 

You're much better off looking at the individual postage stamps to get an idea of what the ensembles are saying when you get to that kind of range.

Which unsurprisingly give little idea of an outcome either, pretty much anything can happen from here, which has to be better than ensembles all singing off the 'lets go mental default zonal' soundtrack of course :)

post-4955-0-79951400-1448890008_thumb.gi

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Which unsurprisingly give little idea of an outcome either, pretty much anything can happen from here, which has to be better than ensembles all singing off the 'lets go mental default zonal' soundtrack of course :)

The common theme in those gefs stamps though Nicholas do reflect the height anomaly forecasts.

Same setup as now really,low to the north,high to the south the jet running across our latitude. 

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post-16336-0-70247800-1448892620_thumb.p

 

NAO prediction for coming weeks from GFS, GEM and ECMWF from WSI. Trending back towards neutral after being highly positive recently.

 

post-16336-0-87553800-1448892622_thumb.p

 

ECMWF monthly prediction precipitation shows a very wet week 1, before drying out in week 2. Becoming slightly wetter than average again for all in week 3 before finally drying out in the north in week 4 but staying wetter further south. The removal of the drier anomalies over Europe in weeks 3 + 4  and introduction of drier anomalies in Scotland  could indicate possibly a trough getting into NW Europe through that period with some ridging up north.

 

post-16336-0-11551100-1448893174_thumb.p

 

JMA Ensemble weeks 3 & 4

Pattern maybe starting to change middle to late December with a ridge building to the west with lower heights and a trough to our east. 

Edited by bradythemole

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thanks Fred but is it not possible to give links or show the actual chart you feel is representative of your views as routine. It would sure help me to understand what you mean-please?

The other comment I would make and will perhaps get howled down is this.

Currently the GFS is not consistent that deep cold will flood south from about 14 December. Not surprising really considering how far away that is. No data from ECMWF goes that far out. What other help can we get for data around 14 December.

You guessed it, the anomaly charts. So let us have a look, NEAFS goes well beyond that date so what is it suggesting?

http://www.meteociel.fr/modeles/naefs_cartes.php?ech=192&code=0&mode=0&map=1&runpara=

looking at the output T+300 and it has a slight indication of a pattern at 500mb than could give a 500mb flow from a point north of west. But to me it is only, at the moment, a slight hint, nothing like the full blow deep cold suggested by GFS.

The only other help might be the NOAA 8-14, link below

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

That shows no suggestion, and does not over the last couple of runs of the 500mb flow setting up to give a cold north of west flow into the UK.

How about the MJO, GFS version?

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foroper.shtml

It is too close to the origin to be of any predictive use so no help there.

To me, yet, not enough solid and consistent prediction for any major change in the current flow pattern, south of and north of. Put another way a continuation of the unsettled, at times rather wet and windy, with temporary incursions of cold Polar air, more especially for the northern part, pricipally Scotland and occasionally N Ireland and the more northern parts of norther England at times.

Won't be popular I know but to those new to watching the model thread it is as objective as I can be.

I suppose one could say a north to south split with colder interludes more likely, at least with snow which is what most are searching for, in the north.

 

 

How far out do you think this pattern holds in terms of confidence, John?  Are the anomalies already sufficiently "set" to be able to consider the suggested mid-December pattern change a non-starter to a reasonable confidence interval?

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thanks Fred but is it not possible to give links or show the actual chart you feel is representative of your views as routine. It would sure help me to understand what you mean-please?

 

Hi John

Its only the theme but if they crop up and I save them right I'll try to do that on occasions as on my Dec forecast one stayed and the other rubbed itself out hence why I don't always post charts. I'm clearly doing something wrong, but also what PM posted supports what I said and was getting at, its been showing on GFS for a few days now not just today and that was the 'main' point of my post.   

 

BFTP 

Edited by BLAST FROM THE PAST

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If the GFS is onto something then we could see a change in respect to the polar profile with perhaps an eastward shift of the main core of the polar vortex which means low pressure tends to be centred more to the north of the UK, so a potential change to cooler conditions albeit probably near normal over the UK as opposed to the very mild conditions forecast in the south over the coming week (always cooler in the north mind you)

Anomaly for a few of the extended day range

gens-21-5-300.png?6

gens-21-5-384.png?6

 

At this point the GFS operational looks rather optimistic with a general unsettled westerly pattern favoured. As stated by a few others above.

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How far out do you think this pattern holds in terms of confidence, John?  Are the anomalies already sufficiently "set" to be able to consider the suggested mid-December pattern change a non-starter to a reasonable confidence interval?

 

hi Chris

I don't think that the signal out to 14 December on the NOAA anomalies shows anything that would 'allow' if that is the correct term, for a long cold spell. They don't really look conducive to more than any 24-48 cold burst behind one of the active surface weather systems. I only quoted the MJO output as it can give a lead when nothing else is doing that.

I honestly do not know what may happen beyond 14 December from the data I regularly use. Another 4-5 days and the anomaly charts SHOULD give some view one way or the other out into that time scale. of course they may be wrong but I would be reluctant to support any long term change if none of them show some kind of hint at the very least.

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I think we know better to believe any FI from the GFS, it's the fact it's had a few runs back to back that have got people wondering, along with potential changes that were talked about at one time by Ian F a few days back (potential). 

The charts change every day, lets see what the next set bring - I like to use Knockers info as a guide as he isn't a cold ramper...If he and Ian F start saying thinks are looking good for us coldies then it's time to get a little more confident...All the same, cold FI charts are still good to see and talk about.

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I think we know better to believe any FI from the GFS, it's the fact it's had a few runs back to back that have got people wondering, along with potential changes that were talked about at one time by Ian F a few days back (potential). 

The charts change every day, lets see what the next set bring - I like to use Knockers info as a guide as he isn't a cold ramper...If he and Ian F start saying thinks are looking good for us coldies then it's time to get a little more confident...All the same, cold FI charts are still good to see and talk about.

 

Yes, the showing of a cold spell in FI has grabbed my attention over the last day or two as it has shown in a series of runs and around the same dates, but I am by no means excited yet as it is indeed in FI and there's a lot of water to flow under the bridge before then. Still, something to look at, and hardly unusual in this sort of Atlantic set up. It will be interesting to see how it's either furthered or dropped in future runs.

 

In the slightly shorter term, I am more interested in the prospect of some high pressure from mid next week. Then again, I suppose that's about as likely as a northerly at the moment.

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I think we know better to believe any FI from the GFS, it's the fact it's had a few runs back to back that have got people wondering, along with potential changes that were talked about at one time by Ian F a few days back (potential). 

The charts change every day, lets see what the next set bring - I like to use Knockers info as a guide as he isn't a cold ramper...If he and Ian F start saying thinks are looking good for us coldies then it's time to get a little more confident...All the same, cold FI charts are still good to see and talk about.

 

Yes, sound enough advice but also, no one person is able to forecast FI timescales accurately yet alone earlier conclusions. With FI beginning as early as D4 occasionally and as late as D10 in other situations, perhaps beyond, I believe we need to watch our forecasting attempts, I guess this precisely why those with greatest experience don't get hung up on all the surface details beyond such timeframes. Same can be said for all those inter and intra-run differences from the ECM, Met O, GFS or whichever model suite one uses, Mother Nature will often have the last laugh at any of our own forecasting efforts anyway. Not to say, we cannot try though as that is simply human nature, eyes down to this afternoon's and evening runs we go then. Officially the start of DECEMBER tomorrow, wahoo.  :drunk:

Edited by gottolovethisweather

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...compare/contrast where the larger (just) majority of the two clusters from EC 12z takes us by the same timeframe out into the distant yonder...

Rookie question here, but what is this chart suggesting? Is it high pressure building up in Atlantic up towards Greenland (blocking) therefore allowing Low pressure systems to flood south from the pole?

Edit: oops, the chart didn't show up on my 'quote!' It's from a few pages back, sorry!

Edited by Sperrin

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Here comes another interesting FI I think, lets see if the ensembles start picking up on the trend....

 

Not quite as good as earlier, but similar theme.  It looks like around day 12 the PV starts being obliterated, not quite in ECM range but getting there. 

Edited by Ali1977

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npsh500.pngnpsh500.png

 

Indeed - despite plopping on the idea of a nice ridge of high pressure in 8-10 days time for the UK, the polar theme remains as interesting as ever. The presence of increased heights in the Svalbard area at around +216 hinted at high latitude blocking to come - it's one of my 'markers' for serious polar vortex disruption.

 

 

This run follows a similar theme to the 00z GFS det. run in that it splits the vortex between the UK and central/eastern Asia rather than going with a clean displacement of the whole vortex to western/central Asia as per the 06z det. run.

 

It leads to issues with getting the trough in the right place to bring that cold air in, but also lends more support for blocking to our NW to keep the Atlantic at bay.

 

All nice viewing but I'm wary of the model overdoing the response to the usual fluctuations in background signals, in particular how it changes the AAM.

 

gfsgwo_1.png

 

The AAM tendency soared yesterday, flying in the face of what GEFS were seeing until very late on. Remember it was only about 5 days ago that the model had the AAM cycling within the central circle - now it's looking to perform a high amplitude orbit entirely typical of the El Nino basic state.

 

In light of this, that drop away of AAM through 8/1 in the latter stages of the outlook has to be viewed with great skepticism - and here's the thing; the last time we had GEFS predicting such a drop-off, the det. runs were coming up with height rises to the northwest and blocking scenarios. Over the following week, the AAM drop was toned down further and further, and that blocking potential was reduced to the transient - but potent - cold snap of the weekend before last.

 

So I hate to say it, but I'd be not at all surprised to see a similar chain of events this time around. This does not, however, rule out a short spell of weather capable of delivering severe frost and widespread snow. So in my opinion, that's what's worth hoping for with respect to the third week of the month. Just my angle, mind!

Edited by Singularity

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